Coccygeal nerve(s)
Nerve to obturator internus
and superior gemellus Nerve(s) to levator ani
and coccygeus
Nerve to quadratus femoris
and inferior gemellus
Pudendal nerves
Posterior femoral cutaneous nerve


True pelvis, pelvic floor and perineum
1230
8
noiTces
Pudendal nerve (in the pelvis) geus, joins the minute coccygeal ventral ramus that emerges from the
sacral hiatus, and curves round the lateral coccygeal margin, piercing
The pudendal nerve arises from the ventral divisions of the second,
coccygeus to reach the pelvis. The small trunk that is formed in this way
third and fourth sacral ventral rami and is formed just above the supe-
is the coccygeal plexus. Anococcygeal nerves arise from it and form a
rior border of the sacrotuberous ligament and the upper fibres of ischi-
few fine filaments that pierce the sacrotuberous ligament to supply the
ococcygeus (Klink 1953, Sato 1980). It leaves the pelvis via the greater
adjacent skin.
sciatic foramen between piriformis and ischiococcygeus (see Fig.
73.10), enters the gluteal region and passes dorsal to the sacrospinous
Pelvic part of the sympathetic system
ligament, close to its attachment to the ischial spine, where it lies
medial to the internal pudendal vessels. It accompanies the internal
pudendal artery through the lesser sciatic foramen into the pudendal The pelvic sympathetic trunk lies in the extraperitoneal tissue, anterior
(Alcock’s) canal on the lateral wall of the ischio-anal fossa. In the pos- to the sacrum beneath the presacral fascia (Fig. 73.11), and supplies
terior part of the canal, it gives rise to the inferior rectal and perineal sympathetic innervation to the pelvic organs and vascular system. It lies
nerves; the dorsal nerve of the penis or clitoris continues ventrally medial or anterior to the anterior sacral foramina and has four or five
from this origin. interconnected ganglia. Above, it is continuous with the lumbar sym-
pathetic trunk. The right and left trunks converge below the lowest
Sacral visceral branches
ganglia and unite in the small ganglion impar anterior to the coccyx.
Visceral branches – the pelvic splanchnic nerves – arise from the second Grey rami communicantes pass from the ganglia to sacral and coccygeal


to fourth sacral ventral rami and innervate the pelvic viscera. spinal nerves but there are no white rami communicantes. Medial
branches connect across the midline, and twigs from the first two
Sacral muscular branches
ganglia join the inferior hypogastric plexus or the hypogastric ‘nerve’.
Several muscular branches arise from the fourth sacral ventral ramus to
Other branches form a plexus on the median sacral artery.
supply the superior surface of levator ani and the upper part of the
external anal sphincter. The branches to levator ani enter the superior Vascular branches
(pelvic) surface of the muscle whilst the branch to the external anal
Preganglionic fibres for the vessels supplying the pelvis and lower limb
sphincter (also referred to as the perineal branch of the fourth sacral
are derived from the lower three thoracic and upper two or three lumbar
nerve) reaches the ischio-anal fossa by running either through ischio-
spinal segments. They reach the lower thoracic and upper lumbar
coccygeus, or between ischiococcygeus and iliococcygeus. It supplies the
ganglia through white rami communicantes and descend through the
skin between the anus and coccyx via its cutaneous branches.
sympathetic trunk to synapse in the lumbar ganglia. Postganglionic
fibres pass from these ganglia via grey rami communicantes to the
Coccygeal plexus
femoral nerve, which carries them to the femoral artery and its branches.
Some fibres descend through the lumbar ganglia to synapse in the
The coccygeal plexus is formed by a small descending branch from the upper two or three sacral ganglia, from which postganglionic axons pass
fourth sacral ramus and by the fifth sacral and coccygeal ventral rami. through grey rami communicantes to the roots of the sacral plexus.
The fifth sacral ventral ramus emerges from the sacral hiatus, curves Those in the pudendal and superior and inferior gluteal nerves accom-
round the lateral margin of the sacrum below its cornu, and pierces pany the arteries of the same name to the gluteal and perineal tissues;


ischiococcygeus from below to reach its upper, pelvic, surface. Here it branches may also supply the pelvic lymph nodes. Those joining the
is joined by a descending branch of the fourth sacral ventral ramus; the tibial nerve are carried to the popliteal artery and distributed via its
small trunk so formed descends on the pelvic surface of ischiococcy- branches to the leg and foot.
A Left sacral
Superior hypogastric plexus sympathetic trunk
B
Left sympathetic
trunk and ganglion
Right hypogastric nerve
Right inferior
hypogastric
plexus
Obturator
nerve
Sacral
sympathetic
ganglia
Ganglion impar
Right inferior
hypogastric plexus
Sacral sympathetic nerves
Autonomic fibres to pelvic vicera Pelvic parasympathetic nerves (S2,3,4)
Fig. 73.11 Autonomic nerves of the pelvis.


perineum
1231
37
reTpaHc
Sympathetic denervation of vessels in the lower limb can be effected deep fascia of the anal triangle
by removing or ablating the upper three lumbar ganglia and the inter- The deep fascia (fascia musculorum) lines the inferior surface of levator
vening parts of the sympathetic trunk, which is used, rarely, in treating ani and is continuous at its lateral origin with the fascia over obturator
vascular insufficiency of the lower limb. internus below the attachment of levator ani. It lines the deep portion
of the ischio-anal fossa and its lateral walls.
PERINEUM Ischio-anal fossa
The ischio-anal fossa is an approximately horseshoe-shaped region
MUSCLES AND FASCIAE OF THE PERINEUM filling the majority of the anal triangle. Although often referred to as a
space, it is filled with loose adipose tissue and occasional blood vessels
and nerves (see Fig. 73.12). The ‘arms’ of the horseshoe are triangular
The perineum is an approximately diamond-shaped region that lies
in cross-section because levator ani slopes medially from its lateral
below levator ani, between the inner aspects of the thighs and anterior
pelvic origin towards the anorectal junction (see Fig. 66.44). The anal
to the sacrum and coccyx. It is usually described as if from the position
canal and its sphincters lie in the centre of the horseshoe. Above them,
of an individual lying supine with the hip joints in abduction and
the medial limit of the fossa is formed by the deep fascia over levator
partial flexion. The surface projection of the perineum and the form of
ani. The outer boundary of the fossa is formed anterolaterally by the
the skin covering it vary considerably, depending on the position of the
fascia over obturator internus and the periosteum of the ischial tuber-
thighs, whereas the deep tissues themselves occupy relatively fixed posi-
osities. Posterolaterally, the outer boundary is formed by the lower
tions. The perineum is bounded anteriorly by the pubic symphysis and
border of gluteus maximus and the sacrotuberous ligament.


its arcuate ligament, posteriorly by the coccyx, anterolaterally by the
There is an anterior recess to the ischio-anal fossa that lies cranial to
ischiopubic rami and the ischial tuberosities, and posterolaterally by
the perineal membrane and transverse perineal muscles. It extends
the sacrotuberous ligaments. The deep limit of the perineum is the
anteriorly as far as the posterior surface of the pubis, below the attach-
inferior surface of the pelvic diaphragm, and its superficial limit is the
ment of levator ani. Posteriorly, the fossa contains the attachment of
skin that is continuous with that over the medial aspect of the thighs
the external anal sphincter to the tip of the coccyx; above and below
and the lower abdominal wall. An arbitrary line joining the ischial
this, the adipose tissue of the fossa is uninterrupted across the midline.
tuberosities (the inter-ischial line) divides the perineum into an ante-
These continuations of the ischio-anal fossa mean that infections,
rior urogenital triangle and a posterior anal triangle. The urogenital
tumours and fluid collections within not only may enlarge relatively
triangle faces downwards and forwards, whereas the anal triangle faces
freely to the side of the anal canal, but also may spread with little resist-
downwards and backwards at an approximate angle of 120° from the
ance to the contralateral side and deep to the perineal membrane. The
plane of the urogenital triangle.
internal pudendal vessels and accompanying nerves lie in the lateral
The male urogenital triangle contains the bulb and attachments of
wall of the ischio-anal fossa, enclosed in fascia forming the pudendal
the penis (Fig. 73.12) (Ch. 76), and the female urogenital triangle
canal. The inferior rectal vessels and nerves cross the fossa from the
contains the mons pubis, the labia majora, the labia minora, the clitoris
pudendal canal and often branch within it.
and the vaginal and urethral orifices (Ch. 77).
The ischio-anal fossa is an important surgical plane during resections


Anal triangle of the anal canal and anorectal junction for malignancy. It provides an
easy, relatively bloodless, plane of dissection that encompasses all of
the muscular structures of the anal canal and leads to the inferior
The structure of the anal triangle is similar in males and females, the
surface of levator ani, through which the dissection is carried.
main difference reflecting the wider transverse dimension of the triangle
in females that is associated with giving birth. The anal triangle contains External anal sphincter
the anal canal and its sphincters, and the ischio-anal fossa and its con- The external anal sphincter is a band of striated muscle that surrounds
tained nerves and vessels. It is lined by superficial and deep fascia. the lowest part of the anal canal (Oh and Kark 1972, Dalley 1987,
Lawson 1974b). The uppermost (deepest) fibres blend with the lowest
superficial fascia of the anal triangle fibres of puborectalis; the two are seen to be contiguous on endoanal
The superficial fascia (subcutaneous tissue; tela subcutanea) of the ultrasound and magnetic resonance imaging. Anteriorly, some of these
region is thin and is continuous with the superficial/subcutaneous upper fibres decussate into the superficial transverse perineal muscles.
fascia of the skin of the perineum, thighs and buttocks. Posteriorly, fibres are attached to the anococcygeal raphe. The majority
Fig. 73.12 Muscles and fasciae
Corpus cavernosum
of the male perineum. On the left
Corpus spongiosum side, the skin and superficial
fascia of the perineum only have
Ischiocavernosus Dorsal artery of the penis been removed. The posterior
scrotal (perineal) artery has been
Bulbospongiosus
Deep artery of the penis shown as it runs forwards into
Posterior scrotal the scrotal tissues. On the right
(perineal) artery side, the corpora cavernosa and
Artery of the bulb corpus spongiosum and their
Perineal membrane
associated muscles, the
Superficial transverse Deep transverse superficial perineal muscles and
perineal muscle perineal muscle perineal membrane have been


Transverse perineal artery Puborectalis removed to reveal the underlying
Perineal body Internal pudendal artery deep muscles and arteries of the
Ischio-anal fat Levator ani (iliococcygeal) perineum. All veins and nerves
have been omitted for clarity.
Inferior rectal artery
Lower fibres of external Upper fibres of external
anal sphincter anal sphincter
Anococcygeal raphe
Coccyx


True pelvis, pelvic floor and perineum
1232
8
noiTces
of the middle fibres of the external anal sphincter surround the lower genital diaphragm – consisting of urogenital sphincter muscles sand-
part of the internal sphincter and are attached anteriorly in the perineal wiched between two layers of fascia and connected to the perineal body,
body, and posteriorly to the coccyx via the anococcygeal ligament. Some the periosteum of the ischiopubic rami and the arcuate ligament of the
fibres from each side of the sphincter decussate in these areas to form pubis, and perforated by the urethra and vagina. Oelrich introduced the
a sort of commissure in the anterior and posterior midline. The anterior alternative term ‘perineal membrane’ (Oelrich 1983). Recent detailed
and posterior attachments of the external anal sphincter give the mus- histological examination of serial cross-sections supports the concept
cular tube an oval profile lying anteroposteriorly. A subcutaneous of the perineal membrane as part of a larger interconnected support
portion encircles the anal verge and creates the radial skin creases sur- apparatus. It has distinct dorsal and ventral portions that are intimately
rounding the anus. The lower fibres lie below the level of the internal connected with levator ani: the dorsal portion is related to the support
anal sphincter and are separated from the lowest anal epithelium by of the perineal body and lateral vaginal wall by its attachment to the
submucosa. The thickness of the external anal sphincter in children is ischiopubic ramus, and the ventral portion is contiguous with the ure-
positively correlated with age (de la Portilla and López-Alonso 2009, thral supportive apparatus (Stein and DeLancey 2008). The perineal
Rehman et al 2011). membrane is particularly thick where it is attached to the arcuate liga-
ment of the pubis, and is here referred to as the transverse perineal liga-
anococcygeal ligament and iliococcygeal raphe ment. The posterior border of the perineal membrane is continuous


The anococcygeal ligament is a musculotendinous structure running with the deep part of the perineal body at its dorsal margin, and is
between the middle portion of the external anal sphincter and the continuous with the fascia over the superficial transverse perineal
coccyx. The iliococcygeal raphe (the decussation of the posterior fibres muscles.
of iliococcygeus) lies just above the anococcygeal ligament and is sepa- In the male, the perineal membrane is crossed by several structures:
rated from the rectum by presacral fascia. These structures are often the urethra, which traverses it 2–3 cm behind the inferior border of the
referred to as the postanal plate. Division of the anococcygeal raphe pubic symphysis; the vessels and nerves to the bulb of the penis; the
may cause descent of the anal canal and a lowering of the posterior part ducts of the bulbourethral glands, posterolateral to the urethral orifice;
of the anal triangle, but does not demonstrably interfere with the the deep dorsal vessels and dorsal nerves of the penis, behind the pubic
process of defecation. arch in the midline; and the posterior scrotal vessels and nerves, ante-
rior to the transverse perinei.
Urogenital triangle In the female, the perineal membrane is divided almost into two
halves by the vagina and urethra, such that it forms a triangle on each
side of these structures. The lateral margins of the vagina are attached
The urogenital triangle is bounded posteriorly by the inter-ischial line,
to the perineal membrane at the level of the hymenal ring, and levator
which usually overlies the posterior border of the transverse perineal
ani lies on its cranial surface. The ducts of Bartholin’s glands are at this
muscles. Anteriorly and laterally, it is bounded deeply by the pubic
level in the posterior lateral introitus. The deep dorsal vessels and dorsal
symphysis and ischiopubic rami. In males, the urogenital triangle
nerves of the clitoris lie within its fibres.
extends superficially to encompass the scrotum and the root of the


penis. In females, it extends to the lower limit of the labia and mons
Urethral sphincter mechanism
pubis. The urogenital triangle is divided into two parts by a strong
perineal membrane: the deep perineal space lies above the membrane,
and the superficial perineal space lies below it. The urethral sphincter mechanism consists of both striated and smooth
The female urogenital triangle includes muscles, fasciae, erectile muscle sphincters (Oelrich 1980, Oelrich 1983, Huisman 1983). The
structures and spaces similar to those in the male. There are some dif- striated urogenital sphincter has an upper circular element that sur-
ferences in size and disposition caused by the presence of the vagina rounds the urethra in the female and the apex of the prostate in the male,
and female external genitalia. between the vesical neck and perineal membrane. In the female, at the
level of the perineal membrane, it extends laterally outside of the urethra
Deep perineal space
in two arch-shaped bands that lie on the cranial surface of the perineal
perineal membrane membrane (Fig. 73.13). One, the compressor urethrae, follows the pubic
For many years, it was thought that the anterior pelvic outlet was arch to attached connective tissue in this area near the inner surface of
spanned by a triangular, trilaminar, musculofascial structure – the uro- the ischiopubic ramus. The other, the urethrovaginal sphincter, extends
A B
Pubic symphysis Body of clitoris
Pubis Urethra
Urinary bladder
Crus of clitoris
Inferior pubic ramus
Vagina
Ischiocavernosus
Compressor
Bulbospongiosus urethrae
Cut edge of superficial Bulb of vestibule
Sphincter
perineal fascia
Deep transverse urethrae
Vaginal wall
perineal muscle
Perineal membrane
Compressor
Superficial transverse Perineal body urethrae
perineal muscle
Sacrotuberous
Puborectalis ligament Urethra
Levator ani Anus
(iliococcygeus)
External Vagina Sphincter


anal sphincter urethrovaginalis
Gluteus maximus
Coccyx
Fig. 73.13 Muscles of the female perineum. A, On the right side, the membranous layer of superficial fascia has been removed (note the cut edge). On
the left side, superficial perineal muscles and overlying fascia have been removed to show the deep perineal muscles. B, The continuity of the deep
perineal muscles with sphincter urethrae.


perineum
1233
37
reTpaHc
caudally to surround the lateral margin of the vaginal wall. In the male, ligament of the penis or clitoris, and the fasciae of external oblique and
these lateral extensions are not well developed and the sphincter in this the rectus sheath.
area primarily encircles the membranous urethra, forming a robust con-
strictor at this level. The smooth muscle sphincter consists of circularly Superficial and subcutaneous perineal
orientated smooth muscle cells that lie between the striated sphincter pouches
and the longitudinal smooth muscle and urethral lumen. It is not well
subcutaneous perineal pouch
developed. In children, the inner diameter of the urethral sphincter
The subcutaneous perineal pouch lies between the deep perineal fascia
increases with age: a cutoff value of 3 mm has been reported to predict
and the superficial perineal fascia. Under normal circumstances, these
detrusor–sphincter incoordination (Kakizaki et al 2003).
two layers are only separated by relatively thin subcutaneous connective
tissue; the skin of the anterior perineum and external genitalia is rela-
Innervation The urethral sphincter mechanism extends from the peri-
tively mobile over the deeper structures. However, this pouch is capable
neum through the urogenital hiatus into the pelvic cavity. It probably
of expanding considerably in the presence of fluid accumulation; blood,
receives innervation via the perineal branch of the pudendal nerve from
urine or fluid collecting in the subcutaneous pouch following trauma
below, and direct branches from the sacral plexus and the pelvic
or surgery on the urogenital triangle will spread throughout the tissues
splanchnic nerves from above. All these nerves originate in the second,
of the triangle, including the scrotum or labia majora, but cannot pass
third and fourth sacral spinal segments.
posteriorly into the anal triangle or laterally into the medial thigh
because of the firm tethering of the posterior attachments of the sub-
Actions Urinary incontinence is primarily a problem that affects cutaneous fascia. Since the superficial perineal fascia is in continuity


women and is more common after childbirth. Continence in women with the fascia of the anterior abdominal wall, fluid, blood or pus may
is maintained by an elegantly orchestrated system of muscles and con- also track freely between the subcutaneous tissues of the anterior
nective tissue that involves the urethral sphincters and the tissues that abdominal wall and the subcutaneous perineal pouch (e.g. postsurgical
support them. The urethral sphincter mechanism compresses the mid- haematomas of the abdominal wall readily cause discolouration of the
urethra in females and membranous urethra in males, particularly perineal and genital skin).
when the bladder contains fluid. Its location around the region of
highest urethral closing pressure suggests that it plays an important role superficial perineal pouch
in the continence of urine. At rest, activity of both the smooth and stri- The superficial perineal pouch lies below the perineal membrane and
ated sphincters contributes to this closure and, during times of increased is limited superficially by the deep perineal fascia (investing fascia of
need, voluntary contraction of the striated sphincter augments this the superficial perineal muscles) (Fig. 73.14). It contains the corpora
closure. In the distal portion of the urethra, where it is adjacent to the cavernosa and corpus spongiosum, ischiocavernosus, bulbospongiosus
perineal membrane, arch-shaped components of the striated sphincter and the superficial transverse perineal muscles, and branches of the
(compressor urethrae and urethrovaginal sphincter) pass between the pudendal vessels and nerves. In the female, it is crossed by the urethra
urethra and pubic bone, and contraction compresses the lumen until it and vagina and contains the clitoris. In the male, it contains the urethra
is closed. All muscles are relaxed during micturition to aid voiding, but as it runs in the root of the penis. It is a fully confined space; injuries
striated muscle contraction can help to expel final drops of urine, or of to the contents of the space (such as bleeding into the urethra in the
semen in the male, from the bulbar urethra. penile root) do not communicate with the deep or subcutaneous


During increases in abdominal pressure that occur, for example, pouches unless the fascial coverings are also lacerated or breached.
during a cough, bladder pressure rises above the normal urethral
closure pressure that keeps the lumen of the urethra closed. In this perineal body
situation, the rise in urethral closure pressures (called pressure trans- The perineal body is not a structure but an aggregation of fibromuscular
mission) that prevents urine leakage occurs because the urethra is tissue located in the midline at the junction between the anal and
compressed against the fascial tissues that lie between it and the urogenital triangles, just ventral to the anal sphincter (Oh and Kark
vaginal wall. If this layer is stable and unyielding, the urethra can be 1973). It is attached to many structures in both the deep and superficial
compressed closed against it, but if it is not well supported, this mech- urogenital spaces. Posteriorly, it merges with fibres from the middle part
anism is less effective and leakage can occur (DeLancey 1994). Overall of the external anal sphincter and the conjoint longitudinal coat. Supe-
continence during such events is a combination of sphincter constric- riorly, it is continuous with the rectoprostatic or rectovaginal septum,
tion due to the actions of the muscles in the urethral wall and pressure including fibres from levator ani (puborectalis or pubovaginalis). Ante-
transmission; sphincter function is the predominant factor (DeLancey riorly, it receives a contribution from the deep and superficial transverse
et al 2008). perineal muscles and bulbospongiosus (see Figs 73.4, 73.13). The peri-
neal body is continuous with the perineal membrane and the superfi-
Superficial and deep perineal fasciae
cial perineal fascia. Since the latter runs forwards into the skin of the
superficial perineal fascia perineum, the perineal body is tethered to the central perineal skin,
The tissue commonly referred to as the superficial fascia of the peri- which is often puckered over it. In males, this is continuous with the


neum (Colles’ fascia) forms a clear, surgically recognizable, plane perineal raphe in the skin of the scrotum. In females, the perineal body
beneath the skin of the anterior perineum (Tobin and Benjamin 1949). lies directly posterior, and is attached, to the posterior commissure of
It is firmly attached posteriorly to the fascia over the superficial trans- the labia majora and the introitus of the vagina.
verse perineal muscles and the posterior limit of the perineal mem- Spontaneous lacerations of the perineal body sustained during
brane. Laterally, it is attached to the margins of the ischiopubic rami as childbirth are often associated with damage to the anterior fibres of the
far back as the ischial tuberosities. From here, it runs more superficially external anal sphincter. The deliberate division of the perineal body to
to the skin of the urogenital triangle, lining the skin of the external facilitate delivery (episiotomy) is sometimes angled laterally to avoid
genitalia; in the male, it is also continuous with the fascial layer in the such sphincteric injuries. The perineal body is often used to position
skin of the scrotum that contains the dartos muscle. In females, the radiological markers in the assessment of pelvic floor dysfunction.
fascia follows the same limits but is much less extensive in the labia
majora. This layer runs anteriorly and superiorly into the skin of the superficial transverse perineal muscles
lower abdominal wall where it is continuous with the membranous The superficial transverse perineal muscles are narrow strips of muscle
fascia (Scarpa’s fascia). English-speaking anatomists refer to these tissue that run more or less transversely across the superficial perineal space
layers as a ‘superficial fascia’ but this is a misnomer; more accurately, anterior to the anus, from the medial and anterior aspects of the ischial
they constitute the membranous layer of subcutaneous tissue (tela tuberosities to the perineal body (see Fig. 73.13). A few fibres may also
subcutanea). pass into the ipsilateral bulbospongiosus or external anal sphincter.
They are occasionally small and may be absent.
deep perineal fascia (investing fascia of the


superficial perineal muscles) Bulbospongiosus
The tissue commonly referred to as the deep perineal fascia is a layer Bulbospongiosus differs between the sexes. In the male, it lies in the
of fascia that overlies the superficial muscles of the perineum midline, anterior to the perineal body (see Fig. 73.12). It consists of
(bulbospongiosus, ischiocavernosus, superficial transverse perineal two symmetrical parts united by a median fibrous raphe. The fibres
muscles). It is, in effect, the investing fascia of the superficial perineal attach to the perineal body, in which they decussate, and to the trans-
muscles and, as such, is firmly attached to the borders of the muscles verse superficial perinei and the external anal sphincter; they diverge
at attachments to the ischiopubic rami, posterior margin of the perineal like the sides of a feather from the median raphe. A thin layer of pos-
membrane and perineal body. Anteriorly, it fuses with the suspensory terior fibres joins the posterior portion of the perineal membrane. The


True pelvis, pelvic floor and perineum
1234
8
noiTces
Bladder Fascia over levator ani
White line of pelvic fascia Thick fascia over
obturator internus
Tendinous arch
of levator ani
Ilium
Obturator internus
Urethra
Obturator membrane
Levator ani
Thin fascia over
Prostate
obturator internus
Corpus spongiosum Thin endopelvic fascia
Ischiopubic ramus
Corpus cavernosum
Deep
perineal fascia
Ischiocavernosus
Deep transverse
perineal muscle
Bulbospongiosus
Perineal membrane
Skin of perineum and thigh
Superficial
perineal fascia
Fig. 73.14 Muscles and fasciae of the male perineum: coronal view. The section passes through the bulb of the penis at the level of the urethra. The
deep perineal space is continuous with the ischio-anal fossa posteriorly. The visceral and parietal fasciae have been omitted for clarity. The pelvic fascia
over the ‘pelvic’ aspect of the deep transverse perinei is very thin and does not form a distinct layer: in places it blends with the parietal pelvic fascia
over the inferior aspect of levator ani.
majority of the middle fibres encircle the bulb of the penis and adjacent VASCULAR SUPPLY AND LYMPHATIC DRAINAGE OF
corpus spongiosum, and attach to an aponeurosis on the dorsal sur- THE PERINEUM
faces. The anterior fibres spread out over the sides of the corpora cav-
ernosa, ending partly in them, anterior to ischiocavernosus, and partly Arteries of the perineum
in a tendinous expansion that covers the dorsal vessels of the penis. In
the female, bulbospongiosus also attaches to the perineal body, but the
Internal pudendal artery (in the perineum)
muscle on each side is separate and covers the superficial parts of the
The internal pudendal artery enters the perineum around the posterior
vestibular bulbs and greater vestibular glands (see Fig. 73.13). Fibres
aspect of the ischial spine and runs on the lateral wall of the ischio-anal


run anteriorly on either side of the vagina to attach to the corpora
fossa in the pudendal (Alcock’s) canal with the pudendal veins and the
cavernosa clitoridis, and a few fibres cross over the dorsum of the body
pudendal nerve. The canal lies about 4 cm above the lower limit of the
of the clitoris.
ischial tuberosity and is formed by connective tissue binding the vessels
and nerve to the medial surface of the fascia covering obturator inter-
Actions In the male, bulbospongiosus helps to empty the urethra of
nus. As the artery approaches the margin of the ischial ramus, it pro-
urine after the bladder has emptied. It may assist in the final stage of
ceeds above or below the perineal membrane, along the medial margin
erection as the middle fibres compress the erectile tissue of the bulb
of the inferior pubic ramus, en route to its target structures.
and the anterior fibres contribute by compressing the deep dorsal vein
In the male, the internal pudendal artery distal to the perineal artery
of the penis. It contracts six or seven times during ejaculation, assisting
gives a branch to the bulb of the penis before it divides into the cavern-
in the expulsion of semen. In the female, bulbospongiosus acts to
ous (deep, cavernosal) and dorsal arteries of the penis (see Fig. 73.12).
constrict the vaginal orifice and express the secretions of the greater
Given its distribution, the internal pudendal artery distal to its perineal
vestibular glands. Anterior fibres contribute to erection of the clitoris
branch has been named the artery of the penis. The artery to the bulb
by compressing its deep dorsal vein.
supplies the corpus spongiosum, and the cavernous artery of the penis
supplies the corpus cavernosum on each side. The dorsal artery runs
ischiocavernosus
on the dorsal aspect of the penis and supplies circumflex branches
In the male, ischiocavernosus covers the crus penis. It is attached by
to the corpora cavernosa and corpus spongiosum that end by anasto-
tendinous and muscular slips to the medial aspect of the ischial tuber-
mosing in the coronal sulcus and supplying the glans penis and its


osity posteriorly, and to the ischial ramus on both sides of the crus (see
overlying skin.
Fig. 73.12). These fibres end in an aponeurosis that is attached to the
In the female, a similar branch of the pudendal artery is distributed
sides and undersurface of the crus penis. In the female, ischiocavernosus
to the erectile tissue of the corpus spongiosum and vagina. The cavern-
is related to the crus of the clitoris but is otherwise similar to the cor-
ous artery supplies the corpora cavernosa of the clitoris; the dorsal artery
responding muscle in the male (Figs 73.15–73.16).
supplies the glans and prepuce of the clitoris.
Branches of the internal pudendal artery are sometimes derived from
Actions Ischiocavernosus compresses the crus penis in males and may an accessory pudendal artery, which is usually a branch of the pudendal
help to maintain penile erection. The muscles form a triangle on each artery before its exit from the pelvis; effectively, the artery is double
side of the midline with bulbospongiosus medially and the superficial before it leaves the pelvis.
transverse perineal muscles posteriorly, attached to the perineal mem-
brane; when contracted, the two ischiocavernosi act together to stabilize Inferior rectal artery
the erect penis. In the female, ischiocavernosus may help to promote The inferior rectal artery arises just after the internal pudendal artery
increased pressure in the clitoris. enters the pudendal canal on the lateral wall of the ischio-anal fossa. It


perineum
1235
37
reTpaHc
Thick fascia over obturator internus
Tendinous arch of levator ani
Fascia over levator ani
White line of pelvic fascia
Ilium
Bladder
Obturator internus
Obturator membrane
Thin fascia over obturator internus
Levator ani
Urethra
Thin endopelvic fascia
Crus of clitoris
Ischiopubic ramus
Ischiocavernosus
Deep perineal fascia
Bulbospongiosus
Deep transversus perineal muscle
Bulb of vestibule
Perineal membrane
Superficial perineal fascia
Skin of perineum and thigh
Fig. 73.15 Muscles and fasciae of the female perineum – coronal view. The section passes through the bulb of the clitoris at the level of the urethra. The
deep perineal space is continuous with the ischio-anal fossa posteriorly. The visceral and parietal fasciae have been omitted for clarity. The pelvic fascia
over the ‘pelvic’ aspect of the deep transverse perinei is very thin and does not form a distinct layer: in places it blends with the parietal pelvic fascia
over the inferior aspect of levator ani.
Uterine Fig. 73.16 Muscles and fasciae of the female
cavity perineum: coronal T2-weighted magnetic
resonance image. (Courtesy of Dr J Lee and Ms K
Wimpey, Chelsea and Westminster Hospital,
Bladder London.)
Acetabulum
Obturator
internus Deep perineal space
Urethra
Levator ani
Deep transverse
perineal muscle
Ischiopubic ramus
Crus of clitoris
Superficial perineal
fascia Ischiocavernosus
Skin of perineum and thigh
runs anteromedially through the adipose tissue of the ischio-anal fossa contralateral artery and with the posterior scrotal and inferior rectal
to reach the deep portion of the external anal sphincter, and often arteries. It supplies the transverse perinei, the perineal body and the
branches before reaching the sphincter. During dissections of the anal posterior attachment of the bulb of the penis. The posterior scrotal


canal, particularly during perineal excisions of the anorectum, the infe- arteries are usually terminal branches of the perineal artery but may
rior rectal vessels are encountered in the ischio-anal fossa and must be also arise from its transverse branch. They are distributed to the scrotal
secured before division; otherwise, they tend to retract laterally to the skin and dartos muscle in the male and supply the perineal muscles.
canal, where they can cause troublesome bleeding. In the female, the perineal artery runs an almost identical course to that
in the male and gives off the posterior labial arteries (see Fig. 77.4).
Perineal artery
The perineal artery is a branch of the internal pudendal artery that arises
Veins of the perineum: internal
near the anterior end of the pudendal canal and runs through the peri-
pudendal veins
neal membrane. In the male, it approaches the scrotum in the superfi-
cial perineal space, between bulbospongiosus and ischiocavernosus (see
Fig. 76.24). A small transverse branch passes medially, inferior to the The internal pudendal veins are venae comitantes of the internal puden-
superficial transverse perineal muscle, to anastomose with the dal artery and unite as a single vessel ending in the internal iliac vein.


True pelvis, pelvic floor and perineum
1236
8
noiTces
The perineal tributaries receive veins from the penile bulb and the Perineal nerve
scrotum (males), or clitoris and labia (females), and the inferior rectal
veins join towards the posterior end of the pudendal canal.
The perineal nerve is the inferior and larger terminal branch of the
pudendal nerve in the pudendal canal. It runs forwards below the
Lymphatic drainage of the perineum
internal pudendal artery and accompanies the perineal artery, dividing
into posterior scrotal or labial and muscular branches. The posterior
The lymphatics from the skin of the penis and scrotum (male), or skin scrotal or labial nerves are usually double; they have medial and lateral
of the clitoris and labia (female), drain together with lymphatics from branches that run over the perineal membrane and pass forwards in the
the perineal skin to the superficial inguinal nodes and, from there, to lateral part of the urogenital triangle with the scrotal or labial branches
the deep inguinal nodes. The glans, corpora cavernosa and corpus of the perineal artery. They supply the skin of the scrotum or labia
spongiosum of the penis or clitoris drain directly to the deep inguinal majora, overlapping the distribution of the perineal branch of the pos-
nodes (see Fig. 78.10). terior femoral cutaneous and inferior rectal nerves. In females, the
posterior labial branches also supply sensory fibres to the skin of the
lower vagina.
INNERVATION OF THE PERINEUM: PUDENDAL
Muscular branches arise directly from the pudendal nerve to supply
NERVE (IN THE PERINEUM) the superficial transverse perineal muscles, bulbospongiosus, ischiocav-
ernosus, sphincter urethrae and the anterior parts of the external anal
The pudendal nerve gives rise to the inferior rectal and perineal nerves sphincter and levator ani. In males, a nerve to the bulb of the urethra
and to the dorsal nerves of the penis or clitoris. The course of its leaves the nerve to the bulbospongiosus, pierces this muscle to supply


branches parallels the pudendal vessels (see Figs 76.24, 77.4). The the corpus spongiosum penis, and ends in the urethral mucosa.
pudendal nerve occupies a very constant position over the ischial spine
and is readily found. It may be ‘blocked’ by infiltration with a local Dorsal nerve of the penis or clitoris
anaesthetic applied via a needle passed through the lateral wall of the
vagina to numb the perineal and anal skin. It may also be palpated over The dorsal nerve of the penis or clitoris runs anteriorly above the inter-
the ischial spine through the lateral wall of the rectum and motor ter- nal pudendal artery along the ischiopubic ramus, deep to the perineal
minal latencies may be measured. membrane. It supplies the corpus cavernosum and accompanies the
dorsal artery of the penis or clitoris between the layers of the suspensory
Inferior rectal nerve ligament. In males, the dorsal nerve of the penis runs on the dorsum
of the penis to end in the glans.
The inferior rectal nerve runs through the medial wall of the pudendal
canal with the inferior rectal vessels. It crosses the ischio-anal fossa to
supply the external anal sphincter, the lining of the lower part of
Bonus e-book images
the anal canal and the circumanal skin. It frequently breaks into termi-
nal branches before reaching the lateral border of the sphincter. Its
cutaneous branches that are distributed around the anus overlap the
cutaneous branches of the perineal branch of the posterior femoral Fig. 73.7 The relationship between anteroposterior diameters of the
right common, internal and external iliac arteries and body surface
cutaneous nerve and of the scrotal or labial nerves. The inferior rectal
area (BSA) in boys and girls between the ages of 1 and 16 years.
nerve occasionally arises directly from the sacral plexus and crosses the
sacrospinous ligament or reconnects with the pudendal nerve. In
females, the inferior rectal nerve may supply sensory branches to the
lower part of the vagina.
KEY REFERENCES


Dalley AF 1987 The riddle of the sphincters. Am Surg 53:298. This study, along with its companion article concerning the male urethral
A review of the anatomy of the external anal sphincter that brings clarity to sphincter anatomy, dispelled the longstanding errors surrounding a
the discussion of controversial and competing concepts. ‘urogenital diaphragm’ and corrected the anatomy of the urethral sphincter.
Huisman AB 1983 Aspects on the anatomy of the female urethra with Reiffenstuhl G 1982 The clinical significance of the connective tissue planes
special relation to urinary continence. Contrib Gynecol Obstet 10:1. and spaces. Clin Obstet Gynecol 25:811.
A detailed and comprehensive account of the anatomy of the urethra based The complex 3-dimensional network of the pelvic connective tissues has been
on histological examination. confusing to many; this clearly illustrated article shows the different
elements of the pelvic fasciae.
Klink EW 1953 Perineal nerve block: an anatomic and clinical study in the
female. Obstet Gynecol 1:137. Ricci JV, Lisa JR, Thom CH, et al 1947 The relationship of the vagina to
Lawson JO 1974a Pelvic anatomy. I. Pelvic floor muscles. Ann R Coll Surg adjacent organs in reconstructive surgery. Am J Surg 74:387.
Engl 54:244. A great deal has been written about the ‘fascia’ of the female pelvis as it
An objective evaluation of the anatomy of levator ani based on serial relates to the problem of pelvic organ prolapse. Ricci’s approach, using
histological sections. whole-pelvic cross-sectional anatomy, brings clarity to this discussion.
Nesselrod JP 1936 An anatomic restudy of the pelvic lymphatics. Ann Surg Roberts WH, Krishingner GL 1967 Comparative study of human internal
104:905. iliac artery based on Adachi classification. Anat Rec 158:191.
An account of the importance of the pelvic lymphatic system in tumour A description of the considerable variation in the anatomy of the internal
spread and treatment that provides an accurate description of its component iliac artery.
parts. Tobin CE, Benjamin JA 1949 Anatomic and clinical re-evaluation of


Oelrich TM 1980 The urethral sphincter muscle in the male. Am J Anat Camper’s, Scarpa’s and Colles’ fasciae. Surg Gynecol Obstet 88:545.
158:229–46. A description of the anatomy of Camper’s, Scarpa’s and Colles’ fasciae that
See comments for Oelrich 1983. clarifies understanding of these structures, which are often poorly described
or incorrectly illustrated.
Oelrich TM 1983 The striated urogenital sphincter muscle in the female.
Anat Rec 205:223.


True pelvis, pelvic floor and perineum
1236.e1
37
reTpaHc
REFERENCES
Campbell RM 1950 The anatomy and histology of the sacrouterine liga- Oelrich TM 1980 The urethral sphincter muscle in the male. Am J Anat
ments. Am J Obstet Gynecol 59:1. 158:229–46.
Dalley AF 1987 The riddle of the sphincters. Am Surg 53:298. See comments for Oelrich 1983.
A review of the anatomy of the external anal sphincter that brings clarity to Oelrich TM 1983 The striated urogenital sphincter muscle in the female.
the discussion of controversial and competing concepts. Anat Rec 205:223.
DeLancey JO 1992 Anatomic aspects of vaginal eversion after hysterectomy. This study, along with its companion article concerning the male urethral
Am J Obstet Gynecol 166:1717. sphincter anatomy, dispelled the longstanding errors surrounding a
‘urogenital diaphragm’ and corrected the anatomy of the urethral sphincter.
DeLancey JO 1994 Structural support of the urethra as it relates to stress
urinary incontinence: the hammock hypothesis. Am J Obstet Gynecol Oh C, Kark AE 1972 Anatomy of the external anal sphincter. Br J Surg
170:1713–23. 59:717.
DeLancey JO, Trowbridge ER, Miller JM et al 2008 Stress urinary inconti- Oh C, Kark AE 1973 Anatomy of the perineal body. Dis Colon Rectum
nence: relative importance of urethral support and urethral closure 16:444.
pressure. J Urol 179:2286–90. Range RL,Woodburne RT 1964 The gross and microscopic anatomy of the
de la Portilla F, López-Alonso M 2009 Endosonography of the anal canal: transverse cervical ligaments. Am J Obstet Gynecol 90:460.
findings in children. Dis Colon Rectum 52:711–4. Rehman Y, Stensrud KJ, Morkrid L et al 2011 Endosonographic evaluation


Dogan R, Dogan OF, Oc M et al 2003 A rare vascular malformation, Klippel- of anal sphincters in healthy children. J Pediatr Surg 46:1587–92.
Trenaunay syndrome. Report of a case with deep vein agenesis and Reiffenstuhl G 1982 The clinical significance of the connective tissue planes
review of the literature. J Cardiovasc Surg 44:95–100. and spaces. Clin Obstet Gynecol 25:811.
Doyle JF 1970 The perforating veins of the gluteus maximus. Ir J Med Sci The complex 3-dimensional network of the pelvic connective tissues has been
3:285–8. confusing to many; this clearly illustrated article shows the different
Emans JB, Ciarlo M, Callahan M et al 2005 Prediction of thoracic dimen- elements of the pelvic fasciae.
sions and spine length based on individual pelvic dimensions in chil- Ricci JV, Lisa JR, Thom CH, et al 1947 The relationship of the vagina to
dren and adolescents: an age-independent, individualized standard for adjacent organs in reconstructive surgery. Am J Surg 74:387.
evaluation of outcome in early onset spinal deformity. Spine 30: A great deal has been written about the ‘fascia’ of the female pelvis as it
2824–9. relates to the problem of pelvic organ prolapse. Ricci’s approach, using
Gupta NP, Kumar M, Karan SC et al 1999 Lower ureteral obstruction due to whole-pelvic cross-sectional anatomy, brings clarity to this discussion.
a persistent umbilical artery. Urol Int 63:249–51.
Roberts WH, Krishingner GL 1967 Comparative study of human internal
Huisman AB 1983 Aspects on the anatomy of the female urethra iliac artery based on Adachi classification. Anat Rec 158:191.
with special relation to urinary continence. Contrib Gynecol Obstet A description of the considerable variation in the anatomy of the internal
10:1. iliac artery.
A detailed and comprehensive account of the anatomy of the urethra based
on histological examination. Roberts WH, Habenicht J, Krishingner G 1964 The pelvic and perineal
fasciae and their neural and vascular relationships. Anat Rec 149:707.


Kakizaki H, Moriya K, Ameda K et al 2003 Diameter of the external urethral
Roberts WH, Harrison CW, Mitchell DA et al 1988 The levator ani muscle
sphincter as a predictor of detrusor-sphincter incoordination in chil-
and the nerve supply of its puborectalis component. Clin Anat 1:256.
dren: comparative study of voiding cystourethrography. J Urol 169:
655–8. Sato K 1980 Amorphological analysis of the nerve supply of the sphincter
ani externus, levator ani and coccygeus. Acta Anat Nippon 44:187.
Klink EW 1953 Perineal nerve block: an anatomic and clinical study in the
female. Obstet Gynecol 1:137. Stein TA, DeLancey JO 2008 Structure of the perineal membrane in females:
gross and microscopic anatomy. Obstet Gynecol 111:686–93.
Lawson JO 1974a Pelvic anatomy. I. Pelvic floor muscles. Ann R Coll Surg
Engl 54:244. Tobin CE, Benjamin JA 1949 Anatomic and clinical re-evaluation of
An objective evaluation of the anatomy of levator ani based on serial Camper’s, Scarpa’s and Colles’ fasciae. Surg Gynecol Obstet 88:545.
histological sections. A description of the anatomy of Camper’s, Scarpa’s and Colles’ fasciae that
clarifies understanding of these structures, which are often poorly described
Lawson JO 1974b Pelvic anatomy. II. Anal canal and associated sphincters. or incorrectly illustrated.
Ann R Coll Surg Engl 54:288.
Wendell-Smith CP, Wilson PM 1991 The vulva, vagina and urethra and the
Munk A, Darge K, Wiesel M et al 2002 Diameter of the infrarenal aorta and
musculature of the pelvic floor. In: Philipp E, Setchell M, Ginsburg J
the iliac arteries in children: ultrasound measurements. Transplantation
(eds) Scientific Foundations of Obstetrics and Gynaecology. Oxford:
73:631–5.
Butterworth–Heinemann, pp. 84–100.


Nesselrod JP 1936 An anatomic restudy of the pelvic lymphatics. Ann Surg
104:905.
An account of the importance of the pelvic lymphatic system in tumour
spread and treatment that provides an accurate description of its component
parts.


CHAPTER
74
Kidney and ureter
and narrower than the right and lies nearer the median plane (Fig.
KIDNEY
74.1). The long axis of each kidney is directed inferolaterally and the
transverse axis posteromedially, which means that the anterior and
The kidneys excrete end-products of metabolism and excess water. posterior aspects usually described are, in fact, anterolateral and pos-
These actions are essential for the control of concentrations of various teromedial. An appreciation of this orientation is important in percu-
substances in the body, maintaining electrolyte and water balance taneous and endo-urological renal surgery.
approximately constant in the tissue fluids. The kidneys also have In adults, each kidney is typically 11 cm in length, 6 cm in breadth
endocrine functions, producing and releasing erythropoietin, which and 3 cm in anteroposterior dimension. The left kidney may be 1.5 cm
affects red blood cell formation; renin, which influences blood pres- longer than the right; it is rare for the right kidney to be more than
sure; 1,25-di-hydroxycholecalciferol (the metabolically active form of 1 cm longer than the left. The average weight is 150 g in men and 135 g
vitamin D), which is involved in the control of calcium absorption and in women. In thin individuals with a lax abdominal wall, the lower
mineral metabolism; and various other soluble factors with metabolic pole of the lower right kidney may just be felt in full inspiration by
actions. bimanual lumbar examination, but this is unusual. In the fetus and the
In the fresh state, the kidneys are reddish-brown. They are situated newborn, the kidney normally has 12 lobules; in the adult, these
posteriorly behind the peritoneum, on each side of the vertebral lobules are fused to present a smooth surface, although traces of lobula-
column, and are surrounded by adipose tissue. Superiorly, they are level tion may remain and can mimic a renal mass on radiographic imaging.
with the upper border of the twelfth thoracic vertebra, and inferiorly,
with the third lumbar vertebra. The right is usually slightly inferior to Absent and ectopic kidneys A single absent kidney, resulting


the left, reflecting its relationship to the liver. The left is a little longer from the failure of the metanephric blastema to join a ureteric bud on
Stomach, cardia
Coeliac trunk
Hepatic artery proper
Hepatic portal vein Left suprarenal gland
Suprarenal gland
Splenic artery and vein
Bile duct
Inferior mesenteric vein
Superior mesenteric
artery and vein
Duodenum, descending part
Head of pancreas,
Left kidney
uncinate process
Ureter
Abdominal aorta
Left colic artery
Inferior vena cava
Testicular artery and vein
Inferior mesenteric artery and vein
Common iliac artery Superior rectal artery
and vein Sigmoid arteries and veins
Femoral nerve
Sigmoid colon
External iliac artery and vein
Urinary bladder
Inferior epigastric artery
and vein
Fig. 74.1 Relationships of the kidneys and ureters in the male retroperitoneum. (With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of
Human Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright 2013.) 1237


Kidney and ureter
1238
8
nOitCeS
the affected side, is seen in 1 in 1200 individuals. There are no clinical cal development. The ureters curve anterior to the isthmus and often
sequelae, but the ipsilateral vas (ductus) deferens and/or epididymis have a high insertion into the renal pelvis (Fig. 74.3).
may also be absent and there may be other congenital anomalies, The blood supply to horseshoe kidneys is variable. One vessel to
including imperforate anus, cardiac valvular anomalies and oesopha- each moiety is seen in 30% of horseshoe kidneys but multiple anoma-
geal atresia. A single kidney often shows compensatory hypertrophy lous vessels are common; the isthmus may be supplied by a vessel
but, provided the single kidney is anatomically and functionally directly from the aorta or from branches of the inferior mesenteric,
normal, the life expectancy of individuals with a single kidney is no common iliac or external iliac arteries. In view of this variable arterial
different from that of those with two kidneys. anatomy, angiography or computed tomography (CT) scanning with
Failure of the kidney to ascend into the renal fossa in utero results vascular reconstruction is very helpful when planning renal surgery on
in renal ectopia. An ectopic kidney is found in the pelvis in 1 in 2500 horseshoe kidneys. Horseshoe kidneys may exhibit an associated con-
live births. Kidneys so placed often have associated malrotation anoma- genital ureteropelvic junction obstruction in up to 30% of cases and
lies and may have marked fetal lobulation. Pelvic kidneys frequently have a chromosomal anomaly in 56% of cases (Scott 2002). Anoma-
become hydronephrotic as a result of an anteriorly placed ureter and lous vessels crossing the ureter, and the abnormal course of the ureter
an anomalous arterial supply; an associated ureteropelvic junction as it passes over renal substance, may also cause obstruction.
obstruction is often present.
Very rarely, and despite the normal location of the ureteric orifices
within the bladder, the two kidneys may be on the same side (crossed PERIRENAL FASCIA
renal ectopia) and are usually fused (crossed-fused ectopia). A solitary


crossed renal ectopia may be associated with skeletal and other geni- The perirenal fascia, sometimes referred to as Gerota’s fascia (p. 1084),
tourinary anomalies. A number of different anatomical patterns can is a dense, elastic connective tissue sheath that envelops each kidney
result, all of which are extremely rare (Fig. 74.2). and suprarenal gland, together with a layer of surrounding perirenal fat
(Fig. 74.4; see Fig. 62.2). The kidney and its vessels are embedded in
Horseshoe kidney Horseshoe kidneys are found in 1 in 400 indi- perirenal fat, which is thickest at the renal borders and extends into the
viduals. A transverse bridge of renal tissue, the isthmus, often contain- renal sinus at the hilum.
ing functioning renal substance, connects the two renal masses. The The perirenal fascia was originally described as being made up of
isthmus lies between the inferior poles, most commonly anterior to the two separate entities, the posterior fascia of Zuckerkandl and the ante-
great vessels; it is often inferior to the inferior mesenteric artery because rior fascia of Gerota, which fused laterally to form the lateroconal fascia
this vessel obstructs the normal ascent of the kidney during embryologi- (Burkhill and Healy 2000). According to this view, the lateroconal fascia
A B C
Unilateral fused kidney Unilateral fused kidney Sigmoid or S-shaped kidney
(inferior ectopia) (superior ectopia)
D E F
Lump kidney L-shaped kidney Disc kidney
Fig. 74.2 Crossed renal ectopia: the possible arrangements of crossed ectopic kidneys.


Kidney
1239
47
retPaHC
A A
Renal veins; renal artery Eleventh rib
Twelfth rib
Liver
Posterior lamina Anterior lamina
of renal fascia of renal (Gerota’s)
fascia
Peritoneum
Vessel of
renal hilum
Right colic
Right ureter Left ureter flexure
B
Rectus abdominis
External oblique
Internal oblique
Transversus
abdominis
Fascia
transversalis
B
Peritoneum
Colon
Anterior
lamina of
renal fascia
Kidney
Perirenal fat
Quadratus lumborum
Psoas major Erector spinae
Fig. 74.4 A, A sagittal section through the posterior abdominal wall,
showing the relations of the renal fascia of the right kidney. B, A
transverse section, showing the relations of the renal fascia.
which, at a variable point, divides into a thin anterior lamina, passing
C anterior to the kidney as the anterior perirenal fascia, and a thicker
posterior lamina that continues anterolaterally as the lateroconal fascia
Fig. 74.3 A, A horseshoe kidney. Note the ureters pass anterior to the and fuses with the parietal peritoneum.
isthmus, and the relatively high insertion of the ureters into the renal Classically, the anterior perirenal fascia was thought to blend into
pelvis. B, Axial contrast-enhanced computed tomography (CT) image. the dense mass of connective tissue surrounding the great vessels in the
C, Coronal maximal intensity projection (MIP) image of the abdomen. root of the mesentery behind the duodenum and pancreas, thereby
B and C demonstrate midline connection of the parenchyma of the two preventing communication between perirenal spaces across the midline.
kidneys below the inferior mesenteric artery (B, arrow), in a horseshoe However inspection of CT images or of anatomical sections of cadavers,
configuration, in keeping with a horseshoe kidney. (A, With permission following injection of contrast or coloured latex, respectively, into the
from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, perirenal space, revealed that fluid could extend across the midline at


15th ed, Elsevier, Urban and Fischer. Copyright 2013.) the third to fifth lumbar levels through a narrow channel measuring
2–10 mm in anteroposterior dimension. In the midline superiorly, the
anterior and posterior renal fasciae fuse and are attached to the crura
continued anterolaterally behind the colon to blend with the parietal of their respective hemidiaphragms. Inferiorly, the fasciae separate for
peritoneum. However, work by Mitchell (1950) showed that the peri- a variable craniocaudal distance. The posterior perirenal fascia fuses
renal fascia is not made up of distinct fused fasciae but is, in fact, a with the muscular fascia of psoas major, while the anterior perirenal
single multilaminated structure that is fused posteromedially with the fascia extends across the midline anterior to the great vessels; commu-
muscular fasciae of psoas major and quadratus lumborum. It then nication between the two sides is permitted, although is very rarely of
extends anterolaterally behind the kidney as a bilaminated sheet, clinical significance. Below this level, the two fasciae once again merge


Kidney and ureter
1240
8
nOitCeS
and are attached to the great vessels or iliac vessels. The containment A
of fluid to one side of the perirenal space that is observed in over two-
thirds of clinical cases is attributed to the presence of fibrous septa. Superior Perinephric fat
Above the suprarenal glands, the anterior and posterior perirenal suprarenal arteries Fibrous capsule
fasciae were previously said to fuse with each other and to the diaphragm-
atic fascia. This description of a closed superior cone is not universally
Middle
accepted. Cadaveric experiments have shown the superior aspect of the suprarenal
perirenal space to be open and in continuity with the bare area of the arteries
liver on the right and the subphrenic extraperitoneal space on the left.
The posterior fascial layer blends bilaterally with the fascia of psoas Suprarenal gland
major and quadratus lumborum, as well as the inferior phrenic fascia. Suprarenal vein
The anterior fascial layer on the right blends with the right inferior
Inferior suprarenal
coronary ligament at the level of the upper pole of the kidney and bare
artery
area of the liver. On the left, the anterior layer fuses with the gastro-
splenic ligament at the level of the suprarenal gland. Renal artery,
There is some debate concerning the inferior fusion of the perirenal posterior branch
fascia. Many investigators believe that, inferiorly, the anterior and pos-
terior leaves of the perirenal fascial fuse to produce an inverted cone Renal vein
that is open to the pelvis at its apex. Laterally, the anterior and posterior
Hilum of kidney Renal
leaves fuse with the iliac fascia; medially, they fuse with the periureteric
Renal artery, pelvis
connective tissue. The inferior apex of the cone is open anatomically
anterior branch
towards the iliac fossa but rapidly becomes sealed in inflammatory
Left testicular/ovarian
disease. An alternative view is based on the dissection of recently
vein
deceased cadavers after injections of coloured latex into the perirenal
Ureter
space, which have shown that the anterior and posterior perirenal
fasciae merge to form a single multilaminar fascia that contains the


ureter in the iliac fossa. Anteriorly, this common fascia is loosely con-
nected to the parietal peritoneum, and so denies free communication
between the perirenal space and the pelvis, and between the perirenal
and pararenal spaces.
A simple nephrectomy for benign disease removes the kidney from B
within perirenal fascia; a radical nephrectomy (for cancer) classically Superior suprarenal arteries
removes the entire contents of the perirenal space, including the peri-
renal fascia and suprarenal gland, in order to give adequate clearance
around the tumour.
Superior border
Suprarenal gland
RELATIONS
Suprarenal gland, hilum
Middle suprarenal
The superior poles of both kidneys are thick and round, and related to Perinephric fat arteries
their respective suprarenal glands (Fig. 74.5). The inferior poles are Suprarenal veins
Fibrous capsule
thinner and extend to within 2.5 cm of the iliac crests. The lateral
borders are convex. The medial borders are convex adjacent to the poles
Medial border
and concave between them, and slope inferolaterally. In each, a deep
vertical fissure opens anteromedially as the hilum, which is bounded
by anterior and posterior lips and contains the renal vessels and nerves,
and the renal pelvis. The relative positions of the main hilar structures
are the renal vein (anterior), the renal artery (intermediate) and the Inferior suprarenal artery
pelvis of the kidney (posterior) (Fig. 74.6). Usually, an arterial branch
from the main renal artery runs over the superior margin of the renal
pelvis to enter the hilum on the posterior aspect of the pelvis, and a Renal artery
renal venous tributary often leaves the hilum in the same plane. Above
the hilum, the medial border is related to the suprarenal gland and
below to the origin of the ureter. Renal vein
The convex anterior surface of the kidney actually faces anterolater- Hilum of kidney
ally and its relations differ on the right and left. Likewise, the posterior
surface of the kidneys, in reality, faces posteromedially. Its relations are
Ureter
similar on both sides of the body (Fig. 74.7).


A small area of the superior pole of the right kidney is in contact with
the right suprarenal gland, which may overlap the upper part of the
medial border of the superior pole (Fig. 74.8). A large area below this is
immediately related to the right lobe of the liver, separated by a layer of
peritoneum. A narrow medial area is directly related to the retroperito-
neal descending part of the duodenum. Inferiorly, the anterior surface is
directly in contact laterally with the retroperitoneal right colic flexure
and medially with part of the intraperitoneal small intestine.
A small medial area of the superior pole of the left kidney is related Fig. 74.5 A, The posterior aspect of the left kidney and suprarenal gland.
to the left suprarenal gland (see Fig. 74.8). The lateral half of the ante- B, The posterior aspect of the right kidney and suprarenal gland. Note
rior surface is related to the spleen, from which it is separated by a layer that the left suprarenal vein enters the left renal vein. This is an important
of peritoneum. A central quadrilateral area lies in direct contact with relationship to identify when performing a left nephrectomy. (With
the retroperitoneal pancreas and the splenic vessels. Above this, a small, permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
variable, triangular region, between the suprarenal and splenic areas, is Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright 2013.)
in contact with the stomach, separated by a layer of peritoneum. Below
the pancreatic and splenic areas, a narrow lateral strip that extends to of the greater sac. Behind the peritoneum covering the jejunal area,
the lateral border of the kidney is directly related to the retroperitoneal branches of the left colic vessels are related to the kidney.
left colic flexure and the beginning of the descending colon. An exten- The posteromedial surface of the kidneys is embedded in fat and
sive medial area is related to intraperitoneal loops of jejunum. The devoid of peritoneum. The right and left kidneys are related to similar


gastric area is covered with the peritoneum of the lesser sac (omental structures. Superiorly are the diaphragm and the medial and lateral
bursa), and the splenic and jejunal areas are covered by the peritoneum arcuate ligaments. More inferiorly, moving in a medial to lateral


Kidney
1241
47
retPaHC
direction, are psoas major, quadratus lumborum and the aponeurotic INTERNAL MACROSTRUCTURE
tendon of transversus abdominis, the subcostal vessels, and the subcos-
tal, iliohypogastric and ilioinguinal nerves. The upper pole of the right The postnatal kidney has a thin fibrous capsule composed of collagen-
kidney is level with the twelfth rib, and that of the left with the eleventh rich connective tissue with some elastic and smooth muscle fibres. In
and twelfth ribs. The diaphragm separates the kidney from the pleura, renal disease, the capsule may become adherent.
which descends to form the costodiaphragmatic recess; diaphragmatic The kidney itself can be divided into an internal medulla and
muscle is sometimes defective or absent in a triangle immediately above external cortex (Fig. 74.9). The renal medulla consists of pale, striated,
the lateral arcuate ligament, and this allows perirenal adipose tissue to conical renal pyramids; their bases are peripheral, and their apices
contact the diaphragmatic pleura. converge to the renal sinus. At the renal sinus, they project into calyces
as papillae.
The renal cortex (see Fig. 74.14) is subcapsular, arching over the
bases of the pyramids and extending between them towards the renal
sinus as renal columns. Its peripheral regions are termed cortical arches
and are traversed by radial, lighter-coloured, medullary rays, separated
by darker tissue, the convoluted part. The rays taper towards the renal
capsule and are peripheral prolongations from the bases of renal pyra-
mids. The cortex is histologically divisible into outer and inner zones.
The inner zone is demarcated from the medulla by tangential blood
RA
vessels (arcuate arteries and veins), which lie at the junction of the two;
however, a thin layer of cortical tissue (subcortex) appears on the med-
ullary side of this zone. The cortex close to the medulla is sometimes
RV termed the juxtamedullar cortex.
Renal pelvis and calyces


Fig. 74.6 An intraoperative view of the dissected renal hilum. The kidney The hilum of the kidney leads into a central renal sinus, lined by the
is seen enveloped by Gerota’s fascia in the superior aspect of the renal capsule and almost filled by the renal pelvis and vessels; the
operative field. The renal artery (RA) is noted in its posterior location remaining space is filled by fat. Dissection into this plane can be chal-
adjacent to the larger renal vein (RV). lenging but is important in surgery on the renal pelvis, particularly open
Gallbladder Superior mesenteric vein Superior mesenteric artery Spleen Stomach Pancreas
C
Duodenum Left kidney
A Liver Gallbladder
Liver Head of pancreas Left renal vein Left kidney Spleen
Liver Right kidney Right suprarenal gland Left suprarenal gland Spleen
B D
Left psoas major Left kidney Right hepatic flexure Duodenum Right kidney
Fig. 74.7 Multislice CT scans of the kidneys. A, An axial CT scan of the kidneys showing the anatomical relationships of the kidneys at the renal hilum.
B, A coronal reformat showing both kidneys and the suprarenal glands. C, A sagittal reformat of the left kidney lying posterior to the stomach, spleen
and pancreas. D, A sagittal reformat of the right kidney lying posterior to the right lobe of the liver, hepatic flexure and duodenum.


Kidney and ureter
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Right Left Stomach
B Left Right
A Right suprarenal gland Left suprarenal gland Spleen
Pancreas Eleventh rib
Liver Left colic
flexure
Descending part
Descending
of duodenum
colon
Right colic
flexure
Jejunum
Twelfth rib
Psoas major
Small intestine
Quadratus lumborum
Transversus abdominis
Fig. 74.8 The surfaces of the kidneys. A, Anterior, showing the areas related to neighbouring viscera. The areas where overlying viscera are separated
from the kidney by peritoneum are shown. B, Posterior, showing the areas of relation to the posterior abdominal wall. (With permission from Drake RL,
Vogl AW, Mitchell A, Tibbitts R, Richardson P (eds), Gray’s Atlas of Anatomy, Elsevier, Churchill Livingstone. Copyright 2008.)
A B
Renal cortex
Renal column
Renal medulla,
Branch of renal artery
renal pyramids
Fibrous capsule
Major calyces Interlobar
arteries
Renal artery
Pelvis of kidney Minor calyces Cribriform area, openings
of papillary ducts
Renal vein
Margin of hilum Renal sinus, fat body
Pyramid in
renal medulla
Renal sinus Renal pelvis
Ureter
Ureter Base of pyramid
Arcuate artery
Renal papilla
Fig. 74.9 The left kidney, oblique vertical hemisection: normal macroscopic appearance of the renal cortex and renal medulla, and the major structures
at the hilum of the kidney. A, The fat body of the renal sinus and most of the major vessels at the hilum have been removed, and the renal pelvis has not
been opened. B, The renal pelvis has been opened to reveal the interlobar arteries. (B, With permission from Waschke J, Paulsen F (eds), Sobotta Atlas
of Human Anatomy, 15th ed, Elsevier, Urban and Fischer. Copyright 2013.)
stone surgery. Within the renal sinus, the collecting tubules of the extrarenal. The funnel-shaped renal pelvis tapers as it passes infero-


nephrons of the kidney open on to the summits of the renal papillae medially, traversing the renal hilum to become continuous with the
to drain into minor calyces, which are funnel-shaped expansions of the ureter (see Figs 74.9–74.10). It is rarely possible to determine precisely
upper urinary tract. The renal capsule covers the external surface of the where the renal pelvis ceases and the ureter begins; the region is usually
kidney and continues through the hilum to line the sinus and fuse with extrahilar and normally lies adjacent to the lower part of the medial
the adventitial coverings of the minor calyces. Each minor calyx sur- border of the kidney. Rarely, the entire renal pelvis has been found to
rounds either a single papilla or, more rarely, groups of two or three lie inside the sinus of the kidney so that the pelviureteric region occurs
papillae. The minor calyces unite with their neighbours to form two, or either in the vicinity of the renal hilum or completely within the renal
possibly three, larger chambers: the major calyces. There is wide varia- sinus.
tion in the arrangement of the calyces. As the posterior aspect of the The calyces, renal pelvis and ureter are well demonstrated radiologi-
kidney rotates laterally during its ascent in utero, the calyces that were cally following an intravenous injection of radio-opaque contrast that
lateral in utero become positioned anteriorly, and the medial calyces is excreted in the urine (computed tomographic urography, CTU) (Fig.
move more posteriorly. The calyces drain into the infundibula. The 74.10), or after the introduction of radio-opaque contrast into the
renal pelvis is normally formed from the junction of two infundibula ureter by catheterization through a cystoscope (ascending or retrograde
– one from the upper and one from the lower pole calyces – but there pyelography). Normal cupping of the minor calyces by projecting renal
may be a third, which drains the calyces in the mid portion of the papillae may be obliterated by conditions that cause hydronephrosis:


kidney. The calyces are usually grouped so that three pairs drain into chronic distension of the ureter and renal pelvis due to upper or lower
the upper pole infundibulum and four pairs into the lower pole urinary tract obstruction, resulting in elevated intrapelvic pressure. An
infundibulum. If there is a middle infundibulum, the distribution is appreciation of the rotation of the kidneys, which results in the poste-
normally three pairs at the upper pole, two in the middle, and two at rior calyces lying relatively medially and the anterior calyces lying later-
the lower pole. There is considerable variation in the arrangement of ally, is essential when interpreting contrast imaging of the collecting
the infundibula and in the extent to which the pelvis is intrarenal or system of the kidneys.


Kidney
1243
47
retPaHC
Pelvis of kidney Fig. 74.10 A 39-year- (Schneider et al 2013). Rarely, accessory renal arteries arise from the
old man with a history coeliac or superior mesenteric arteries near the aortic bifurcation, or
of intrinsic sphincter from the common iliac arteries.
deficiency: coronal The subdivisions of the renal arteries are described sequentially as
CT urogram. A, A segmental, lobar, interlobar, arcuate and interlobular arteries, and affer-
maximum-intensity ent and efferent glomerular arterioles (Fig. 74.14).
projection (MIP).
B, A volume-rendered Segmental arteries
image. Both images Renal vascular segmentation was originally recognized by John Hunter
demonstrate collecting in 1794, but the first detailed account of the primary pattern was pro-
systems, ureters and
duced in the 1950s from casts and radiographs of injected kidneys. Five
bladder that appear
arterial segments have been identified (Fig. 74.15). The apical segment
normal.
occupies the anteromedial region of the superior pole. The superior
(anterior) segment includes the rest of the superior pole and the central
anterosuperior region. The inferior segment encompasses the whole
lower pole. The middle (anterior) segment lies between the anterior and
inferior segments. The posterior segment includes the whole posterior
A
region between the apical and inferior segments. This is the pattern
most commonly seen, and although there can be considerable varia-
Bladder ureter tion, it is the pattern that clinicians most frequently encounter when
performing partial nephrectomy. Whatever pattern is present, it is
important to emphasize that vascular segments are supplied by virtual
end arteries. In contrast, larger intrarenal veins have no segmental
organization and anastomose freely.
Brödel described a relatively avascular longitudinal zone (the ‘blood-
less’ line of Brödel) along the convex renal border, which was proposed
as the most suitable site for surgical incision (Brödel 1911). However,
many vessels cross this zone, and it is far from ‘bloodless’; planned
radial or intersegmental incisions are preferable. Knowledge of the
vascular anatomy of the kidney is important when undertaking partial


nephrectomy for renal cell cancers. In this surgery, the branches of the
renal artery are defined so that the surgeon may safely excise the renal
substance containing the tumour while not compromising the vascular
supply to the remaining renal tissue (Novick 1998).
Lobar, interlobar, arcuate
and interlobular arteries
The initial branches of segmental arteries are lobar, usually one to each
renal pyramid. Before reaching the pyramid, they subdivide into two or
three interlobar arteries, extending towards the cortex around each
pyramid. At the junction of the cortex and medulla, interlobar arteries
dichotomize into arcuate arteries, which diverge at right angles. As they
B arch between cortex and medulla, each divides further, ultimately sup-
plying interlobular arteries that diverge radially into the cortex. The ter-
minations of adjacent arcuate arteries do not anastomose but end in the
cortex as additional interlobular arteries. Though most interlobular arter-
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
ies come from arcuate branches, some arise directly from arcuate, or even
terminal, interlobar arteries (see Fig. 74.14). Interlobular arteries ascend
Renal arteries towards the superficial cortex or may branch occasionally en route. Some
are more tortuous and recurve towards the medulla at least once before
The paired renal arteries take about 20% of the cardiac output to supply proceeding towards the renal surface. Others traverse the surface as per-
organs that represent less than 1% of total body weight. They branch forating arteries to anastomose with the capsular plexus (which is also
laterally from the aorta just below the origin of the superior mesenteric supplied from the inferior suprarenal, renal and gonadal arteries).
artery (see Fig. 59.6; Fig. 74.11A). Both cross the corresponding crus of
the diaphragm at right angles to the aorta. The right renal artery is afferent and efferent glomerular arterioles
longer and often higher, passing posterior to the inferior vena cava, right Afferent glomerular arterioles are mainly the lateral rami of interlobular


renal vein, head of the pancreas, and descending part of the duodenum. arteries. A few arise from arcuate and interlobar arteries, when they vary
The left renal artery is a little lower and passes behind the left renal their direction and angle of origin: deeper ones incline obliquely back
vein, the body of the pancreas, and splenic vein. It may be crossed towards the medulla, the intermediate pass horizontally, and the more
anteriorly by the inferior mesenteric vein. superficial approach the renal surface obliquely before ending in a
A single renal artery to each kidney is present in approximately 70% glomerulus (see Fig. 74.14). Efferent glomerular arterioles from most
of individuals (Fig. 74.12). The arteries vary in their level of origin and glomeruli (except at juxtamedullary and, sometimes, at intermediate
in their calibre, obliquity and precise relations (Fig. 74.11B). In its cortical levels) soon divide to form a dense peritubular capillary plexus
extrarenal course, each renal artery gives off one or more inferior supra- around the proximal and distal convoluted tubules; there are, thus, two
renal arteries, a branch to the ureter, and branches that supply peri- sets of capillaries – glomerular and peritubular – in series in the main
nephric tissue, the renal capsule and the pelvis. Near the renal hilum, renal cortical circulation, linked by efferent glomerular arterioles. The
each artery divides into an anterior and a posterior division, and these vascular supply of the renal medulla is largely from efferent arterioles
divide into segmental arteries supplying the renal vascular segments of juxtamedullary glomeruli, supplemented by some from more super-
(Fig. 74.11C). Accessory renal arteries are common (30% of individu- ficial glomeruli, and ‘aglomerular’ arterioles (probably from degener-
als), and usually arise from the aorta above or below (most commonly, ated glomeruli). Efferent glomerular arterioles passing into the medulla
below) the main renal artery and follow it to the renal hilum (Merklin are relatively long, wide vessels, and contribute side branches to neigh-


and Michels 1958). They are regarded as persistent embryonic lateral bouring capillary plexuses before entering the medulla, where each
splanchnic arteries. Accessory vessels to the inferior pole cross anterior divides into 12–25 descending vasa recta. As their name suggests, these
to the ureter and may, by obstructing the ureter, cause hydronephrosis run straight to varying depths in the renal medulla, contributing side
(Fig. 74.13). In children with pelviureteric junction obstruction, a branches to a radially elongated capillary plexus applied to the descend-
crossing vessel is found in 28% of cases (Veyrac et al 2003). Three ing and ascending limbs of renal loops and to collecting ducts. The
anatomical variants of aberrant lower pole crossing vessels have been venous ends of capillaries converge to the ascending vasa recta, which
described: anterior to the dilated pelvis or pelviureteric junction, or drain into arcuate or interlobular veins. An essential feature of the vasa
inferior to the pelviureteric junction, causing kinking of the ureter recta (particularly in the outer medulla) is that both ascending and


Kidney and ureter
1243.e1
47
retPaHC
A
B
Fig. 74.13 Marked dilation of the right renal pelvis (*) and calyces, and
non-dilation of the right ureter (without an associated lesion) due to
ureteropelvic junction obstruction. Note a crossing inferior right renal vein
(arrow) at the level of the obstruction. A, A coronal maximum-intensity
projection of the abdomen. B, An axial contrast-enhanced CT image of
the abdomen.


Kidney and ureter
1244
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nOitCeS
B
Abdominal aorta
Superior mesenteric artery Renal artery
Right renal artery Aorta Left renal artery
Superior renal
polar artery
13% 10%
Superior renal Inferior renal
polar artery polar artery
A
7% 5%
1
2
Fig. 74.11 A, An axial multislice CT renal angiogram. B, Variations in the
number and patterns of branching of the renal artery (percentages are
approximate). C, An intraoperative angiogram of the left kidney,
demonstrating the main renal artery (1), segmental renal arteries (2) and their
subsequent branches. (B, With permission from Waschke J, Paulsen F (eds),
C Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban and Fischer.
Copyright 2013.)
descending vessels are grouped into vascular bundles, within which the Arcuate veins drain into interlobar veins, which anastomose and form
external aspects of both types are closely apposed, bringing them close the renal vein.
to the limbs of renal loops and collecting ducts. As these bundles con- The large renal veins lie anterior to the renal arteries and open into
verge centrally into the renal medulla, they contain fewer vessels; some the inferior vena cava almost at right angles (see Fig. 59.7; Fig. 74.17).
terminate at successive levels in neighbouring capillary plexuses. This The left is three times longer than the right (7.5 cm and 2.5 cm, respec-
proximity of descending and ascending vessels to each other and to tively), and for this reason, the left kidney is the preferred side for live
adjacent ducts provides the structural basis for the countercurrent donor nephrectomy. The left renal vein runs from its origin in the renal
exchange and multiplier phenomena (Fig. 74.16). These complex renal hilum, posterior to the splenic vein and the body of pancreas, and then
vascular patterns show regional specializations that are closely adapted across the anterior aspect of the aorta, just below the origin of the
to the spatial organization and functions of renal corpuscles, tubules superior mesenteric artery. Nutcracker syndrome, characterized by left
and ducts (see below). renal vein hypertension secondary to compression of the vein between


the aorta and the superior mesenteric artery, has been associated with
haematuria and varicocele in children. The left gonadal vein enters the
Renal veins
left renal vein from below, and the left suprarenal vein, usually receiving
one of the left inferior phrenic veins, enters it above but nearer the
Fine radicles from the venous ends of the peritubular plexuses converge midline. The left renal vein enters the inferior vena cava a little superior
to join interlobular veins, one with each interlobular artery. Many inter- to the right. The right renal vein is behind the descending duodenum
lobular veins begin beneath the fibrous renal capsule by the conver- and, sometimes, the lateral part of the head of the pancreas. It can be
gence of several stellate veins, which drain the most superficial zone of extremely short (less than 1 cm), such that safe nephrectomy may
the renal cortex and so are named from their surface appearance. Inter- require excision of a cuff of the inferior vena cava.
lobular veins pass to the corticomedullary junction and also receive The left renal vein may be double, one vein passing posterior, and
some ascending vasa recta before ending in arcuate veins (which accom- the other anterior, to the aorta before joining the inferior vena cava.
pany arcuate arteries), and anastomose with neighbouring veins. This is sometimes referred to as persistence of the ‘renal collar’. The


Kidney
1245
47
retPaHC
Fig. 74.12 A resin corrosion cast of human
kidneys. Ureters, pelves and calyces are yellow;
aorta, renal arteries and their branches are red.
(Prepared by the late DH Tompsett of the Royal
College of Surgeons of England. With permission
from the Museums of The Royal College of
Surgeons.)
Juxtamedullary renal corpuscle
Cortical renal corpuscle
Renal
lobe Renal lobule Arcuate artery and vein
Interlobular artery
Capsular network
Medullary rays
Capsule
Outer
cortex
Cortex
Juxtamedullary
cortex
Outer
medulla
Renal
Vasa recta
column
Pyramid Interlobar artery and vein
Inner
medulla
Papilla
Minor calyx
Area cribrosa
Major calyx
Fig. 74.14 The major structures in the kidney cortex and medulla (left), the position of cortical and juxtamedullary nephrons (middle), and the major
blood vessels (right).


Kidney and ureter
1246
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Apical Apical
Apical
Superior
Superior
Superior
Posterior
Posterior
Middle Middle
Middle
Inferior Inferior
Inferior
Anterior Lateral Posterior
Fig. 74.15 The segmental arterial anatomy of the right kidney. The posterior division branches near the hilum before the anterior division divides into the
other segmental arteries.
anterior vein may be absent so that there is a single retro-aortic left renal Renal corpuscle
vein. The left renal vein may have to be ligated during surgery for aortic
Renal corpuscles are small, rounded structures averaging 0.2 mm
aneurysm because it has such a close relationship with the aorta; this
in diameter, visible in the renal cortex deep to a narrow peripheral corti-
seldom results in any harm to the kidney, provided that the ligature is
cal zone (Fig. 74.18; see Fig. 74.16). Each has a central glomerulus of
placed medial to the draining gonadal and suprarenal veins, since these
vessels and a glomerular (Bowman’s) capsule, from which the renal
usually provide adequate collateral venous drainage. The right renal
tubule originates.
vein has no significant collateral drainage and cannot be ligated with
There are about 1 million renal corpuscles in each kidney, their
impunity.
number (which may be determined, in part, by intrauterine factors)
decreasing with age; this process is accelerated by raised blood pressure.
Lymphatic drainage
After birth, new nephrons cannot be developed; a lost nephron can
never be replaced. The decrease in corpuscular numbers with age is
Renal lymphatic vessels begin in three plexuses: around the renal reflected in a corresponding reduction in the rate of glomerular filtra-
tubules, under the renal capsule, and in the perirenal fat (the latter two tion from the fourth decade onwards.
connect freely). Collecting vessels from the intrarenal plexus form four
or five trunks that follow the renal vein to end in the lateral aortic nodes; Glomerulus
the subcapsular collecting vessels join them as they leave the hilum. A glomerulus is a collection of convoluted capillary blood vessels,


The perirenal plexus drains directly into the same nodes. united by a delicate mesangial matrix and supplied by an afferent arte-
riole which enters the capsule opposite the urinary pole, where the
filtrate enters the tubule (Davies et al 2001). (The term glomerulus is
INNERVATION
used most frequently to describe the entire renal corpuscle.) An efferent
arteriole emerges from the same point, the vascular pole of the corpus-
Rami from the coeliac ganglion and plexus, aorticorenal ganglion, cle. Glomeruli are simple in form until late prenatal life; some remain
lowest thoracic splanchnic nerve, first lumbar splanchnic nerve and so for about 6 months after birth, the majority maturing by 6 years and
aortic plexus form a dense plexus of autonomic nerves around the renal all by 12 years. Low birth weight, defined as a weight less than 2500 g
artery (see Figs 59.4, 59.5). at birth, is associated with a reduction in the number and volume of
Small ganglia occur in the renal plexus, the largest usually behind glomeruli (Manalich et al 2000).
the origin of the renal artery. The plexus continues into the kidney
around the arterial branches and supplies the vessels, renal glomeruli Bowman’s capsule
and, especially, the cortical tubules. Axons from plexuses around the Bowman’s capsule is the blind expanded end of a renal tubule, and is
arcuate arteries innervate juxtamedullary efferent arterioles and vasa deeply invaginated by the glomerulus. It is lined by a simple squamous
recta, which control the blood flow between the cortex and medulla epithelium on its outer (parietal) wall; its glomerular, juxtacapillary
without affecting the glomerular circulation. Axons from the renal (visceral) wall is composed of specialized epithelial podocytes. Between
plexus contribute to the ureteric and gonadal plexuses. the two walls of the capsule is a flattened urinary (Bowman’s) space,
continuous with the proximal convoluted tubule (Fig. 74.18B; see Fig.
74.16).
MICROSTRUCTURE


Podocytes are stellate cells. Their major (primary) foot processes
curve around the capillary loops and branch to form secondary pro-
The kidney is composed of many tortuous, closely packed uriniferous cesses that are applied closely to the basal lamina; secondary or tertiary
tubules, bounded by a delicate connective tissue in which run blood processes give rise to terminal pedicels (Fig. 74.19A). Pedicels of one
vessels, lymphatics and nerves. Each tubule consists of two embryologi- cell alternate with those of an adjacent cell and interdigitate tightly with
cally distinct parts, the nephron, which produces urine, and the collect- each other, separated by narrow (25 nm) gaps: the filtration slits (Fig.
ing duct, which completes the concentration of urine and through 74.19B). The latter are covered by a dense, membranous, slit diaphragm,
which urine passes out into the calyces of the kidney, the renal pelvis, through which filtrate must pass to enter the urinary space. The dif-
the ureter and urinary bladder. ferentiation of the adult podocyte phenotype is associated with the
presence of several specific proteins, including nephrin, podocin, syn-
Nephron
aptopodin and GLEPP-1. Mutations in these proteins can cause impor-
tant functional problems, e.g. the classic Finnish form of congenital
The nephron consists of a renal corpuscle, concerned with filtration nephritic syndrome is caused by a mutation of NHPS1, coding for
from the plasma, and a renal tubule, concerned with selective resorp- nephrin. The luminal membrane and the slit diaphragm are covered by
tion from the filtrate to form the urine (see Fig. 74.14). Collecting ducts a dense surface coat rich in sialoglycoproteins, which gives this surface
carry fluid from several renal tubules to a terminal papillary duct, a very high negative charge and is one of the key characteristics of the
opening into a minor calyx at the apex of a renal papilla. Papillary perm-selectivity barrier. Differentiated podocytes cannot replicate.
surfaces show numerous minute orifices of these ducts and pressure on The glomerular endothelium is finely fenestrated. The principal
a fresh kidney expresses urine from them. barrier to the passage of fluid from capillary lumen to urinary space is


Kidney
1247
47
retPaHC
RENAL CORPUSCLE
Parietal wall of glomerular capsule
Afferent arteriole
Afferent arteriole Granular juxtaglomerular cells
Smooth muscle cell
Macula densa
Extraglomerular
mesangial cells ‘Polar cushion’
(lacis cells)
Distal convoluted tubule Granular juxtaglomerular cells
(renin-secreting)
Juxtaglomerular
apparutus Efferent arteriole Urinary space
Basal lamina Fenestrated endothelial cell
Podocyte nucleus
Mesangial cell
Efferent arteriole
Filtration slits
Glomerular capsule (parietal layer)
Urinary (Bowman's) space
Podocyte of visceral layer of glomerular capsule Glomerular capillaries
Selective resorption
and secretion
Ultrafiltration
Na+
Cl–
Distal convoluted tubule
Water
Glucose Selective
Amino acids resorption
Proteins
Ascorbic acid
HCO–
3
Proximal convoluted tubule
A Collecting duct
Countercurrent
exchange and
multiplication
Loop of Henle and vasa recta
ADH controlled
water resorption
B
Thick segment
Increased Thin segment
osmolality
Vasa recta
Fig. 74.16 The regional microstructure and principal activities of a kidney nephron and collecting duct. For clarity, a nephron of the long loop
(juxtamedullary) type is shown. Abbreviations: ADH, antidiuretic hormone.


Kidney and ureter
1248
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nOitCeS
BV
I A
G
G
A
A
Inferior vena cava Left renal vein
G
B
Fig. 74.18 A, A low-power histological section of the renal cortex,
containing glomeruli (G), proximal and distal convoluted tubules and
blood vessels (BV). B, A higher-power view of the section demonstrating
several glomeruli (G) within a network of mesangium. The glomerular
basement membrane of the capillaries is continuous with Bowman’s
capsule (short arrow) of the glomerulus, and is separated from it by
Bowman’s space (long arrow).
thickness of the glomerular basement membrane increases throughout
B
childhood; the rate of increase decreases after the age of 11 years
(Ramage et al 2002).
Right kidney Right renal vein Left kidney
Left testicular vein Irregular mesangial cells, with phagocytic and contractile properties,
lie within and secrete the glomerular mesangium, a specialized connec-
Fig. 74.17 A, A coronal maximum-intensity projection contrast-enhanced
magnetic resonance angiogram image obtained during the arterial phase tive tissue that binds the loop of glomerular capillaries and fills the
of enhancement. It demonstrates normal-appearing single renal arteries spaces between endothelial surfaces that are not invested by podocytes
(short arrows), normal-appearing single renal veins (long arrows), a (see Figs 74.18B, 74.16). Mesangial cells are related to vascular pericytes
normal-appearing abdominal aorta (A), and a normal-appearing suprarenal and are concerned with the turnover of glomerular basement membrane.
inferior vena cava (I). The infrarenal inferior vena cava has not yet been They clear the glomerular filter of immune complexes and cellular
enhanced. B, A CT renal venogram, acquired from a multislice CT debris, and their contractile properties help to regulate blood flow.
examination and reconstructed as a three-dimensional, surface-shaded Similar cells, the extraglomerular mesangial (lacis) cells, lie outside the
reformat. glomerulus at the vascular pole and form part of the juxtaglomerular
apparatus.
Renal tubule


the glomerular basal lamina, the fused endothelial and podocyte basal
laminae (see Fig. 74.19B). This is usually 0.33 µm thick in humans, and A renal, or uriniferous, tubule consists of a glomerular capsule that
acts as a selective filter, allowing the passage from blood, under pres- leads into a proximal convoluted tubule, connected to the capsule by
sure, of water and various small molecules and ions in the circulation. a short neck and continuing into a sinuous or coiled convoluted part
Haemoglobin may cross the filter, but larger molecules and those of (see Fig. 74.16). This straightens as it approaches the medulla, and
similar size with a negative charge are largely retained. Most protein becomes the descending thick limb of the loop of Henle, and then the
that does enter the filtrate is selectively resorbed and degraded by cells ascending limb by an abrupt U-turn. The limbs of the loop of Henle
of the proximal convoluted tubule. are narrower and thin-walled within the deeper medullary tissue, where
The glomerular basement membrane serves as the skeleton of the they become the descending and ascending thin segments. The ascend-
glomerular tuft. Its outer aspect is completely covered by podocytes, ing thick limb continues into the distal tubule. The tubule wall shows
and the interior is filled by capillaries and a delicate mesangial matrix a focal thickening, the macula densa, where it comes close to the vas-
(mesangium). The major components of the glomerular basement cular pole of its parent glomerulus at the start of the convoluted part
membrane are laminin and type IV collagen (both of which are of the distal tubule. The nephron finally straightens once more as the
expressed as unique isoforms), and heparin sulphate proteoglycans. The connecting tubule, which ends by joining a collecting duct.


Kidney
1249
47
retPaHC
CC
V
P
CC P
P V
CC
A
Fig. 74.20 A histological cross-section of a part of the renal medulla.
Note the large collecting ducts and small, thin segments of the loop of
P
Henle, interspersed with vasa recta (V) (trichrome-stained).
E numerous other enzymes concerned with ion transport. Water and
F P 1 other solutes pass between cells (paracellular transport) passively, along
osmotic and electrochemical gradients, probably through leaky apical
FS tight junctions. Pinocytotic vesicles are found near the apical surface,
BL FS P 1 and represent the means by which small proteins and peptides from
P 2 P BL the filtrate are internalized and degraded by associated lysosomes. Per-
P 2 1 E oxisomes and lipid droplets abound in the cytoplasm.
BL
The loop of Henle consists of a thin segment (30 µm in diameter),
E C
lined by low cuboidal to squamous cells, and a thick segment (60 µm
P 2 F F in diameter), composed of cuboidal cells like those in the distal con-
B C voluted tubule. The thin segment forms most of the loop in juxtamedul-
lary nephrons, which reach deep into the medulla. Few organelles
P
1 appear in cells lining the thin segment, indicating that these cells play
Fig. 74.19 A, A scanning electron micrograph showing podocytes forming a passive, rather than an active, role in ion transport. The thick segment
the visceral layer of Bowman’s capsule in the renal corpuscle. Their cell is composed of cuboidal epithelium with many mitochondria, deep
bodies (P) send out primary processes that branch several times and end basolateral folds and short apical microvilli, indicating a more active
in fine pedicels, which wrap tightly around the glomerular capillaries (C), metabolic role. The thick limb of the loop of Henle is the source of
and interdigitate with similar pedicels from a neighbouring podocyte.
Tamm–Horsfall protein in normal urine.
B, An electron micrograph demonstrating the glomerular filtration
Cells of the distal tubule are cuboidal and resemble those in the