L3
Psoas major
Third lumbar Dorsal group
inferior phrenic arteries
The inferior phrenic arteries usually arise either from the aorta, just
Psoas major
L4 above the level of the coeliac trunk, or directly from the coeliac trunk;
tendinous
arches Fourth lumbar occasionally, they originate from the renal artery (Loukas et al 2005a,
Gwon et al 2007). They contribute to the arterial supply of the dia-
phragm. Each artery ascends laterally, anterior to the crus of the dia-
phragm, near the medial border of the ipsilateral suprarenal gland. It
then divides into an ascending and a descending branch. The left
ascending branch passes behind the oesophagus and then runs anteri-
L5 orly on the left side of the oesophageal hiatus, where it bifurcates; one
branch curves forwards to anastomose with its counterpart in front of
the central tendon of the diaphragm and the other branch approaches
the thoracic wall to anastomose with the musculophrenic and pericar-
diacophrenic arteries. The right ascending branch passes behind the
Common iliac Median sacral
inferior vena cava and then bifurcates; one branch runs anteriorly on
Fig. 62.9 The branches of the abdominal aorta. the right side of the diaphragmatic opening for the inferior vena cava
(which it supplies) before anastomosing with its counterpart in front
of the central tendon of the diaphragm, and the other branch passes


Posterior abdominal wall and retroPeritoneum
1090
8
noitCes
2 1 Inferior
phrenic
27
3
34 4
Hepatic veins
28 12 7
13
10
9125
6
8
29 14
11
12
30 15 12
Hemiazygos
Left suprarenal
17 vein
31
Right
Subcostal
suprarenal
18 19 Lumbar azygos
33
Right renal Left gonadal vein
First lumbar
32
Ascending lumbar
23 Right gonadal
Second lumbar
24 21 16 22
26 Third lumbar
Third lumbar
20
25
Fourth lumbar
Fourth lumbar
Fig. 62.10 The abdominal aorta and its branches. A 36-year-old female
investigated by CT aortogram for possible Marfan’s aortic dissection; only
the normal abdominal aorta part of the dataset is shown in this three- Iliolumbar
dimensional reconstruction. Surface shaded display. Key: 1, apex of left
Common iliac
ventricle; 2, low thoracic aorta; 3, approximate position of diaphragmatic
hiatus; 4, coeliac trunk; 5, common hepatic artery; 6, splenic artery; 7, left
gastric artery; 8, proper hepatic artery; 9, left hepatic artery; 10, right
hepatic artery; 11, gastroduodenal artery; 12, superior mesenteric artery;
13, right renal artery; 14, left renal artery partly obscured by proper Median sacral
hepatic artery lying more superficial (with arrow); 15, inferior mesenteric
Fig. 62.11 Tributaries of the inferior vena cava and lumbar veins. Only the
artery; 16, superior rectal artery; 17, aortic bifurcation in front of L4; 18,
left lumbar venous system is shown, for clarity.
right common iliac artery; 19, left common iliac artery; 20, right external
iliac artery; 21, right internal iliac artery; 22, left external iliac artery; 23,
left internal iliac artery; 24, right superior gluteal artery; 25, right inferior


spinal branch known as the arteria radicularis magna (the artery of
epigastric artery; 26, left inferior epigastric artery; 27, right T12 segmental
Adamkiewicz) (p. 770), which frequently originates from an upper
artery; 28, right L1 segmental artery; 29, right L2 segmental artery; 30,
right L3 segmental artery; 31, right L4 segmental artery; 32, right lumbar artery, particularly on the left side (Biglioli et al 2004) (Ch. 45).
iliolumbar artery; 33, median sacral artery; 34, right superior epigastric Injury to this vessel, e.g. during thoracoabdominal aortic surgery, can
artery (continuing from right internal thoracic artery). cause spinal cord infarction.
The lateral branch of each lumbar artery runs posterior to psoas
major and the lumbar plexus, then across the anterior surface of quad-
laterally on the undersurface of the diaphragm. The descending branches ratus lumborum, before piercing the posterior limit of transversus
on each side supply the muscular diaphragm and anastomose with the abdominis to run forwards between it and the internal oblique. Perfo-
lower posterior intercostal and musculophrenic arteries. Each inferior rating branches pass posteriorly to supply the muscles and skin of the
phrenic artery gives off two or three small suprarenal branches. The posterior abdominal wall (Kiil et al 2009). The lumbar arteries anasto-
abdominal oesophagus, capsule of the liver, and upper pole of the mose with one another and the lower posterior intercostal, subcostal,
spleen may also receive small arterial twigs. iliolumbar, deep circumflex iliac and inferior epigastric arteries.
The inferior phrenic artery may be a source of significant collateral The dorsal branch of each lumbar artery passes backwards between
blood flow to large hepatocellular cancers and is sometimes specifically the adjacent transverse vertebral processes to supply the dorsal muscles,
occluded, along with the relevant hepatic artery, when treating such vertebrae, joints and skin of the back.
tumours by arterial embolization.
median sacral artery
lumbar arteries The median sacral artery is a small branch that arises from the posterior


There are usually four lumbar arteries on each side, in series with the aspect of the aorta a little above its bifurcation. It descends close to the
posterior intercostal arteries. They arise from the posterolateral aspect midline, anterior to the fourth and fifth lumbar vertebrae, sacrum and
of the abdominal aorta, opposite the lumbar vertebrae. A fifth, smaller, coccyx. At the level of the fifth lumbar vertebra, it is crossed by the left
pair occasionally arise from the median sacral artery, but lumbar common iliac vein and often gives off a small lumbar artery (arteria
branches of the iliolumbar arteries often take their place. The lumbar lumbales imae), small branches of which reach the anorectum via the
arteries run posterolaterally on the first to the fourth lumbar vertebral anococcygeal ligament. Anterior to the fifth lumbar vertebra, the median
bodies, passing behind the sympathetic trunk and tendinous arches sacral artery anastomoses with a lumbar branch of the iliolumbar artery.
formed by the attachments of psoas major to the vertebral bodies. The Anterior to the sacrum, it anastomoses with the lateral sacral arteries
right lumbar arteries pass posterior to the inferior vena cava. The upper and sends branches into the anterior sacral foramina.
two right lumbar arteries and the first left lumbar artery lie behind the
corresponding crus of the diaphragm. Just beyond the intervertebral
foramina, each lumbar artery divides into a medial branch, which gives INFERIOR VENA CAVA
off spinal and ganglionic branches; a middle branch, from which dorsal
and anastomotic branches arise; and a lateral branch, which supplies The inferior vena cava (Figs 62.11–62.12) conveys blood to the right
the abdominal wall (Arslan et al 2011). Of particular importance is the atrium from almost all of the structures below the diaphragm. Most of


Vascular supply and lymphatic drainage
1091
26
retPaHC
iliac artery. From below upwards, its anterior surface is crossed obliquely
1 by the root of the small bowel mesentery and its contained vessels and
9
20 nerves, the right gonadal artery and the third part of the duodenum.
Further cranially, it lies behind the head of the pancreas and first part
of the duodenum, separated from these structures by the common bile
10 21 duct and portal vein. Above the duodenum, its anterior surface is
2 covered by the peritoneum of the posterior abdominal wall, which
22
forms the posterior wall of the epiploic foramen, and which separates
3 5 the inferior vena cava from the right free border of the lesser omentum
4
and its contents. Above this, it is intimately related to the liver
23
anteriorly.
The posterior relations of the inferior vena cava include the lower
6
three lumbar vertebral bodies and their intervertebral discs, the anterior
24
longitudinal ligament, sympathetic trunk, right third and fourth lumbar
11
arteries, and the right psoas major. Superior to these structures, the
inferior vena cava is related posteriorly to the right renal and middle
suprarenal arteries, the medial part of the right suprarenal gland, the
25
12 7 right coeliac ganglion and the right inferior phrenic arteries.
14 The right ureter, medial border of the right kidney, second part of
26 8 the duodenum, and the right lobe of the liver are all lateral to the right
side of the inferior vena cava. The abdominal aorta, right crus of the
diaphragm and the caudate lobe of the liver are left-sided relations.
The normal diameter of the adult inferior vena cava is up to 30 mm
15
(Moeller and Reif 2000); its cross-sectional shape and calibre reflect the
16 13 degree of venous filling. Anatomical variants of the inferior vena cava
related to its complex embryogenesis are well described. Among these
17 18 are a double inferior vena cava (the left-sided vessel usually joins the
19 left renal vein); azygos continuation of the inferior vena cava; or a left-
sided inferior vena cava (which may exist in isolation or as part of situs


inversus) (Ang et al 2013, Spentzouris et al 2014).
Tributaries
The inferior vena cava usually receives the common iliac veins at its
origin and the lumbar, right gonadal, renal, right suprarenal, hepatic
and inferior phrenic veins throughout its course (see Figs 62.11–
62.12).
Fig. 62.12 A 41-year-old male investigated for microscopic haematuria.
Lumbar veins
CT intravenous urogram. Normal study. Late phase acquisition. Oblique
coronal, mid-abdominal 15 mm slab, maximal intensity projection (MIP) Four pairs of lumbar veins collect blood from the territories supplied
reformats. Key: 1, inferior vena cava, hepatic segment; 2, inferior vena by the corresponding lumbar arteries (see above), including the dorsal,
cava, peritonealized segment; 3, inferior vena cava, renal segment; 4, lateral and anterior abdominal wall. These branches anastomose pos-
right renal vein; 5, left renal vein crossing in front of the aorta; 6, inferior teriorly with tributaries of the azygos and hemiazygos veins, and ante-
vena cava, infrarenal segment; 7, inferior vena cava, confluence (partly riorly with branches of the epigastric, circumflex iliac and lateral
obscured by right common iliac artery); 8, left common iliac vein (coursing thoracic veins. These superficial anastomoses provide alternative routes
posteriorly out of slab; right common iliac vein obscured); 9, right hepatic of venous drainage from the pelvis and lower limbs to the heart in
vein joining inferior vena cava; 10, liver parenchyma; 11, right kidney the presence of inferior vena caval obstruction. The lumbar veins also
lower pole parenchyma; 12, right ureter (with excreted contrast); 13, communicate with the external and internal vertebral venous plexuses,
urinary bladder (with excreted contrast); 14, right psoas major; 15, right providing an additional collateral pathway for venous return. The
iliacus; 16, right external iliac artery; 17, right external iliac vein; 18, left paired longitudinal ascending lumbar veins connect ipsilateral lumbar


external iliac artery; 19, left external iliac vein; 20, low thoracic aorta; 21, veins. The third and fourth lumbar veins usually pass forwards on the
coeliac axis; 22, superior mesenteric artery; 23, right renal artery passing
sides of the corresponding vertebral bodies to enter the posterior
behind inferior vena cava; 24, aorta, infrarenal segment; 25, aortic
aspect of the inferior vena cava; the left lumbar veins pass behind the
bifurcation (partly obscured); 26, right common iliac artery (left common
abdominal aorta and are, therefore, longer. The first and second
iliac artery courses posteriorly out of slab).
lumbar veins are much more variable; they may drain into the inferior
vena cava, ascending lumbar, lumbar azygos and renal vein (on the
left), and are often connected to each other. Indeed, the first lumbar
vein often passes inferiorly to join the second lumbar vein or, less
its course is within the abdomen, but a small segment lies within the
commonly, drains directly into the ascending lumbar vein or passes
pericardium in the thorax.
forwards over the L1 vertebral body to join the lumbar azygos vein.
The inferior vena cava is formed by the junction of the left and right
The second lumbar vein may join the inferior vena cava at or near the
common iliac veins anterior to the fifth lumbar vertebral body, about
level of the renal veins or, less commonly, joins the third lumbar or
1 cm to the right of the midline. It ascends anterior to the vertebral
ascending lumbar vein.
column, to the right of the aorta, and lies in a deep groove on the
posterior surface of the liver, sometimes completely embedded by liver Ascending lumbar veins
tissue. It traverses the central tendon of the diaphragm between its
The paired ascending lumbar veins run medial to psoas major and
median and right ‘leaves’, and passes through the fibrous pericardium
connect ipsilateral common iliac, iliolumbar and lumbar veins. The
and a posterior inflection of the serous pericardium to open into the
ascending lumbar vein is variable in its course and connections; rarely,
posteroinferior part of the right atrium. The abdominal portion of the


the whole vein or a segment may be absent on one side (Lolis et al
inferior vena cava is devoid of valves.
2011). It commonly joins the subcostal vein to form the azygos vein on
The inferior vena cava can be encircled and controlled between the
the right and the hemiazygos on the left. The azygos and hemiazygos
renal veins below and the hepatic veins above (e.g. when operating on
veins run forwards over the twelfth thoracic vertebral body, and pass
a renal cell carcinoma extending into the inferior vena cava).
deep to or through the right and left crus of the diaphragm, respectively,
into the thorax (Ch. 56). The ascending lumbar vein is usually joined
Relations of the abdominal part of the
by a small vein, the lumbar azygos vein, from the back of the inferior
inferior vena cava
vena cava or left renal vein. Sometimes, the ascending lumbar vein ends
in the first lumbar vein, which then joins the lumbar azygos vein at the
The inferior vena cava lies behind the peritoneum of the posterior level of the first lumbar vertebra. Blood flow in the ascending lumbar
abdominal wall. At its origin, it is related anteriorly to the right common veins can occur in either direction (Morita et al 2007).


Posterior abdominal wall and retroPeritoneum
1092
8
noitCes
Gonadal veins (approximately L2); the pattern of lymphatic spread from a testicular
malignancy suggests that lymph from the left testis drains to left para-
The right gonadal vein enters the inferior vena cava directly on its right
aortic nodes en route to the cisterna chyli, whereas lymph from the
anterolateral aspect at an acute angle about 2 cm inferior to the left
right testis drains to right and then left para-aortic nodes before reach-
renal vein in adults; occasionally, it drains into the right renal vein
ing the cisterna chyli. Lymph from the ovary may also drain via lym-
(Barber et al 2012). The left gonadal vein terminates in the left renal
phatics in the broad ligament and round ligament to internal iliac and
vein. Both veins may be replaced by multiple vessels in the lower
inguinal lymph nodes, respectively. Lymphatic drainage of the ureters
abdomen and sometimes remain double as far as their termination. Of
is less well defined but follows a regional pattern to nearby nodes.
the two gonadal veins, the left is more prone to develop venous
The lymphatic drainage of the retroperitoneal colon and rectum is
incompetence.
described in Chapter 66. The pancreas drains to numerous peripancre-
Renal veins atic nodes (Ch. 69) as well as portal, splenic, paracaval, superior
The renal veins are large-calibre vessels, which lie anterior to the renal mesenteric and coeliac nodes. The lymphatic drainage of the duode-
arteries and open into the inferior vena cava almost at right angles (Ch. num is not well described but the lymphatics generally drain to nodal
74). The left is three times longer than the right (approximately 7.5 cm stations related to local arteries (Ch. 65). Whilst the clinical pattern of
and 2.5 cm, respectively). The left vein lies on the posterior abdominal nodal metastases usually reflects normal lymphatic drainage pathways,
wall posterior to the splenic vein and body of the pancreas. It passes to the lymphatic obstruction may lead to metastases at unusual nodal sites.
right in the angle between the abdominal aorta posteriorly and the supe-


rior mesenteric artery anteriorly, to empty into the inferior vena cava. Cisterna chyli and abdominal lymph trunks
Occasionally, the left renal vein or an accessory left renal vein is retro-
aortic. The right renal vein lies posterior to the second part of the duode- The abdominal origin of the thoracic duct usually lies to the right of
num and, sometimes, the lateral part of the head of the pancreas. the midline at the level of the twelfth thoracic vertebral body or the
Suprarenal vein thoracolumbar intervertebral disc. It receives almost all the lymph from
below the diaphragm via the cisterna chyli, a localized lymphatic dila-
Most commonly, a single vein drains each suprarenal gland (Ch. 71).
tion formed most commonly by the union of the intestinal lymph trunk
The short right suprarenal vein drains directly into the inferior vena cava
and the left lumbar trunk (Phang et al 2014). The cisterna chyli is a
at the level of the twelfth thoracic vertebra; the longer left vein usually
saccular or fusiform lymphatic dilation measuring, on average, about
joins the left renal vein and may receive the left inferior phrenic vein.
1 cm wide and 2 cm long in the cadaver (Loukas et al 2007b). Recent
Numerous anatomical variations have been described (Cesmebasi et al
studies using magnetic resonance imaging (MRI) in vivo have shown
2014).
remarkable postural variations in the cross-sectional area of the cisterna
Inferior phrenic veins chyli, which expands considerably when moving from supine to sitting,
and again from sitting to standing (Niggemann et al 2010). The cisterna
The inferior phrenic veins usually originate on the superior surface of
chyli usually lies in front of the first and second lumbar vertebrae behind
the diaphragm but run mostly on its inferior surface to drain into the
the right crus of the diaphragm to the right of the abdominal aorta but
posterolateral aspect of the inferior vena cava. Both veins receive several
may be located at a higher vertebral level. The formation of the cisterna
diaphragmatic tributaries. The left vein runs to the left of the oesopha-
chyli is variable. The most common configuration, found in approxi-


geal hiatus, whereas the right courses to the right of the opening in the
mately two-thirds of individuals, is a single structure formed from the
diaphragm for the inferior vena cava, each receiving an oesophageal
union of the intestinal lymph trunk and the left (or, less commonly,
tributary (Loukas et al 2005b). Further, the left inferior phrenic vein
the right) lumbar lymph trunk (Loukas et al 2007b). In most other
frequently communicates with the left gastric vein and hence may
individuals, it is formed by the confluence of the intestinal and both
become prominent in portal hypertension. Both inferior phrenic veins
lumbar lymph trunks, with additional small branches from intercostal
usually drain directly into the inferior vena cava just below the dia-
lymphatics and retro-aortic lymph nodes. The upper two right lumbar
phragm, sometimes joining anteriorly to form a short common trunk.
arteries and the right lumbar azygos vein lie between the cisterna chyli
The right may occasionally drain into the right hepatic vein or inferior
and the vertebral column. The medial edge of the right crus of the
vena cava above the diaphragm. In contrast, the left frequently drains
diaphragm lies anterior to the abdominal confluence of lymph trunks.
into the left suprarenal, left renal or left hepatic vein.
The lumbar lymph trunks are formed by lymphatic vessels draining
Collaterals in inferior vena caval occlusion para-aortic nodes. The intestinal lymph trunk (which may be double)
Obstruction of the inferior vena cava from thrombosis, embolism, receives vessels draining from pre-aortic nodes, i.e. coeliac, superior and
extrinsic compression or intrinsic disease results in the development of inferior mesenteric nodes, which drain the entire abdominal gastroin-
an extensive venous collateral circulation via tributaries that ultimately testinal tract down to the anal canal. The thoracic duct leaves the supe-
connect to the superior vena cava. These include the azygos–hemiazygos rior end of the cisterna chyli and passes through the aortic hiatus of the
venous system, the vertebral venous plexuses, and superficial body wall diaphragm posterolateral to the right side of the aorta. Its thoracic
veins. The lumbar veins contribute significantly to these pathways continuation is described on page 979.


(Golub et al 1992). The major lymphatic vessels adjacent to the abdominal aorta are at
risk of injury during surgical procedures that involve peri-aortic dissec-
tion and/or lymphadenectomy. Damage to these lymphatic trunks or
their obstruction by malignant disease may cause major lymph leaks
LYMPHATIC DRAINAGE
manifesting as chylous ascites or chylothorax.
Lymph from the skin and subcutaneous tissues of the abdominal wall
drains via small-calibre superficial lymphatics to axillary and inguinal Retroperitoneal lymph node groups
nodes (Tourani et al 2013). The midline and the level of the umbilicus
form inconstant and variable watershed boundaries for these drainage The lymphatic drainage of the rectum, colon, stomach, pancreas,
territories. Lymphatics from the deeper layers of the body wall and the oesophagus and other organs is often described in terms of lymph node
abdominal and pelvic viscera drain almost exclusively to the cisterna stations and levels of dissection that relate to the management of malig-
chyli and thoracic duct. The former drains via ipsilateral retroperitoneal nant disease. The terminology and classification of retroperitoneal
lymph nodes that are concentrated around the external iliac and lymph nodes are based on their location. In classic anatomical descrip-
common iliac vessels and along the lateral aspects of the aorta and tions, the lymph nodes of the retroperitoneum around the abdominal
inferior vena cava. There is considerable overlap between the lymphatic aorta are grouped into pre-aortic, lateral or para-aortic, and retro-aortic
drainage basins of individual viscera. At certain sites, there is a cranio- groups (Fig. 62.13). However, it should be noted that adjacent nodal
caudal sequence of lymph nodes, e.g. para-oesophageal, retrocrural and groups merge into one another with no clear demarcating boundaries.
para-aortic nodes; mediastinal and gastro-oesophageal nodes; and para- Normal lymph node dimensions are very variable. Cross-sectional
sternal, superior and inferior epigastric nodes. Some lymphatic drainage imaging frequently uses 10 mm as an approximate measure for the
occurs directly across the diaphragm to the chest from the bare area of upper limit of normal lymph node dimensions in the adult (Moeller


the liver. and Reif 2000), even though some normal retroperitoneal nodes, such
The paired retroperitoneal viscera drain to lateral aortic (also termed as the portacaval node, are typically larger.
para-aortic) nodes around the origin of their arterial supply. Thus, the
Pre-aortic nodes
kidneys and suprarenal glands drain to nodes around the renal hilum
and to lateral aortic nodes around the origin of the renal arteries (L1–2 The pre-aortic nodes drain the gastrointestinal viscera, including
vertebral level). The testes drain to para-aortic and paracaval nodes the pancreas, liver, and spleen. These nodes lie anterior to the aorta


innervation
1093
26
retPaHC
Pre-aortic Lateral chains. Lymphatic drainage from the right testis is via lymphatics travel-
ling with the gonadal vessels to the right para-aortic and aortocaval
nodes at the level of the second lumbar vertebra, whereas the left testis
drains to the left para-aortic nodes just inferior to the left renal vein
(Paño et al 2011).
Coeliac Iliac nodes
The paired iliac nodes are distributed around the common, external and
Abdominal confluence internal iliac arteries and veins. Constituent groups include: common
Suprarenal
of lymph trunks
Renal iliac, external iliac, internal iliac, circumflex iliac and obturator nodes.
Obturator nodes are located near the obturator foramen and, along
Superior
mesenteric Upper with the iliac nodes, are a common site of lymph node metastasis in
lateral
prostate cancer. ‘Pelvic side-wall’ nodes, lying adjacent to the ilium but
Right lumbar
not associated with a large artery or vein, are also described in the clini-
lymph trunk Gonadal
cal literature. The iliac nodes drain the pelvic viscera and walls, except
Intestinal for the ovaries and those parts of the rectum drained by superior rectal
lymph trunk
drainage pathways (see above). They also drain lymph from the inguinal
nodes and lower limbs.
Inferior
mesenteric
INNERVATION
The posterior abdominal wall contains the lumbar plexus and numer-
Lower
ous autonomic plexuses and ganglia, which lie close to the abdominal
lateral and
aorta and its branches (Fig. 62.14).
common iliac
Median sacral
LUMBAR PLEXUS
The lumbar ventral rami pass laterally into the posterior part of psoas
major, anterior to the transverse processes of the lumbar vertebrae; the
plexus lies in a coronal plane that is in line with the posterior part of
Fig. 62.13 Peri-aortic lymph node groups. The main pre-aortic groups are the vertebral body at L1 but becomes more anterior in the lower lumbar


shown. Only the left-sided lateral aortic (para-aortic) nodes are shown, for spine (Moro et al 2003, Benglis et al 2009) (see Fig. 62.14; Fig. 62.15).
clarity. N.B. The cisterna chyli is more commonly formed by the intestinal
The first four lumbar ventral rami, together with a contribution from
lymph trunk and the left lumbar lymph trunk (rather than the right lumbar
the twelfth thoracic ventral ramus (the dorsolumbar nerve), form the
lymph trunk shown in this diagram).
lumbar plexus. Although there are many variations, the most common
arrangement of the plexus is described here.
The first lumbar ventral ramus is joined by a branch from the twelfth
clustered around its anterior unpaired visceral arteries and can be sub- thoracic ventral ramus, and these roots contribute to the formation of
divided into coeliac, superior mesenteric and inferior mesenteric nodes. the iliohypogastric and ilioinguinal nerves, which run laterally on the
Efferent lymphatics from these nodes contribute to the formation of posterior abdominal wall (see Fig. 62.14). A branch from the ventral
the intestinal lymph trunk. ramus of L1 unites with a branch from the second lumbar ventral ramus
to form the genitofemoral nerve. The second, third and most of the
Coeliac nodes fourth lumbar ventral rami divide into ventral and dorsal divisions; the
These drain lymph from nodes around the stomach, hilum of the ventral divisions unite to form the obturator nerve, while most of
spleen, porta hepatis, cystic duct, lesser omentum, portacaval nodes, the nerve fibres in the dorsal divisions form the femoral nerve. The
peripancreatic nodes and pancreaticoduodenal nodes. They also receive remaining fibres from the fourth lumbar ventral ramus join the fifth
lymph from superior and inferior mesenteric lymph nodes. Efferent lumbar ventral ramus to form the lumbosacral trunk, which descends
lymphatics drain to the intestinal lymph trunk. to join the sacral plexus (p. 1229). Branches from the dorsal divisions
of the second and third lumbar rami unite to form the lateral femoral


superior mesenteric nodes cutaneous nerve (lateral cutaneous nerve of thigh). The accessory obtu-
There is extensive overlap with the drainage territory of coeliac nodes, rator nerve, when present, usually arises from the third and fourth
with subsidiary nodal groups that include peripancreatic, pancreatico- ventral divisions. The lumbar plexus is supplied by branches from the
duodenal, portacaval, small bowel mesenteric, ileocolic, mesocolic and lumbar vessels that supply psoas major.
inferior mesenteric nodes. Efferent lymphatics drain directly to the The branches of the lumbar plexus are listed in Table 62.1.
intestinal lymph trunk or via coeliac nodes. Division of constituent ventral rami into ventral and dorsal branches
is not as clear in the lumbar and sacral plexuses as it is in the brachial
inferior mesenteric nodes plexus. Lateral cutaneous branches of the twelfth thoracic and first
These nodes drain lymph from the hindgut, which includes the distal lumbar ventral rami are drawn into the gluteal skin, but otherwise these
transverse colon, descending and sigmoid colon, and rectum (including nerves are similar to intercostal nerves. The second lumbar ventral
superior rectal, mesorectal and presacral nodes). ramus is more complex. It not only contributes substantially to the
femoral and obturator nerves, but also has an anterior terminal branch
Lateral aortic groups
(the genital branch of the genitofemoral) and a lateral cutaneous
The lateral aortic (or para-aortic) nodes lie on either side of the abdomi- branch (which contributes to the lateral femoral cutaneous nerve and
nal aorta and inferior vena cava anterior to the medial margins of psoas the femoral branch of the genitofemoral nerve). Anterior terminal
major, diaphragmatic crura and sympathetic trunks. Constituent nodal branches of the third to fifth lumbar and first sacral rami are suppressed,
groups that are recognized clinically include: retrocrural (posterior to but the corresponding branches of the second and third sacral rami
the diaphragmatic crura at the aortic hiatus); left and right renal hilar; supply perineal skin.


and aortocaval, paracaval, retrocaval and precaval nodes. Retro-aortic The furcal nerve is an independent nerve with its own ventral and
lymph nodes are also para-aortic and are, therefore, sometimes included dorsal rootlets most commonly arising alongside the L4 nerve root. Its
within the lateral aortic group. The lateral aortic nodes drain into the branches contribute to the femoral and obturator nerves arising from
paired lumbar lymph trunks, one on each side, which terminate directly the lumbar plexus and to the lumbosacral trunk, which joins the sacral
or indirectly in the cisterna chyli and thoracic duct. Lymphatic connec- plexus (Harshavardhana and Dabke 2014). The term furcal refers to its
tions exist between lateral aortic, pre-aortic, retro-aortic and contralat- forked nature since it links the lumbar and sacral plexuses. Occasion-
eral lateral aortic nodes. ally, the furcal nerve arises at the level of the third or the fifth lumbar
The lateral aortic nodes drain the deep layers of the body wall, ret- nerve roots, in which case the sacral plexus is considered prefixed or
roperitoneal paired viscera (including the gonads) and the iliac nodal postfixed, respectively.


Posterior abdominal wall and retroPeritoneum
1094
8
noitCes
Oesophageal opening
Medial arcuate Aortic opening
T12
ligament
Lateral arcuate
L1 ligament
Twelfth rib
Left crus
L2 Psoas major (cut)
Quadratus
Subcostal nerve
lumborum
Iliohypogastric nerve
L3
Transversus Ilioinguinal nerve (cut)
abdominis
Psoas major L4
Psoas minor
Obturator nerve
Iliacus
L5
Lateral femoral
cutaneous nerve Lumbosacral trunk
Sympathetic trunk
Genitofemoral nerve
Sciatic nerve
Femoral nerve
Genital branch of the Psoas major (cut)
genitofemoral nerve
Fig. 62.14 Muscles and nerves of the posterior abdominal wall. The left psoas major has been removed to expose the origins of the lumbar plexus and
quadratus lumborum.
Inflammatory processes, such as retrocaecal appendicitis on the right Sensory
and diverticular abscess on the left, may occur in the posterior abdomi- The iliohypogastric nerve supplies sensory fibres to transversus
nal wall in the tissues immediately anterior to psoas major. These may abdominis, internal oblique and external oblique, and innervates the
irritate one or more branches of the lumbar plexus, causing pain or posterolateral gluteal and suprapubic skin.
sensory disturbance in the distribution of the affected nerves, e.g. the
skin of the thigh, hip or buttock. Injury
The nerve is occasionally injured by a surgical incision in the right iliac
Muscular branches fossa (e.g. during an inguinal hernia repair, open appendicectomy or
trocar placement) but there is rarely any noticeable sensory loss because
Small branches from the lumbar roots supply adjacent muscles such as the suprapubic skin is innervated from several sources. Division of the
psoas major and quadratus lumborum. iliohypogastric nerve above the anterior superior iliac spine may weaken
the posterior wall of the inguinal canal and predispose to formation of
Iliohypogastric nerve a direct inguinal hernia.
Distribution Ilioinguinal nerve


The iliohypogastric nerve usually originates from the L1 ventral ramus
but may arise wholly or in part from the T12 ventral ramus (Klaassen Distribution
et al 2011). It emerges from the upper lateral border of psoas major, The ilioinguinal nerve usually originates from the L1 ventral ramus but
and crosses obliquely behind the lower renal pole on the anterior may receive a contribution from T12 or L2 (Klaassen et al 2011). It
surface of quadratus lumborum. Above the iliac crest, it enters the emerges from the lateral border of psoas major, with or just inferior to
posterior part of transversus abdominis and then runs forwards between the iliohypogastric nerve. It passes obliquely across quadratus lumbo-
transversus abdominis and internal oblique, which it supplies. It gives rum and the upper part of iliacus and enters transversus abdominis
off a lateral cutaneous branch that pierces internal and external oblique about 3 cm medial and 4 cm inferior to the anterior superior iliac spine
above the iliac crest and supplies the posterolateral gluteal skin. It (in the adult); at this site, it is readily blocked by local anaesthetic. In
continues forwards, pierces the internal oblique approximately 3 cm this region, a branch may connect with the iliohypogastric or lateral
medial and 1 cm inferior to the anterior superior iliac spine (in adults), femoral cutaneous nerve (see Fig. 61.5). It pierces internal oblique a
and then penetrates the external oblique aponeurosis approximately little lower down, supplies it, and then traverses the inguinal canal
3 cm above and medial to the superficial inguinal ring to supply the superficial to the spermatic cord or round ligament. It emerges with the
suprapubic skin. The iliohypogastric nerve frequently connects with the cord from the superficial inguinal ring and divides into terminal sensory
ilioinguinal nerve and, less commonly, with the subcostal nerve (see branches.
Fig. 61.5). Numerous anatomical variations are described (Al-dabbagh 2002,
Ndiaye et al 2007). The ilioinguinal and genitofemoral nerves may


Motor interconnect within the inguinal canal and, consequently, each inner-
The iliohypogastric nerve contributes motor nerves to transversus vates the skin of the genitalia to a variable extent (Rab et al 2001,
abdominis and internal oblique, including the conjoint tendon. Cesmebasi et al 2015). The ilioinguinal nerve may pierce the external


innervation
1095
26
retPaHC
T12 Iliohypogastric nerve
Ilioinguinal nerve
L1
Psoas major
L2
Nerve to iliacus
L3
Genitofemoral nerve
L4
Ventral branches of the ventral rami
L5 Femoral nerve
Dorsal branches of the ventral rami
S1
Superior and
Nerve to levator ani inferior gluteal nerves
and external anal sphincter
Sciatic nerve
Pudendal nerve
Perineal nerve
Dorsal nerve of penis or clitoris
Inguinal canal
Ilioinguinal nerve
Nerve to sartorius
Genital branch
Genitofemoral nerve
Femoral branch
Lateral
Obturator externus Intermediate Femoral cutaneous nerves
Medial
Adductor longus
Obturator nerve,
branches to Adductor brevis
Rectus femoris
Adductor magnus
Vastus lateralis
Gracilis Nerves to quadriceps
Vastus intermedius
Cutaneous branch of obturator nerve
Vastus medialis
Posterior femoral cutaneous nerve
Saphenous nerve
Common fibular
Sciatic nerve
Tibial
Fig. 62.15 The lumbar plexus and its branches.
Table 62.1 Branches of the lumbar plexus supplies its territory. Rarely, it may arise as a branch of the genitofemo-
ral nerve.
Muscular T12, L1–4
Iliohypogastric L1 Motor
Ilioinguinal L1 The ilioinguinal nerve supplies motor nerves to transversus abdominis
Genitofemoral L1, L2 and internal oblique; these fibres are given off before the nerve enters
Lateral femoral cutaneous L2, L3 the lateral end of the inguinal canal.
Femoral L2–4 dorsal divisions
Obturator L2–4 ventral divisions Sensory
Accessory obturator L3, L4 The ilioinguinal nerve supplies sensory fibres to transversus abdominis
and internal oblique. It innervates the skin of the proximal medial thigh
and the skin over the root of the penis and upper part of the scrotum
in males, or the skin covering the mons pubis and the adjoining labium


oblique aponeurosis proximal to the superficial inguinal ring or divide majus in females.
into terminal branches within the inguinal canal. It may form a
common trunk with the iliohypogastric nerve as far as the midpoint of Injury
the inguinal canal. It may be very small or completely absent, in which The nerve may be injured or entrapped during inguinal surgery, par-
case the iliohypogastric and genital branch of the genitofemoral nerves ticularly for inguinal hernia, leading to sensory disturbances and pain


Posterior abdominal wall and retroPeritoneum
1096
8
noitCes
over the skin of the genitalia and upper medial thigh (Ndiaye et al Obturator nerve
2007).
The obturator nerve descends within the substance of psoas major to
Genitofemoral nerve emerge from its posteromedial border near the L5 vertebra (Kirchmair
et al 2008). It passes posterior to the common iliac vessels and lateral
Distribution to the internal iliac vessels. It then descends on the lateral wall of the
The genitofemoral nerve originates from the L1 and L2 ventral rami and pelvis attached to the fascia over obturator internus and lies antero-
is formed within the substance of psoas major. It descends obliquely superior to the obturator vessels before running into the obturator
forwards through the muscle to emerge on its anterior surface nearer foramen to enter the thigh. It has no branches in the abdomen or pelvis.
the medial border, opposite the third or fourth lumbar vertebra (Moro The further course and distribution are described on page 1372.
et al 2003). It then descends beneath the peritoneum on psoas major,
crosses obliquely behind the ureter, and divides into genital and femoral Accessory obturator nerve
branches; it may divide close to its origin such that its branches emerge
separately from psoas major. The genital branch crosses the lower part The accessory obturator nerve is sometimes present, more often on the
of the external iliac artery, enters the inguinal canal through the deep left (Katritsis et al 1980). It is usually formed by the ventral rami of L3
ring and accompanies the spermatic cord or round ligament. It exits the and L4. It emerges from the medial border of psoas major and runs
superficial inguinal ring, usually dorsal to the spermatic cord or round along the posterior surface of the superior pubic ramus posterior to
ligament, and supplies the cremaster muscle and skin of the external pectineus, where it gives off branches to supply pectineus and the
genitalia. The femoral branch descends lateral to the external iliac artery hip joint, and may join with the anterior branch of the obturator nerve


before crossing the deep circumflex iliac artery, to pass behind the (p. 1372).
inguinal ligament (occasionally, through it) (Rab et al 2001) and enter
the femoral sheath lateral to the femoral artery. It pierces the anterior
layer of the femoral sheath and fascia lata, and supplies the skin of the LUMBAR SYMPATHETIC SYSTEM
upper part of the femoral triangle. It may connect with the lateral
femoral cutaneous and intermediate femoral cutaneous nerves.
The lumbar part of each sympathetic trunk usually contains four inter-
connected ganglia lying in extraperitoneal connective tissue on the
Motor
anterolateral aspects of the lumbar vertebrae along the medial margin
The genitofemoral nerve innervates cremaster via the genital branch.
of psoas major (see Fig. 62.14). Superiorly, it is continuous with the
thoracic sympathetic trunk posterior to the medial arcuate ligament at
Sensory
the L1/2 vertebral level (Feigl et al 2011). Inferiorly, it passes posterior
The genitofemoral nerve innervates the skin of the scrotum in males,
to the common iliac vessels and is continuous with the sacral sympa-
or that of the mons pubis and labium majus in females, via its genital
thetic trunk. On the right side, it lies posterior to the inferior vena
branch; there is considerable overlap and variability with the cutaneous
cava; on the left, it is posterior to the lateral aortic lymph nodes. It is
distribution of the ilioinguinal nerve (Cesmebasi et al 2015). It also
anterior to most of the lumbar vessels but may pass behind some
innervates the anteromedial skin of the thigh via its femoral branch.
lumbar veins.
The genitofemoral nerve is also understood to play a critical role in
The first, second and, sometimes, the third lumbar ventral rami are
inguinoscrotal descent of the developing testis (Hutson et al 2015).
each connected to the lumbar sympathetic trunk by a white ramus
communicans. All lumbar ventral rami are joined near their origins by
Injury
long, slender grey rami communicantes from the four lumbar sympa-


Like the ilioinguinal nerve, the genital branch may be injured during
thetic ganglia. Their arrangement is irregular: one ganglion may give
inguinal surgery (open and laparoscopic), leading to neuralgic pain
rami to two or three lumbar ventral rami, one lumbar ventral ramus
(Cesmebasi et al 2015).
may receive rami from two ganglia, or grey rami may leave the sympa-
thetic trunk between ganglia (Murata et al 2003).
Femoral nerve
The lumbar sympathetic trunks are vulnerable during retroperito-
neal nodal dissection and their injury can impair seminal emission and
The femoral nerve descends through psoas major and emerges on or lead to retrograde ejaculation.
under its lateral border, about 4 cm above the inguinal ligament (Moore
and Stringer 2011). It passes between psoas major and iliacus deep to
the iliac fascia and runs posterior to the inguinal ligament into the LUMBAR PARASYMPATHETIC SYSTEM
thigh. It gives off branches that supply iliacus and pectineus, and sends
sensory fibres to the femoral artery. Posterior to the inguinal ligament,
The parasympathetic supply to the abdominal viscera is provided by
it lies lateral to the femoral artery and sheath. The further course and
the vagus nerve to the coeliac and superior mesenteric plexuses, and by
distribution are described on page 1372.
pelvic splanchnic nerves that are distributed through the hypogastric
and inferior mesenteric plexuses (Ch. 59).
Lateral femoral cutaneous nerve (lateral
cutaneous nerve of the thigh)
PARA-AORTIC BODIES
The lateral femoral cutaneous nerve (lateral cutaneous nerve of the
thigh) is usually derived from the ventral rami of L2 and 3, but variable The para-aortic bodies (also known as paraganglia or, collectively, as
contributions from L1 to L3 are described (de Ridder et al 1999). It the organ of Zuckerkandl) are collections of neural crest-derived
emerges from the posterolateral border of psoas major and crosses chromaffin tissue found in close relation to the aortic autonomic plex-


iliacus obliquely towards the anterior superior iliac spine. It supplies uses. They are relatively large in the fetus, where they may have a role
sensory fibres to the parietal peritoneum in the iliac fossa. On the right, in maintaining blood pressure by catecholamine secretion. They reach
the nerve passes posterolateral to the caecum, separated from it by the a maximum size at around 3 years of age, and have usually regressed
iliac fascia and peritoneum. The left nerve passes behind the lower part by adulthood. They are usually found as a pair of bodies lying antero-
of the descending colon. Both nerves usually pass behind the inguinal lateral to the aorta in the region of the inferior mesenteric and
ligament about 1–2 cm medial to the anterior superior iliac spine; superior hypogastric plexuses, but multiple smaller collections may
occasionally, they pass through or, rarely, anterior to the ligament (Ray be present. Occasionally, they are found as high as the coeliac plexus
et al 2010). Occasionally, the nerve lies anterior or superior to the ante- or as low as the inferior hypogastric plexus in the pelvis, or are
rior superior iliac spine as it enters the thigh. In the thigh, the lateral closely applied to the sympathetic ganglia of the lumbar chain.
femoral cutaneous nerve usually passes anterior or lateral to sartorius Scattered cells that persist into adulthood may, rarely, be the sites of
but may pierce the muscle. The further course and distribution are paraganglioma (extra-adrenal phaeochromocytoma) (Subramanian
described on page 1371. and Maker 2006).


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26
retPaHC
Key references
KEY REFERENCES
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of the fused enteric mesenteries in the human adult. Am J Anat 70: description of the anatomy of the ilioinguinal and iliohypogastric nerves and
251–9. underline the importance of the ilioinguinal nerve in clinical practice.
Culligan K, Remzi FH, Soop M et al 2013 Review of nomenclature in colonic Loukas M, Wartmann CT, Louis RG Jr et al 2007b Cisterna chyli: a detailed
surgery – proposal of a standardised nomenclature based on mesocolic anatomic investigation. Clin Anat 20:683–8.
anatomy. Surgeon 11:1–5. This article revises traditional concepts about the cisterna chyli and its
Making sense of mesocolic anatomy based on findings from modern formation.
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Mirjalili SA, McFadden SL, Buckenham T et al 2012b A reappraisal of adult
Dodds WJ, Darweesh RMA, Lawson TL et al 1986 The retroperitoneal spaces abdominal surface anatomy. Clin Anat 25:844–50.
revisited. AJR Am J Roentgenol 147:1155–61. A paper that challenges some traditional surface anatomical landmarks by
An important radiologic perspective on the retroperitoneal ‘spaces’. investigating results from analysis of CT scans in living supine adults.
Klaassen Z, Marshall E, Tubbs RS et al 2011 Anatomy of the ilioinguinal and Willard FH, Vleeming A, Schuenke MD et al 2012 The thoracolumbar fascia:
iliohypogastric nerves with observations of their spinal nerve contribu- anatomy, function and clinical considerations. J Anat 221:507–36.
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Ndiaye A, Diop M, Ndoye JM et al 2007 Anatomical basis of neuropathies thoracolumbar fascia.
and damage to the ilioinguinal nerve during repairs of groin hernias


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CHAPTER
63
Peritoneum and peritoneal cavity
The peritoneum is the largest serous membrane in the body, and its colic ligament (Meyers 1973). Passage across the midline to the left
arrangements are complex. In males it forms a closed sac, but in females subphrenic space is prevented by the falciform ligament. Peritoneal
it is open at the lateral ends of the uterine tubes. Although its smooth fluid flows in a predominantly clockwise direction around the perito-
appearance is unremarkable, its structure is complex and varies greatly neal cavity (Fig. 63.1); it reaches the surface of the greater omentum,
in different locations. Directly beneath the monolayer of mesothelium where it is processed by the immune system (Meyers et al 1987, Meyers
is a well-developed basement membrane, outside which is a rich lym- 1994). Malignant cells may become trapped within peritoneal recesses
phatic plexus. Microscopic mesothelial pores or peritoneal stomata are or in the milky spots of the greater omentum, where they may prolifer-
distributed throughout the peritoneum but particularly on the under- ate and produce visible and palpable tumour deposits. These sites must
surface of the diaphragm and anterior abdominal wall (Wassilev et al be deliberately examined when searching for peritoneal metastases
1998). At peritoneal stomata, the mesothelium is in close proximity to (Zonca et al 2008). Gross infiltration of the omentum by cancer, often
underlying lymphatic endothelial cells and there is no intervening base- referred to as an ‘omental cake’, emphasizes the capacity of the omentum
ment membrane. Both peritoneal stomata and sites of lymphoid aggre- to trap malignant cells. The movement of peritoneal fluid explains the
gates (‘milky spots’) in the omenta contribute to peritoneal fluid presence of disease at sites such as the undersurface of the right hemidi-
absorption, and their occlusion by malignant cells may result in ascites aphragm and the pelvic pouches. An example is the Fitz–Hugh–Curtis


(Hagiwara et al 1994). Neighbouring mesothelial cells are joined by syndrome, in which gonorrhoea or chlamydia organisms enter the peri-
junctional complexes but probably permit the passage of macrophages. toneal cavity through the uterine tubes and are transported in the
The submesothelial connective tissue may also contain macrophages, peritoneal fluid to the right upper quadrant, where they cause perihe-
lymphocytes and adipocytes (in some regions). Mesothelial cells may patic inflammation. Disruption of the integrity of the peritoneum by
transform into fibroblasts, which may play an important role in inflam- percutaneous puncture, laparoscopy or open surgery profoundly affects
mation of the peritoneum and the formation of peritoneal adhesions its defensive function and can create ‘sticky’ sites where pathogens or
after surgery (Schnüriger et al 2011). malignant cells can settle and proliferate.
The normal pressure within the peritoneal cavity is about 2–10 mmHg Direct communication of abdominal and pleural spaces called
(higher in pregnancy and obese individuals) (Sanchez et al 2001). It pleuro peritoneal fenestrae may rarely exist (Pestieau et al 2000,
can be measured directly using a catheter inserted into the abdomen, Simmons and Mir 1989).
or indirectly, by monitoring the pressure in the bladder or stomach. The
pressure inside the abdomen may increase after trauma as a result of
PERITONEAL ATTACHMENTS
the accumulation of blood, fluid or oedema, leading to an ‘abdominal
compartment syndrome’. In such patients, monitoring of intra-
abdominal pressure can identify major increases in pressure (above The parietal peritoneum is attached to the muscular layers of the
about 25 mmHg) that could jeopardize the blood flow to vital organs abdominal wall by extraperitoneal connective tissue. Around the
and dictate the need for urgent decompression. bladder and rectum, it is only loosely attached to allow for alterations
in the size of these viscera, whereas it is firmly adherent to the inferior
surface of the diaphragm and linea alba. The extraperitoneal tissue over
PERITONEAL FLUID
the posterior abdominal wall frequently contains large amounts of fat,
especially in obese males. The visceral peritoneum is firmly adherent to


The peritoneal cavity is a potential space between the parietal perito- the underlying viscera and often blends with connective tissue in the
neum, which lines the abdominal wall, and the visceral peritoneum, wall of the organ; it rarely contains loose connective or adipose tissue.
which covers the abdominal viscera and associated mesenteries within The visceral peritoneum is often considered as part of the underlying
the cavity. It contains a small amount of peritoneal fluid that rarely viscus for clinical and pathological purposes such as the staging of
exceeds 5 ml in healthy males and postmenopausal females (Yoshikawa cancer. Because of its attachments, removal of the parietal peritoneum
et al 2013). In healthy young females, up to 25 ml of fluid may be in the management of peritoneal metastases is possible without resec-
present, depending on the phase of the menstrual cycle (Koninckx et al tion of underlying tissues, whereas cancer deposits on visceral perito-
1980). The fluid lubricates the mobile viscera, allowing them to glide neum usually require partial resection of the viscus for complete
freely on the abdominal wall and against each other within the limits removal (see Video 63.1).
imposed by their attachments. However, the parietal peritoneum can
be surgically removed without necessarily having adverse effects on gut
GENERAL ARRANGEMENT OF THE PERITONEUM
function (Sugarbaker 2012). Normal peritoneal fluid contains water,
proteins (less than 30 g of protein per litre), electrolytes and solutes
derived from interstitial fluid in the adjacent tissues and from plasma The alimentary tract develops as a single tube suspended in the coe-
in local capillaries. It also contains a few cells, including desquamated lomic cavity by ventral and dorsal mesenteries (Ch. 60). Ultimately, the
mesothelium, nomadic peritoneal macrophages, mast cells, fibroblasts, ventral mesentery is largely resorbed, although some parts persist in the
lymphocytes and other leukocytes. Macrophages migrate freely between upper abdomen and form structures such as the lesser omentum and
the peritoneal cavity and the surrounding connective tissue. In females, falciform ligament. The mesenteries of the intestines in the adult are


blood or fluid may enter the peritoneal cavity from a ruptured ovarian the remnants of the dorsal mesentery. The migration and subsequent
follicle (mittelschmerz) or from the retrograde flow of menstrual fluid fixation of parts of the gastrointestinal tract produce the so-called ‘ret-
along the uterine tubes (which may cause endometriosis). Peritoneal roperitoneal’ segments of bowel (most of the duodenum, ascending
fluid is absorbed via peritoneal stomata and milky spots (see above). colon, descending colon, and rectum) (Fig. 63.2), and four separate
Under normal circumstances, the peritoneal cavity never contains gas. intraperitoneal bowel loops suspended by mesenteries of variable
The peritoneum and its fluid have important defensive properties lengths. These are all covered by visceral peritoneum, which is continu-
(Autio 1964). Peritoneal fluid gravitates to dependent sites within ous with the parietal peritoneum covering the posterior abdominal
the peritoneal cavity; diaphragmatic respiratory movements, negative wall. The first intraperitoneal loop is formed by the abdominal oesopha-
intrathoracic pressure and intestinal peristalsis encourage flow from the gus, stomach and first part of the duodenum. The second loop is made
pelvis to the subphrenic regions, even when the individual is erect. Fluid up of the duodenojejunal junction, jejunum, ileum and usually the
preferentially ascends from the lower abdomen and pelvis to the right caecum. The third loop contains the transverse colon, and the final loop
subhepatic and subphrenic ‘spaces’ via the right paracolic gutter, which contains the sigmoid colon and occasionally the distal descending
1098 is deeper than the left paracolic gutter and has no obstructing phrenico- colon.


General arrangement of the peritoneum
1099
36
RETPAHC
Falciform ligament Fig. 63.1 The peritoneal cavity.
Left subphrenic space Arrows indicate the flow of
peritoneal fluid. (Courtesy of CM
Left triangular ligament Brown, Office of Visual Media
Right subphrenic space IUSM 2011.)
Retrohepatic bare area
Lesser sac
Right triangular ligament
Phrenicocolic ligament
Right infracolic compartment
Left paracolic gutter
Root of the mesentery
Right paracolic gutter
Left infracolic compartment
Sigmoid mesocolon
Right pararectal space Left pararectal space
Where visceral peritoneum encloses or suspends organs within the and Hricak 1999). It has a complex attachment to the wall of the
peritoneal cavity, the peritoneum and related connective tissues form abdominal cavity and forms the falciform ligament, coronary liga-
‘peritoneal ligaments’, omenta or mesenteries. All but the greater ments, lesser omentum (gastrohepatic and hepatoduodenal ligaments),
omentum are composed of two layers of visceral peritoneum separated greater omentum (including the gastrocolic ligament), gastrosplenic
by variable amounts of fatty connective tissue. The greater omentum is ligament, splenorenal ligament and phrenicocolic ligament (see Fig.
folded back on itself and therefore consists of four layers of visceral 63.2; Figs 63.3–63.5).
peritoneum separated by variable amounts of adipose tissue. Mesenter-
ies attach their respective viscera to the posterior abdominal wall; the Falciform ligament
attachment of the mesentery of the small intestine to the posterior
abdominal wall is referred to as the root of the mesentery (see Fig.
The falciform ligament is a thin anteroposterior double fold of perito-
63.2). The mesenteries contain the neurovascular bundles and lym-
neum that connects the liver to the posterior aspect of the anterior
phatic channels that supply the suspended organs. In obese individuals,
abdominal wall just to the right of the midline. Adjacent to the ante-
extensive adipose tissue within the mesenteries and omenta may


rior abdominal wall, it contains a variable amount of fat (Feldberg and
obscure these neurovascular bundles. In contrast, in the very young, the
van Leeuwen 1990). It extends inferiorly to the level of the umbilicus
elderly or the malnourished, the mesenteries and omenta may contain
and superiorly it narrows to a depth of 1–2 cm as the distance between
little adipose tissue and the neurovascular bundles are more obvious.
the liver and anterior abdominal wall decreases. Its two peritoneal
Although they are described as intraperitoneal, the suspended
layers separate to enclose the liver, to which it is firmly adherent. Supe-
viscera, strictly speaking, do not lie within the peritoneal cavity because
riorly, the two peritoneal layers are continuous with the parietal
they are covered by visceral peritoneum. They are in continuity with
peritoneum on the undersurface of the diaphragm but are reflected
extraperitoneal tissues, including the retroperitoneum. The loose
laterally to form the superior layer of the coronary ligament of the liver
areolar connective tissue that forms the extraperitoneal and retroperi-
on the right and the left triangular ligament of the liver on the left. The
toneal tissues is often divided into potential ‘spaces’ as evidenced by
inferior aspect of the falciform ligament forms a free border, where the
the presence of discrete collections of fluid or blood in pathological
two peritoneal layers are continuous with each other as they enclose
conditions (see Figs 62.4–62.6).
the ligamentum teres. Because the peritoneum of the falciform liga-
ment is in continuity with that covering the posterior abdominal wall
and with the parietal peritoneum of the anterior abdominal wall,
PERITONEUM OF THE UPPER ABDOMEN blood from a retroperitoneal haemorrhage (commonly, acute haemor-
rhagic pancreatitis) may track between the folds of peritoneum and
The abdominal oesophagus, stomach, liver and spleen all lie within a appear as haemorrhagic discolouration around the umbilicus (Cullen’s
double fold of visceral peritoneum that runs from the posterior to the sign). The bloodstained fluid reaches the periumbilical region via the


anterior abdominal wall. This fold has no recognized name but has lesser omentum and falciform ligament or via the pararenal spaces and
been referred to as the mesogastrium, from which it is derived (Coakley abdominal wall.


PERiTonEum And PERiTonEAl CAviTy
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noiTCES
W X Y
Left triangular ligament of liver
Upper recess of lesser sac
A A
Oesophagus
Coronary ligament of liver
Left gastric artery
Splenorenal ligament
Right triangular ligament of liver Epiploic foramen
B B
Cut edge of lesser omentum Common hepatic artery
C C
Root of transverse mesocolon,
adherent to posterior layers
of greater omentum
Root of the mesentery
Root of sigmoid mesocolon
W X Y
Fig. 63.2 The posterior abdominal wall, showing the lines of peritoneal reflection, after removal of the liver, spleen, stomach, jejunum, ileum, caecum,
transverse colon and sigmoid colon. The various sessile (retroperitoneal) organs can be seen through the posterior parietal peritoneum. Note the
ascending and descending colon, duodenum, kidneys, suprarenal glands, pancreas and inferior vena cava. Line W–W represents the plane of Figure
63.3. Line X–X represents the plane of Figure 63.4. Line Y–Y represents the plane of Figure 63.5. Line A–A represents the plane of Figure 63.6A. Line
B–B represents the plane of Figure 63.6B. Line C–C represents the plane of Figure 63.6C.
Peritoneal connections of the liver
kidney is known as the hepatorenal pouch (of Morison) (Stringer
2009). In the supine position, this is the most dependent part of the
The liver is almost completely covered in visceral peritoneum; only the peritoneal cavity in the upper abdomen and is a site where fluid or
‘bare area’ posteriorly is in direct contact with the right hemidiaphragm. peritoneal metastases may localize.
Peritoneal ligaments run from the liver to the surrounding viscera and The lower layer of the coronary ligament is continuous with the
to the abdominal wall and diaphragm (see Fig. 63.2; Fig. 63.6); they peritoneum that descends over the anterior surface of the right kidney
are described in detail in Chapter 67. and to the front of the first part of the duodenum and hepatic flexure


The coronary ligament is formed by the reflection of the peritoneum of the colon (see Fig. 63.2). Medially, it passes in front of a short
from the diaphragm on to the superior and posterior surfaces of the segment of the inferior vena cava lying between the first part of the
right lobe of the liver. Between the two layers of this ligament, a large duodenum below and the caudate process of the liver above, forming
triangular area, the ‘bare area’ of the liver, is devoid of peritoneal cover- the posterior wall of the epiploic foramen. This narrow strip broadens
ing. Here, the liver is connected to the diaphragm by areolar tissue, out as the peritoneum continues across the midline on to the posterior
which is in continuity inferiorly with the anterior pararenal space. On wall of the lesser sac.
the right, the two layers of the coronary ligament converge laterally to The right triangular ligament is a short, V-shaped fold at the right
form the right triangular ligament. On the left, the two layers fuse to lateral limit of the bare area of the liver, where the two layers of the
form the left triangular ligament. The upper layer of the coronary liga- coronary ligament converge. It is continuous with the peritoneum of
ment is reflected superiorly on to the undersurface of the diaphragm the right posterolateral abdominal wall. Surgical division of the right
and inferiorly on to the right and superior surfaces of the liver. The triangular and coronary ligaments allows the right lobe of the liver to
lower layer of the coronary ligament is reflected inferiorly from the be retracted forwards, exposing the lateral aspect of the inferior vena
posterior surface of the liver on to the posterior abdominal wall over cava behind the liver.
the right suprarenal gland and kidney. The peritoneal recess formed The left triangular ligament is a double layer of peritoneum that
between the inferior surface of the liver and the upper pole of the right extends for a variable length over the superior border of the left lobe


General arrangement of the peritoneum
1101
36
RETPAHC
of the liver. Medially, the anterior leaf is continuous with the left layer ment allows the left lobe of the liver to be mobilized. The left triangular
of the falciform ligament, while the posterior layer is continuous with ligament is an important stabilizing factor for the left lobe after excision
the lesser omentum. The left triangular ligament lies in front of the of the right lobe of the liver.
abdominal oesophagus, the upper limits of the lesser omentum, and The peritoneum of the left triangular ligament is continuous with
part of the fundus of the stomach. Division of the left triangular liga- that lining the undersurface of the left dome of the diaphragm, which,
in turn, is continuous with that lining the posterior abdominal wall.
Here it passes behind the spleen on to the most lateral part of the
mesentery of the transverse colon and the splenic flexure. It continues
down lateral to the descending colon into the pelvis, forming the left
Diaphragm paracolic gutter. Medially, the peritoneum covering the left upper pos-
terior abdominal wall is reflected anteriorly to merge with the upper
Right subphrenic space end of the lesser omentum, the peritoneum overlying the left aspect of
the abdominal oesophagus, and the left layer of the gastrosplenic liga-
ment (see Fig. 63.2).
Bare area of the liver Parietal peritoneum lines the posterior abdominal wall over the
diaphragmatic crura, the upper abdominal aorta and its associated
branches, lymph nodes and nerve plexuses, and the upper anterior
surface of the pancreas. Below the liver, it continues down the posterior
Right suprarenal gland abdominal wall, forming the right paracolic gutter between the antero-
lateral abdominal wall and the ascending colon.
Right subhepatic space
Lesser omentum
Right kidney The lesser omentum is formed by two layers of peritoneum separated
by a variable amount of connective tissue and fat. It is derived from the
Second part of the
ventral mesogastrium. It runs between the inferior visceral surface of
duodenum
the liver and the abdominal oesophagus, stomach, pylorus and first part
of the duodenum. Superiorly, its attachment to the inferior surface of


Right end of transverse
the liver forms an L shape. The vertical component of the L is formed
mesocolon
by the fissure for the ligamentum venosum; inferiorly, the attachment
turns horizontally to complete the L in the porta hepatis. The part of
the lesser omentum running between the liver and the stomach is
Right end of
known as the gastrohepatic ligament and the part between the liver and
transverse colon
duodenum is the hepatoduodenal ligament. The right and left gastric
vessels, branches of the vagus nerves and lymph nodes are contained
within the two layers of the gastrohepatic ligament close to its gastric
attachment. An accessory or replaced left hepatic artery is sometimes
present (p. 1166). The anterior layer of the lesser omentum descends
from the fissure for the ligamentum venosum on to the anterior surface
of the abdominal oesophagus, stomach and duodenum. The posterior
layer descends from the fissure and runs on to the posterior surface of
Fig. 63.3 A sagittal section through the abdomen to the right of the the stomach and pylorus. At the lesser curvature of the stomach, the
epiploic foramen along the line of W–W in Figure 63.2. peritoneal layers of the lesser omentum split to enclose the stomach
Fig. 63.4 A section through the upper part of
the abdominal cavity, along the line X–X in
Figure 63.2. The boundaries of the epiploic
foramen are shown and a small recess of the
Liver lesser sac is displayed anterior to the head
of the pancreas. Note that the transverse
colon and its mesocolon are adherent to the
posterior two layers of the greater omentum.
Four peritoneal layers contribute to the
formation of the greater omentum because
Accessory hepatic vein
the apron of omentum is folded back on
itself.
Right branch of hepatic artery
Epiploic foramen
Bile duct
Duodenum, first part
Inferior vena cava
Head of pancreas
Transverse mesocolon,
adherent to greater omentum
Transverse colon
Greater omentum
Duodenum, third part
Superior mesenteric vein


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Fig. 63.5 A sagittal section through the
abdomen, approximately in the median
plane. Compare with Figure 63.2. The section
cuts the posterior abdominal wall along the
line Y–Y in Figure 63.2. The peritoneum is
shown in blue except along its cut edges,
which are left white.
Lesser omentum in fissure
for ligamentum venosum
Caudate lobe of liver
Lesser omentum
Lesser sac
Hepatic artery
Neck of pancreas
Antrum of stomach
Superior mesenteric artery
Uncinate process of head of pancreas
Duodenum, third part
Transverse mesocolon, adherent to
posterior layers of greater omentum
Transverse colon
Mesentery of the small intestine
Greater omentum
and are continuous with the visceral peritoneum covering the anterior sheet and is attached to the greater curve of the stomach (see Fig. 63.5);
and posterior surfaces of the stomach. The posterior layer of the lesser this supracolic part of the greater omentum is known as the gastrocolic
omentum forms part of the anterior surface of the lesser sac (see ligament. The most anterior layer of peritoneum of the greater omentum
Fig. 63.5). is continuous with the visceral peritoneum over the anterior surface of
The free right lateral border of the lesser omentum is thickened and the stomach and duodenum. The anterior sheet descends from the
extends from the porta hepatis to the junction between the first and greater curvature of the stomach and first part of the duodenum for a
second parts of the duodenum. This free border forms the anterior variable distance into the peritoneal cavity and then turns sharply back-
boundary of the epiploic foramen and contains the portal vein (poste- wards on itself to ascend as the posterior sheet. The posterior sheet
riorly), the bile duct (anteriorly to the right), and hepatic artery proper passes anterior to the transverse colon and transverse mesocolon, and
(anteriorly to the left) (see Fig. 63.6B), together with lymphatics, lymph is attached to the posterior abdominal wall above the origin of the


nodes and hepatic autonomic nerves. An accessory or replaced right transverse mesocolon and anterior to the head and body of the pancreas
hepatic artery arising from the superior mesenteric artery may some- (see Figs 63.2, 63.5). The anterior peritoneal layer of the posterior sheet
times be found in the free edge of the lesser omentum, usually running is continuous with the peritoneum of the posterior wall of the lesser
posterior to the portal vein. Occasionally, the free margin of the lesser sac. The posterior peritoneal layer is reflected sharply inferiorly and is
omentum extends to the right and runs on to the gallbladder, when it continuous with the anterior layer of the transverse mesocolon. The
is referred to as the cystoduodenal ligament (Ashaolu et al 2011). posterior sheet is adherent to the transverse colon and its mesentery. In
The upper border of the lesser omentum is short and runs over the early fetal life, the greater omentum and transverse mesocolon are sepa-
inferior surface of the diaphragm between the liver and medial aspect rate structures, and this arrangement occasionally persists. During
of the abdominal oesophagus. The lesser omentum is thinner in this surgery, the natural adhesions between the transverse mesocolon and
region and may be fenestrated or incomplete; variations in thickness greater omentum can be divided, and the greater omentum can be
are dependent on the amount of connective tissue, especially fat. detached from the transverse colon and mesocolon if required. Access
into the lesser sac can then be obtained by dividing the upper part of
the posterior sheet of greater omentum. This gives a relatively bloodless
Greater omentum
surgical approach to the posterior wall of the stomach and the anterior
surface of the pancreas.
The greater omentum is the largest peritoneal fold and hangs inferiorly On the left side of the abdomen, the greater omentum is continuous
from the greater curvature of the stomach. When the undisturbed with the gastrosplenic ligament; on the right side, it extends to the
abdomen is opened, the greater omentum is frequently draped over the beginning of the duodenum (see Fig. 63.2). A fold of peritoneum, the


upper abdominal organs, but often not in the even distribution shown hepatocolic ligament, may run from either the inferior surface of
in many illustrations. It is usually thin but always contains some the right lobe of the liver or the first part of the duodenum to the right
adipose tissue and is a common site for storage of fat in obese individu- side of the greater omentum or hepatic flexure of the colon. The right
als, particularly males (Coulier 2009). The greater omentum is a double border of the greater omentum is usually adherent to the anterior
sheet: each sheet consists of two layers of peritoneum separated by surface of the hepatic flexure and upper ascending colon but its perito-
a scant amount of connective tissue. The two sheets are folded back neal layers are not continuous with the visceral peritoneum over this
on themselves and firmly adherent to each other below the transverse part of the colon. The right border of the greater omentum may also be
colon. Above this level the anterior sheet separates from the posterior attached to a thin but vascular peritoneal band (Jackson’s membrane),


General arrangement of the peritoneum
1103
36
RETPAHC
A
Falciform ligament Left anterior perihepatic space
Left posterior perihepatic space
Right lobe of liver
Upper limit of lesser omentum
Superior recess of lesser sac
Fundus of stomach
Right subphrenic space
Aorta Left anterior subphrenic space
Inferior vena cava Spleen
Bare area of liver
Left posterior subphrenic space
Right inferior pleural recess
Inferior lobe of left lung
B
Falciform ligament
Hepatic artery
Stomach
Free border of the lesser omentum
Left gastroepiploic artery
within gastrosplenic ligament
Right lobe of liver
Gallbladder
Spleen
Common bile duct
Portal vein
Splenic artery within
splenorenal ligament
Epiploic foramen
Inferior vena cava Superior recess of lesser sac
Aorta Left suprarenal gland
C
Pylorus
Falciform ligament
Right lobe of liver
Stomach
Gallbladder
Gastroduodenal artery Lesser sac
Neck of pancreas
Transverse mesocolon
Head of pancreas
Transverse colon
Common bile duct
Left end of greater omentum
Portal vein
Descending colon
Inferior vena cava
Body of pancreas
Aorta
Fig. 63.6 Transverse sections through the abdomen. A, At the level of the line A–A in Figure 63.2. The line passes through the bare area of the liver at
the superior end of the lesser omentum. The parts of the left subphrenic space are clearly seen, although they are continuous with each other. B, At the
level of line B–B in Figure 63.2, viewed from below. The peritoneal cavity is shown by blue shading; the peritoneum and its cut edges are in pale blue.
C, A transverse section through the abdomen at the level of the line C–C in Figure 63.2, viewed from below. Colours as in Figure 63.2.


PERiTonEum And PERiTonEAl CAviTy
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which, when present, runs from the anterior aspect of the ascending extends from the splenic flexure of the colon to the diaphragm at about
colon and caecum to the posterolateral abdominal wall. Other perito- the level of the eleventh rib. Inferiorly, it is continuous with the perito-
neal folds between the ascending colon and posterolateral abdominal neum of the lateral end of the transverse mesocolon near the tip of the
wall in the right lateral paracolic gutter are occasionally present. Less pancreatic tail, and the splenorenal ligament at the hilum of the spleen.
commonly, the left border of the greater omentum is adherent to the Undue traction on the peritoneal attachments of the spleen at
anterior surface of the descending colon. surgery may cause a capsular tear and serious bleeding. Downward trac-
The greater omentum has a rich blood supply derived from the right tion on the phrenicocolic ligament during mobilization of the splenic
and left gastroepiploic vessels that run between the two peritoneal flexure is particularly hazardous; medial traction on the greater
layers of the anterior sheet of greater omentum, close to the greater omentum may also injure the spleen if the omentum is adherent to the
curvature of the stomach. These vessels give off numerous omental splenic capsule.
(epiploic) branches that run the length of the omentum. Microscopic
capillary convolutions, sometimes termed ‘omental glomeruli’, lie
directly beneath the mesothelium of the greater omentum. They are PERITONEUM OF THE LOWER ABDOMEN
surrounded by aggregations of macrophages and lymphocytes (milky
spots) that drain into lymphatic channels (Shimotsuma et al 1993); the The posterior surface of the lower anterior abdominal wall is lined by
macrophages form clusters near the mesothelial surface, while B and T parietal peritoneum, which extends from the linea alba centrally to the
lymphocytes are grouped around vessels. The fenestrated endothelium lateral paracolic gutters, where it is reflected over the front and sides of


lining the omental glomeruli and the mesothelium overlying the milky the ascending colon on the right and the descending colon on the left
spots share a similar mesodermal origin and together they form sites (see Fig. 63.2). Occasionally, the ascending and descending colon are
of leukocyte migration and peritoneal fluid absorption (Platell et al suspended by a short mesentery from the posterior abdominal wall
2000). The number and size of milky spots increase in the presence of (Ch. 66). Between the ascending and descending colon, the peritoneum
peritoneal inflammation, highlighting their defensive role. covers the posterior abdominal wall, except where it is reflected over
The greater omentum serves several important functions. It is highly the oblique root of the mesentery of the small intestine. Over the pos-
mobile and frequently becomes adherent to inflamed viscera or foreign terior abdominal wall, it covers psoas major and quadratus lumborum,
bodies within the abdominal cavity. This can limit the spread of infec- the inferior vena cava, duodenum, vertebral column and both ureters.
tion, as in the walling off of acute appendicitis, and promote haemo- In the upper abdomen, the posterior parietal peritoneum is reflected
stasis. However, it may also block peritoneal drains and catheters (such anteriorly where it is continuous with the peritoneum of the posterior
that omentectomy is sometimes performed when placing some intra- layer of the transverse mesocolon.
peritoneal catheters). It absorbs peritoneal fluid. It contains macro-
phages and lymphoid tissue capable of destroying pathogens; Transverse mesocolon
macrophages and neutrophils readily migrate from the greater omentum
into the peritoneal cavity in the presence of peritonitis. It promotes
The mesentery of the transverse colon is a broad fold of visceral peri-
neovascularization of structures to which it becomes adherent and thus
toneum reflected anteriorly from the posterior abdominal wall. It sus-
promotes healing of ischaemic tissues and supports splenic autotrans-
pends the transverse colon in the peritoneal cavity. The root of the
plantation (Ch. 70). It is rarely the site of primary pathology; reports
transverse mesocolon passes obliquely from the anterior aspect of the


of segmental infarction, torsion or other disorders are rare.
second part of the duodenum, over the head and neck of the pancreas,
The remarkable capacity of the greater omentum to participate in
superior to the duodenojejunal junction over the upper pole of the left
reparative processes is highlighted by its use as an omental pedicle flap
kidney to the splenic flexure (see Fig. 63.2). It varies considerably in
or free flap in reconstructive surgery. It has been used to close gastroin-
length but is shortest at either end. It contains the middle colic vessels
testinal perforations, fill ‘dead space’ after surgical excision of pathol-
and their branches, together with autonomic nerves from the aortic
ogy, and cover wound defects. A greater omental pedicle or free flap
plexus, lymphatics and lymph nodes. Near the splenic flexure, the
based on the right gastroepiploic vessels may be mobilized by dividing
ascending branch of the left colic artery terminates within the transverse
the gastric branches of these vessels close to the surface of the stomach
mesocolon. Its two peritoneal layers pass to the posterior surface of the
and the left gastroepiploic vessels near their origin.
transverse colon, where they separate to invest the colon. The upper
layer of peritoneum is continuous with the posterior layer of the greater
Peritoneal connections of the spleen omentum, to which it is adherent (see Fig. 63.5). The lower layer of
peritoneum of the transverse mesocolon is continuous with the perito-
neum of the posterior abdominal wall. Lateral extensions of the trans-
The peritoneal connections of the spleen anchor it in the left upper
verse mesocolon produce two folds: on the right, the duodenocolic
quadrant of the abdomen; they include the gastrosplenic, splenorenal
ligament extends from the transverse mesocolon at the hepatic flexure
and phrenicocolic ligaments. The gastrosplenic ligament runs between
to the second part of the duodenum; on the left, the phrenicocolic liga-
the greater curvature of the stomach and the hilum of the spleen, and
ment extends from the transverse mesocolon at the splenic flexure to


is in continuity with the left side of the greater omentum. The peritoneal
the diaphragm. The root of the transverse mesocolon is closely related
layers of the gastrosplenic ligament separate to enclose the spleen and
to the upper limit of the root of the mesentery of the small intestine
then rejoin to form the splenorenal and phrenicocolic ligaments. The
near the uncinate process of the pancreas.
splenorenal ligament extends from the spleen to the posterior abdomi-
nal wall, and the phrenicocolic ligament connects the splenic flexure of
Mesentery of the small intestine
the colon to the diaphragm.
The splenorenal ligament is formed from two layers of peritoneum
(see Fig. 63.6B). The anterior layer is continuous medially with the The mesentery of the small intestine is arranged as a complex fan that
peritoneum of the posterior wall of the lesser sac over the left kidney is formed from two layers of peritoneum (anterosuperior and postero-
and runs up to the splenic hilum, where it is continuous with the pos- inferior) separated by fatty connective tissue containing vessels and
terior layer of the gastrosplenic ligament. The posterior layer of the nerves. The root of the mesentery lies along a line running diagonally
splenorenal ligament is continuous laterally with the peritoneum over from the duodenojejunal flexure on the left side of the second lumbar
the inferior surface of the diaphragm and runs on to the splenic surface vertebral body to the right sacroiliac joint (see Fig. 63.2). The root
over the renal impression. The splenic vessels lie between the layers of crosses over the third part of the duodenum, abdominal aorta, inferior
the splenorenal ligament, and the tail of the pancreas is usually present vena cava, right ureter and right psoas major. The average length of the
in its lower portion. root of the mesentery is 15 cm in adults while along its intestinal
The gastrosplenic ligament is also formed from two layers of perito- attachment it measures the same length as the small intestine (approxi-


neum (see Fig. 63.6B). The posterior layer is continuous with the peri- mately 5 m). Consequently, the mesentery is usually thrown into mul-
toneum of the splenic hilum and the peritoneum over the posterior tiple folds along its intestinal border. The average depth of the mesentery
surface of the stomach. The anterior layer is continuous with the peri- from the root to the intestinal border is 20 cm, but this varies along the
toneum reflected off the gastric impression of the spleen and with the length of the small intestine: it is shortest at the jejunum and terminal
peritoneum over the anterior surface of the stomach. The short gastric ileum, and longest in the mid-ileal region. Its two peritoneal layers
and left gastroepiploic branches of the splenic artery, with their corre- contain the jejunal and ileal branches of the superior mesenteric vessels,
sponding veins, pass between the layers of the gastrosplenic ligament. nerves related to the superior mesenteric plexus, lymphatics and
A fan-shaped fold of peritoneum often extends from the anterior aspect regional lymph nodes. The length and mobility of the mesentery may
of the gastrosplenic ligament below the inferior pole of the spleen and make it difficult to determine the site and orientation of a loop of small
blends with the phrenicocolic ligament. The phrenicocolic ligament intestine through a small surgical incision. Tracing the continuity of a


General arrangement of the peritoneum
1105
36
RETPAHC
peritoneal layer of the mesentery on to the posterior abdominal wall
may be useful in orientating an isolated loop if the duodenojejunal Umbilicus
flexure or ileocaecal junction is not readily accessible. The mesentery of Posterior
the small intestine is sometimes joined to the transverse mesocolon at layer of
the duodenojejunal flexure by a peritoneal band. Occasionally, the rectus
fourth part of the duodenum possesses a very short mesentery that is sheath
continuous with the upper end of the root of the mesentery of the small Arcuate
intestine. Additional bands of peritoneum may connect the terminal line
ileum to the posterior abdominal wall. The root of the mesentery of Inferior
the small intestine is continuous with the peritoneum that surrounds epigastric
the appendix and caecum in the right iliac fossa. vessels
Testicular
Mesoappendix vessels
The mesentery of the appendix is a fatty, triangular fold of peritoneum External iliac
that passes between the posterior surface of the mesentery of the termi- artery and vein
nal ileum close to the ileocaecal junction and the vermiform appendix. Lateral
It may end short of the tip of the appendix, in which case a thin, shallow inguinal
fold of peritoneum containing fat is present towards the tip. It encloses fossa Medial
the blood vessels, nerves and lymph vessels of the vermiform appendix, umbilical fold
and usually contains a lymph node. A small fold of peritoneum runs Median
Medial
between the terminal ileum and the anterior layer of the mesoappendix inguinal fossa umbilical fold
(the ‘bloodless fold of Treves’), and another fold of peritoneum con-
Supravesical fossa Ureter
taining the anterior caecal artery may extend from the terminal ileal
mesentery to the anterior wall of the caecum (see below). Urinary bladder Vas deferens
Fig. 63.7 The infra-umbilical part of the anterior abdominal wall of a male
Sigmoid mesocolon subject: posterior surface, with the peritoneum in situ.