with an estimated 70,530 new cases and 14,680 deaths in the united states in 2010 , bladder cancer is the most common malignancy of the urothelium and kidneys .
metachronous disease is common , and surveillance for additional tumors is a lifelong challenge in patients with bladder cancer .
ct urography ( ctu ) is defined as a ct examination of the urinary tract that is performed both before and after intravenous ( iv ) contrast material , and includes excretory phase images .
ctu is emerging as the imaging test of choice for the evaluation of the urinary tract for a variety of disorders , including hematuria .
although the precise role of ctu has not been defined , recent data suggest that ctu can be used to detect bladder cancer with a sensitivity and specificity close to cystoscopy .
this article reviews the anatomic variants and benign entities that mimic bladder cancer at ctu .
although techniques vary among institutions , the goal of ctu is to achieve a set of images that include a fully opacified and distended intrarenal collecting system , ureters , and bladder .
we obtain an unenhanced ct scan of the abdomen and pelvis to identify calculi , including those in the bladder , that could be masked by excreted contrast material .
unenhanced ct scans also allow measurement of the native attenuation of masses throughout the urinary tract that can be used to assess for enhancement . in patients over the age of 40 years , we image the kidneys in the nephrographic phase at 100  s after contrast material injection ( 80  ml of iodinated contrast material ; 370  mg i / ml ) , to detect and characterize renal masses
. an excretory phase scan of the abdomen and pelvis is obtained at 15  min . in patients 40 years or younger , a split - bolus , two - phase protocol is used to limit radiation exposure . following an unenhanced scan of the abdomen and pelvis , 40  ml of iv contrast medium are administered . after an 8-min delay , 80  ml of iv contrast medium are administered and followed by a scan of the abdomen and pelvis at 100  s. both protocols may be augmented with 250  ml of iv normal saline infused during the delay periods .
we prefer to administer 10  mg of iv furosemide ( lasix ; abbott laboratories , north chicago , il ) 23  min before the intravenous contrast material in patients over the age of 40 years .
furosemide , and to some extent saline , contribute to distension of the upper urinary tracts and bladder during excretory phase imaging .
an underdistended bladder can appear thickened , particularly along its anterior wall , and mimic bladder cancer ( fig .
1 ) . since the specific gravity of contrast medium is higher than urine , incomplete mixing of unopacified urine and contrast material often results in a urine contrast level .
furosemide increases urinary flow rate , thereby increasing both distention and mixing of the contrast material , the latter likely via an increased ureteral jet phenomenon .
others have used a log - rolling technique to promote mixing of contrast material and urine in the bladder .
wide window settings may be required , particularly if ctu is not supplemented with furosemide , as dense contrast material may obscure small urothelial masses ( fig .
2 ) . 
 figure 1(a ) a 67-year - old man with painless hematuria .
axial image from the unenhanced phase of a ct urogram shows apparent thickening of the anterior bladder wall ( arrowheads ) concerning for bladder cancer .
( b ) axial image from the excretory phase of a ct urogram supplemented with iv furosemide demonstrates that the bladder is normal .
the bladder is well distended , and the urine and contrast material are mixed providing a homogeneous background ideal for detection of bladder masses . 

axial image from the excretory phase of a ct urogram ( window level 50 , window width 350 ) supplemented with iv normal saline demonstrates a distended bladder with dense contrast material layering dependently .
( b ) same image viewed with a wider windowing ( window level 50 , window width 630 ) demonstrates a 2-mm papillary urothelial carcinoma ( arrowhead ) that was obscured using soft tissue windows .
axial image from the unenhanced phase of a ct urogram shows apparent thickening of the anterior bladder wall ( arrowheads ) concerning for bladder cancer .
( b ) axial image from the excretory phase of a ct urogram supplemented with iv furosemide demonstrates that the bladder is normal .
the bladder is well distended , and the urine and contrast material are mixed providing a homogeneous background ideal for detection of bladder masses .
axial image from the excretory phase of a ct urogram ( window level 50 , window width 350 ) supplemented with iv normal saline demonstrates a distended bladder with dense contrast material layering dependently .
( b ) same image viewed with a wider windowing ( window level 50 , window width 630 ) demonstrates a 2-mm papillary urothelial carcinoma ( arrowhead ) that was obscured using soft tissue windows .
the distended bladder has a round or oval form with a peritoneum - covered dome .
the remaining surfaces of the bladder abut the extraperitoneal space . the apex of the bladder , connected to the umbilicus by the urachus during embryologic development , is directed anterosuperiorly ; the bladder neck is positioned inferiorly .
a prominent urachal remnant may cause focal nodularity at the anterosuperior aspect of the bladder and mimic a mass ( fig .
3 ) . this pitfall may be avoided by noting that the thickening is limited to the serosal side of the bladder , midline , and is contiguous with the fibrous urachal remnant ( the median umbilical ligament ) extending anterosuperiorly towards the umbilicus . 

figure 3(a ) a 31-year - old woman with hematuria and a prominent urachal remnant .
axial image from the excretory phase of a ct urogram demonstrates focal thickening of the anterior bladder wall in the midline ( arrow ) .
( b ) sagittal image from the excretory phase of a ct urogram demonstrates thickening limited to the serosal surface of the bladder wall ( arrow ) .
also note a thin linear remnant extends from the bladder dome to the umbilicus ( arrowheads ) .
the urine analysis was normal 2 years after the examination , and no cause for the patient s hematuria was found .
( a ) a 31-year - old woman with hematuria and a prominent urachal remnant .
axial image from the excretory phase of a ct urogram demonstrates focal thickening of the anterior bladder wall in the midline ( arrow ) .
( b ) sagittal image from the excretory phase of a ct urogram demonstrates thickening limited to the serosal surface of the bladder wall ( arrow ) . also note a thin linear remnant extends from the bladder dome to the umbilicus ( arrowheads ) .
the urine analysis was normal 2 years after the examination , and no cause for the patient s hematuria was found .
the internal urethral orifice is located at the bladder neck at the inferior angle of the trigone .
the ureters traverse a short , oblique , intramuscular course before opening at the posterolateral angles of the trigone at the ureterovesical junction ( uvj ) .
the intramural ureter may appear to protrude into the bladder lumen , and can simulate a bladder mass depending on the location of the uvj , the angle at which the ureter inserts , and the imaging plane ( fig .
a tumor can often be excluded by noting that the bulge is subtle , located at the uvj , and bilateral , with symmetry in at least one imaging plane . in contradistinction ,
5 ) typically cause more mass effect . however , benign processes such as post - operative changes ( fig . 6 ) and endometriosis ( fig .
figure 4(a ) an 84-year - old man with a history of bladder cancer and normal ct urogram .
axial image from the excretory phase of a ct urogram shows apparent thickening of a normal left ureterovesical junction ( uvj ) ( arrow ) .
( b ) coronal reformations demonstrate normal symmetric appearance of the bilateral ureterovesical junctions ( arrows ) .
axial image from the excretory phase of a ct urogram shows mild asymmetric thickening of the left uvj ( arrow ) .
axial image from the excretory phase of a ct urogram demonstrates focal wall thickening ( arrow ) just anterolateral to the right uvj ( arrowhead ) , at the site of the previous resection .
urine cytology was negative , and cystoscopic biopsy demonstrated postoperative inflammatory changes . note the normal left uvj ( curved arrow ) . 

axial image from the excretory phase of a ct urogram demonstrates focal mass - like wall thickening just superolateral to the right uvj ( arrow ) .
( a ) an 84-year - old man with a history of bladder cancer and normal ct urogram .
axial image from the excretory phase of a ct urogram shows apparent thickening of a normal left ureterovesical junction ( uvj ) ( arrow ) .
( b ) coronal reformations demonstrate normal symmetric appearance of the bilateral ureterovesical junctions ( arrows ) .
axial image from the excretory phase of a ct urogram shows mild asymmetric thickening of the left uvj ( arrow ) .
cystoscopic biopsy demonstrated urothelial carcinoma . a 71-year - old man with a history of resected bladder cancer .
axial image from the excretory phase of a ct urogram demonstrates focal wall thickening ( arrow ) just anterolateral to the right uvj ( arrowhead ) , at the site of the previous resection .
axial image from the excretory phase of a ct urogram demonstrates focal mass - like wall thickening just superolateral to the right uvj ( arrow ) .
8) , schistosomiasis , tuberculosis , and radiation - induced cystitis generally cause diffuse , symmetric bladder wall thickening .
diffuse or multifocal bladder cancer typically causes asymmetric , multifocal wall thickening ( fig . 9 ) . rarely , inflammatory conditions such as cystitis glandularis ( fig .
11 ) , and those associated with diffuse wall thickening are likely benign . however , urothelial carcinoma may calcify ( fig .
12 ) , and therefore cancer should be suspected when calcification is associated with a mass . 
 figure 8a 55-year - old man with gross hematuria .
coronal image from the excretory phase of a ct urogram shows diffuse bladder wall thickening with irregularity of the urothelial surface ( arrowheads ) .
the left ureter ( curved arrow ) is mildly obstructed due to the thickened wall . 

coronal image from the excretory phase of a ct urogram demonstrates multifocal nodular wall thickening ( arrows ) involving most of the bladder , and causing bilateral hydronephrosis and hydroureter ( arrowheads ) .
axial image from the excretory phase of a ct urogram shows focal thickening of the posterior bladder wall ( arrow ) , and an enlarged left external iliac lymph node ( arrowhead ) .
figure 11a 75-year - old woman with a history of bladder cancer treated with intravesical bacillus calmette - gurin ( bcg ) .
axial image from the excretory phase of a ct urogram demonstrates foci of bladder wall calcification ( arrows ) without associated mass or wall thickening .
biopsy revealed chronic inflammation and granulomas at all sites , related to prior bcg treatment . 

axial image from the excretory phase of a ct urogram shows a mass along the right lateral bladder wall with calcifications ( arrowheads ) .
coronal image from the excretory phase of a ct urogram shows diffuse bladder wall thickening with irregularity of the urothelial surface ( arrowheads ) .
the left ureter ( curved arrow ) is mildly obstructed due to the thickened wall . a 53-year - old man with gross hematuria and urothelial carcinoma .
coronal image from the excretory phase of a ct urogram demonstrates multifocal nodular wall thickening ( arrows ) involving most of the bladder , and causing bilateral hydronephrosis and hydroureter ( arrowheads ) .
surgical pathology at cystectomy revealed multifocal high grade urothelial carcinoma . a 75-year - old man with hematuria .
axial image from the excretory phase of a ct urogram shows focal thickening of the posterior bladder wall ( arrow ) , and an enlarged left external iliac lymph node ( arrowhead ) .
a 75-year - old woman with a history of bladder cancer treated with intravesical bacillus calmette - gurin ( bcg ) .
axial image from the excretory phase of a ct urogram demonstrates foci of bladder wall calcification ( arrows ) without associated mass or wall thickening .
biopsy revealed chronic inflammation and granulomas at all sites , related to prior bcg treatment . a 57-year - old man with hematuria and urothelial carcinoma of the bladder .
axial image from the excretory phase of a ct urogram shows a mass along the right lateral bladder wall with calcifications ( arrowheads ) .
in patients with a history of bladder cancer , prior surgical treatment may cause focal wall thickening and abnormal enhancement that may be indistinguishable from recurrent tumor , even at cystoscopy ( figs .
patients who have received intravesical immunotherapy with bacillus calmette - gurin ( bcg ) may develop granulomatous changes in the bladder wall , mimicking bladder cancer ( fig .
knowledge of past history and the presence of radiation - induced changes in nearby small bowel loops can help reach the diagnosis . 

figure 13a 56-year - old man with hematuria 6 weeks following transurethral resection of superficial bladder cancer .
axial image from the excretory phase of a ct urogram shows focal wall thickening at the site of prior resection ( arrow ) .
axial image from the excretory phase of a ct urogram demonstrates focal bladder wall thickening along the left lateral wall ( arrowheads ) , at the site of previous resection .
cystoscopy revealed no evidence of malignancy . a 56-year - old man with hematuria 6 weeks following transurethral resection of superficial bladder cancer .
axial image from the excretory phase of a ct urogram shows focal wall thickening at the site of prior resection ( arrow ) .
cystoscopic biopsy and urine cytology revealed no evidence of residual malignancy . a 62-year - old man with a history of resected bladder cancer .
axial image from the excretory phase of a ct urogram demonstrates focal bladder wall thickening along the left lateral wall ( arrowheads ) , at the site of previous resection .
blood clots can simulate bladder neoplasms , however , they are typically odd - shaped or linear , smoothly marginated ; they do not enhance .
also , they are luminal findings , and multiplanar reformations can be used to demonstrate that they do not arise from the bladder mucosa ( fig .
cystoscopy may be needed to distinguish clots that abut or adhere to the bladder wall , from urothelial cancer ( fig .
axial image from the excretory phase of a ct urogram shows irregular soft tissue at the bladder base , projecting into the bladder lumen ( arrows ) .
( b ) coronal reformations demonstrate linear structures in the bladder lumen without attachment to the bladder mucosa ( arrows ) .
axial image from the excretory phase of a ct urogram shows an apparent papillary mass at the bladder base ( arrow ) , concerning for bladder cancer .
cystoscopy revealed a blood clot adherent to the bladder wall , without evidence of bladder cancer .
axial image from the excretory phase of a ct urogram shows irregular soft tissue at the bladder base , projecting into the bladder lumen ( arrows ) .
( b ) coronal reformations demonstrate linear structures in the bladder lumen without attachment to the bladder mucosa ( arrows ) . also note nodular enlarged prostate gland indenting the bladder base ( curved arrow ) .
axial image from the excretory phase of a ct urogram shows an apparent papillary mass at the bladder base ( arrow ) , concerning for bladder cancer .
cystoscopy revealed a blood clot adherent to the bladder wall , without evidence of bladder cancer .
benign prostatic hyperplasia ( bph ) can cause bladder outlet obstruction and bladder wall thickening due to detrusor muscle hypertrophy ( fig .
19 ) can cause protrusion of nodular , mass - like tissue into the bladder at its base .
this nodular tissue may be asymmetric , and can have either a smooth or an irregular surface . distinguishing a bladder base cancer from an enlarged prostate gland
therefore may be difficult with excretory phase imaging , even using coronal reformations ( fig .
since urothelial cancers are typically hypervascular , bladder base urothelial cancers can be differentiated from the prostate gland when the pelvis is examined 70  s after the injection of iv contrast material , when the bladder is distended with unopacified urine .
however , addition of these images to the ctu protocol described above would increase the radiation dose of the examination . 

figure 17an 83-year - old man with a prolonged history of urinary frequency , urgency and dysuria secondary to benign prostatic hyperplasia .
severe diffuse symmetric bladder wall thickening ( arrows ) due to detrusor muscle hypertrophy is mildly obstructive , manifested as mild left hydroureteronephrosis ( arrowheads ) and mild right hydroureter ( curved arrow ) . 

axial image from the excretory phase of a ct urogram shows papillary - appearing soft tissue at the bladder base ( arrows ) .
coronal image from the excretory phase of a ct urogram shows a smooth nodular soft tissue mass contiguous with prostate , projecting into the bladder base ( arrow ) to the left of a urinary catheter ( curved arrow ) .
coronal image from the excretory phase of a ct urogram shows an apparent mass ( arrows ) at the bladder base inseparable from the prostate gland .
an 83-year - old man with a prolonged history of urinary frequency , urgency and dysuria secondary to benign prostatic hyperplasia .
severe diffuse symmetric bladder wall thickening ( arrows ) due to detrusor muscle hypertrophy is mildly obstructive , manifested as mild left hydroureteronephrosis ( arrowheads ) and mild right hydroureter ( curved arrow ) . a 76-year - old man with urinary frequency , urgency and dysuria .
axial image from the excretory phase of a ct urogram shows papillary - appearing soft tissue at the bladder base ( arrows ) .
coronal image from the excretory phase of a ct urogram shows a smooth nodular soft tissue mass contiguous with prostate , projecting into the bladder base ( arrow ) to the left of a urinary catheter ( curved arrow ) .
coronal image from the excretory phase of a ct urogram shows an apparent mass ( arrows ) at the bladder base inseparable from the prostate gland .
knowledge of normal anatomy and benign conditions that mimic neoplastic disease will help reduce the number of false - positive ct urograms . although cystoscopy will be needed to differentiate benign from malignant bladder processes in some situations , continued experience with ctu and knowledge of the appearance of benign conditions will help limit the number of patients needing further investigation .
 abstractthe objective of this review article is to learn how to recognize anatomic variants and benign entities that mimic bladder cancer at computed tomography ( ct ) urography . 
 building on recent data that suggest that ct urography can be used to diagnose bladder cancer , recognition of anatomic variants and benign entities will help improve radiologists ability to diagnose bladder cancer . 
Introduction
CT urography technique
Normal anatomy
Inflammatory processes
Treatment effects
Blood clot
Enlarged prostate gland