Anatomy of the Ureters

The ureters are muscular tubes with an internal lining of urothelium (previously called transitional epithelium). During development, each ureter begins as a ureteric bud arising from the mesonephric duct near the cloaca. The ureteric bud elongates in a cephalad direction until it reaches the metanephric blastema, which is induced to form a kidney.

Each ureter begins at a cone-shaped junction with the renal pelvis, the ureteropelvic junction (UPJ), then courses anterior to the psoas muscles in the retroperitoneum and enters the bladder at the trigone. The trigone is the triangular portion of bladder between the bladder neck and the two ureteral orifices (often called the UO by urologists). The ureters normally pass dorsal to the gonadal vessels and ventral to the iliac vessels. Organized antegrade peristaltic waves work in cooperation with gravity to facilitate passage of urine from each kidney to the bladder.

Anatomy of the Bladder

The urinary bladder is a highly distensible, muscular reservoir for urine that fills with continuous flow from the ureters and empties periodically through the urethra. Urothelium lines the lumen, and the detrusor muscle forms the bulk of the bladder wall. When empty (or nearly empty), the bladder is relatively flat in the craniocaudal direction. A layer of peritoneum rests over the dome of the bladder like a blanket. As it fills, the bladder becomes ellipsoid, lifting the peritoneum from the anterior abdominal wall (like peeking under the blanket). Therefore, the anterior bladder wall is in continuity with the extraperitoneal prevesical space (of Retzius). In women, the peritoneum drops behind the bladder before rising to encase the uterus, creating a peritoneal recess called the vesicouterine pouch. A similar peritoneal recess between the rectum and bladder in men is called the rectovesical pouch.

Early in development, the bladder empties through the umbilicus through a tube called the urachus. The urachus involutes in utero to form the median umbilical ligament, a long cord just superficial to the peritoneum that stretches from the bladder dome to the umbilicus. In the sagittal plane, the collapsed bladder dome is usually tented up anteriorly by its attachment to the median umbilical ligament (Fig. 19-1). A variety of abnormalities occur when obliteration of the lumen of the urachus is incomplete.

Figure 19-1 Sagittal reformation from multidetector computed tomographic examination demonstrates tenting of the collapsed urinary bladder by the median umbilical ligament, a normal remnant of the urachus.

The interureteric ridge is a promontory on the posterior bladder wall between where the ureters enter the bladder. The uterovesical junction (UVJ) describes the short segment of ureter that courses through the muscular bladder wall, often protruding slightly into the bladder at the trigone (Fig. 19-2). These small normal protuberances of the UVJ are a helpful landmark when searching for ureteral jets by ultrasound.

Figure 19-2 Axial image from computed tomographic urogram demonstrates normal appearance of the uterovesical junction (UVJ) on both sides.

Anatomy of the Female Urethra

The female urethra is a short tube (usually less than 4 cm) that provides an outlet from the cone-shaped bladder neck to the perineum. The urethra adheres firmly to the anterior wall of the vagina just posterior to the pubic symphysis. The urethral orifice opens within the vestibule just anterior to the vagina. The female urethra is lined along the proximal one-third with urothelium and along the distal two-thirds with stratified squamous epithelium. Several paraurethral glands near the meatus are known as Skene’s glands. These are lined with columnar epithelium and secrete into the urethra via two Skene’s ducts that may dilate to form palpable cysts. The secretions are similar to those made by the prostate, prompting some to hypothesize that Skene’s glands are a prostate homologue. Some urologists even use the term female prostatitis to describe symptoms related to periurethral inflammation within the glands.

Anatomy of the Male Urethra

Male urethral anatomy is slightly more complex than that of the female urethra, although familiarity with several landmarks facilitates accurate identification of normal anatomic structures. From the bladder to meatus, the male urethra is divided into four main segments: prostatic, membranous, bulbous, and penile (Fig. 19-3). Combined, the prostatic urethra and membranous urethra make up the posterior urethra; the bulbous and penile comprise the anterior urethra.

Figure 19-3 Illustration superimposed on a retrograde urethrogram demonstrates anatomic segments of the male urethra.

The bladder narrows like a funnel into the bladder neck. Below the bladder neck, the prostatic urethra appears almost as an elongated teardrop with a posterior impression representing the verumontanum. The lumen of the prostatic urethra is lined with the same type of urothelium that lines the bladder, ureter, and renal pelvis. The verumontanum contains the urethral outlets for the ejaculatory ducts.

Just below the verumontanum, the urethra tapers for a segment about 1 cm in length, usually at or just below the inferior 1 cm or so of the pubic symphysis. This mildly narrowed segment is the membranous urethra. The membranous urethra opens into the long, curved bulbous urethra. The proximal bulbous urethra often has a mild hourglass impression from the pars nuda muscle, but the remainder of the bulbous urethra should have a larger diameter than any other part of the urethra. The bulbous urethra swings down then back up over the suspensory ligament to emerge from the scrotum as the penile urethra. The urothelium of the prostatic urethra progresses to stratified columnar epithelium in the bulbous and proximal penile urethra. As the penile urethra widens slightly at the fossa navicularis near the meatus, squamous epithelium predominates.

Two different types of glands make secretions that keep the urethral mucosa moist. A pair of Cowper glands is situated with one gland on each side of the membranous urethra. The secretions of each Cowper gland are delivered to the bulbar urethra through a thin Cowper duct. Multiple glands of Littré surround the penile urethra; each of these small glands secretes directly into the underlying mucosa through a short duct.

Normal Imaging Appearance of the Ureters

For decades, intravenous urography (IVU) and retrograde urography were the mainstays of ureteral imaging. Typically, a ureter exits each renal pelvis at approximately L2 to L3 and parallels the spine overlying the transverse processes. As the ureters enter the pelvis, they course first laterally, then curve toward the bladder trigone, entering at an angle that is variable but often approximates 45 degrees.

The ureters are usually divided into proximal, middle, and distal segments when describing abnormalities. Although radiologists often apply these terms loosely, a methodical system is commonly used by urologists when planning interventions. The proximal ureter refers to the segment from the UPJ to the superior margin of the sacrum, the midureter is the segment that overlies the sacrum (also referred to as the sacral ureter), and the distal ureter is the short segment between the inferior margin of the sacrum and the ureteral orifice (Fig. 19-4).

Figure 19-4 Image from an excretory urogram is used to illustrate convention used by urologists to divide the ureters into proximal, mid, and distal segments.

Often, radiologists prefer to localize lesions within the ureter, dividing each ureter into thirds of equal length. Because this may cause miscommunication between radiologists and urologists, it is best to use the terms proximal third, middle third, and distal third for clarification when using this geometric division of the ureter. Using anatomic landmarks (e.g., “at the level of the left L3 transverse process”) also helps to avoid confusion.

Today, ureters are examined by computed tomography (CT) more often than with any other modality. Even without intravenous (IV) contrast, the course of the ureter can be followed from the renal pelvis to the bladder in most patients. At the level of the inferior margin of the renal hila, the ureters course lateral to the gonadal veins. Just inferior to the lower renal poles, each ureter typically crosses posterior to the ipsilateral gonadal veins from lateral to medial. Identifying the gonadal veins on each study prevents confusion between the vein and the ureters on more inferior images. This is particularly important because gonadal vein phleboliths can easily be confused with ureteral calculi.

It is sometimes difficult to continue following the ureters as they cross anterior to the iliac vessels, particularly if there is a paucity of fat in the retroperitoneum. One remedy is to identify where the ureters enter the bladder at an angle of approximately 45 degrees (Fig. 19-5). The ureters can then be followed back (a retrograde noncontrast-enhanced computed tomography [NCCT] study!) to the level of the iliac vessels. With practice, one may become as comfortable following each ureter retrograde as antegrade, allowing a stone protocol CT examination to be viewed in a “U” configuration, following one ureter from kidney to bladder and the other ureter from bladder to kidney.

Figure 19-5 Axial unenhanced computed tomographic image of the bladder demonstrates how the uterovesical junction can be used to identify the distal ureters.

On contrast-enhanced CT, the normal ureter may enhance slightly in the arterial and portal venous phases. Excretion of contrast into the ureters usually starts by about 2 minutes after injection. The high attenuation of excreted contrast defines the ureteral lumen well but can obscure the thin ureteral wall. Coronal images (often using thin-slab maximum intensity projection [MIP]) provide visualization of longer segments of the ureters, and even small abnormalities can be detected on coronal reformations using isotropic data. Using a thicker MIP technique allows longer segments to be viewed on fewer coronal sections but also limits detection of small filling defects.

On unenhanced magnetic resonance (MR) images, the ureters contain high-signal-intensity urine on T2-weighted images. On early excretory phase images after IV gadolinium-based contrast media administration, the urine within the ureteral lumen enhances on T1-weighted images. Unlike CT, the ureteral lumen does not become brighter as the excreted contrast agent becomes progressively more concentrated. Instead, T2^* effects prevail at greater concentrations of gadolinium, causing loss of signal intensity. On T2-weighted images performed during the excretory phase of contrast-enhanced MRI, the ureters appear dark.

Administering a low dose of a diuretic such as furosemide (typically 5-10 mg) aids in ureteral distention and dilution of excreted contrast media. This reduces the negative effects that concentrated gadolinium has on signal intensity and permits contrast-enhanced excretory urography to be performed with MRI. Excretory-phase, gadolinium-enhanced, T1-weighted images can be acquired in the coronal plane to create an MR urogram (Fig. 19-6). Diuretic administration also benefits CT urography by distending the collecting systems and dispersing excreted contrast material more evenly.

Figure 19-6 Coronal thick-slab maximum intensity projection image from T1-weighted magnetic resonance urogram performed after the administration of intravenous (IV) contrast media. IV furosemide was administered to optimize ureteral opacification.

(Reprinted from Leyendecker JR, Barnes CE, Zagoria RJ: MR urography: techniques and clinical applications, Radiographics 28:23-46, 2008, by permission.)

Normal Imaging Appearance of the Bladder

The bladder is often seen on a kidneys, ureter, and bladder radiograph (KUB) as a flattened ellipsoid (when empty) to elongated oval-shaped (when distended) soft-tissue density arising from the middle of the pelvic floor. In women, the uterus can often be seen faintly as it rests over the bladder dome. Looking for the normal bladder on each KUB helps with the detection of unsuspected bladder distension or bladder calcification.

On IVU and conventional cystography (including voiding cystourethrography [VCUG]), the empty bladder has a flattened configuration with multiple smooth bladder folds defining heaped up mucosa when the detrusor muscle is contracted. As the bladder becomes distended with opacified urine, the detrusor and mucosa are stretched smooth.

The appearance of the urinary bladder on CT depends on the phase of enhancement. On NCCT, differentiation between the low-attenuation urine and soft-tissue bladder wall is subtle but often can be defined. Each ureteral orifice often can be identified as an area of focal thickening of the posterior bladder wall approximately one third of the way up from the bladder neck. During the arterial phase of contrast administration, the mucosa often enhances slightly more than the muscle, improving discrimination between bladder wall and the urine within. The detrusor muscle remains slightly dense during the portal venous phase. Although imaging with excreted contrast within the bladder improves the detection of filling defects, the contrast is often of such high attenuation that it causes beam-hardening artifact, which may obscure findings. This “blooming effect” can be minimized by windowing the images so that the dense contrast appears gray rather than bright white.

MRI provides excellent characterization of the bladder, even without contrast media. The urine is bright on T2-weighted images, providing excellent contrast with the mucosal surface. Similar to difficulties with very-high-attenuation contrast on CT, it is often helpful to window the urine to a gray level to avoid obscuring subtle features of the bladder wall on T2-weighted images. T1-weighted images performed after gadolinium-based contrast injection but before the excretory phase allows detection of subtle enhancement in the normal bladder wall, as well as brighter enhancement in mucosal lesions. Once the excreted contrast material fills the bladder, a stratified appearance is common, particularly on delayed images. This appearance is not related to true contrast layering, but rather results when thresholds in concentration are reached that result in relatively abrupt changes in signal intensity despite gradual changes in gadolinium concentration.

Normal Imaging Appearance of the Female Urethra

After filling the bladder with radiopaque contrast media, voiding demonstrates a slightly undulating, funnel-shaped structure that extends inferiorly from the bladder neck. This shape is often described as a “spinning top,” and the undulations reflect impressions of the pelvic floor musculature.

Because of its short length, retrograde urethrography (RUG) of the female urethra is not a simple matter. A balloon within the lumen would occupy much of its length and contrast is likely to fill the bladder preferentially, leaving the urethra poorly distended. When necessary, these challenges can be overcome with a double-balloon urethrogram. This requires a bladder catheter designed specifically for this purpose (Fig. 19-7). Fortunately, the urethra usually can be imaged effectively with cross-sectional imaging. With careful inspection, urethral diverticula can be seen with CT, particularly if they contain stones (Fig. 19-8). Large masses can also be seen with CT if they enlarge the urethra or invade adjacent structures.

Figure 19-7 Illustration of double balloon catheter positioned for female retrograde urethrography.

Figure 19-8 Axial image from a contrast-enhanced computed tomographic scan at the level of the urethra in a female patient demonstrates a small stone within a urethral diverticulum.

The female urethra is best demonstrated with MRI, particularly when an endovaginal coil is used to produce high-resolution images. On axial sections obtained with an external surface coil, the urethra is posterior to the pubic symphysis and anterior to the vagina, contained within an inverted cone-shaped space created by the puborectalis muscle. The anus is situated at the apex of that inverted cone (Fig. 19-9).

Figure 19-9 Axial T2-weighted magnetic resonance image of the female perineum demonstrates normal anatomic structures.

Ultrasound has been used effectively by some for evaluation of the female urethra. Transperineal, endovaginal, and endorectal techniques have all been described. Endourethral ultrasound can also be performed with a specialized transducer.

Normal Imaging Appearance of the Male Urethra

VCUG is the most commonly performed imaging technique for evaluation of the male urethra (Fig. 19-10). During voiding, the bladder neck opens, and the prostatic and membranous urethra widen. The bulbous and penile urethra usually become moderately distended and are typically of uniform caliber.

Figure 19-10 Normal male urethral anatomy demonstrated by (A) voiding cystourethrography and by (B) retrograde urethrography.

RUG is appropriate in the setting of trauma or suspected stricture. A Foley catheter is inserted into the urethra, and the balloon inflated with approximately 1 to 2 ml saline in the fossa navicularis. Alternatively, a catheter tip syringe can be inserted gently into the urethral meatus until snug. With the patient in an oblique position (providing relatively uniform body density throughout the length of the urethra by superimposing it over the thigh), water-soluble contrast is injected under fluoroscopy and images are obtained. The penile and bulbous segments are distended more with RUG than with VCUG (see Fig. 19-10). The posterior urethra, however, is generally less distended. A jet of contrast is often seen mixing with unopacified urine within the bladder and can have a bizarre appearance to the uninitiated.

Duplication

During fetal development, part of the mesonephric duct forms a ureteral bud that migrates cranially. When the ureteric bud reaches the metanephric blastema, it branches into multiple divisions and induces development of the kidney around a branched collecting system. Early branching or complete duplication of the ureteric bud results in duplication of all or part of the affected renal collecting system and ureter. If the bud divides completely at its origin, duplication is complete (two ureteral orifices). Any division of the ureteric bud proximal to the bladder trigone leads to variable lengths of duplication between the renal pelvis and the bladder (Fig. 19-11). Some form of duplication is present in up to 4% of people, and although it is usually an incidental radiographic finding, it occasionally has significant health implications.

Figure 19-11 Illustration demonstrating the spectrum of ureteral duplication.

Partial duplications that unite to form a common ureter rarely cause symptoms (Fig. 19-12). However, it is useful to have knowledge of duplicated anatomy in the event of procedures that place the ureters at potential risk, such as donor nephrectomy, pelvic surgery, or radiofrequency ablation. On occasion, partial duplication of the ureters (probably paired with abnormalities of peristalsis) results in channeling of urine down one ureter and up the other, so-called yo-yo reflux.

Figure 19-12 Volume-rendered three-dimensional image from computed tomographic urogram demonstrating low union of a partial ureteral duplication. UVJ, Ureterovesical junction.

Most cases of medically significant duplication are complete. With complete duplication, the ureter from the lower pole usually inserts into a normal location in the bladder trigone. The ureter from the superior pole is ectopic, usually entering the bladder inferior and medial to the expected location (Weigert–Meyer rule). The most common location for the ectopic upper pole ureter is near or within the bladder neck. Even with complete duplication, if the ectopic ureteral orifice has normal morphology, it is not usually of clinical significance. However, when an ectopic ureter protrudes or herniates into the bladder lumen because of an abnormal angle of entry, it forms a ureterocele. Ectopic ureteroceles are prone to obstruction (Fig. 19-13). In addition, mass effect from a large ectopic ureterocele can distort the orifice of the orthotopic ureter, resulting in reflux to the lower pole.

Figure 19-13 Axial images from noncontrast-enhanced computed tomography (CT) performed for suspected ureterolithiasis at the level of the superior pole (A), at the level of the renal hilum (B), and at the level of the perineum (C) demonstrate chronic obstruction of the upper pole from previously undiagnosed duplication. In this case, infection caused the symptoms that prompted evaluation with CT at age 20.

The ectopic ureter from the upper pole can also insert into the urethra, vagina, prostate, or seminal vesicle. Female individuals with a ureteral orifice in the vagina or distal urethra suffer from incontinence. This leads to early diagnosis and favors preservation of some function in the upper pole moiety. Male individuals are more likely to have continent ectopia, with insertion into the prostate, seminal vesicle, or vas deferens. By the time many men are diagnosed with ectopic ureteral insertion, the upper pole moiety has severely compromised function because of obstructive uropathy.

Ureterocele

Simple ureteroceles occur without duplication and are located at the expected location of the normal ureteral orifice. Sometimes called orthotopic ureteroceles, these represent incomplete obliteration of the embryologic membrane between the ureter and bladder (Chwalla membrane). The flow of urine pushes the membrane, like wind filling a sail, causing the end of the ureter to push into the bladder. Simple ureteroceles are usually small and incidental (Fig. 19-14). Larger ureteroceles are prone to obstruction and stone formation (Fig. 19-15).

Figure 19-14 Axial image from a contrast-enhanced computed tomographic scan of the bladder demonstrates a simple right ureterocele on an examination performed for suspected acute appendicitis.

Figure 19-15 Images from an excretory urogram show multiple stones within a ureterocele and distal ureter.

An everting ureterocele can occur when a ureterocele coexists with any cause of increased bladder pressure (usually benign prostatic hypertrophy). In such cases, the increased pressure within the bladder pushes the ureterocele back into the ureter, resulting in distal ureteral obstruction. On CT, an everting ureterocele results in the appearance of a membrane within the lumen of the ureter (Fig. 19-16). Because antegrade urography can push the ureterocele down into the bladder, combined antegrade urography and cystography may be required to confirm the diagnosis.

Figure 19-16 Axial images of the pelvis during (A) CT cystography and (B) during antegrade CT pyelography via nephrostomy tube demonstrate an everting ureterocele in a 52-year-man with urinary obstruction. C, Diagnosis was confirmed during simultaneous catheter injections under fluoroscopy.

Ectopic Ureter

Just as ureteroceles can occur either with duplication or as an isolated abnormality, ectopic ureters can also occur without associated duplication. Isolated ureteral ectopia follows the same sex rules as duplication. Female individuals have a low insertion (bladder neck, urethra, or vagina) with associated incontinence and infections. In male individuals, ectopic ureters insert into the prostate, seminal vesicle, or vas deferens and can cause recurrent episodes of epididymoorchitis. In up to 5% of ectopic ureters, no ureteral orifice is found and the ureter is assumed to be a blind-ending pouch. Most ectopic ureters cause obstruction. When the system is not duplicated, obstructive nephropathy damages the entire kidney. Because onset of the insult is in utero, kidneys can be dysplastic or hypoplastic when discovered (Fig. 19-17).

Figure 19-17 Simple ectopic ureter. A, Axial image from a contrast-enhanced computed tomographic (CT) scan at the level of the kidneys demonstrates hypoplasia of the left kidney caused by congenital partial obstruction. B, Axial image at the level of the bladder from the same CT examination demonstrates a cystic structure in the expected location of the distal left ureter. At surgery, ureteral insertion into the left seminal vesicle was confirmed.

Circumcaval and Retrocaval Ureter

The portion of the inferior vena cava (IVC) below the renal vein usually develops from the supracardinal vein, which is posterior to the ureter. If, instead, the infrarenal IVC develops from the right subcardinal or postcardinal veins (these are anterior to the ureter), part of the ureter may become trapped behind the IVC. In the most common form of this variant, the proximal right ureter courses posterior to the IVC at the L4 level, and loops around medial then anterior to the IVC before assuming a normal location for the distal segment. This loop around the IVC is cause for the name circumcaval ureter. This may give the illusion that the ureter is “hung up” on the L4 pedicle (Fig. 19-18). This anatomic variant often presents when a ureteral stone becomes obstructed in the circumcaval segment (Fig. 19-19). This can be confusing on unenhanced CT if a calculus is lodged posterior to the IVC. Following the ureters carefully from kidney to bladder on sequential axial images allows accurate diagnosis.

Figure 19-18 Image from an intravenous urogram demonstrates dilatation of the proximal ureter to the level of a circumcaval segment (arrows).

Figure 19-19 Retrograde urogram demonstrates a stone in a circumcaval segment of the ureter.

Rarely, the right ureter gets caught by a posterior branch from the IVC so that a segment courses posterior to the IVC. The ureter in such cases reemerges laterally and is called a retrocaval ureter.

Blind-Ending Ureteral Duplication

What happens if a ureteric bud never reaches the metanephric blastema? Without induction of the kidney, the bud never develops the familiar arborization of the intrarenal collecting system. Instead, it remains a blind-ending pouch. In an unduplicated system, the bud usually atrophies and the kidney never develops, accounting for some cases of renal agenesis. If, however, the bud had already divided into a potential duplication, refluxing urine maintains patency of the bud, which persists as a blind-ending ureteral duplication, sometimes called a ureteral diverticulum. In most cases, these are incidental findings on imaging examinations, although resection for infection and for pain have been reported.

Refluxing excreted contrast media can opacify a blind ending ureteral duplication during excretory urography, but these anomalies are often better opacified on retrograde urography (Fig. 19-20). In some cases, expansion of the blind-ending ureter caused by reflux results in misdiagnosis as an ovarian cyst. Today, blind-ending ureters are more likely to be discovered with CT, although detection requires a methodical approach. Similar to identification of the ureter and gonadal vein on every examination, it is important to follow any dilated tubular structure in the retroperitoneum to confirm its beginning and end to avoid confusing a diverticulum with an obstructed ureter (Fig. 19-21).

Figure 19-20 Blind-ending ureteral duplication demonstrated by retrograde urography. Because of saccular dilatation of the pouch, these are occasionally mistaken for adnexal cysts on ultrasound.

Figure 19-21 Sagittal-oblique reformatted image from excretory phase of computed tomography performed for nonurinary complaints demonstrates blind-ending ureteral duplication.

Urachal Anomalies

The urachus is a tube that empties the bladder through the umbilicus during early fetal development. The urachus usually narrows and then closes late in development or at birth. The closed urachus becomes the median umbilical ligament, an extraperitoneal cord that extends from the bladder dome to the umbilicus between the transversalis fascia and parietal peritoneum. The median umbilical ligament can be seen on virtually every multidetector computed tomography examination of the pelvis. Minimal soft-tissue thickening, trace calcification, or both are commonly present in the bladder dome where the median umbilical ligament inserts (Fig. 19-22).

Figure 19-22 Benign urachal remnant on computed tomography (CT). Axial image from a contrast-enhanced CT scan demonstrates a small soft-tissue nodule protruding slightly from the anterior bladder dome.

Failure of urachal closure may be complete (patent urachus), may involve the bladder end (urachal diverticulum), may involve the umbilical end (urachal sinus), or may be sequestered in the middle (urachal cyst) (Fig. 19-23). A patent urachus presents with urine leaking from the umbilicus. Urachal diverticula often occur when urachal closure is impeded by bladder outlet obstruction. Urachal sinuses and cysts usually present when they become infected (Fig. 19-24).

Figure 19-23 Illustrations demonstrating the spectrum of abnormalities related to closure of the urachus. A, Normal median umbilical ligament. B, Patent urachus. C, Urachal diverticulum. D, Urachal sinus. E, Urachal cyst.

Figure 19-24 Midline sagittal reformation of computed tomographic examination demonstrates an infected urachal cyst. The diagnosis was confirmed at surgery.

Urachal carcinoma is the most dreaded consequence of persistent urachal tissue. Tumor can arise anywhere along the urachal remnant but most commonly occurs just anterior to the bladder dome. Adenocarcinoma accounts for 80% of cases, with urothelial and squamous cell carcinomas occurring considerably less often. Hematuria is absent when the tumor does not communicate with the bladder lumen. Because no vital structures are compressed by a mass in this region, urachal carcinomas are usually large at presentation (mean size, 8 cm), and initial symptoms may be related to a palpable anterior pelvic mass or metastatic disease. Masses range from solid to low attenuation on computed tomography, often with heterogeneous areas of contrast enhancement (Fig. 19-25). Dystrophic calcifications are common.

Figure 19-25 Axial image from a contrast-enhanced computed tomographic scan demonstrates a large, heterogeneously enhancing mass extending from the bladder dome toward the anterior abdominal wall. This was removed surgically and proved to be urachal carcinoma.