Overview: Fibrotic regression of the urachus typically extends from the umbilicus toward the bladder, resulting in the formation of the median umbilical ligament.1,2 Failure of the urachus to normally regress results in one of four disorders: (1) patent urachus (50%), (2) urachal sinus (15%), (3) urachal diverticulum (3-5%), and (4) urachal cyst (30%) (Fig. 121-1).³ Clinical symptoms include umbilical discharge, local infection, lower abdominal pain, and urinary tract infection.⁴

Imaging: Abdominal ultrasound, voiding cystourethrography (VCUG), and fistulography are the primary imaging diagnostic tools for initial evaluation of suspected urachal anomalies.⁵ In a patent urachus, the urachus fails to obliterate, resulting in a vesicoumbilical fistula (Fig. 121-2). The diagnosis may be confirmed by catheterization of the bladder through the umbilicus (Fig. 121-3) or by VCUG with films in the lateral projection. In urachal sinus, the urachus is closed at the level of the bladder but remains patent at the umbilicus (e-Fig. 121-4). The diagnosis of urachal sinus can be made only by catheterization and opacification of the umbilical fistula. In urachal diverticulum, the urachus is obliterated at the level of the umbilicus but communicates with the bladder. Ultrasound readily demonstrates this, but urachal diverticula are best shown on a cystogram in the lateral projection (Fig. 121-5). In urachal cyst, the urachus is obliterated at both ends but remains patent in its midportion. Multiple small urachal cysts may occur as a result of segmental urachal obliteration (e-Fig. 121-6).¹

Treatment: Urachal remnants in children younger than 6 months are likely to resolve with nonoperative management. However, if symptoms persist or the urachal remnant fails to resolve after 6 months of age, it should be excised to prevent recurrent infection.1,2,6

Overview: Bladder diverticula, which may be primary (congenital), secondary, or iatrogenic (postoperative) (Box 121-1),⁷ are the most common, are seen more often in males than in females, may be single or multiple, and occur most frequently in the trigonal area.^8,9 Secondary bladder diverticula are the result of chronically increased intravesical pressure and occur most commonly in the paraureteral area. Iatrogenic diverticula are seen most often in the anterior wall of the bladder at the site of a previous vesicostomy or suprapubic drainage catheter, and at the ureterovesical junction after ureteral reimplantation. Patients present with recurrent urinary tract infection, urinary retention, incontinence, stone formation, vesicoureteral reflux, and ureteral and bladder outlet obstruction.¹⁰

Imaging: VCUG is the most efficient method of detection.¹¹ Bladder diverticula may become visible only during voiding when contractions of the bladder force urine into the diverticulum (Fig. 121-7). A paraureteral diverticulum or Hutch diverticulum¹² is located laterally and cephalad to the ureteral orifice (e-Fig. 121-8). If the diverticulum is large, it may engulf the ureteral meatus and the ureter may empty into the diverticulum. Associated vesicoureteral reflux is present in about half of the cases (e-Fig. 121-9).¹³

Treatment: Surgical diverticulectomy may be performed by an intravesical, extravesical, or combined approach with satisfactory results.¹⁴ The muscular defect in the bladder wall should be meticulously repaired. Surgical diverticulectomy often restores normal voiding dynamics.^10,15,16

Overview: Rhabdomyosarcoma (RMS) is the most common and important neoplasm of the lower genitourinary tract and accounts for about 20% of all RMS seen in children. RMS is the most frequent bladder neoplasm in children in the first two decades of life, presenting typically at ages 2 to 6 years or 15 to 19 years.17,18 In males, more than 50% of the cases arise from the prostate. In females, RMS arises from the vagina and the uterine cervix. Histologically, the tumor is divided into three subtypes: (1) embryonal, (2) alveolar, and (3) polymorphic. Embryonal RMS is further subdivided into three categories: (1) classic embryonal, (2) botryoid, and (3) spindle cell. The embryonal form is, by far, the most common, accounting for approximately 90% of all RMS. The embryonal botryoid subtype accounts for one fourth of the cases and has a lobulated, polypoid appearance, resembling a bunch of grapes, hence the name sarcoma botryoides.^17,19–21

RMS spreads by local extension from the bladder, prostate, and vagina into regional and retroperitoneal lymph nodes and muscle. Lymph node involvement or distant tumor spread is found at initial diagnosis in 10% to 20% of patients.²² Although RMS can metastasize to almost any site, it does so most commonly to the lungs, cortical bone, and lymph nodes, and less frequently to the bone marrow and liver. Hematuria, dysuria, frequency, urinary retention, and obstruction are the most frequent clinical manifestations. An abdominal mass may be palpated in some cases. In females, a vaginal tumor may manifest as a prolapsing mass in the introitus.¹⁹

Imaging: On ultrasound, RMS is hyperechoic or hypoechoic, compared with surrounding healthy tissue, with or without focal anechoic regions representing necrosis and hemorrhage. Color and duplex Doppler evaluation show hypervascularity.²² VCUG shows a filling defect in the posteroinferior aspect of the bladder (e-Fig. 121-10). When originating in the prostate (Fig. 121-11 and e-Fig. 121-12), the cystogram shows an upward displacement of the bladder floor or a smooth, lobulated mass at the base of the bladder.^19,22 Contrast-enhanced CT identifies RMS of the prostate or bladder base as a bulky pelvic mass of heterogeneous attenuation that may invade periurethral and perivesical tissues or may extend into the ischiorectal fossa. Calcification is rare. Vaginal tumors often arise high in the anterior vaginal vault and may be indistinguishable from a primary bladder tumor.¹⁹ On magnetic resonance imaging (MRI) scans, RMS demonstrates nonspecific, low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted sequences. After the administration of MRI contrast, RMS typically enhances heterogeneously.

Treatment: The Children’s Oncology Group and Intergroup Rhabdomyosarcoma Study staging and clinical system for neoplasms of the genitourinary system is given in Box 121-2.¹⁸ Treatment combines surgical removal of as much of the tumor as possible, chemotherapy, and radiation therapy. Tumors of the urinary bladder and prostate have an overall 5-year survival rate of approximately 70%. Tumors originating in nonbladder or prostatic sites (paratesticular, vagina, and cervix) have better 5-year survival rates, between 84% and 89%.²³ Botryoid histology has the most favorable prognosis compared with all other histologies.²⁴

Overview and Imaging: Hemangioma of the bladder is probably the most common benign neoplasm (0.6% of all bladder tumors). Hemangioma presents as a discrete solitary mass of variable size (<1 cm to more than 10 cm), usually projecting from the posterior or lateral walls of the bladder.²⁵ Hematuria is the most common clinical presentation. Ultrasound will demonstrate bladder wall thickening, intramural anechoic spaces, and occasional calcification. CT and MRI may be required to fully define the extent of the lesion and for preoperative planning, since cystoscopy may only reveal a small portion of the mass.²⁶

Nephrogenic adenoma is a rare benign papillary lesion of the bladder. In most cases. a history of upper urinary tract infection, inflammation, trauma or recent surgery (ureteral re-implantation), calculi, or catheterization is present. The bladder is the most common site in children.²⁷ The female to male ratio in children is 3 : 1. Clinical presentation includes hematuria, frequency or urgency, and nocturia. Ultrasound demonstrates a nonspecific, echogenic papillary mass projecting from the bladder wall (Fig. 121-13).²⁸ Most nephrogenic adenomas are less than 1 cm in size; however, they may be as large as 7 cm.²⁹ Treatment consists of transurethral resection and fulguration. The recurrence rate in children is 80%, with peak recurrence at approximately 4 years after treatment.^28,30

Overview: Posterior urethral valves (PUVs), more recently considered congenital obstructive posterior urethral membranes, are the most common cause of congenital bladder outlet obstruction.31–34 The valves are identified at the base of the verumontanum, and the obstruction leads to posterior urethral dilation and chronic bladder outlet obstruction. The degree of urethral obstruction, however, is variable.^32,35–37 When detected prenatally, varying degrees of renal dysplasia result from pressure damage to the developing renal pelvis, collecting ducts, and parenchyma. If the fetus survives, up to 45% will develop renal insufficiency or end-stage renal disease requiring renal dialysis or transplantation before 5 years of age.^38–41 Those children who escape antenatal detection may present in the first months or years of life with urinary tract infections, sepsis, voiding disorders, hematuria, vomiting, failure to thrive, urinary retention, hydronephrosis, ascites, and congestive heart failure. At the other end of the spectrum are patients with late presentation of PUVs. These patients have a mild form of disease, and detection may be delayed as late as adolescence. These children may present with functional voiding disorders or urinary tract infections.^42,43

Imaging: Ultrasound shows varying degrees of hydroureteronephrosis and bladder wall thickening (e-Fig. 121-14). Dysplastic kidneys with increased echogenicity, decreased corticomedullary differentiation, and cortical cyst formation may be seen. Perinephric fluid collections (urinomas) are usually related to forniceal rupture (Fig. 121-15 and e-Fig. 121-16). When unexplained ascites is discovered in a male newborn, the diagnosis of urinary tract obstruction caused by PUVs should be strongly considered. Associated hydroureteronephrosis may not be present because the forniceal rupture and communication to the peritoneal cavity act as a “pop off” mechanism, allowing one or both kidneys to decompress. Transperineal ultrasound can show the dilated posterior urethra, especially if the child is voiding at the time of the examination (e-Fig. 121-17).^44–50

VCUG is the diagnostic study of choice for PUVs (Fig. 121-18 and e-Fig. 121-19). VCUG directly shows the PUVs and their effect on the urinary bladder; wall thickening, trabeculation with cellulae and sacculi, diverticula, and hypertrophy of the interureteric ridge (e-Fig. 121-20). Vesicoureteral reflux occurs in about one half to two thirds of male children with PUV, of whom approximately two thirds have unilateral reflux (e-Fig. 121-21) (Box 121-3).^34,35,51,52

Treatment: Transurethral resection or fulguration of the obstructing valvular structures is the recommended treatment for PUVs. Residual valve tissue with obstruction is not uncommon, and stricture formation at the site of previous urethral valves or in the membranous urethra as a complication of surgery may occur. Urethroscopy is usually more reliable than the urethrogram in the diagnosis of these lesions.53–63

Overview: Urethral polyps typically arises from the posterior urethra and consist of an elongated, freely movable mass on a long stalk originating from the region of the verumontanum (Box 121-4).⁶⁴ The lesion is typically diagnosed in the first decade of life at a mean age of 8 to 10 years. The classic symptoms are those of intermittent urethral obstruction with straining on voiding, abnormal voiding pattern, and urinary retention.^65,66 Hematuria (30%–60%) and urinary tract infections may also be observed.^64–67