Ureterocele

INTRODUCTION — A ureterocele is a cystic dilatation of the terminal ureter either entirely within the bladder or extending into the urethra (figure 1). It may be noted as an incidental finding on antenatal ultrasonography, or it may be identified postnatally because of symptoms due to urinary tract infection (UTI) or obstruction.

The pathogenesis, clinical presentation, diagnosis, evaluation, and management of ureteroceles will be reviewed here. Other congenital abnormalities of the urinary tract are discussed separately. (See "Overview of congenital anomalies of the kidney and urinary tract (CAKUT)" and "Evaluation of congenital anomalies of the kidney and urinary tract (CAKUT)".)

EPIDEMIOLOGY — The prevalence of ureteroceles based upon autopsy studies is approximately 1 in 500 individuals [1]. Ureteroceles occur four to six times more frequently in females than in males, and more commonly in White individuals than in other races [2]. Unilateral ureteroceles occur with similar frequency on the right and left, and in 10 percent of cases there is bilateral involvement.

CLASSIFICATION

●Classification by location – Ureteroceles can be classified based upon location as follows (figure 1):

•Intravesical (ie, entirely within the bladder), or

•Ectopic (ie, a portion extends beyond the bladder neck into the urethra)

At times, differentiating between intravesical and ectopic ureteroceles may be difficult. Historically, ectopic ureteroceles that inserted beyond the bladder neck into the urethra were called cecoureteroceles.

This classification system has been adopted by the Section on Urology of the American Academy of Pediatrics [3].

●Classification based upon the collecting system – Ureteroceles also may be classified depending upon whether they are associated with:

•A single collecting system (ie, single ureter and kidney), or

•A double (duplex) collecting system (complete ureteral duplication) (see "Overview of congenital anomalies of the kidney and urinary tract (CAKUT)", section on 'Duplication')

Most ureteroceles (approximately 80 percent) are associated with the upper pole of a duplex collecting system; of these, approximately 60 percent are ectopic [4]. Intravesical ureteroceles are more common in single systems.

PATHOGENESIS — The underlying pathogenesis is unknown, and it appears that a single unifying theory does not explain how all the different types of ureteroceles are formed [4]. A simple explanation is that ureteroceles can be considered a diverticulum of the distal ureter within the bladder, secondary to a stenotic ureteral orifice. Ureteroceles may be one type of abnormal ureteral insertion at the bladder level, along with pseudoureteroceles and ectopic ureters, which have similar etiologies.

More formal proposed embryologic mechanisms resulting in ureterocele formation include [4]:

●An incomplete breakdown of the ureteral membrane between the ureteral bud and mesonephric duct, resulting in an obstruction that causes the formation of a ureterocele. This mechanism explains the formation of the majority of stenotic ureteroceles, but not those with patulous ureteral orifices in the urethra.

●Obstruction of the ureteral orifice by the bladder neck because of developmental delay in the timing of the ureteral bud insertion into the bladder.

●Abnormal induction of the bladder trigone development that results in the absence of trigonal musculature in the intravesical portion of ureteroceles.

CLINICAL PRESENTATION

Antenatal — Many ureteroceles are detected incidentally on routine antenatal ultrasonography [4]. Approximately 2 percent of cases of antenatal hydronephrosis are caused by ureteroceles, which obstruct the distal end of the affected ureter (figure 1 and image 1).

Antenatal ultrasound can accurately detect duplex collecting systems. In a review of the literature, approximately 70 percent of antenatally diagnosed cases of duplex systems with upper pole hydronephrosis were associated with a ureterocele [5].

Postnatal — The most common postnatal presentation is during an evaluation for urinary tract infection (UTI) in the first few months after birth [4]. (See "Urinary tract infections in neonates".)

Some patients have a more insidious course that may include intermittent abdominal or pelvic pain, or failure to thrive [2]. In older children, stasis and infection may predispose to stone formation. Hematuria is a rare presentation.

Some patients may present with a palpable abdominal mass due to ureterocele obstruction of the distal ureter. Most ureteroceles decompress during voiding, so bladder outlet obstruction (ie, urethral obstruction) is a rare event [4]. However, prolapse of an ectopic ureterocele can cause urethral obstruction, and may present as a vaginal mass in females. A female with a large intraurethral ectopic ureterocele may present with urinary incontinence due to laxity of the external urinary sphincter. A few patients, particularly older males with a single system intravesical ureterocele, may be diagnosed incidentally during imaging for other conditions.

DIAGNOSIS AND EVALUATION — The diagnosis is generally made by ultrasonography. Further imaging with voiding cystourethrography (VCUG) is used to determine whether there is associated vesicoureteral reflux (VUR). In patients with duplex collecting systems, radionuclide studies are used to evaluate the relative function of all kidney segments.

Ultrasound — Ultrasonography usually reveals a well-defined cystic intravesical mass in the posterior portion of the bladder. A dilated ureter also may be seen, especially behind the bladder. In duplex systems, there is approximately an 80 percent chance that the other side will be duplex (image 2 and figure 2).

Voiding cystourethrogram — A VCUG is important to identify whether VUR is present. Reflux into the ipsilateral lower pole occurs in approximately 50 percent of patients, where it may be massive, and occurs on the contralateral side in 25 percent [4,6,7]. The contrast material used in this procedure may obscure the ureterocele itself, so early images, as the bladder is filling, are crucial to detect a ureterocele. (See "Clinical presentation, diagnosis, and course of primary vesicoureteral reflux", section on 'Imaging'.)

Renography — Radionuclide renal scans are used to evaluate the relative function of all kidney segments. In patients with a duplex system, the upper kidney segment that is associated with the affected ureter may contribute little or no function, and may not be worth preserving when surgery is performed [4]. In addition, a delay in the isotope washout (especially after the administration of lasix) demonstrates impaired urinary drainage. (See "Radiologic assessment of kidney disease", section on 'Radionuclide studies'.)

MANAGEMENT — Management of a ureterocele depends upon multiple considerations, including the mode and age of presentation (antenatal detection or symptomatic), the type of ureterocele (ectopic or intravesical), the function of the associated renal moiety, and whether reflux is present [4,8,9].

Antenatal diagnosis — Patients with an antenatal diagnosis should receive antibiotic prophylaxis until the postnatal radiologic evaluation is performed and treatment is completed to relieve any associated urinary obstruction. Antibiotic treatment is continued if there is a diagnosis of vesicoureteral reflux (VUR).

There is limited data from a small case series of fetal decompression of severely obstructive ureterocele with oligohydramnios under ultrasound guidance [10]. In this report, 8 of the 10 cases (mean gestational age of 21.6 weeks) recovered normal amniotic fluid volume and a liveborn child with normal renal function was delivered at a mean gestational age of 37.6 weeks. However, two cases underwent termination of pregnancy. Fetal intervention is an experimental procedure and should only be conducted in research centers with clinical expertise. Parents/caregivers need to be fully informed regarding the benefits and risks of fetal intervention versus conservative management.

Surgery — Ureteroceles are treated surgically. An exception is the small minority of patients with single system small ureteroceles without ureteral dilation and without symptoms. Such patients can be followed expectantly.

The most common neonatal surgical intervention is endoscopic incision of the ureterocele (movie 1). However, some patients may require complete open reconstruction. The choice of surgical intervention depends upon the clinical circumstances (eg, duplex versus single system; presence or absence of VUR) [2,4,8,9].

Patients who present with sepsis secondary to obstruction require immediate drainage [11]. In this case, endoscopic incision of the ureterocele often relieves the obstruction [12]. Percutaneous drainage is rarely necessary.

Factors to consider in surgical decisions

Intravesical versus ectopic — The success of endoscopic decompression and the need for reoperation is dependent upon the location of the ureterocele [13]. (See 'Classification' above.)

●Intravesical − With intravesical ureterocele, endoscopic decompression is the definitive procedure in approximately 80 to 90 percent of cases [14]. The need for additional open surgery is related to the presence of lower pole reflux.

●Ectopic − In contrast, endoscopic treatment is effective in only 25 to 30 percent of ectopic ureteroceles [11,14,15]. Initial endoscopic puncture can reduce the size of an obstructed ureter, which facilitates subsequent successful open reimplantation.

The greater the number of kidney units involved with an ectopic ureterocele, the more likely a second surgical procedure will be needed [16]. These cases may need upper tract surgery, which may include upper pole nephrectomy and lower pole reconstruction, ureteral reimplantation, and excision of the ureterocele with reconstruction of the bladder neck.

Duplex versus single system

●Duplex system – In a duplex system, the approach selected depends upon the function of the upper pole segment associated with the ureterocele and its location. In a newborn with associated VUR in the lower pole or contralateral system, the usual approach is endoscopic puncture to decompress the ureterocele. Antibiotic prophylaxis is continued until the child reaches one year of age, when the patient is reevaluated with ultrasound and voiding cystourethrogram (VCUG).

If the upper pole of the kidney has minimal function and there is not associated VUR, a reasonable option is partial nephrectomy to remove the nonfunctional segment (picture 1). If the upper pole is well-functioning and reflux is not present, then the upper pole dilated ureter can be anastomosed to the normal lower pole ureter at the level of the bladder (uretero-ureteostomy).

Patients with a ureterocele associated with a duplex system are more likely to have a second operation than those with a ureterocele with a single collecting system [13].

●Single system – The rate of reoperation after initial endoscopic decompression is lower in patients with a single system ureterocele compared with those with duplex system lesion.

In one case series that included nine patients with a single system ureterocele, all the ureteroceles were intravesical. Only one patient required repeat puncture because of poor decompression from the initial intervention [17]. In another case series of 13 single system ureteroceles, two of the three extravesical ureteroceles required reoperation [14].

Age at presentation — Outcome is better with prenatal identification and early endoscopic decompression of ureteroceles in a duplex system than with treatment after postnatal presentation. This was illustrated in one retrospective study in which outcome was compared in 95 patients who had prenatal (n = 40) or postnatal diagnosis (n = 55) [18]. Urinary tract infection (UTI) occurred less frequently with prenatal diagnosis both before (12 versus 84 percent) and after surgery (15 versus 27 percent) compared with postnatal diagnosis. The need for secondary procedures also was less in the prenatal group (20 versus 46 percent).

In infants and young children, endoscopic decompression is typically performed, as primary reconstruction is more challenging because of the size of the patients [1,14]. Decompression reduces the risk of UTI and facilitates later reconstruction, if it is needed.

Patients who present when older than three to four years of age usually are managed with primary total surgical reconstruction. This approach avoids the need for endoscopic decompression with subsequent radiographic monitoring and the potential need for reoperation.

An observational approach may be successful in the management of some prenatally detected nonobstructive ureteroceles associated with poorly or nonfunctioning renal moieties.

In one series of 52 patients with prenatally detected duplex system ureterocele, 38 had surgical treatment, and 14 with upper pole involvement were managed expectantly with antibiotic prophylaxis [8]. The latter group met criteria that included <10 percent upper renal pole function, unobstructed lower pole, lower pole VUR ≤grade III, and unobstructed bladder outflow. Through follow-up to a median of eight years, none of the expectantly managed children required surgery, had a urinary tract infection, or became symptomatic.

In another study, infants less than two weeks of age with an ectopic ureterocele associated with a duplex system were assigned to receive either immediate endoscopic incision followed by antibiotic prophylaxis (n = 32) or antibiotic prophylaxis until later surgical intervention (n = 40) [9]. Febrile UTIs (three patients in each group) and progressive hydronephrosis (one versus two patients) were similar in the two groups during the first six months after birth.

Reflux — Preoperative VUR is associated with a greater risk of reoperation after initial endoscopic incision or puncture [13]. Bladder reconstruction with excision of the ureterocele and reimplantation of the ureters is the standard approach in patients with persistent VUR in lower pole segments or new reflux into the punctured upper pole segment. In a case series of 54 patients with ectopic ureterocele who underwent total bladder reconstruction and excision of their ureterocele and ureteral reimplantation, long-term follow-up (median of 9.6 years) demonstrated excellent results with continence in almost all of the patients (n = 51) [19]. Only 10 patients required subsequent intervention for persistent VUR. Patients had minimal lower tract complications, including infections.

Our approach — As discussed above, our management depends upon the presentation (incidental finding on antenatal imaging versus symptomatic postnatal presentation), location of ureterocele (ectopic or intravesical), type of collecting system (single versus duplex), function of the associated upper pole kidney segment, and presence or absence of VUR.

●For patients with ureteroceles associated with VUR that are identified by antenatal ultrasound (and confirmed with postnatal imaging), early endoscopic incision is performed to decompress the dilated urinary tract. Decompressing the ureterocele decreases the risk of developing pyelonephritis and facilitates future reconstruction by allowing the dilated ureter to return to a more normal size. Antibiotic prophylaxis is administered until reevaluation at one year of age when definitive surgical therapy is typically performed.  

●For patients without VUR who have a poorly functioning upper pole kidney segment, initial management consists of antibiotic prophylaxis. Definitive surgery by either open or laparoscopic heminephrectomy is usually performed at six months to one year of age.

●For patients without VUR who have a well-functioning upper pole kidney segment, the definitive surgical intervention is uretero-ureteostomy (anastomosis of the upper ectopic ureter to the normal lower pole ureter at the level of the bladder).

●Patients with single system small ureteroceles without ureteral dilation and without symptoms can be followed expectantly. If the patient develops ureteral dilation, VUR, and/or UTIs, intervention may be warranted.

●Patients who present with sepsis secondary to obstruction require immediate drainage of the kidney, which is typically performed by endoscopic incision (movie 2).

OUTCOME — Observational data suggest good outcomes are achieved by the following approach:

●Upper pole heminephrectomy in patients with a poorly functioning upper pole renal unit and no evidence of vesicoureteral reflux (VUR).

●Bladder level surgery with reimplantation of both ureters, and removal of ureterocele with bladder neck reconstruction in patients with VUR and residual ureterocele.

SUMMARY AND RECOMMENDATIONS

●Definition – A ureterocele is a cystic dilatation of the terminal ureter either entirely within the bladder or extending into the urethra (figure 1). (See 'Introduction' above and 'Pathogenesis' above.)

●Prevalence – The estimated prevalence of ureteroceles is approximately 1 in 500 individuals. They occur four to six times more commonly in females than males. (See 'Epidemiology' above.)

●Classification – Ureteroceles can be classified based upon location (intravesical versus ectopic) and the associated collecting system (single versus duplex) (figure 1). Most ureteroceles are associated with the upper pole of a duplex collecting system. (See 'Classification' above.)

●Clinical presentation – Ureteroceles may present as an incidental finding on antenatal ultrasound, particularly if the ureterocele causes obstruction of the affected ureter (eg, upper pole ureter in a duplex system). Postnatally, ureteroceles are most commonly identified during an evaluation for UTI in the first few months of life. Other less common presentations include intermittent abdominal or pelvic pain, abdominal or vaginal mass, failure to thrive, urolithiasis, urinary incontinence, and, rarely, hematuria. (See 'Clinical presentation' above.)

●Diagnosis – The diagnosis of ureterocele is made by ultrasound. Further imaging with voiding cystourethrogram (VCUG) is used to determine if there is associated vesicoureteral reflux (VUR). In patients with duplex collecting systems, radionuclide studies are used to evaluate the function of all kidney segments. (See 'Diagnosis and evaluation' above.)

●Management

•Surgery – Ureteroceles are managed surgically. An exception is the small minority of patients with single-system small ureteroceles without ureteral dilation and without symptoms. Such patients can be followed expectantly. (See 'Surgery' above.)

The most common neonatal surgical intervention is endoscopic incision of the ureterocele (movie 1). However, some patients may require complete open reconstruction. Decisions regarding choice and timing of surgical intervention are complex and depend upon (see 'Factors to consider in surgical decisions' above and 'Our approach' above):

-The presentation (incidental finding on antenatal imaging versus symptomatic postnatal presentation)

-Location of the ureterocele (ectopic or intravesical)

-Type of collecting system (single versus duplex)

-Function of the associated upper pole kidney segment

-Presence or absence of VUR

Patients with sepsis or urinary obstruction caused by the ureterocele require immediate drainage (typically with endoscopic incision).

•Prophylactic antibiotics – For most patients, we suggest prophylactic antibiotic therapy while awaiting definitive surgical intervention (Grade 2C). Antibiotic prophylaxis is continued in patients with ongoing VUR. Additional details regarding prophylactic antibiotics (including agents and dosing) are provided separately. (See "Management of vesicoureteral reflux", section on 'Antibiotic prophylaxis'.)