- Author: Christopher S Cooper, MD, FACS, FAAP; Chief Editor: Edward David Kim, MD, FACS more...
A ureterocele is a cystic out-pouching of the distal ureter into the urinary bladder. It is one of the more challenging urologic anomalies facing pediatric and adult urologists. Ureteroceles may pose a diagnostic and therapeutic dilemma with perplexing clinical symptoms resulting from a spectrum of abnormal embryogenesis associate with anomalous development from the intravesical ureter, the kidney, and the collecting system.
Ureteroceles may be asymptomatic or may produce a wide range of clinical signs and symptoms, from recurrent cystitis to bladder outlet obstruction to renal failure. Because of the obstructive nature of ureteroceles, the activity of the affected renal unit varies from a normal, well-functioning kidney to a nonfunctioning, dysplastic renal segment or kidney. However, with proper diagnosis and treatment, the outcome remains excellent.
For information on pediatric ureterocele, see the article Ureteral Duplication, Ureteral Ectopia, and Ureterocele in the Pediatric: General Medicine volume.
Ureteroceles may be categorized based on their relationship with the renal unit or based on distal ureteral configuration and location.
The following are the different types of ureteroceles classified by their association with the renal unit:
Single-system ureteroceles are those associated with a single kidney, collecting system, and ureter.
Duplex-system ureteroceles are associated with kidneys that have completely duplicated ureters.
Orthotopic (intravesical) ureterocele is a term used for a ureterocele contained within the bladder. An orthotopic ureterocele may prolapse into and beyond the bladder neck, but the origin of the walls of an orthotopic ureterocele are contained within the bladder. The orthotopic ureterocele usually arises from a single renal unit with one collecting system and is more commonly diagnosed in adults.
Ectopic (extravesical) ureterocele refers to ureteroceles with tissue that originates at the bladder neck or beyond, into the urethra. They typically arise from the upper pole moiety of a duplicated collecting system and are more common in the pediatric population.
Keep in mind that not all single-system ureteroceles assume an orthotopic position and that not all duplex collecting system ureteroceles are positioned in an ectopic location.
Another method of classifying ureterocele is based on location and configuration. Stephens proposed a classification system based on the features of the affected ureteral orifice, as follows:
Stenotic ureteroceles are located inside the bladder with an obstructing orifice.
Sphincteric ureteroceles lie distal to the internal sphincter. The ureterocele orifice may be normal or patulous, but the distal ureter leading to it becomes obstructed by the activity of the internal sphincter.
Sphincterostenotic ureteroceles have characteristics of both stenotic and sphincteric ureteroceles.
Cecoureteroceles are elongated beyond the ureterocele orifice by tunneling under the trigone and the urethra.
At present, this classification is used infrequently. The characterization based on the location of the orifice (intravesical vs ectopic) is more commonly used because it has therapeutic implications, especially with respect to the likelihood of the presence of vesicoureteral reflux following transurethral puncture of the ureterocele.
Ureteroceles occur in approximately 1 in every 4000 children and occur most commonly in whites. Females are affected 4-7 times more often than males. A slight left-sided preponderance appears to exist, and approximately 10% of ureteroceles are bilateral. In the adult population, ureteroceles also occur more frequently in females. Orthotopic ureteroceles occur in 17-35% of cases, with an incidence of ectopic ureteroceles of approximately 80% in most pediatric series. Similarly, approximately 80% of ureteroceles are associated with the upper pole moiety of a duplex system. When ectopic ureteroceles are associated with duplicated collecting systems, the upper pole moiety may be dysplastic or poorly functioning. Single-system ectopic ureteroceles are uncommon and are most often found in males.
The precise embryologic etiology of the ureterocele remains unknown. Several theories exist, including obstruction of the ureteral orifice, incomplete muscular development of the intramural ureter, and excessive dilatation of the intramural ureter during the development of the bladder and trigone.
The most commonly accepted theory behind ureterocele formation is the obstruction of the ureteral orifice during embryogenesis, with incomplete dissolution of Chwalla's membrane. This is a primitive, thin membrane that separates the ureteral bud from the developing urogenital sinus. Failure of this membrane to completely perforate during development of the ureteral orifice is thought to explain the occurrence of a ureterocele.
It is important to make a distinction between orthotopic and ectopic ureteroceles since therapeutic options and outcomes differ between these two clinical entities. The development of an ectopic ureterocele is best explained by reviewing the embryogenesis of the kidney and ureter.
Embryogenesis of the kidney and ureter
The ureter forms from the ureteric bud, which branches off the caudal portion of the Wolffian (mesonephric) duct during the first 4-6 weeks of gestation. The cranial portion of the ureteral bud joins with the metanephric blastema, a primitive analog of the kidney, and begins to induce nephron formation. The ureteral bud subsequently branches into the renal pelvis and the calyces and induces nephron formation. Caudally, the mesonephric duct and the ureteral bud are incorporated into the anterior portion of the cloaca (urogenital sinus) as it forms the bladder trigone. At this point, Chwalla's membrane perforates to allow the formation of a normal ureteral orifice. If the membrane does not completely perforate, a ureterocele results.
Importantly, alterations in the number of ureteral buds also result in ureteral anomalies. Before the mesonephric duct is absorbed into the urogenital sinus, it usually produces a single ureteral bud. Complete ureteral duplication occurs when the mesonephric duct produces a second ureteral bud that interacts with the metanephric blastema. The lower ureteral bud which is therefore closest to the urogenital sinus becomes the lower pole ureter, and the bud farther away becomes the upper pole ureter. As the common excretory duct is absorbed into the expanding urogenital sinus, the lower pole ureteral orifice becomes located more cephalad and lateral; the upper pole orifice, which is incorporated later, if at all, will therefore be located more caudal and medial. This is known as the Meyer-Weigert law.
Because the lower pole ureteral bud is located more cephalad and lateral, its detrusor submucosal tunnel is shortened and predisposes the lower pole ureter to reflux. In contrast, the upper pole ureteral bud is absorbed slowly, which results in a longer submucosal tunnel. The timing of incorporation of the ureter into the urogenital sinus as well as the perforation of Chwalla's membrane likely determine if a ureterocele will be orthotopic or ectopic in location.
Currently, most pediatric ureteroceles are found during routine prenatal screening. Adult ureteroceles may also be found incidentally during imaging studies, often obtained for complaints of unrelated symptomatology. Ureteroceles frequently do not have clinical sequelae in the adult population. However, when problems arise, presenting clinical symptoms of ureteroceles may include the following:
Urinary tract infection (UTI)
Obstructive voiding symptoms
Failure to thrive
Cyclic abdominal pain
Pathologic ureteroceles most often affect the pediatric population. In young infants, failure to thrive or urinary tract infection may be the first sign of a symptomatic ureterocele. Complications of ureteroceles in both pediatric and adult populations occur because of the obstructive nature of the ureterocele and its anatomic location. Because of the distal ureteral obstruction, the ipsilateral renal moiety is often hydronephrotic or dysplastic. The degree of hydronephrosis may wax and wane depending on the amount of urine produced by the renal moiety. Cyclical expansion and decompression of the renal pelvis manifests as intermittent abdominal pain in older children and adults.
In the setting of untreated UTIs and hydronephrosis, affected older children and adults may reveal signs and symptoms of pyonephrosis or frank urosepsis. The dilated ureterocele may cause urinary stasis and is a risk factor for ureteral stone formation within the saccular cavity. When distal ureteral stones develop, they cannot pass spontaneously because of the obstructing ureterocele orifice. Presence of stones within a ureterocele is exclusive to the adult population. A prolapsing ureterocele in a female patient may cause physical obstruction of the bladder neck. Anatomic obstruction of the bladder neck by the cystic ureterocele may incite obstructive voiding symptoms or may precipitate acute urinary retention in both pediatric and adult populations. Intravesical ureterocele has also been reported to cause bladder outlet obstruction in an adult male.
During the physical examination, particular attention should be paid to the abdomen and the genitalia. This is true for both pediatric and adult populations. Symptomatic ureteroceles with hydronephrosis may manifest with abdominal tenderness to palpation. An abdominal mass due to a large hydronephrotic kidney may be appreciated in the upper abdominal quadrant in thin adults and young children. Flank tenderness often accompanies the abdominal findings. In infants, an abdominal mass due to hydronephrosis may be noted by transillumination in a dark room.
During a female genital examination, a prolapsing cystic mass may be seen emerging from the external meatus. This is a sign of a prolapsing ureterocele. However, the differential diagnoses of a prolapsing mass in children should also include urethral prolapse, sarcoma botryoides, and urethral caruncle. Prolapsing ureteroceles can also occur in boys, but they are much less common. Duplex systems are more likely to cause urethral obstruction in males, although they occasionally can occur with just a single system. A minority of ureteroceles are discovered incidentally during ureteral reimplantation for vesicoureteral reflux.
Treatment of the ureterocele is indicated to relieve obstruction and to preserve renal function. Indications for surgical intervention include the following:
Urgent decompression with endoscopic incision, followed by a definitive bladder reconstruction, is often required in cases of urosepsis or severe azotemia. Indications for intervention in the pediatric and adult population are identical.
Ureters are paired muscular tubes running from the renal pelvis to the bladder. They travel through retroperitoneal connective tissue in a serpentine fashion. In the adult, the ureter is approximately 30 cm long but varies with body habitus. The ureter is a urinary conduit composed of inner longitudinal smooth muscle fibers and an outer layer of circular and oblique smooth muscle cells. The inner and longitudinal muscle layers are enveloped by a thin layer of adventitia that contains an extensive plexus of ureteral blood vessels and lymphatics that course parallel to the ureter. In a normal state, urine is actively propelled from the renal pelvis down to the bladder via active contractions of the ureter.
The ureter receives numerous sources of blood supply as it courses down the bladder. The segment of the ureter from the renal pelvis to the common iliac artery is referred to as the abdominal ureter. The blood supply of the abdominal ureter includes the renal artery, the aorta, the gonadal artery, and the common iliac artery. The blood supply of the abdominal ureter enters medial to the ureter. The segment of the ureter from the common iliac artery to the urinary bladder is the pelvic ureter. The blood supply of the pelvic ureter includes the internal iliac, vesical, uterine, middle rectal and vaginal arteries. The blood supply of the pelvic ureter enters laterally. The gonadal vessels run parallel to the ureter in the retroperitoneum until it courses obliquely from medial to lateral as it enters the pelvis.
The ureter is most narrow at the ureterovesical junction, followed by the ureteropelvic junction, and then at the crossing of the iliac vessels.
The ureterovesical junction may be divided into 3 sections, as follows:
Terminal portion (juxtavesical ureter)
Submucosal portion (lying under the mucosa of the bladder)
Contraindication for correction of a ureterocele is a small, asymptomatic ureterocele not causing any dilatation of the collecting system.
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