Practice Essentials
A ureterocele is a cystic out-pouching of the distal ureter into the urinary bladder. [1] 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 associated with anomalous development of the intravesical ureter, the kidney, or the collecting system.
Ureteroceles may be categorized on the basis of their relationship with the renal unit or on distal ureteral configuration and location. The following are the different types of ureteroceles classified by their association with the renal unit:
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Single-system ureteroceles are those associated with a single kidney, collecting system, and ureter.
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Duplex-system ureteroceles are associated with kidneys that have completely duplicated ureters.
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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.
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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 [2] :
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Stenotic ureteroceles are located inside the bladder with an obstructing orifice.
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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.
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Sphincterostenotic ureteroceles have characteristics of both stenotic and sphincteric ureteroceles.
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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 may be asymptomatic or may produce a wide range of clinical signs and symptoms, from recurrent cystitis to bladder outlet obstruction to kidney 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.
Management of ureterocele remains both challenging and controversial, with its wide clinical spectrum making development of a standardized approach difficult. Robotic-assisted ureteral reimplantation and heminephrectomy are gaining popularity and will continue to evolve. [3] Open ureteral reimplantation, ureteropyelostomy and heminephrectomy currently remain the criterion standard for surgical management of symptomatic ureteroceles that are not successfully managed endoscopically.
Although different surgical philosophies exist in managing adult and pediatric ureteroceles, the following principles may apply:
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Endoscopic puncture of ureteroceles should be used as a primary treatment modality in any patient with urosepsis or concurrent medical conditions that pose significant anesthesia-related risk.
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Upper pole heminephrectomy with partial ureterectomy is reasonable in the setting of a nonfunctioning upper pole renal moiety without associated vesicoureteral reflux.
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Ureterocelectomy and bladder reconstruction are acceptable in the setting of a ureterocele associated with significant vesicoureteral reflux in either kidney.
For information on pediatric ureterocele, see Ureteral Duplication, Ureteral Ectopia, and Ureterocele.
Relevant Anatomy
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 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 contractions of the ureter.
The ureter receives its blood supply from numerous sources. In the segment of the ureter from the renal pelvis to the common iliac artery, which is referred to as the abdominal ureter, the blood supply 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. In the segment of the ureter from the common iliac artery to the urinary bladder, which is termed the pelvic ureter, the blood supply 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:
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Terminal portion (juxtavesical ureter)
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Intramural portion
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Submucosal portion (lying under the mucosa of the bladder)
Pathophysiology
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, perforation of the Chwalla membrane occurs, allowing 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, which 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 the Chwalla membrane likely determine whether a ureterocele will be orthotopic or ectopic in location.
Etiology
The precise embryologic etiology of the ureterocele remains unknown. Theorized causes include the following:
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Obstruction of the ureteral orifice
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Incomplete muscular development of the intramural ureter
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Excessive dilatation of the intramural ureter during the development of the bladder and trigone
The most commonly accepted theory behind ureterocele formation is obstruction of the ureteral orifice during embryogenesis, with incomplete dissolution of the Chwalla 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.
Epidemiology
Ureteroceles occur in approximately 1 in every 4000 children and occur most commonly in whites. [4] 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.
Prognosis
No single approach is appropriate for all patients with ureteroceles; therefore, each case must be tailored to the individual. An experienced surgeon must be armed with various surgical techniques that can be tailored to effectively treat different types of ureterocele malformations. When an appropriate operation is used to correct a specific abnormality, the outcomes remain excellent in both pediatric and adult patients.
A retrospective comparison of ureterocele treatment with laser puncture in 12 neonates and electrosurgery incision in 20 neonates found that both techniques were highly effective in relieving the obstruction. There were no significant differences regarding hospitalization, need for retreatment, and the occurrence of complications. [5]
A meta-analysis of outcomes of endoscopic treatment of ureteroceles found that rates of secondary operations were higher with ectopic and duplex-system ureteroceles than with intravesical and single-system ureteroceles. Postoperative vesicoureteral reflux (VUR) rates were also significantly higher in patients with ectopic or duplex-system ureteroceles. [6]
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Intravenous urogram demonstrating left hydroureteronephrosis due to a ureterocele represented by the round filling defect located at the left base of the bladder (Courtesy of Steven Kraus, MD, Cincinnati, Ohio)
