Ureterocele

A ureterocele is a congenital anomaly characterized by the cystic dilatation of the intravesical portion of the distal ureter. The anomaly could affect a single-system kidney, but it primarily affects the upper pole of a duplicated renal unit in 80% of cases.  In 1927, Chwalla postulated that ureteroceles are caused by a membrane that occludes the distal ureter (called Chwalla membrane), which is composed of urogenital sinus tissue and ureteric epithelium and fails to dissolve. However, a more complex underlying embryological origin is suggested by the presence of multiple associated anomalies along the course of the Wolffian duct migration. The 2 types of ureteroceles are intravesical and extravesical (ectopic). Intravesical ureteroceles include stenotic ureteroceles and nonobstructed, large ureteric orifices. They are typically associated with nonduplicated renal systems. Extravesical or ectopic ureteroceles comprise sphincteric ureteroceles, sphincter-stenotic ureteroceles, cecoureterocele, and blind ectopic ureteral anomalies. These are more likely to be found in duplicated systems. When ureteroceles are associated with duplicated renal units, about 60% will be extravesical or ectopic. Ureteroceles are more commonly discovered in individuals with single renal units. In approximately 40% of stenotic ureterocele cases, the ureteral orifice is relatively small, leading to partial obstruction of the proximal ureter. This condition typically results in some degree of distal ureteral dilation and may impact a duplicated system's kidney or upper pole. On the other hand, about 5% of nonobstructing intravesical ureterocele cases exhibit a large, open ureteral orifice. Extravesical (ectopic) ureteroceles are more likely than intravesical ureteroceles to be linked with complete renal duplications. The location of their insertion varies, but it generally follows the migratory path of the Wolffian duct. In approximately 40% of cases involving a sphincteric ureterocele, the ureteral orifice may be extravesical, which can either be of normal size or enlarged, extending into the bladder neck and opening anywhere proximal to the external sphincter. In females, the ureterocele meatus may even open beyond the external sphincter. This configuration can obstruct the ureter or the upper pole moiety in completely duplicated systems. When the orifice of the ureterocele is positioned within the internal sphincter, it is more likely to cause proximal dilation due to obstruction. In 5% of cases, a sphincter-stenotic ureterocele is similar to the sphincteric type, but the orifice is obstructed. Notably, the actual orifice of a sphincteric ureterocele tends to remain open and nonstenotic, primarily influenced by sphincter activity. In 5% of cases, a sphincter-stenotic ureterocele resembles the sphincteric type but with an obstructed orifice. In another 5% of cases, a blind ectopic ureterocele is similar to the sphincteric ureterocele but lacks a ureteral orifice. An uncommon type known as a cecoureterocele accounts for 5% of cases. In this variant, the orifice opens within the bladder with a long tubular ureteral extension or a blind pouch that extends into and beyond the bladder neck by tunneling into the submucosa under the trigone. This pouch fills during voiding, causing urethral obstruction and blocking urinary flow. The orifice of the cecoureterocele may be stenotic or open, with stenotic orifices draining exclusively from the kidney, while an open orifice indicates filling from the bladder.