Genitourinary Radiology > Embryology > Metanephros > Ureterocele



A ureterocele is a congenital saccular dilatation of the terminal portion of the ureter. It may be orthotopic, inserting in the normal location or it may be ectopic. Ectopic ureterocele enter the bladder in an abnormal location, such as the bladder neck or urethra. They typically arise from the upper pole moiety of a duplicated collecting systemand are more common in the pediatric population.

Ureteroceles occur in approximately 1 in every 4000 children and occur most commonly in caucasions. Females are affected 4-7 times more often than males.

Radiographically, ureteroceles have a classic appearance known as the "cobra head deformity" and resembles a snake's head bulging into the bladder. It is often best dected on excretory urography.

The most commonly accepted theory behind ureterocele formation is the obstruction of the ureteral orifice during embryogenesis, with incomplete dissolution of the Chwalla membrane. (The Chwalla membrane 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.




Abdominal film following contrast enhanced CT scan shows excretion into two ureters on the left (arrows). In the bladder, a characteristic filling defect (yellow arrow) is seen known as the "cobra head" deforming which represents herniation of the dilated distal ureter bulging into the bladder.


The "cobra head" is more easily seen with the ureterocele flipped upside down and magnified.




Just be glad this isn't in YOUR bladder.











(1)  CT scan and (2) ultrasound through pelvis in patient with known right ureterocele who complains of new right flank and groin pain. Both US and CT show a stone contained within the ureterocele perhaps causing the patients pain from intermittent obstruction. On CT, this stone is radiodense (arrow) and on ultrasound, the stone demonstrates strong acoustic reflection (has a bright interface) and posterior acoustic shadowing (it is black behind the stone because all sound is being reflected at the stones interface).



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