Ureterocele is cystic dilatation of the distal ureter's submucosal segment into the bladder lumen. Two main types exist: (1) orthotopic (intravesical/simple) ureterocele — cystic dilatation at the bladder orifice of a normally positioned single-system ureter; more common in adults, usually incidentally detected; (2) ectopic ureterocele — cystic dilatation at the abnormal orifice (bladder neck, urethra, or beyond) of the upper-pole ureter in a duplicated collecting system; more common in children, leads to obstruction and infection. The most diagnostic imaging finding is the 'cobra-head sign' — on intravenous urography (IVU) or CT urography, the cobra head-like appearance of the contrast-filled dilated ureteral lumen surrounded by a radiolucent halo (ureterocele wall) at the distal ureter's cystic dilatation. On US it appears as a thin-walled cystic structure at the bladder orifice — jet phenomenon (ureteral jet) may be seen from within the ureterocele. On MRI it appears as a hyperintense cystic structure within the bladder lumen on T2. Stone formation within the ureterocele is a frequent complication — due to stasis and drainage impairment. Treatment is planned based on ureterocele type and complications: asymptomatic small orthotopic ureterocele requires follow-up, symptomatic or complicated cases require endoscopic incision or surgical repair.
Age Range
0-50
Peak Age
5
Gender
Female predominant
Prevalence
Uncommon
Ureterocele formation is based on embryological developmental anomaly: in normal development the ureteric bud separates from the mesonephric duct (Wolffian duct) and extends toward the kidney → the distal ureter creates a submucosal tunnel passing through the bladder wall → the ureteral orifice opens at the trigone. Two theories exist for ureterocele formation: (1) Chwalla membrane persistence — in embryological period a thin membrane (Chwalla membrane) exists between the ureter and urogenital sinus, normally resorbed at day 37 of gestation; incomplete resorption of this membrane leads to obstruction and distal ureteral dilatation → ureterocele; (2) ureteral orifice stenosis theory — congenital narrowing of the distal ureteral orifice → urinary flow obstruction → cystic dilatation of the submucosal ureteral segment. Imaging correlation: ureterocele appears as a cystic structure within the bladder lumen because the submucosal ureteral segment dilates and protrudes into the bladder lumen covered by mucosa. Physical explanation of cobra-head sign: on CT urography, opaque urine fills the ureterocele lumen (contrast-filled center) → the ureterocele wall (mucosa + submucosa) does not retain contrast → creates a radiolucent halo → together with surrounding opaque bladder urine produces the cobra-head appearance. Orthotopic ureterocele is usually small and belongs to a single system; ectopic ureterocele belongs to a duplicated collecting system (per Weigert-Meyer rule, upper-pole ureter opens inferiorly and medially, lower-pole ureter at normal position) and tends to be larger and more obstructive. Stasis within ureterocele → stone formation (4-39%); also obstructive uropathy → hydroureteronephrosis → risk of renal function loss.
The cobra head-like appearance of the contrast-filled dilated lumen surrounded by a radiolucent halo (ureterocele wall) at the cystic dilatation of the distal ureter within the bladder lumen on CT urography or IVU. This finding is pathognomonic for ureterocele and the three-layered structure (opaque urine > radiolucent wall > opaque lumen) confirms the diagnosis.
On the delayed (excretory) phase of CT urography, ureterocele appears as the pathognomonic cobra-head sign: the contrast-filled dilated distal ureteral lumen (cobra's 'body') forms an oval/round cystic dilatation within the bladder lumen (cobra's 'head'); since the ureterocele wall (mucosa + submucosa) does not retain contrast, a thin radiolucent halo (1-2 mm) is seen surrounding this dilatation; on the outside, opaque bladder urine surrounds this halo → three-layered appearance: opaque bladder urine > radiolucent wall > opaque ureterocele lumen. This finding is seen in both orthotopic and ectopic ureterocele types. In small ureteroceles the cobra-head sign may be subtle — thin-section (≤2 mm) and multiplanar reformatted (MPR) images increase sensitivity.
Report Sentence
Cystic dilatation consistent with cobra-head sign is seen at the distal ureter on the __ side on delayed phase CT urography; consistent with ureterocele.
Appears as a thin-walled, anechoic/hypoechoic cystic structure at the bladder trigone or orifice region on B-mode US. The ureterocele wall may be visible as a thin echogenic line. On dynamic US, ureterocele size may change with peristaltic waves — swells during peristaltic wave, shrinks after. Ureteral jet phenomenon (urine flow jet from ureteral orifice into bladder on color Doppler) may be seen from within the ureterocele — this finding indirectly shows the degree of ureterocele obstruction: weak/absent jet = significant obstruction. Stone within ureterocele appears as hyperechoic focus + acoustic shadow. Ipsilateral hydronephrosis and dilated ureter may accompany.
Report Sentence
A thin-walled cystic structure measuring __ mm is seen at the bladder trigone on the __ side, consistent with ureterocele; ureteral jet phenomenon has been evaluated.
Appears as a hyperintense (fluid signal) cystic structure within the bladder lumen at the orifice region on T2-weighted MRI. The ureterocele wall may be visible as a thin hypointense line on T2. The dilated distal ureter shows continuity with the ureterocele — coronal T2 imaging best demonstrates the ureter → ureterocele continuity. In duplicated collecting system (ectopic ureterocele), dysplasia/hydronephrosis of the upper-pole renal moiety and normal or reflux-related dilatation of the lower-pole moiety may be seen. On contrast-enhanced T1, the ureterocele wall shows minimal enhancement; content does not enhance. On MR urography (heavily T2-weighted) sequences, ureterocele and ureter morphology is evaluated non-invasively — particularly useful in pediatric cases.
Report Sentence
A thin-walled cystic structure at the bladder orifice region showing continuity with the dilated distal ureter is seen on T2-weighted MRI; consistent with ureterocele.
Hyperdense calculus is seen within the ureterocele — localized at the bladder orifice region and immobile (does not move with positional change, different from free bladder stone). The stone is surrounded by the ureterocele membrane — on contrast or delayed phase, the radiolucent halo of the ureterocele wall surrounding the stone may create a 'ring around stone' appearance. Stone size can range from a few mm to cm scale; large stones may completely occlude the ureterocele orifice causing obstructive uropathy. Non-contrast CT is the most sensitive modality for stone detection.
Report Sentence
A calculus measuring __ mm with __ HU density is seen within the ureterocele, requiring evaluation for orifice obstruction.
Upper urinary tract changes accompanying ureterocele: (1) Ipsilateral hydroureteronephrosis — ureteral and pelvic dilatation due to ureterocele obstruction; (2) Duplicated collecting system (ectopic ureterocele) — upper-pole moiety dysplasia/hydronephrosis, lower-pole moiety normal or dilated due to VUR; (3) Renal parenchymal thinning — cortical atrophy from prolonged obstruction; (4) Contralateral renal compensatory hypertrophy — in ipsilateral function loss. These findings support ureterocele diagnosis and affect treatment planning.
Report Sentence
Hydroureteronephrosis associated with the ureterocele is seen on the __ side; renal parenchymal thickness has been evaluated and functional assessment is recommended.
Ureterocele content shows no diffusion restriction on DWI — fluid within the ureterocele has free water properties and loses signal at high b-value, showing high signal (free diffusion) on ADC map. Infected ureterocele may show diffusion restriction due to intraluminal purulent material — this finding should suggest infection complication. DWI is useful for differentiating solid lesion (tumor, stone) from fluid within ureterocele: solid lesion shows diffusion restriction, fluid does not. In duplicated collecting systems, DWI may show renal diffusion differences for upper-pole dysplasia evaluation.
Report Sentence
No diffusion restriction is detected in the ureterocele content on DWI; compatible with free fluid content with no findings suggesting infection complication.
Criteria
Cystic dilatation at the bladder orifice of a normally positioned single-system ureter; common in adults; usually small (<2 cm); incidentally detected; trigonal location; obstruction usually minimal.
Distinct Features
No treatment needed if asymptomatic. Stone formation is most common complication. Ipsilateral mild hydronephrosis may accompany. Endoscopic incision is sufficient.
Criteria
Cystic dilatation at abnormal orifice (bladder neck, urethra) of upper-pole ureter in duplicated collecting system; common in children; usually large; significant obstruction; Weigert-Meyer rule (upper-pole ureter inferomedial, lower-pole ureter at normal position).
Distinct Features
Upper-pole moiety dysplasia/hydronephrosis, lower-pole moiety carries VUR risk. Large ectopic ureterocele may obstruct bladder outlet (bilateral obstruction). Surgical treatment is usually required.
Criteria
Ureterocele has prolapsed through bladder neck or urethra; more common in girls; appears as cystic mass at introitus/urethral meatus; on US cystic structure at bladder neck/urethra region, extravesical extension in prolapsed state.
Distinct Features
Requires urgent urological evaluation — high risk of urinary retention and infection. Recognized as cystic mass at introitus. Endoscopic incision or surgical reduction is required.
Distinguishing Feature
Diverticulum extends OUTWARD from bladder wall (extravesical); ureterocele is a cystic structure WITHIN the bladder lumen (intravesical). Diverticulum connects to bladder lumen with narrow neck; ureterocele is at the ureteral orifice with ureteral continuity.
Distinguishing Feature
Free bladder stone moves gravity-dependently (rolling stone) and is not surrounded by cystic structure. Stone within ureterocele is surrounded by ureterocele membrane (radiolucent halo) and immobile at the orifice region.
Distinguishing Feature
Urothelial carcinoma is a solid enhancing mass; ureterocele is a fluid-filled cystic structure showing cobra-head sign. Carcinoma is irregular-margined and heterogeneous; ureterocele is smooth, thin-walled, and homogeneously cystic.
Distinguishing Feature
Cystitis is characterized by diffuse wall thickening; ureterocele is a focal cystic structure localized at the orifice region. However, ureterocele may be complicated by infection — in this case ureterocele wall thickens and content may show debris.
Urgency
routineManagement
surveillanceBiopsy
Not NeededFollow-up
12-monthAsymptomatic small orthotopic ureterocele does not require treatment and is followed with annual US. Symptomatic ureterocele (recurrent UTI, obstructive uropathy, stone formation) or ectopic ureterocele requires endoscopic incision (primary treatment) or surgical repair. Endoscopic incision opens the ureterocele wall to allow drainage — simple and minimally invasive treatment with 80-90% success rate. In ectopic ureterocele + duplicated system, treatment is more complex: dysplastic upper-pole moiety + non-functional → upper-pole heminephroureterectomy; functional upper pole → reimplantation. If lower-pole VUR accompanies, antireflux surgery may also be needed. Stone within ureterocele is treated with endoscopic incision + lithotripsy or stone extraction. Prolapsed ureterocele requires urgent intervention — catheterization for bladder decompression followed by surgical repair. Follow-up: US evaluation of upper urinary tract at 3-6 months post-endoscopic incision; long-term follow-up (annual US + VCUG) recommended after surgery.
Ureterocele is usually diagnosed in childhood. The orthotopic type is often asymptomatic and found incidentally. Ectopic ureterocele is associated with duplex kidney and can cause upper pole obstruction and vesicoureteral reflux. Treatment is endoscopic incision or surgical repair. Complications include urinary infection, stone formation, and obstructive uropathy. Prolapsed ureterocele is a rare emergency.