Urachal carcinoma is a rare bladder tumor originating from urachal remnants, accounting for <1% of all bladder cancers. Histologically, >90% are mucinous adenocarcinoma. The urachus is a structure that provides connection between the allantois and bladder during fetal life and transforms into the median umbilical ligament after birth. Urachal carcinoma is typically located at the bladder dome in midline position and may grow toward the bladder lumen or extend extraperitoneally into the space of Retzius. Characteristically contains calcification (in 50-70% of cases) and may show cystic areas due to mucinous component. Diagnostic criteria include Sheldon criteria: tumor at bladder dome, absence of bladder epithelium involvement, absence of ureteral or pelvic extension, and presence of urachal remnant. Prognosis is generally poor as most patients are diagnosed at advanced stages; standard treatment is partial cystectomy with urachal remnant and umbilicus excision (en bloc resection).
Age Range
40-70
Peak Age
55
Gender
Equal
Prevalence
Rare
Urachal carcinoma originates from embryological urachal remnants. The urachus is a tubular structure extending between the bladder dome and umbilicus during fetal life (allantois remnant). It normally obliterates after birth to become the median umbilical ligament; however, in some individuals, urachal lumen remnants (glandular epithelium) persist. This remnant epithelium may undergo malignant transformation due to chronic irritation, infection, or unknown causes. Histopathologically, >90% are mucinous adenocarcinoma — this results from the urachal epithelium showing intestinal-type glandular differentiation. Mucin production explains the cystic/mucinous components and T2 hyperintensity on imaging. Calcification is due to dystrophic calcification within the mucinous matrix — this explains the punctate or peripheral calcification pattern seen on CT. The tumor tends to extend beyond the bladder wall into the space of Retzius (prevesical fat) because the urachus courses extraperitoneally. This extra-luminal growth pattern is the reason the tumor has often reached large size at diagnosis.
The combination of a mass with calcification in midline location at the bladder dome is nearly pathognomonic for urachal carcinoma. No other bladder tumor shows this specific combination of location and calcification with similar frequency. The presence of calcification strongly suggests mucinous adenocarcinoma histology. When this finding is complemented by tumor growth along the urachal axis between bladder dome and umbilicus, the diagnosis is largely confirmed.
Soft tissue mass with calcification in midline location at the anterior bladder dome on non-contrast CT. Calcification may be punctate (stippled), peripheral (shell-like), or coarse. The mass extends between the bladder lumen and prevesical space (space of Retzius) — may appear dumbbell-shaped. May contain low-density cystic areas (10-30 HU) due to mucinous component. Mass size is generally >4-6 cm at diagnosis.
Report Sentence
Heterogeneous mass with calcification in midline location at the bladder dome is observed, consistent with urachal carcinoma.
The mass shows heterogeneous enhancement in portal venous phase — solid components enhance moderately to prominently while mucinous/cystic areas do not enhance. The mass extends between the bladder dome and umbilicus, and prevesical fat in the space of Retzius is obliterated. Mass tissue is seen between the anterior abdominal wall muscles and the bladder. Enhancing solid component reflects the biological aggressiveness of the tumor.
Report Sentence
The mass at the bladder dome shows heterogeneous enhancement in portal venous phase with enhancing solid components and non-enhancing mucinous areas; extension into the space of Retzius is observed.
Prominently hyperintense areas within the mass on T2-weighted images — reflecting high water and mucin content of mucinous components. Solid tumor areas show intermediate signal. Calcification appears hypointense on T2 (signal void). The mass extends from the bladder dome to the space of Retzius and may show supero-anterior growth along the median umbilical ligament. Sagittal T2 images best demonstrate the extent of the mass along the bladder-umbilicus axis.
Report Sentence
Prominently hyperintense areas consistent with mucinous component and hypointense foci consistent with calcification are observed within the mass at the bladder dome on T2-weighted images.
Diffusion restriction in solid components of the mass on DWI — high signal with low values on ADC map. Mucinous/cystic areas show facilitated diffusion (low signal on DWI, high values on ADC). This pattern is important for separating solid from mucinous components and evaluating tumor biological aggressiveness.
Report Sentence
Diffusion restriction is observed in solid components of the mass on DWI while facilitated diffusion is found in mucinous areas; findings are consistent with urachal carcinoma.
Prominent enhancement in solid components and peripheral wall of the mass on contrast-enhanced MRI while central mucinous areas do not enhance. Enhancement pattern is heterogeneous and demonstrates the vascular solid areas of the tumor. Fat-sat T1 post-contrast sequences best demonstrate the difference between enhancing solid tissue and non-enhancing mucinous component. Enhancing solid extension in perivesical fat is important for evaluating the degree of local invasion.
Report Sentence
Prominent enhancement is observed in solid components of the mass on contrast-enhanced images while no enhancement is found in mucinous areas; peripheral enhancement pattern is consistent with mucinous adenocarcinoma.
Mass with mixed echogenicity in midline location at the anterior bladder dome on B-mode ultrasonography. Mucinous components appear hypoechoic/anechoic, solid areas hyperechoic, and calcifications as strongly echogenic foci (with posterior acoustic shadowing). The mass may grow toward the bladder lumen or extend extra-luminally toward the anterior abdominal wall. US is the initial assessment tool but CT/MRI is required for staging.
Report Sentence
Mass with mixed echogenicity containing calcification in midline location at the bladder dome is observed; further evaluation with CT/MRI is recommended; urachal carcinoma is among the differential diagnoses.
Criteria
Most common histological type (>90%). Extracellular mucin production predominates. Calcification present in 50-70% of cases.
Distinct Features
Calcified mass + low-density mucinous component on CT. Prominently hyperintense mucin areas on T2 MRI. Mixed echogenicity on US. Mucinuria clinical finding. CK20+, CDX2+ on immunohistochemistry (intestinal phenotype).
Criteria
Rare subtype (5-10%). Minimal or absent mucin production. Includes intestinal, enteric, or NOS (not otherwise specified) types.
Distinct Features
Calcification and cystic component less frequent. More solid, homogeneous enhancement pattern. Lower signal on T2 compared to mucinous type. Differentiation from primary bladder adenocarcinoma may be difficult — location (dome, midline) is the critical distinguishing criterion.
Criteria
Tumor confined to urachal mucosa, has not extended beyond bladder wall. Very rarely detected as most patients are diagnosed at advanced stages.
Distinct Features
Difficult to detect on imaging — may present as a small mucinous cyst or minimal wall thickening. Best prognosis — 5-year survival >90%.
Distinguishing Feature
Urachal cyst is benign, smooth-walled, simple cystic structure without calcification/solid component. Urachal carcinoma contains calcification, solid component, and heterogeneous enhancement. Infected urachal cyst may show wall thickening but no solid nodular component.
Distinguishing Feature
Primary bladder adenocarcinoma may be in non-midline location at the bladder dome and does not show extension along the urachal axis. Urachal carcinoma extends to the space of Retzius and shows growth toward the umbilicus. Calcification is less common in primary adenocarcinoma compared to urachal carcinoma. Sheldon criteria are used for differentiation.
Distinguishing Feature
Urothelial carcinoma usually located at lateral wall or posterior of bladder; dome midline location is atypical. Mucinous component and calcification are rare in urothelial carcinoma. Enhancement is homogeneous. Clinically, hematuria is more prominent. Histologically shows urothelial differentiation.
Distinguishing Feature
Bladder metastasis usually develops in the setting of known primary malignancy and is not limited to dome midline location. Mucinous component and calcification are not expected in metastasis (except for exceptions depending on primary tumor). Multiple lesions and concurrent other organ metastases favor metastasis.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralTreatment of urachal carcinoma is surgery-based. Standard approach is partial cystectomy with en bloc resection of the bladder dome, urachal remnant, median umbilical ligament, and umbilicus. Negative surgical margins are prognostically critical. Chemotherapy and radiotherapy may be used as adjuvant but evidence level is low. Prognosis is generally poor — most patients diagnosed at advanced stages (Sheldon Stage III-IV). Overall 5-year survival is approximately 40-50%. Recurrence is common and may present as peritoneal carcinomatosis. Regular staging CT is required for follow-up.
Urachal carcinoma is rare but aggressive. Diagnosis is often delayed because extraluminal growth does not produce early symptoms. Hematuria, mucinuria, and suprapubic mass are the most common symptoms. Treatment includes partial cystectomy with en-bloc excision of the urachus and umbilicus. Response to chemotherapy is poor. Five-year survival is approximately 40-50%.