Applied Radiology

Diagnosis

Urachal carcinoma

Findings

Three axial noncontrasted-computed tomography (CT) images demonstrate an elongated cystic structure arising from the dome of the bladder and extending superiorly towards the midline abdominal wall. A soft-tissue mass with stippled calcifications arises from the base of the cystic structure and invades the dome of the bladder.

Discussion

The urachus, or median umbilical ligament, is a remnant of the allantois, which extends from the dome of the bladder to the umbilicus. There is a spectrum of abnormalities, which arise from incomplete obliteration of the channel. A patent urachus is due to failure of the entire urachal channel to close, while a urachal diverticulum and a urachal sinus are due to incomplete closure of one end of the urachal channel. The urachal diverticulum maintains an open connection to the bladder while the urachal sinus communicates with the umbilicus. Lastly, a urachal cyst arises secondary to closure of the both the umbilical and bladder connections with incomplete obliteration of the midportion of the urachus.

Urachal carcinoma may arise within a urachal remnant and tends to present with hematuria and/or mucoid discharge. Of all cancers of the urachus, 85% to 90% of cases are adenocarcinomas. It tends to occur between the ages of 40 and 70, and is 3 times more common in males.

Urachal carcinoma is usually first detected by CT, which demonstrates a mass centered outside of the dome of the bladder, usually within the midline and in the presence of a urachal remnant. Approximately 70% of cases contain calcifications, an uncommon feature for transitional cell carcinoma. Contrast enhancement is generally heterogeneous.

Treatment consists of partial or total cystectomy with complete resection of the urachus up to the umbilicus. However, due to late presentation, the prognosis is poor with a 5-year survival of <15%.

1. Yu JS, Kim KW, Lee HJ, et al. Urachal remnant diseases: spectrum of CT and US finding. Radiographics. 2001;21:451-61.
2. Thali-Schwab CM, Woodward PJ, Wagner BJ. Computed tomographic appearance of urachal adenocarcinomas: Review of 25 cases. Eur Radiol. 2005;15:79-84.