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