A 42-year-old man arrived by ambulance to the Emergency Department eight hours after rolling his ATV the previous evening. He complained of head, neck, back, and hip pain that had been constant since the accident.
Physical exam revealed tenderness to palpation of the lower thoracic spine.
A complete blood count revealed a slightly elevated white blood cell count but was otherwise normal.
Contrast-enhanced CT of the head, abdomen, pelvis, and spine were ordered.

CT reveals a small, anterosuperior outpouching on the dome of the bladder representing a vesicourachal diverticulum.

Vesicourachal diverticulum is one of four urachal anomalies, a rare group of disorders. The urachus is a midline tubular structure extending from the dome of the bladder toward the umbilicus. It is a vestigial remnant of the allantois, which is derived from the embryologic yolk sac, and the cloaca, which eventually forms the fetal bladder. The urachus involutes in the majority of individuals, forming a fibrous band called known as the median umbilical ligament. It lies between the parietal pleura and transversalis fascia, in the space of Retzius.

Urachal anomalies result from failure or incomplete closure of the fetal urachus. A patent urachus is the most common anomaly, accounting for 50% of cases. It presents in the neonatal period with leakage of urine from the umbilicus.

The remaining disorders may be asymptomatic until an acquired disease (infection) brings the anomaly to clinical attention. Umbilical-urachal sinus accounts for 15% of cases and results from the persistence of the superficial segment of the urachus opening onto the surface of the skin. It presents in the first few months of life as periumbilical tenderness and/or umbilical wetness. Sinography is the study of choice for diagnosis.

Vesicourachal diverticulum results from a persistence of the deep segment of the urachus, creating a point or diverticulum off the anterior-superior bladder wall. It is usually asymptomatic and discovered incidentally on CT as in this case presentation. It may be complicated by UTI and stone formation.

Urachal cysts are a persistence of an intermediary segment of the urachus with fibrous attachments to the bladder and umbilicus. It typically occurs in the lower 1/3 of the urachus and presents in childhood as a painful suprapubic mass after becoming infected. Ultrasound is sufficient for diagnosis.

Urachal remnants have the propensity to undergo metaplasia and become malignant. Urachal cancer is a rare form of bladder cancer, but accounts for 34% of bladder adenocarcinoma. Due to this risk, current recommendations call for the complete removal of the urachus and a cuff of the bladder when anomaly is diagnosed.

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