Paediatric Radiology

One month old child, with persistant crying. History of umbilical discharge a few days after birth, but no discharge at present.Ultrasound was performed. What is the diagnosis?

Imaging Diagnosis

Patent urachus, with urachal mass

Discussion

Congenital patent urachus is a lesion that is usually recognized in the neonate as a rare anomaly.

Two forms of congenital patent urachus exist:

(1) persistent patent urachus with a partially distended bladder and

(2) a vesicoumbilical fistula representing failure of the bladder to descend. When the bladder forms, the bladder apex never forms a true urachal tract.

The more common form of a patent urachus results when there is failure of obliteration of the urachal remnant. Persistence of the urachus has been attributed to intrauterine obstruction.

The urachal cyst develops most commonly in the distal one third of the urachus, but it also can occur in the proximal third, depending on the type of urachal termination variant that it occurs in. These cysts rarely manifest in the newborn period but may become symptomatic during late childhood or early adult life. Serious complications of an infected urachal cyst include rupture of the preperitoneal tissues, rupture into the peritoneal cavity causing significant peritonitis, and, rarely, inflammatory involvement of the adjacent bowel and formation of an enteric fistula.

A diagnosis of urachal cyst is most often made by ultrasound, delineating the location of the cyst relative to the bladder and peritoneum and the limited extension. CT studies may be occasionally useful in further delineating the extent of the cyst and involvement of adjacent structures, such as bowel. Other useful diagnostic studies include excretory urography and cystoscopy.

Treatment of the urachal cyst depends on the symptoms. In children who have only a small, asymptomatic mass, watchful waiting may be appropriate. However, in the setting of an infected urachal cyst, the primary treatment includes excision and drainage of the cyst, marsupialization, or percutaneous catheter drainage. Definitive treatment with surgical excision should be performed once the inflammation subsides. The staged approach to treating an infected urachal cyst helps to limit the amount of bladder wall resected and reduces the risk of injury to the adjacent intraperitoneal structures.