Urachal Anomaly

The urachus is the embryonic channel between the bladder dome and the allantois. It normally obliterates in the fifth month of fetal life to form the median umbilical ligament, which runs in the space of Retzius between the umbilicus and the bladder.

Urachal anomalies result from incomplete obliteration and fall into four groups:

• Patent urachus: a communication between the bladder and umbilicus, about 50 percent.
• Urachal cyst: a fluid filled section in the middle, about 30 percent.
• Umbilical urachal sinus: a blind ended tract open at the umbilicus, about 15 percent.
• Vesicourachal diverticulum: an open tract at the bladder end, about 5 percent.

Incidence is about 1 in 150,000 live births for patent urachus and 1 in 5,000 for the other types (cysts are often asymptomatic and found at imaging). They are twice as common in males.

A patent urachus is commonly associated with bladder outlet obstruction (posterior urethral valves, urethral atresia) and prune belly syndrome.

Complications: infection, abscess, stones, haematuria, rupture and, in adults, urachal carcinoma (adenocarcinoma in about 90 percent).

• Patent urachus: continuous or intermittent leakage of clear fluid (urine) from the umbilicus, which worsens with crying or straining, periumbilical dermatitis, and a delay in cord separation or a moist, granulating umbilical stump; urine may drain from a swollen cord.
• Umbilical sinus: persistent serous or purulent umbilical discharge, granuloma and recurrent omphalitis.
• Urachal cyst: often asymptomatic; infected cyst presents with lower abdominal pain, fever, a tender infraumbilical midline mass, and voiding symptoms, sometimes with periumbilical erythema and discharge.
• Vesicourachal diverticulum: usually asymptomatic.
• Adults: recurrent urinary tract infection, haematuria, mucusuria, and a suprapubic mass; urachal carcinoma may present with haematuria, mucus in urine, and pain.
• Differential: omphalomesenteric duct remnants (stool or mucus from the umbilicus), umbilical granuloma, omphalitis, and umbilical hernia.

• Clinical inspection, with probing of the umbilical tract and testing of the discharge for urea and creatinine.
• Ultrasound of the infra umbilical midline: a tubular or cystic structure along the median umbilical ligament, usually between the bladder dome and the umbilicus, with a thickened wall and debris when infected.
• Fistulogram (contrast injection into the umbilical opening) and voiding cystourethrogram show a patent tract, with contrast reaching the bladder; used also to exclude outlet obstruction.
• CT or MRI for suspected infection or malignancy (calcification of the cyst wall, irregular solid mass above the bladder dome).
• Cystoscopy if indicated, and urinalysis and culture.
• Exclude outlet obstruction in infants by urethral evaluation and urodynamics where indicated.

• Asymptomatic urachal remnants found incidentally in infants: observation with ultrasound follow up, because many obliterate spontaneously during the first year. Adults with an asymptomatic remnant are generally excised because of the small risk of malignancy and infection.
• Patent urachus in a newborn: observation for 4 to 6 weeks (some close spontaneously), after treating urinary obstruction if it exists. If it persists, perform surgical excision of the whole tract together with a bladder dome cuff and closure of the bladder, by open surgery (infraumbilical incision) or laparoscopic approach. A urethral catheter is left for 3 to 5 days.
• Infected urachal cyst or abscess: antibiotics according to organism. Initially use amoxicillin clavulanate 25 to 30 mg/kg of the amoxicillin component every 8 hours in children, or 625 mg three times daily in adults; or ceftriaxone 50 to 75 mg/kg daily with metronidazole 7.5 mg/kg every 8 hours.
• Then perform percutaneous or open drainage, followed by interval complete excision after 4 to 12 weeks. Excision during the acute infection carries a high risk of recurrence.
• Umbilical sinus: complete excision, including the tract, and umbilicoplasty.
• Excision of the median umbilical ligament with the cyst, together with a bladder cuff when the tract is connected to the bladder. Recurrence is rare after complete excision.
• Adult urachal tumours: complete en bloc resection (partial cystectomy with removal of the urachal ligament, umbilicus and surrounding tissue), with staging and pelvic lymph node dissection.
• Postoperative follow up: wound care, ultrasound after 3 months in complicated cases, urine culture. The prognosis is excellent after complete removal.