Answer of December 2010

Clinical History:

An 11 year old boy with good past health complained of abdominal pain after being kicked in the abdomen one week ago. Appetite was static; there was no vomiting, no abdominal distention and no anaemic symptoms. He sustained no other injuries. On physical examination he was afebrile and the abdomen was soft, with mild periumbilical tenderness. Blood tests including complete blood count and liver/renal function were all normal.

      Axial CT of the abdomen (non contrast)

                                            Axial CT of the abdomen (post contrast)

Diagnosis:

Infected urachal cyst

Discussion:

The urachus is also known as the median umbilical ligament. It is a midline tubular structure that extends upward from the anterior dome of the bladder towards the umbilicus. It is a vestigial remnant the cloaca and the allantois. Urachal remnant diseases are twice as common in males as females and can be divided into congenital and acquired.

Congenital urachal anomalies are divided into four types: 1) patent urachus 2) umbilical-urachal sinus 3) vesical urachal diverticulum and 4) urachal cysts. Patent urachus accounts for around 50% of congenital urachal anomalies. It is a persistent communication between the bladder lumen and the umbilicus. In the neonatal period, these patients may present with urine leakage. In about a third of cases, this condition is associated with posterior urethral valves or urethral atresia. An umbilical-urachal sinus (15%) is a blind dilatation of the urachus at the umbilical end.  There can be a small opening into the umbilicus and can present with periodic discharge. It is usually associated with an infection of the urachal remnant. A vesical urachal diverticulum (3-5%) occurs when the vesical end of the urachus fails to close and the urachus communicates only with the bladder dome. These patients tend to be asymptomatic. Urachal cysts (30%) develop if the urachus closes at both the umbilicus and the bladder but remains patent in between. Its usually occurs in the lower one-third of the urachus. They become symptomatic when they enlarge or become infected.

Acquired urachal anomalies occur when the urachal remnant reopens in pathological conditions such as infection or tumor. The route of infection maybe lymphatic, hematogenous, or vesical. Infection could be from both gram-positive and gram-negative micro-organisms. Benign tumors include adenomas, fibromas, fibroadenomas or fibromyomas. Malignant tumors are usually adenocarcinomas in 90% of the cases.