Acute urinary retention as a result of a bladder diverticulum.

An 11-month-old infant presented with acute urinary retention. He had presented 3 months earlier with complaints of an enlarging abdominal mass that was initially diagnosed as a mesenteric cyst on ultrasonography. Voiding cystourethrogram revealed a large bladder diverticulum. Bladder diverticulum should be a differential diagnosis in children, especially male, presenting with urinary retention, fever and an abdominal mass.