Urachal inflammatory mass mimicking an intra-abdominal tumor two years after excision of the urachal sinus in a child.

A 2-year-and-2-month-old boy presented with a tender fist-sized mass in the lower abdomen for 3 days. Turbid urine was also a complaint. His urachal sinus and umbilicus had been removed at the age of 2 months. Abdominal ultrasonography and computed tomography revealed a tumor mass beneath the lower abdominal wall. Total excision of the mass was performed. Microscopic examination showed an abscess located next to a small urachal remnant without stitches or foreign body reaction. To our knowledge, an urachal inflammatory mass mimicking an intra-abdominal tumor after excision of the urachal sinus, especially in children, is very rare. The factors causing such an urachal mass are discussed.