[Urachal xanthogranuloma caused by a swallowed fish bone: a case report].

A 30-year-old man was referred to our department with a complaint of bladder irritability and with development of high fever. Physical examination revealed a tender mass in the suprapubic area. Computed tomographic scan and magnetic resonance imaging indicated a cystic mass above the bladder dome, extending toward the umbilicus. Urachal abscess was suspected and the mass was excised en bloc with the urachus. The wall of the mass was thickened, and a linear foreign body was detected in the mass, which was considered to be a fish bone. Pathological diagnosis of the mass was xanthogranuloma. We speculated that a swallowed fish bone had penetrated the bowel and might have migrated into the urachal cyst, which induced a xanthogranulomatous change of the wall.