[Pseudomyxoma peritonei arising from urachal carcinoma].

A 77-year-old man was diagnosed with urachal cyst, but had not been followed-up because of his severe dementia. He visited our department complaining of mucinuria. Ultrasonography showed a tumor with heterogeneous contents above the bladder. Mucinousfluid was found by cystoscopic examination. After the fluid was removed, a non-papillary tumor with mucin secretion was identified at the dome of the bladder. Computed tomography revealed that the peritoneal cavity was filled with a mucinous tumor. Peritonitis was suspected because of the existence of free air and abdominal rebound tenderness, and emergent surgery was performed. Bowel perforation was not found. Tumors could not be removed and the tissue biopsy was performed. It was pathologically diagnosed as pseudomyxoma peritonei arising from urachal carcinoma.