[Rectal pain and tenesmi caused by a large appendix mucocele].

A 60 year-old man presented with rectal pain and tenesmi. On digital rectal examination a pelvic mass was detected. Computed tomography and MR scans showed a 14 × 5.5 × 5 cm large cystic process located in the right side of the pelvis with no clear indication of its origin. Explorative laparotomy revealed a large appendix mucocele based on a cystadenoma. The mucocele was resected in healthy tissue and without perforation. Needle aspiration or drainage should be avoided in cystic intraabdominal processes of unknown origin, and careful operative handling is imperative, because spillage of mucin may result in later development of pseudomyxoma peritonei. Careful digital rectal examination may detect important pelvic pathology.