A 76-year-old man was admitted because of bloody stool. Colonoscopy revealed a protruding lesion in the rectum which was diagnosed as well differentiated adenocarcinoma by biopsy, and a mucocele of the appendix was also found. Anterior resection of the rectum and resection of the cecum were performed. Mucocele of appendix is rare and is difficult to be diagnosed preoperatively. The mucocele of the appendix is often complicated by pseudomyxoma peritonei, malignant alteration and invagination of large intestine. This case is rare because the mucocele of the appendix is accompanied by intussusception of the appendix and advanced rectal cancer.
