A Case of Endometriosis of the Appendix With Adhesion to Right Ovarian Cyst Presenting as Intussusception of a Mucocele of the Appendix

Endometriosis of the appendix is rare, and we present a case of endometriosis of the appendix with adhesion to right ovarian cyst presenting as intussusception of a mucocele of the appendix in a 35-year-old woman with no associated sign of endometriosis. Colonoscopy revealed intussusception-like change and mucosal defect in the mucosa at the orifice of the appendix. Abdominal computed tomography showed a low-density lesion, which seemed to be right ovarian cyst. However, as the appendix was located near this site, differentiation between ovarian cyst and mucocele of the appendix was difficult. Laparoscopic examination disclosed blue berry spots on the Douglas cul-de-sac and right ovarian cyst, and the appendix was atrophied and hardened and tightly adhered to the right ovary. Laparoscopic appendectomy and partial cecectomy was performed, and on pathologic examination, thickening and fibrosis of the muscle layer owing to endometriosis were judged to have caused intussusception-like changes.