Evolution of spontaneous endometriosis in the baboon (Papio anubis, Papio cynocephalus) over a 12-month period.

To document the spontaneous evolution of endometriosis, a repeat laparoscopy was performed in 11 baboons after 10 and/or 12 months. The mean number of endometriotic lesions had increased significantly after 10 months (P less than 0.02) because of a high proportion of new lesions (82%). These implants were mainly subtle (67%) and localized on the uterine peritoneum (58%). Progression of endometriosis did not go beyond revised AFS stage I. Additionally, repeat laparoscopy in 10 baboons with an initially normal pelvis showed an endometriosis incidence of 70% after 10 to 12 months. Remodeling of the lesions was apparent in both groups after 12 months. These results suggest that endometriosis is moderately progressive in the baboon. It is possible that multiple laparoscopies could favor the development of endometriosis.