Prevalence and laparoscopic appearance of spontaneous endometriosis in the baboon (Papio anubis, Papio cynocephalus).

The prevalence of spontaneous endometriosis was investigated by laparoscopy in 52 baboons (Papio anubis and Papio cynocephalus) of proven fertility. Clinical endometriosis was diagnosed in 9 (17%) and 4 (8%) baboons with or without a previous hysterotomy, respectively. Endometriosis was confirmed by histology in 75% of these animals. The 37 endometriotic lesions were classified as typical (13%), subtle (57%), or suspicious (30%); and the percentage of histological confirmation was 100%, 61%, and 50%, respectively. Lesions were found on the uterosacral ligaments and in Douglas' pouch (46%), on the uterine peritoneum and the uterovesical fold (38%), and on uterine-omental adhesions (11%). Only 5% of the lesions were localized on the ovarian ligament, whereas ovarian endometriosis was not found. This study for the first time demonstrates that spontaneous endometriosis occurs in healthy baboons with proven fertility. It also shows that the laparoscopic appearances, the histological aspect, and the localization of the pelvic lesions are comparable to those found in women. We therefore conclude that the baboon is a good animal model for the study of endometriosis.