Clinical relevance of the baboon as a model for the study of endometriosis.

OBJECTIVE: To review the value of the baboon as a model for the study of endometriosis. DATA IDENTIFICATION AND SELECTION: Studies performed at the Institute of Primate Research in Nairobi, Kenya (1990-1994), and published in peer-reviewed journals. RESULT(S): Spontaneous endometriosis was found in about 25% of the baboons, and its prevalence increased with the duration of captivity. The laparoscopic appearance, pelvic localization, and microscopic aspects of the disease were similar to endometriosis in women. Microscopic endometriosis in macroscopically normal peritoneum was rare. Sampson's hypothesis (i.e., retrograde menstruation causes endometriosis) was supported by the increased incidence of retrograde menstruation in baboons with spontaneous endometriosis, the observation that cervical occlusion could cause retrograde menstruation and endometriosis, and the finding that intrapelvic injection of menstrual endometrium caused experimental moderate to severe endometriosis similar to the spontaneous disease. During follow-up of more than 2 years, endometriosis in baboons appeared to be a progressive disease, with active remodeling between several types of lesions. Progression was stimulated by high-dose immunosuppression. Fertility was normal in baboons with minimal disease but was reduced in baboons with mild, moderate, or severe endometriosis, possibly related to an increased incidence and recurrence of the luteinized unruptured follicle syndrome. CONCLUSION(S): The baboon is a good model for the study of endometriosis.