Development of spontaneous endometriosis in baboons.

Abstract

To determine the incidence of spontaneous endometriosis over a 32-month period in baboons with initially normal pelves. In this observational longitudinal study, which was performed at the Institute of Primate Research, Nairobi (Kenya), 24 baboons with laparoscopically confirmed normal pelves underwent 67 serial laparoscopies (mean 2.8 +/- 1.9, median 3, range 1-6) after 1-3 months (n = 8), 4-6 months (n = 11), 7-9 months (n = 9), 10-12 months (n = 17), 13-15 months (n = 6), 16-18 months (n = 4), 19-21 months (n = 3), 22-24 months (n = 4), 25-27 months (n = 1), and 30-32 months (n = 4). During each laparoscopy, the pelvis was examined for the presence of endometriosis. The number, size, and type of endometriotic implants were noted on a pelvic map, and the endometriosis score and stage were tabulated according to the revised classification of the American Fertility Society. Taking into account the variable length of follow-up, we used life-table analysis to calculate the cumulative incidence of endometriosis. The cumulative incidence of minimal endometriosis (proven by histology) was 64% up to 32 months of follow-up. The eight baboons that developed proven endometriosis were followed over longer periods of time and had undergone more laparoscopies than the animals that did not develop the condition. There is a high incidence of minimal endometriosis in baboons, which increases with the time of follow-up and the number of repeat laparoscopies.