Incidence, time trends, laterality, indications, and pathological findings of unilateral oophorectomy before menopause

Unilateral oophorectomy (UO) is a common surgical practice, yet it remains understudied. We investigated trends in incidence rates, indications, and pathological differences in the right and left ovaries in women younger than 50 years.The Rochester Epidemiology Project medical records linkage system was used to identify all women in Olmsted County, MN, who underwent UO between 1950 and 2007 (n = 1,838). We studied the incidence rates, indications, and pathologies of UO by laterality, and investigated trends across time.Pooling all oophorectomies across a 58-year period, we found that the incidence of UO was higher than the incidence of bilateral oophorectomy through the age of 39 years; however, bilateral oophorectomy surpassed UO thereafter. The incidence of UO increased from 1950 to 1974 but decreased thereafter and was surpassed by the rate of bilateral oophorectomy after 1979. Before 1985, left ovaries were removed more frequently than right ovaries with or without a medical indication for UO. Ovaries removed with a medical indication showed pathological differences between the right ovary and the left ovary, with endometriosis being more common in the left ovary. Ovaries removed without a medical indication did not differ in pathology by side.There have been major changes in incidence rates of UO across six decades. Medically indicated UO has been more common on the left side due, in part, to the higher prevalence of endometriosis. However, UO without a medical indication has also been more common on the left side because of surgical preferences and traditions. The long-term consequences of right or left UO on timing of menopause, morbidity, and mortality need further study.