Observations on multiple sperm granulomas in the rat epididymis following vasectomy.

Seven epididymides of long-term vasectomized rats showing multiple sperm granulomas were studied in serial histological sections. Despite the presence of the multiple granulomas, only two rats showed continuity of the epididymal duct with the central sperm mass of a granuloma. A further three specimens showed breaks in the epididymal epithelium at sites of local distension in the epididymal tail. Granulomas in the epididymal body seem to receive spermatozoa only transiently. The spermatozoa at the center of granulomas in continuity with the epididymal duct showed evenly distributed sperm heads. A number of others showed clumping of spermatozoa, attributed to stagnation of flow and fluid resorption. In many granulomas, folds in the macrophage layer with a connective tissue core rich in lymphocytes and plasma cells projected into the central sperm mass. We conclude that the sperm granuloma is a dynamic structure that shows changes with age and that the sperm granuloma closest to the testis must not be assumed to be the one that is draining the spermatozoa. Copyright 2000 Wiley-Liss, Inc.