The development and fate of spermatocoeles induced in the rat epididymal pathway by giving a single dose of ethylenedimethanesulphonate has been followed histologically for almost 5 months. Many of the retention cysts, which have intact walls, resolve completely but large spermatocoeles may persist. Their content of dead spermatozoa is removed and replaced by viable spermatozoa as the testis recovers from the antispermatogenic action of the compound. The presence of such residual cysts is then compatible with normal fertility. Rupture of the cyst walls with the formation of permanent spermgranulomata sometimes occurs.
No definite relationship to the loss of androgen support induced by the compound has been found, since concurrent treatment with testosterone did not prevent the formation of lesions.