Fertility in cryptorchidism: improved timing of fixation and treatment in an experimental model.

Modifications were made in an experimental model in the rat to make it more analogous to human cryptorchidism and more useful in evaluating treatment. The age of experimental bilateral cryptorchidism was changed from 3 days to 11 days. Neither group was able to father offspring. The age at orchiopexy also was modified from the range of 21 to 28 days to exactly 21 days. The ability to father offspring improved significantly (72 versus 30 per cent) and it was not significantly different from previously reported sham operated rats (84 per cent). The current experimental model demonstrates that early surgical treatment can restore fertility to mechanically cryptorchid animals. The model can be used to evaluate the effects of varying types and timing of treatment.