Testicular undescent and torsion.

The higher the testis resides above the scrotum, the more dysgenetic the morphology is likely to be. High testes are rarely responsive to HCG and should be treated by orchiopexy by the age of 2 to 3 years. The undescended testis does not mature normally after the age of 2 years and may produce adverse effects on the contralateral descended testis, possibly by an autoimmune mechanism. A course of HCG for boys with low-lying undescended testes, both unilateral and bilateral, may produce descent in as many as 15 per cent of patients and may make the technical aspects of orchiopexy easier in those who do not respond. Unilateral cryptorchid testes that are dysplastic or located high should generally be removed before adolescence.