[New views on the significance and treatment of undescended testis (author's transl)].

Undescended testis is of clinical importance because there are increased risks of milignancy and torsion and disturbances of fertility and psychosexual development. New quantitative morphologic investigations show that human prepubertal testicular maturation does not occur in phases but is continuous. This made it necessary to investigate afresh the causes of disturbance of fertility and the treatment of indescended testis. Our own investigations show that damage to the germ epithelium need not be congenital but may develop because of its ectopy. If, in dogs, a testis is placed into the abdomen, not only this but also the normally placed testis in the scrotum is damaged. The diameter of the tubules and their surfaces as well as the numbers of pachtenous primary spermatocytes are significantly reduced both in the displaced and the normally placed testis. Nuclear surfaces and density of the cells involved in spermatogenesis differ from those in the controls. The findings support the plea for early hormonal or surgical treatment in order to prevent later disturbances of fertility.