[Electron microscopy studies of undescended testis in boys under 5 years of age].

Electron-microscope studies have been carried out on the undescended testicle since 1974. Material examined comprised 25 sections of undescended testicles from boys under five. The studies demonstrated that the ultrasctucture of undescended testes shows pathological changes even in the second year of life, and that these affect all the cellular structures, the seminiferous epithelium, supporting elements, seminal tubules and interstitial tissues. It is therefore concluded that operative treatment of retentio testis should be completed during the second year of life.