[Undescended testes. Current state of knowledge]

Undescended states are a frequent abnormality, which still has a controversial pathogenesis. The gubernaculum testis plays a major part, with a double hormonal control by anti-müllerian and androgenic hormones. Undescended testes present with acquired histological lesions that start developing during the 2nd year of life. Similar lesions can appear in the normally descended contralateral testis. Once acquired, these lesions are hardly or not reversible, and often associated with abnormalities of the epididymis and of the vas deferens. Infertility and cancer of the testis are the major risks of evaluation of this affection. The risks of cancer have been reassessed, and are now estimated to be 5 to times as high as for healthy men. Surgical descent of the testis does not decrease the risks. Cancer of the testis can be prevented by searching for in situ carcinoma on surgical biopsies. However, a population at higher risks, in which screening would be effective, still has to be defined among the patients with undescended testis, as the incidence of in situ carcinoma in a population with a history of undescended testis is about 2%. Hormonal treatments with HCG our LH-RH must always be used as first-intention treatments as they are innocuous, but they are not very effective. The treatment of an undescended testis is therefore mainly surgical. The decision must be made during the second year of life, before histological lesions of the testes occur.