The undescended testis in children and adolescents. Part 1: pathophysiology, classification, and fertility- and cancer-related controversies

Undescended testis (UDT) is defined as failure of a testis to descend into the scrotum. It is one of the most common reasons for consultation in pediatric surgery and urology with an incidence of 3% in live-born male infants. Decades ago, classical studies established that the failure of a testis to descend alters the development of its germ cells increasing the risk of infertility and testicular cancer in adulthood. More recent publications have rebutted some of the myths and raised controversies regarding the management of these patients, which, far from being limited to surgical treatment, should include pathophysiological and prognostic aspects for a comprehensive approach to the condition. Therefore, here we present an updated review divided into two parts: the first assessing the pathophysiological aspects and risks of these patients focused on fertility and cancer, and the second addressing the different treatment options for UDT.