Undescended testes (also called cryptorchidism or UDT) describes a condition where the testes, which form inside the abdomen, fail to move down into the scrotal sac. This occurs in about 20 percent of premature infant boys and 3 percent of full
The testes usually descend within the first few months of life. By 1 year of age, about 1 percent of boys have an undescended testis. Also, 10 to 15 percent of boys with undescended testes have bilateral (both sides) involvement.