The dog has two testicles, housed within the scrotum. Testicular diseases in dogs include congenital abnormalities, such as cryptorchidism (testicle fails to descend into scrotum and is retained in the abdomen); infections; trauma; torsion; and tumors. Dogs with testicular disease may present with a swelling in the scrotum or problems during breeding. Dogs that will not be used for breeding should be castrated (surgical removal of the hormone producing testicles) to prevent pet overpopulation, avoid unwanted behaviors (e.g.: inter-dog aggression and roaming to find a mate), and potentially cure the disease.