Clinical Diagnosis of the Cryptorchid Stallion

Cryptorchidism, or failure of testicular descent, can be a challenging clinical diagnosis, particularly in horses with an unknown castration history. Etiology of cryptorchidism is multifactorial and includes a genetic component. Diagnosis is centered on a detailed physical examination. Transrectal ultrasonography and endocrinologic assays including baseline testosterone, estrone sulfate, and human chorionic gonadotrophin stimulation are diagnostic aids. Treatment of cryptorchidism in horses is surgical removal of testicular tissue. A review of testicular descent, proposed etiologic mechanisms of cryptorchidism, as well as diagnosis and treatment options are presented.