Diagnostic approach of the cryptorchid stallion

The diagnosis of cryptorchidism in horses is often a challenge. Based on the history, clinical and rectal examinations and ultrasonography, a definitive diagnosis is not always possible. Various endocrinological diagnostic assays, such as the determination of testosterone, androstenedione, estrogens, urinary steroids and the anti-Mullerian hormone, which demonstrate the presence of testicular tissue, have been described. These tests all have their advantages and disadvantages, which are discussed in this article in order to help practitioners in the field.