Testicular Descent and Cryptorchidism

Anti-Müllerian hormone as an indicator of hemi-castrated unilateral cryptorchid horses

“…Cryptorchidism, the failure of one or both testes to descend normally, is most frequently found in humans, pigs, and horses, although it does occur in many other mammalian species [ 7 , 21 ]. The percentage of foals with cryptorchidism is estimated to be 5–8% (males), and most cases are unilateral cryptorchidism [ 3 ]. Horses with unilateral cryptorchidism are usually fertile, but bilateral cryptorchids are sterile.…”

“…The interstitial (Leydig) cells, which produce testosterone, are not as heat sensitive as the cells of the seminiferous epithelium. Thus, although bilateral cryptorchid horses do not produce viable sperm, they usually exhibit masculine behavior [ 3 ]. In some cases, unilaterally cryptorchid horses have their single normally descended testis removed by incomplete castration and are erroneously considered geldings.…”

“…The diagnosis of cryptorchidism can be complicated if a single normally descended testis has been removed [ 3 ]. A complete history, including behavior and previous surgery, is essential to make a correct diagnosis of cryptorchidism [ 17 ].…”

“…Some practitioners conduct rectal examinations on stallions to determine the testis location; however, the usefulness of rectal palpation to determine the location of a retained testis is controversial. Only some authors have found this test reliable [ 3 ]. In a previous study, preoperative diagnosis by rectal palpation of the vaginal rings was 87% accurate [ 19 ].…”

Canine Cryptorchidism: A Concise Review of its Origin, Diagnosis and Treatment Caroline Spangenberg

“…The term 'cryptorchid' refers to the birth defect that occurs when one or both of the testicles does not descend from the abdomen into the scrotum. [1][2][3][4][5][6] Unilateral cryptorchidism occurs when only one testis does not descend, while bilateral cryptorchidism occurs when neither testis descends. [5] In the case of a unilateral cryptorchid, only one testicle will have descended while the other remains retained somewhere in the abdomen, in the inguinal canal, or the pre-scrotal area.…”