Cryptorchidism in Horses

Cryptorchidism occurs only in male horses – for obvious reasons. It is characterized by the failure of one or both of the testicles to drop down from the abdominal cavity after birth. It can affect any male horse, and is suspected to be an inherited condition.

Cryptorchidism is not apparent at birth, as the testes do not drop from the abdominal space, through the inguinal canal and ring and into the scrotum – where they remain – until around two weeks of age. In some cases, the testes appear normal, and the stallion will behave in a normal way, as testosterone production is not affected.

There are different types of  cryptorchidism, depending on where in the abdominal body the testes are retained, whether one or both of the testes are retained, or whether the male horse was gelded without ever having been diagnosed with cryptorchidism (which can become a behavioral issue). In some cases, the horse may have been without one of its testicles, though this is rare.

If one or both of the testicles remain in the abdomen, the horse is said to be a rig, or ridgling.

Symptoms and Types

Bilateral cryptorchids/Complete rig

• Both testicles remain in the abdomen
• Physically appears as a gelding (testes cannot be palpated)
• Infertility
• Stallion-like behavior

Unilateral cryptorchids

• One testicle remains in abdomen
• May still be fertile

False Rig

• Stallion-like behavior in a gelding
• No presence of testicular tissue
• Infertility
• Deemed more as social rather than hormonal behavior

Physical lack of testicles

• May still exhibit stallion behavior

Causes

Cryptorchidism can be due to hereditary or developmental issues, whereby the testicles fail to drop after birth (around two weeks). Some breeds appear to be more prone to developing this disorder, including saddlebreds and quarter horses.

Diagnosis

Your veterinarian will begin by palpating the scrotum and abdomen, both externally and by rectal examination. For a better view of the abdomen and inguinal canal, your doctor can use ultrasound imaging and/or laparoscopy. This latter method uses a small camera that is attached to a flexible tube, and which can be inserted into the abdominal space for a close examination.

In some cases, if the testes can be located in an easy to access place in the abdomen, a laparoscope can also be used to remove the testes. If the testicle is found in the inguinal canal, the surgery may be more complicated, but can still be performed relatively quickly and easily, with a short recovery time.

If your horse is already a gelding, but is exhibiting stallion-like behavior, your doctor will examine the young horse for higher than normal testosterone levels, along with the abdominal and rectal examinations.