Cryptorchidism in Horses: Undescended Testicle in Colts and Stallions

Quick Answer
  • Cryptorchidism means one or both testicles do not fully descend into the scrotum.
  • A unilateral cryptorchid horse may still be fertile, and many affected horses continue to show stallion-like behavior because retained testicular tissue can still make hormones.
  • Diagnosis often combines a physical exam with blood testing for anti-Müllerian hormone (AMH) and testosterone, and sometimes ultrasound or hCG stimulation testing.
  • Definitive treatment is surgical removal of all testicular tissue. Leaving a retained testicle behind can lead to ongoing hormone-driven behavior and future complications.
  • Typical 2025-2026 US cost range for diagnosis and treatment is about $400-$6,000+, depending on testing, whether the retained testicle is inguinal or abdominal, and whether referral surgery or laparoscopy is needed.
Estimated cost: $400–$6,000

What Is Cryptorchidism in Horses?

Cryptorchidism is a congenital reproductive condition where one or both testicles fail to move normally into the scrotum. In horses, the retained testicle may stay in the inguinal canal or remain inside the abdomen. A horse with one retained testicle is called a unilateral cryptorchid. If both are retained, he is a bilateral cryptorchid.

This matters because retained testicular tissue can still produce hormones, especially testosterone. That means an affected colt or stallion may act like a stallion even if only one testicle is visible, or even after an incomplete castration. If only one testicle is retained, the descended testicle may still produce sperm, so fertility can remain possible.

Many pet parents first notice the problem when a young male horse has only one testicle in the scrotum, or when a horse believed to be gelded still shows mounting, aggression, or other stallion-like behavior. While this is not always an emergency, it does need veterinary evaluation so your vet can confirm whether testicular tissue is still present and discuss safe treatment options.

Symptoms of Cryptorchidism in Horses

  • Only one testicle visible in the scrotum
  • No testicles visible in the scrotum
  • Stallion-like behavior after supposed gelding
  • Difficulty confirming sex status on exam
  • Inguinal swelling or palpable tissue near the groin
  • Breeding ability despite one missing testicle

Cryptorchidism itself is often painless, so many horses seem otherwise healthy. The biggest clues are a missing testicle, persistent stallion-like behavior, or confusion about whether the horse is truly gelded.

See your vet promptly if your horse has groin swelling, pain, fever, drainage after castration, or severe behavior changes that create a handling risk. Those signs can point to additional problems beyond a retained testicle and deserve faster evaluation.

What Causes Cryptorchidism in Horses?

Cryptorchidism is considered a congenital condition, meaning the problem starts during development before birth. Normally, the testicles form in the abdomen and then descend through the inguinal canal into the scrotum. In cryptorchid horses, that process does not finish normally.

The exact cause is not always clear in an individual horse, but heredity is strongly suspected. Because of that concern, affected stallions are generally not considered good breeding candidates. Your vet may advise against breeding a horse with confirmed cryptorchidism, especially if the retained testicle is unilateral and fertility is still possible.

The retained testicle may be located high in the abdomen, close to the internal inguinal ring, or within the inguinal canal. That location matters because it affects how easy the testicle is to find, what diagnostic tests are most helpful, and whether surgery can be done in the field or is safer at a referral hospital.

How Is Cryptorchidism in Horses Diagnosed?

Diagnosis starts with a careful history and physical exam. Your vet will look at the scrotum, palpate the inguinal area, and review whether the horse has ever been castrated. In some horses, especially if the retained testicle is near the inguinal canal, your vet may be able to feel suspicious tissue during the exam.

Blood testing is often the next step. Anti-Müllerian hormone, or AMH, is one of the most useful tests for detecting testicular tissue in horses. Testosterone testing may also be used, either from a single sample or with an hCG stimulation test to see whether hormone levels rise after stimulation. These tests help your vet distinguish a true gelding from a cryptorchid horse or a horse with retained testicular remnants.

Ultrasound can sometimes help locate retained tissue, especially in the inguinal region, but it does not find every retained testicle. If the diagnosis is still uncertain, referral evaluation may be recommended. In some cases, the exact location is confirmed during surgery, particularly when the retained testicle is abdominal and cannot be identified reliably from the outside.

Treatment Options for Cryptorchidism in Horses

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$400–$1,200
Best for: Horses that are stable, not in immediate distress, and need confirmation before a surgical plan is made. This can also fit pet parents who need to stage care over time.
  • Farm or clinic exam
  • Scrotal and inguinal palpation
  • Review of prior castration history
  • Baseline bloodwork such as AMH and/or testosterone
  • Targeted ultrasound if available
  • Short-term behavior and handling plan while arranging surgery
Expected outcome: Good for reaching a diagnosis and planning next steps, but this is not definitive treatment if testicular tissue remains.
Consider: Conservative care confirms the problem but does not remove the retained testicle. Stallion-like behavior, fertility risk in unilateral cases, and future surgical needs may continue until definitive treatment is completed.
Most Common

Recommended Standard Treatment

$1,500–$3,500
Best for: Most unilateral cryptorchid horses with a retained testicle that is suspected to be inguinal or otherwise reasonably accessible.
  • Pre-op exam and sedation or anesthesia planning
  • Surgical removal of both the retained and descended testicular tissue when present
  • Open inguinal or standing inguinal approach for accessible retained testicles
  • Routine perioperative pain control and monitoring
  • Short hospital or same-day discharge depending on case complexity
  • Post-op recheck instructions
Expected outcome: Very good when all testicular tissue is identified and removed. Most horses recover well and hormone-driven behavior often improves over time.
Consider: Cost and recovery are greater than routine castration. If the retained testicle is actually abdominal or hard to locate, surgery may take longer or require referral and a different approach.

Advanced / Critical Care

$3,500–$6,000
Best for: Bilateral cryptorchids, abdominal retained testicles, horses with uncertain anatomy, repeat surgeries, or pet parents who want the broadest diagnostic and surgical options.
  • Referral hospital evaluation
  • Advanced imaging and repeat hormone testing when needed
  • Laparoscopic or more complex abdominal surgery
  • General anesthesia or specialized standing laparoscopic technique
  • Hospitalization for 1-3 days in many cases
  • Management of difficult anatomy, prior incomplete castration, or bilateral cryptorchidism
Expected outcome: Good to excellent in experienced hands, especially at equine surgical centers. Advanced approaches can improve visualization and help ensure complete removal of retained tissue.
Consider: Higher cost range, travel to a referral center, and more intensive perioperative care. Not every horse needs this level of treatment, but it can be the safest fit for complex cases.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Cryptorchidism in Horses

Bring these questions to your vet appointment to get the most out of your visit.

  1. You can ask your vet whether my horse is likely unilateral or bilateral based on the exam.
  2. You can ask your vet which blood tests make the most sense here, such as AMH, testosterone, or an hCG stimulation test.
  3. You can ask your vet whether the retained testicle seems inguinal or abdominal, and how that changes the surgical plan.
  4. You can ask your vet if this procedure can be done safely on the farm, at a clinic, or if referral to an equine hospital is the better option.
  5. You can ask your vet what cost range to expect for diagnosis, surgery, anesthesia, hospitalization, and follow-up care.
  6. You can ask your vet how long recovery usually takes and when normal turnout or training can resume.
  7. You can ask your vet how likely stallion-like behavior is to improve after all testicular tissue is removed.
  8. You can ask your vet whether this horse should be excluded from breeding because cryptorchidism may have a hereditary component.

How to Prevent Cryptorchidism in Horses

There is no reliable way to prevent cryptorchidism in an individual foal once development is underway. Because the condition is congenital and likely has a hereditary component, prevention focuses more on breeding decisions than on management after birth.

If a colt has one or both testicles undescended, your vet may recommend monitoring early on because normal descent can still occur in some young horses. If the testicle remains undescended, timely evaluation helps avoid confusion later, especially before sale, training, or breeding decisions.

The most practical preventive step is to avoid using affected horses for breeding unless your vet and breeding team have a clear reason otherwise. Good recordkeeping also helps. Document whether both testicles were present before castration and keep surgical records, because that history can be very important if a horse later shows stallion-like behavior.

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