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Cryptorchidism, Retained Testicle

Synonyms: High Flanker, Rig

In normal horses, the testicles have descended into the scrotum at birth. Cryptorchidism is the failure of one or both testicles to descend into the scrotum. Cryptorchidism is a common congenital (hereditary) disorder in horses.

The incidence of testicular retention is approximately equal for left and right testicles. However, there may be differences in the specific location of the testicle in left versus right cryptorchids. A horse that is actually born with only one testicle is extremely rare. One large study suggests that retention of both testicles is rare, 13.2% of cases.

In normal foals, the testicles are present and can be felt in the scrotum at birth. If you cannot feel both testes in the scrotum by 1-2 years of age, the likelihood of descent is very low. In some cases, your vet can feel all or part of a testicle higher up in the inguinal canal. Routine castrations on colts with both testicles are generally performed in the field. If your vet can feel the tip of the testicle, they may choose to remove the partially retained testicle in the field. However, since cryptorchid castration is a more complicated procedure, the standard of care is for it to be performed at a surgical facility.

Diagnosis is by exam by your vet via physical examination and often rectal exam.

Treatment is cryptorchid castration, a more complicated procedure usually performed at a surgical hospital.


  • Is there a genetic basis for this?
  • What are the options for castration?
  • Do you feel confident in castrating my horse in the field, or should it be performed at a surgical facility?

    Do not breed cryptorchid stallions. The condition has a genetic component and is likely to be passed on to progeny.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Helpful Outside ResourcesCredible Equine Health Information on the Internet

    Author: Doug Thal DVM Dipl. ABVP


    Hartman R,Hawkins JF, Adams SB, Moore GE, Fessler JF. Cryptorchidectomy in Equids: 604 Cases (1977-2010) JAVMA, Vol 246, No. 7, April 1, 2015


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