Approach to the cryptorchid horse

Cryptorchidism (‘hidden testis’) is the failure of one or both testes to descend from the developmental position close to the kidney to the normal adult position in the scrotum. The term cryptorchid is used to describe the non‐descended testis and, by extension, affected horses, although a number of colloquial terms are also used for the condition, including rig, ridgling and original. Cryptorchidism is thought to be an inherited condition and is the most common, non‐lethal developmental abnormality in horses. Although it has been reported in a variety of different breeds, those most commonly affected include percherons, saddlebreds, quarter horses, native‐breed ponies and crossbred horses; thoroughbreds have the lowest prevalence. This article gives an overview of the anatomy of the testes and describes the challenges involved in diagnosing the condition and the techniques that are available for treatment.