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Case Study - Not a classical castration!

Sunny, a 12 month old colt initially presented for a routine castration. After a full physical exam, it was determined that only one of his testicles had descended into the scrotum. The second one was not there, making Sunny known as a cryptorchid, or a ‘rig’. This can be quite common, however the castration could not be done at the time, as a more invasive surgery was now required. He was booked in for another day.


Normally, during the gestational period, the testicles will form as the foetus develops and will slowly descend to take their place within the scrotum by 6 months of age (Figure 1). Occasionally this does not happen as it should, as it did in Sunny’s case. Horses with this are referred to as ‘cryptorchid’, which is the most common developmental defect of the horse. It is really the failure of the testicle to descend properly and can be bilateral or unilateral with the testicles positioned either in the abdomen, inguinally (within the inguinal canal, where they pass from the abdomen to the scrotum), or subcutaneously not within the scrotum. In any of these cases, they do need to be removed as can pose a risk later in life if left.

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Figure 1. Illustration of the normal path of the testicles (T) during development. They begin within the abdominal cavity next to the kidneys (K), migrate through the vagina ring (V) and inguinal canal and end up in the scrotum.

Sunny visited the Illawarra Equine Centre clinic for removal of his testicles. One had descended normally while the other one had not so he was unilateral cryptorchid. He was given some sedation to relax him before surgery. He was then anaesthetised and maintained on this during the procedure. He was put on his back and supported on either side of his body. There are four different techniques available to remove the testicles including the inguinal approach, parainguinal approach, suprapubic paramedian approach and the flank approach. The parainguinal approach was used for Sunny, with a small incision made through his abdominal muscles just in front of his hind legs (Figure 2). This incision is made just next to the inguinal canal where the testicle should have descended from, and using the first and middle finger, they were used to essentially ‘go fishing’ for the testicle. It was found within the abdomen and pulled to the outside where the normal castration procedure could be performed. Ligatures were tied around the cord to cut off the blood supply and the testicle was removed (Figure 3). As the second testicle was in the normal position, removal of that one was done through the scrotum itself.

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Figure 2. Illustration of the parainguinal incision site (small black line) just next to the inguinal canal. This was used for Sunny to remove his testicle.

Both incision sites, within the abdominal wall and through the scrotum were closed and cleaned and Sunny was recovered. As this was a slightly more invasive procedure than a routine castration he was put on a course of antibiotics for 5 days and was kept at the clinic so his medication could be given and his wound could be monitored. He went home well a few days after surgery. Currently he is a healthy, spritely young horse that is eating and doing really well. These procedures are very easily performed at Illawarra Equine Centre with the horses very well looked after by all the vets and support staff that work there.


Thank you Dr Mitch Brown and Dr Caitlin Marscham for looking after Sunny.

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Schumacher, J 2019, ‘Chapter 60 – Testis’ in Equine Surgery (fifth edition), ed JA Auer, JA Stick, JM Kümmerle & T Prange, Elsevier, Saint Louis, 994-1034


Burns, T, Chenier T & Munroe G 2011, ‘Chapter 2.2 – Male reproductive tract’ in Equine Clinical Medicine, Surgery, and Reproduction (first edition), ed GA Munroe & JS Weese, Manson Publishing/The Veterinary Press, London, 326-373

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