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Updated: Feb 24, 2022

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Castrations are the most commonly performed surgical procedure in the horse. Assuming most of them will receive a post-op course of antibiotics and anti-inflammatories, complication rate should be low. However, castrations are left open to heal by “second intention” therefore post-op contamination is always possible. A bit of swelling is normal and will develop straight away, peak in 4-5 days after the op and subside in 10-14 days. Equally a bit of bleeding is normal: after all we are leaving a surgical site open to heal on its own. Luckily the vast majority of complications can be managed at the yard and are resolved routinely. Older horses develop complications more frequently than yearlings, due to presence of larger vascular structures.

This review includes only most common complications.


  • If it feels hard to palpation, and there is some degree of gooey discharge, and possibly some smell, chances are the surgical site is infected and the horse needs to go back on antibiotics for a few days to clear up.

  • If it feels soft, like a balloon filled with water, this is due to accumulation of fluid within the scrotum (which probably has closed very rapidly, limiting drainage by gravity). This type of swelling is defined as a seroma (a cavity filled with fluid) and might need to be opened to promote drainage. Do not do this yourself or you will inevitably get it infected.


Any castration that has developed significant swelling and has a temperature (above 38.5C) should be treated as infected. Most of them clear up with a few days of oral antibiotics. If the infection of the cord becomes chronic (ongoing over time), and the skin closes on top, the cord might continue to enlarge and will eventually form an abscess. This circumstance is called a scirrhous cord and might need surgical removal. It may take months or even years to become evident.


All horses will bleed for a bit following castration. Most of them stop within a few hours. As a rule of thumb, if you can count the drips, it will stop, if it’s free-flowing like the kitchen tap, call the vet. In case of an ongoing, profuse haemorrhage, the vet will try to identify what’s bleeding and stop it. In these cases, haemorrhage can be stopped by packing the site with sterile gauzes and leaving them in situ for 24h. These complications are generally sorted at the premises.

Omentum prolapse

The omentum is a layer of thin, fat-filled tissue that occasionally protrudes from the castration site. It just needs removal- should not lead to other complications.


This is a real emergency, but luckily this is a fairly rare event. Unfortunately, it’s often fatal. It occurs when a loop of bowel protrudes from the belly through the surgical site: this generally happens within the first 6h from surgery. It needs immediate referral for abdominal surgery. A piece of bowel might die in the process so the horse will need colic surgery as well. Inevitably there will be some degree of abdominal infection to deal with.



What are they?

As the name says, these are problems that occur following a castration and might need veterinary intervention to be corrected.

Time Window

These can occur from the immediate post-op period (in the first few hours) in case of bleeding, to years later in case of deep abscessation. Some of them need immediate veterinary attention, some of them can be managed by the yard staff.


  • Discomfort

  • Temperature (above 38.5C)

  • Discharge

  • Swelling

  • Pocketing of fluid

  • Lameness

  • Bleeding

  • Protrusion of soft tissue

  • Protrusion of small intestine (this is a real emergency)

What should I do?

It depends on the complication: as a general rule give the vet a call and describe what you see.

Some complications benefit from a bit of exercise and painkillers, other need to be confined and examined ASAP.

What NOT to do

- DO NOT PANIC IN CASE OF BLEEDING - most of them stop over time.

- Do not interfere with the wound - this inevitably predisposes to development of infection.

- Do not underestimate these complications: if dealt rapidly they are often quick and inexpensive to correct, and vice versa. Ring the vet for a chat!

What will the vet do?

Depending on the complication, it will be treated medically (i.e., with drugs) or surgically.

What should I do after the vet has left?

  • In case of evisceration: immediate referral.

  • In case of bleeding: stable confinement for 24 hours and monitor bleeding. Sedatives might be beneficial. Ring the vet if bleeding continues or starts again.

  • In case of infection/swelling: We advise walking as much as possible. Walking exercise favours dispersion of swelling and which makes the gelding more comfortable. It also promotes natural discharge through the incision (if left open to heal).


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