Equine Castration Complications Reviewed

Although castrations are routine procedures for many equine practitioners, the risk for complications remains. And while most complications are generally mild, some have life-threatening implications. To better understand these complications, a University of California, Davis (UC Davis), research team recently took a closer look at their prevalence and outcomes.

"Complications that result from castration, including scrotal swelling, edema (fluid swelling), hemorrhage, incisional infections, bacterial infection of the spermatic cord, omental (the omentum is a fold of the abdominal tissue surrounding the organs) herniation, eventration (a segment of small intestine travels from the abdomen down through the inguinal canal), penile trauma, hydrocele formation (a collection of fluid within the vaginal cavity, where the testicle resided), and peritonitis (inflammation of the membrane lining the abdomen) have been reported," explained Isabelle Kilcoyne, MVB. "Most postoperative complications are mild and not considered life-threatening, but eventration, hemorrhage, and peritonitis may be fatal."

To gain a better understanding of complication rates and to identify possible risk factors, Kilcoyne, an equine surgery resident at UC Davis' William R. Pritchard Veterinary Medical Teaching Hospital (VMTH), and colleagues conducted a retrospective study in which they reviewed castration complications in an ambulatory practice over a 10-year period.

"A complete understanding of these factors can help veterinarians minimize the development of these complications and treat them more effectively when they do occur," she said.

In the study, the research team reviewed the medical records of equids castrated by the VMTH's Equine Field Service between Jan. 1, 1998, and Dec. 31, 2008. The team collected and analyzed a variety of data from 324 cases' (311 horses or ponies, 10 mules, and three donkeys) medical records to determine if any factors were associated with the development of complications following routine castration. If complications were noted in the medical records, the team classified them as Grade I (complications developed more than 24 hours after surgery that did not require emergency treatment), Grade 2 (complications requiring more intensive emergency management 24 hours or less after surgery), or Grade 3 (complications resulting in death or euthanasia).

All of the castrations were performed by senior veterinary students while under the direct supervision of an experienced veterinarian. According to medical records, 33 of the 324 equids (10.2%) experienced complications, and only one complication proved fatal; Kilcoyne said this means the overall incidence of complications association with castration was low in the current study and the mortality rate was very low at 0.3%.

The team also found that, overall, complications associated with castration were mild in nature. Of the 33 horses that developed complications, 25 were classified as Grade 1, seven as Grade 2, and one as Grade 3. Grade 1 complications included mild swelling in five equids, seroma (fluid accumulation in the tissues that can become bone infection) formation in 11 equids, infection or abscess at the surgical site in seven equids, and fever with respiratory signs in two equids. Grade 2 complications included hemorrhage in six equids and tissue protruding from the incision site in one case. The Grade 3 complication was a small intestine eventration and was the only complication to result in euthanasia. The remaining 32 equids recovered with appropriate therapy and without further complications.

Kilcoyne explained that horses can be castrated using three different surgical techniques; open, closed or semi-closed. When an open castration is performed the parietal tunic (the sac or lining surrounding the testis) is incised allowing direct crushing or emasculation of the spermatic cord. Using the closed and semi-closed techniques the parietal tunic is removed with the testis. Veterinarians chose different techniques based on the breed of horse, age, size of the testicles and spermatic cord as well as individual experience with each technique, she said.

All of the horses included in this study were castrated using the closed or semi-closed technique. In the study population 247 of 324 equids were castrated using the closed technique, and 15 (6.1%) of those animals developed problems. Veterinarians performed the semi-closed technique on 77 equids; 18 (23.8%) of those horses developed complications. The team concluded that the latter group "had significantly higher odds of developing a complication after surgery," making surgical technique selection a possible risk factor for complication development. Kilcoyne noted possible reasons for this difference, including the need for more tissue handling with the semi-closed procedure, increased contamination potential, and/or a longer surgery duration than with other techniques due to the extra dissection required.

The majority of the castrations were performed (293 of 324, or 90.4%) under general anesthesia, 28 (9.6%) of which developed complications. The remaining 31 horses were castrated standing with local sedation. Researchers noted that all of the horses castrated standing were older than one year, and five (16.1%) developed complications.

The team also found that, of the horses castrated under general anesthesia, additional anesthetics to maintain anesthesia were administered to 201 horses. Kilcoyne and colleagues determined that horses receiving additional anesthetics had a significantly higher complication rate than horses that didn't receive additional anesthetics. Although the exact reason for the difference remains unclear, Kilcoyne suggested that the need for additional anesthetics could point to these surgeries taking a longer time to perform.

And finally, although the team didn't identify an association solely between age and complication development, Kilcoyne noted that "horses that were castrated via the semi-closed technique were typically older than those castrated via the closed method. Horses castrated via the semi-closed technique had significantly higher odds of developing a complication than did those castrated via the closed technique, and this may have been confounded by age."

While veterinarians leave owners with instructions for castration aftercare, Kilcoyne suggested a few tips for owners to help keep patients comfortable after surgery:

  • Stall rest with restricted exercise is recommended for the first 24 hours to prevent hemorrhage and to allow recovery from the surgery.
  • Following this initial period, forced exercise consisting of hand walking or trotting daily for up to 14 days is of upmost importance to help reduce swelling, the risk of the incisions closing prematurely, and seroma formation. "Simply turning a horse out into pasture will not necessarily ensure sufficient movement to promote drainage, and the benefits of forced exercise cannot be overemphasized," she said.
  • Isolate the new gelding from mares for at least two to three days.
  • Carefully monitor the horse for excessive swelling (usually the most swelling is noted at four to five days after surgery), drainage from the incisions, signs of colic, and evidence of tissue protruding from the surgical sites. The incisions should heal by three weeks after surgery.

"If there are any concerns you should always call your vet," Kilcoyne stressed.

She said that while stallions can be gelded at any age, "ideally the procedure should be performed at a younger age, usually as yearlings or 2-year-olds before masculine behavior becomes too difficult to manage. Also, younger horses tend to have smaller testicles with less redundant scrotal tissue present postoperatively, which may interfere with drainage."

She also stressed that the possible risks associated with castration should not deter owners from choosing to geld their intact males: "The risks associated with the procedure are low, and most complications resolve easily with appropriate treatment. The benefits of castration far outweigh the risks associated with the procedure."

The study, "Incidence, management, and outcome of complications of castrations in equids: 324 cases (1988 to 2008)," appeared in March in the Journal of the American Veterinary Medical Association.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.