Is My Horse Too Old for Colic Surgery?

The decision to take your horse to colic surgery isn’t one to make lightly, whether your animal is a young prospect or an old pasture pet. Surgery inherently carries a number of risks, and making an informed decision about such a costly and invasive procedure requires familiarity with the factors that affect prognosis. But what makes a horse less likely to recover from abdominal surgery? And does age play a role? Using data collected at the University of London’s Royal Veterinary College, three researchers from the University of Pennsylvania School of Veterinary Medicine (Penn Vet), in Kennett Square, tried to answer these questions.

First, the good news: A senior horse (in this case defined as >16 years) is not more likely than its younger, adult counterpart to die after undergoing colic surgery. While a previous Penn Vet study showed that 39% of geriatric horses that undergo surgery are euthanized before recovering from anesthesia, the team on this project determined that if you remove risk factors related to anesthesia from the equation, “age should not negatively impact an owner’s decision to pursue surgery.’’

“The reality is that many older horses that colic are euthanized because of a perceived poor prognosis or financial constraints associated with surgical treatment of an intestinal strangulation,” said Louise Southwood, BVSc, MS, PhD, Dipl. ACVS, ACVECC, associate professor of emergency medicine and critical care at Penn Vet, who worked on the most recent study with Sophie Boorman, BVetMed, and Darko Stefanovski, MS, PhD.

In their study the researchers analyzed medical records from 83 patients hospitalized at the Royal Veterinary College’s equine clinic between 2009 and 2015. Their goal was to identify risk factors associated with nonsurvival in the first few days after undergoing small intestine surgery.

They identified an association between elevated packed cell volume and elevated blood glucose concentration at admission—both indicative of longer disease duration and greater severity—with postoperative death. Another predisposing factor for death the team identified? Nasogastric reflux. A common complication of colic surgery, reflux consists of fluid accumulating in the stomach because of a small intestine blockage. Study results have shown that up to half of the horses that reflux after colic surgery die (Torfs et al. 2009), making this an unpredictable and serious complication. The authors found that horses already refluxing when they arrived at the hospital were more likely to develop high-volume (>20L in 24 hours) post-operative reflux (POR), which correlates with a higher mortality rate. While POR is a serious, expensive complication of small intestinal surgery, the authors determined that “it is equally likely in geriatric and mature horses.”

Now, the fine print: While old age alone does not correlate directly with a higher incidence of POR or death after colic surgery, a horse’s risk of having a severe lesion—especially a strangulating one—does increase with age. In a previous study Southwood and colleagues showed that geriatric horses that colic are twice as likely to suffer from a strangulating small intestine lesion than their younger, mature counterparts. The problem is twofold: Strangulating lesions carry a more guarded prognosis than simpler ones and are often associated with nasogastric reflux, both before and after surgery. Additionally, correcting such lesions often results in a lengthy surgery, further decreasing the chance of survival, said Southwood’s team.

Take-Home Message

So how might this information influence your decision to send your senior horse to colic surgery?

“Old age is not a disease,” Boorman said. “The veterinarian and owner alike shouldn’t feel that the older horse is more likely to have complications and not survive the surgery.”

She and her research partners hope their study will help change the mindset of owners who decide that their horse is “too old” for colic surgery because they believe aged animals “get sicker after surgery anyway.”