Horses experiencing multiple bouts of colic in a single year are battling recurrent colic—a very challenging and poorly understood condition that can cause significant pain and great financial expense and sometimes necessitate euthanasia.

Thanks to recent research efforts, though, scientists are starting to get a better handle on this problem and recognize new aspects of its multifaceted complexity. A leading expert on the topic recently said the starting point for addressing recurrent colic in any patient is multidisciplinary cooperation.

“It requires a team approach to try and help manage these cases,” said Louise L. Southwood, BVSc, PhD, Dipl. ACVS, ACVECC, a professor in emergency medicine and critical care at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, in Kennett Square.

This means there’s collaboration with the owners, caregivers, primary care veterinarian, specialists, and even clinical researchers—to try and learn more about what’s actually going on in these horses,” she said during the 2022 American Association of Equine Practitioners Convention, held Nov. 18-22 in San Antonio, Texas.

What Causes Recurrent Colic in Horses?

Scientists define recurrent colic as at least two unique episodes of colic within a year, although some research groups give tighter time frames of six months or even one month. To be considered unique, the episode must begin at least 48 hours after the previous episode has completely resolved.

Recurrent colic has a wide range of known causes—and likely many more that are yet to be discovered, she said.

Clinicians have already associated recurrent colic with structural issues such as repeated intestinal displacement or impaction, yet the underlying cause of these problems is often unknown, said Southwood.

Alternatively, the horses might be ingesting sand or gravel found in their pastures or paddocks, or consuming other foreign objects like bits of wire or twine, which could lead to intestinal blockages, perforations, or the formation of enteroliths.

Horses that have already had colic surgery, particularly small intestine or small colon surgery, might have scar tissue (adhesions) that provoke regular colic episodes, she said.

“Adhesions are uncommon in horses with large colon problems,” Southwood later told The Horse. ‘However, colonic displacements and volvulus (twisting of the colon) can recur in 10-15% of cases. It was interesting that in one unpublished study of horses with large colon displacements and volvulus, horses that had problems with colic after surgery were those horses that had multiple colic episodes prior to surgery. This finding suggests that perhaps there is an underlying colonic dysfunction and, importantly, it is not the surgery per se that causes a problem.”

Exploring the Potential Roles of Microbiomes and Management in Recurrent Colic

Intestinal biopsies could help veterinarians pick up on signs of inflammatory and motility disorders in the digestive tract that might cause recurrent colic. Histological analyses have already identified issues such as myopathies, secondary neuromuscular disorders, myenteric ganglionitis (inflammation of nerve cell clusters that innervate the smooth muscle of the GI tract), fibrosis of the intestinal muscle layers, inflammatory bowel disease, and decreased density of the interstitial cells of Cajal (specialized cells in the GI tract, some of which help generate slow waves that help digestion) as likely culprits, she said.

Studies linking the horse’s gut microbiome to recurrent colic are being proposed and funding sought, said Southwood. Researchers have shown clear differences between the microbiomes of horses that present for colic and those that present for a non-colic elective surgical procedure. In one case study in her clinic, Southwood and Alicia Long, DVM, emergency and critical care fellow at New Bolton, successfully altered one equine patient’s gut microbiome through fecal transplants from healthy donors. Even so, it’s too soon to draw definite conclusions about the relationship between recurrent colic and the microbiome, she said.

Researchers on epidemiological studies have reported that management might also play a role, Southwood said. Dental disorders, parasite problems, diet and management, and possibly stressful lifestyles that favor stereotypies, such as crib-biting, and the development of gastric ulcers appear to make recurrent colic more likely.

Many of the horses Southwood sees with recurrent colic are those receiving the most intense management attention from their caregivers, she added.

In addition, plasma biochemistry profiles, peritoneal fluid analyses, specific disease testing, ultrasound examinations, abdominal radiography, and even exploratory surgery might be helpful, she said.

Depending on the results of the work-up, the veterinary team might recommend various types of surgeries and/or medications. In cases where management might be at the root of the problem, clinicians could suggest just getting the horses out of their stalls. “Potentially, turning them out to pasture may actually make things better,” she said.

Finally, clinicians should be prepared to discuss euthanasia as an option when the horse responds poorly to treatment or if the financial burden becomes overwhelming, said Southwood.

Nevertheless, while recurrent colic can be a fatal or welfare-threatening condition, new research should bring hope for better understanding and, ultimately, effective treatments, she said.