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Lots Of Theories, Few Answers On Colic

Each colic type has its own prognosis and treatment.

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From the first clinical sign of severe abdominal pain in horses, veterinarians must be quick to diagnose and treat colic, the No. 1 equine killer. Intestines can be irreparably damaged in as little as three to five hours in the case of ischemic strangulating obstructions.

Accurately determining each colic type—digestive, intestinal accidents/strangulation, impaction, sand and spasmodic—is vital, as each has its own prognosis and treatment.

The American Association of Equine Practitioners has assembled a panel of veterinarians to search for answers to colic, which strikes 1 in 10 horses and kills 10 percent of those.

Among the veterinarians serving on the panel are Anthony Blikslager, DVM, Ph.D., Dipl. ACVS, and Frank Andrews, DVM, MS, Dipl. ACVIM. Dr. Blikslager is a professor of surgery and gastroenterology in North Carolina State University’s Department of Clinical Sciences. Dr. Andrews serves on the Louisiana Veterinary Medical Association’s Equine Committee and is director of the Equine Health Studies Program at at Louisiana State University’s School of Veterinary Medicine.

“A veterinarian needs to know if the clients want the horse saved at all costs, as well as at what point the owners will allow the veterinarian to refer the animal for surgery,” Blikslager says. “Survival rates are much better if we can refer the horses as fast as possible.”

When to Refer

Blikslager says a referral should be made when the veterinarian “is called back a second time or has to administer a second dose of medication for pain on the same horse.”

“Ninety percent of horses don’t have recurrent colic,” he says. “We need to take extra care with the other 10 percent.”

Blikslager encourages veterinarians to get horse owners, trainers and barn managers to set up a pre-need colic plan, preferably written by a lawyer, on what to do for the horse that colics when a decision-maker isn’t on site.

Andrews says owners must be prepared.

“Critical-care medicine is expanding every day,” Andrews says. “And more complicated procedures can really push the bill up for clients. So it is important for the referring veterinarian to know how involved the horse owners want to become.

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“Owners need to be clear about how much treatment costs and that euthanasia is a viable alternative if the horse is suffering inhumanely or treatment is not affordable.”

Blikslager says veterinarians may unintentionally put colic on the lower level of emergencies. “There is a tendency to treat all colic calls all the same,” he says, “but we have an obligation to give the horse the best care possible, on the farm or in the clinic.”

Andrews notes that with all that has been learned about colic, veterinary medicine still doesn’t know what causes it.

“Myriad factors—the anatomy of the GI tract, diet or change of diet, weather, barometric pressure changing the colonic air and water levels, sand, stress—might be causes,” he says.

Parasitic load is another potential cause. Large strongyles, among other internal parasites, can damage intestinal arteries, causing them to scar and clot. Ascarids may cause blockage of the small intestine in young horses, especially after deworming. Small strongyle larvae burrow into the large intestine, where they can cause colon dysfunction and colic. Tapeworms (Anoplocephala perfoliat) cause physical blockage (ileal impaction) and ulcerated tissue between the ileum and the cecum, which may lead to thickening of the mucosa.

A recent study at the University of Perugia in Italy identified the damage tapeworms can do to the enteric nervous system of the intestinal tract as well as to the mucosa and submucosa, further correlating these parasites and colic.

Horses should be maintained on a broad-spectrum deworming schedule based on the parasite load and the potential to infect other horses, the researchers say. 

Diagnostic Tools

Hoyt Cheramie, DVM, MS, Dipl. ACVS, a large-animal veterinary services manager at Merial Ltd., suggests that technological improvements in diagnostic equipment may help in examination and treatment of colic.

Ultrasound is excellent for evaluating the bellies of foals, Dr. Cheramie says. “You can visualize lesions in the field and get a better idea for best treatment,” he says. 

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Portable ultrasounds get a lot of use, so they make a good investment for most veterinarians, Cheramie says. Andrews says he would use an ultrasound on every case of colic.

Abdominal radiographs can be hard to perform but are lifesavers in some geographic areas. For instance, Cheramie says, some horses in Southern California are at greater risk of developing enteroliths. The stones often cause impactions and may compromise the intestines, and X-rays help veterinarians treat the animal more appropriately.

For colic caused by sand in the intestines, Andrews recommends using psyllium to pass the sand.

Surgery is an opportunity to address ileus and remove adhesions. Blikslager says good results have been achieved through an infusion of lidocaine in ileus.

“Lidocaine has categorically been shown to have a positive effect on the small intestinal motility,” he says. “It reduces ileus and acts as an anti-inflammatory, though we are not sure why. Inflammatory cells are involved with keeping the bowel from moving correctly.”

Intravenous lidocaine has been shown to reduce inflammation and pain before and after surgery. 

A multicenter clinical trial performed at the University of Minnesota, Utrecht University, University of Tennessee, University of Missouri and Michigan State University found that “lidocaine treatment resulted in shorter hospitalizations time for survivors, equivalent survival to discharge, no clinically significant changes in physical or laboratory variables, and no difference in the rate of incisional infections, jugular thrombosis, laminitis or diarrhea” (Intravenous Continuous Infusion of Lidocaine for Treatment of Equine Ileus, August 2005).

As part of “belly jelly,” the lidocaine also can be poured into the abdomen at the start of surgery. Studies at North Carolina State showed that subsequent to lidocaine being used in this way, the colic surgery survival rate was higher.

A non-steroidal anti-inflammatory drug called Equioxx, made by Merial Ltd. of Duluth, Ga., is making a difference in treatment, Blikslager and Andrews agree.

This new COX-2 inhibitor, Andrews says, doesn’t cause kidney or intestinal damage the way phenylbutazone (bute) and flunixin meglumin can.

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“Equioxx in the first new labeled NSAID in 15 years,” Andrews says. “Veterinarians should at least take a look at it.”

Andrews says Boehringer Ingelheim Vetmedica’s FDA-approved Sedivet (romifidine hydrochloride), is a longer-acting sedative and analgesic for use in colic and as a preanesthetic agent.

Cheramie suggests a connection between mild colics and gastric ulcers.

He and Andrews administered antacids and lidocaine through a nasogastric tube into the stomach. Immediate pain relief suggests a stomach ulcer.

Gastric ulcers and colic have associated symptoms, Cheramie says, and the colic may help lead to the diagnosis. He cited a study of performance horses by Rick Mitchell, DVM, that evaluated hunter/jumpers and dressage horses for poor performance. Cheramie says 87 percent of the horses presenting for complaints of colic had ulcers. Of all the horses diagnosed with ulcers first, 49 percent had colic.

“If a horse colics more than once,” Cheramie says, “a gastroscopy exam is probably in order. He likely has an ulcer.”

Adequate fiber content in feed has been shown to reduce the chance of colic, Blikslager says. Too fine a fiber and the horse swallows too fast. The improperly chewed hay clogs at the ileum.

“We can’t just feed a horse what is convenient or cheap for horse owners,” Cheramie says.

Andrews says that high-sugar diets contribute to gastric ulcers by altering stomach bacteria, which ferment starches into volatile fatty acids and lactic acid. These fermentation byproducts, in the presence of hydrochloric acid, can contribute to gastric ulcer formation.  

And high sugar/starch diets can cause bacterial overgrowth in the large intestine, which can lead to gas accumulation and colic (cecal tympany). Feed companies are making low starch feeds to help prevent a dietary cause of colic.

“The stomach is the window to the rest of the horse,” Andrews says. “The presence of stomach ulcers could be the primary problem, or they could mean the horse is stressed somewhere else.”

This article first appeared in the July 2010 issue of Veterinary Practice News. Click here to become a subscriber.

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