A look at 14 kinds of equine colic and their prognoses
Flank-watching or -biting, pawing, trying to roll, an elevated heart rate, a lack of gut sounds or bowel movements. While these signs and others are pretty clear, common indicators your horse is colicking, what they don’t tell you is the type of abdominal pain he’s experiencing. Within that cavernous abdomen are a number of organs, with which a variety of things can go wrong. A piece of intestine can twist, a foreign object or lump of ingested material can cause a blockage, and infectious organisms can inflame the gut.
Depending on a colic’s cause, treatment steps and prognoses can vary widely. So in this article we’ll break these cases down by type—nonstrangulating, strangulating, and inflammatory. We hope you won’t be faced with this potentially life-threatening condition, but if you are you’ll have a better understanding of what your veterinarian is describing and the road that lies ahead.
A nonstrangulating obstruction (NSO) is a physical blockage or narrowing of some part of the gastrointestinal (GI) tract that prevents fluid and digesta from flowing through normally. These colics are by far the most common—Diana Hassel, DVM, PhD, Dipl. ACVS, ACVECC, associate professor of Equine Emergency Surgery & Critical Care at Colorado State University, in Fort Collins, estimates they make up at least 80% of colic cases in most regions of the country.
Veterinarians further subcategorize these obstructions based on their location and cause, including:
These are some of the most common NSOs and occur frequently in the large colon, particularly at the hairpin bend around the pelvic flexure and the bend into the transverse colon. Forages and fibers simply get lodged in these areas sometimes.
Impactions can also occur in the ileum, which is the final part of the small intestine. “Ileal impactions occur almost exclusively in adult horses in the southeastern United States, from North Carolina down to Florida over to Texas,” says Anthony Blikslager, DVM, PhD, Dipl. ACVS, professor of equine surgery and gastroenterology at North Carolina State University, in Raleigh. While veterinarians don’t know the exact reason for this regional risk, he says feeding coastal Bermuda hay—which is fine and stemmy—in these areas might have something to do with it.
Horses also experience small colon and stomach impactions, though these are less common.
Horses eating off sandy soils can ingest enough sand that it accumulates in the large colon.
This obstruction is seen almost exclusively in weanlings, which tend to carry ascarid parasites when not dewormed regularly. Colic can occur shortly after a youngster with a heavy ascarid burden gets dewormed—the mass of dying parasites can cause an obstruction as it makes its way through the small intestine.
These mineral stones can develop in the large and small colon, requiring surgical removal if they grow large enough to cause a blockage. Blikslager says they tend to occur more frequently on the West Coast than the East, with California horses being the most severely affected.
Left or right dorsal displacement of the large colon
The horse’s large colon is essentially suspended from the upper body wall at a single attachment point, allowing it to move around the abdomen. Rarely, it shifts to the point it gets trapped against other organs, causing an obstruction.
“The majority of nonstrangulating obstructions we’re able to successfully manage medically (i.e., with pain relief, intravenous and oral fluids, laxatives, nasogastric tube, and walking),” says Hassel. “However, some of them will not respond to medical therapy, in particular those cases with displaced colons.”
Stomach impactions or intestinal obstructions that are so firmly impacted they won’t loosen with medical therapy are almost always surgery candidates, adds Blikslager.
Fortunately, the prognosis for most nonstrangulating colics is quite good, because the bowel doesn’t usually get damaged. Long-standing impactions, however, can apply so much pressure on the intestinal wall that the bowel begins to degenerate. Blikslager recommends keeping an eye out for signs of potentially fatal endotoxemia (e.g., abnormal-colored gums, delayed capillary refill time when you press on the gums, and high protein and white blood cell counts in the abdominal fluid) in these cases.
Strangulating obstructions (SO), while not as common as nonstrangulating, are far more serious and always require surgery. They occur when part of the GI tract twists or gets entrapped, cutting off blood flow to that region.
This article continues in the January 2020 issue of The Horse: Your Guide to Equine Health Care. Subscribe now and get an immediate download of this issue, including this in-depth feature on 14 kinds of equine colic and their prognoses.