Impaction Colic

Colic is an equine problem familiar to all people who work with horses. Many colics are simply gas colics and can resolve themselves quickly with little or no intervention. In some cases, the home remedy of walking the horse or loading the horse in a van and giving it a ride around the farm has relieved symptoms of colic. Other horsemen concede that the symptoms often seem to abate by the time the horse has reached the equine clinic after a brief van ride.

But not every colic resolves itself in such a simple manner. Impaction colics--those caused by an ob-struction in the bowel--can be persistently painful and dangerous for horses. But when a horse begins to show signs of colic, surgery is by no means the first treatment indicated.

Even if the colic is caused by an impaction, many colics can be resolved with medical treatment, thereby avoiding the risks associated with surgery.

Most horses will respond to treatment involving administration of laxatives, fluids, and analgesics. The aim of that treatment is to control pain, reduce the spasms aflicting the intestines, and assure enough liquid in the colon to allow the feces to pass and restore normal digestive function.

When a severe impaction occurs, however, and the signs of distress in the horse worsen--continuing abdominal pain, increased heart and respiratory rates, and signs of shock--surgery might be the only answer.

The nature of the impaction might indicate whether surgery is indicated. A 1977 paper delivered at the New Bolton Center in Pennsylvania recounted several cases of impaction colics that resulted from horses eating rubberized fencing materials or fences made of nylon-based materials. In those cases, the fencing materials had begun to unravel and, as they did, the horses ingested fragments. Being neither digestible nor biodegradable, the resulting masses that led to colic did not respond to traditional medical treatments.

"Due to the non-degradable nature of the impacting mass in this type of colic, syptomatic therapy is of no value. Thus, surgical intervention is necessary," wrote Charles L. Boles, DVM, and Catherine W. Kohn, VMD, in that paper.

As for symptoms, they were similar to impaction colics resulting from other causes.

"All horses had mild to moderate abdominal pain, as manifested by pawing, stretching, or lying down excessively. All were depressed and had been passing scant feces since the onset of signs of colic," they wrote.

Similarly, surgery was required for the 47 horses and 1 pony included in a study of sand colics made in the mid-1980s at the College of Veterinary Medicine, University of Florida. In all the horses, symptoms of the colic included "intractable pain, deteriorating vital signs, or rectal palpation findings typical of large-colon displacement or torsion," wrote T. E. Specht, DVM, and Patrick T. Colahan, DVM.

Sand colic was diagnosed after sand impactions were palpated, feeling hard, granular, and difficult to indent.

The Florida study found a disproportianate incidence of sand colic in females: 30 out of the 48 in the study. Additionally, while there were admissions for sand colic throughout the year, the greatest number clustered in the second half of the year, with 66.6% admitted from July to December. That, the researchers found, coincided with the rainiest part of the year for the regions where the horses lived. While sand colic can often be associated with more arid regions, this study showed it can occur in areas with high annual rainfall.


Another type of impaction that often requires surgical intervention, even though more natural, are those that result when enteroliths form in the colon. Enteroliths, as the name suggsets, are stones that form inside the horse's colon. They begin to develop when a small mass forms in the colon. As additional sand or other materials pass through the colon, it can be "caught" by the original mass, causing it to grow. An enterolith recently removed from a horse at Rood and Riddle Equine Hospital in Lexington, Ky., attained the size of a softball by the time it was removed surgically by Steve Hance, DVM.

"These turn up more commonly in California and the Southwest," Hance said. Ordinarily one will turn up in Lexington only once in a year and a half, he added. But recently, two horses with enteroliths were admitted to Rood and Riddle for surgical removal of the blockage, including the one with the large stone.

Studies of impactions in general point to several factors that might give rise to an impaction colic. Most studies show a predominance of females among the horses afflicted with impaction colics. However, no clear-cut reason for the greater frequency in fillies and mares has been discovered. Other factors that are sometimes associated with impaction colics are freezing temperatures, poor dentition, poor feed, or changes in feeding routine, and, as mentioned above, with the rubberized fencing or ingesting non-digestible objects. Also common is a change in routine shortly before the onset of the colic and the discovery of the impaction. A study completed in 1991 at the Marion duPont Scott Equine Medical Center in Virginia found changes in routine in 53.7% of the horses treated for impaction colics. "Management changes included exercise restriction by enforced stall confinement because of a musculoskeletal injury (tendinitis, fracture, or laceration) or after arthroscopic surgery," wrote Robin Dabareiner, DVM, MS, and Nathaniel A White, DVM, MS.

Dabareiner and White went on to speculate about the relationship between confinement and impactions.

"Several possibilities existed for this apparent association between stall confinement and large colon impaction. An inadequate water supply may have resulted in a reduction in water intake and subsequent impaction, or changes in feeding practices may have upset normal intestinal motility patterns. Adequate exercise also may be important in maintaining normal large intestine function in horses," they wrote.

About the Author

Jacalyn Carfagno

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