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Impaction Colic

Know the signs and what to do.

Every season in equine practice brings with it a unique set of ailments that keeps the veterinarians at GVEC occupied. Spring has its foaling problems, while summer brings injuries from competition. Fall and winter usher in a type of illness known as impaction colic. Colic is a general term suggesting gastro-intestinal distress. This can be anything from a minor gas bubble to a major twist of the intestines. An impaction is a blockage of feed material in any part of the over 90 feet of intestines that are packed into the horse’s abdominal cavity.

Impaction colics occur in horses for a combination of reasons. The large intestine has several areas where the colon makes a 180° turn, creating opportunities for easy blockage. At one of these turns, the colon also reduces in diameter by at least one-half, again making a stoppage easy. Also, the function of the colon varies at different points along its course. Coincidentally, at the location where it makes a hairpin turn and the diameter reduces, the consistency of the ingesta (the consumed feed) changes from being relatively liquid to quite dry.

Why then, is this type of colic more common in the fall and winter? Presumably, as the weather gets cooler, horses drink less, making the ingesta in their colons even drier, and thus more prone to getting stuck. Also in the winter the grass dies down. As you know, horses that are on lush grass tend to have soft manure, and lack of grass in the winter tends towards drier feces. A third factor in this equation is the change from competition and training to winter rest, which can affect intestinal motility and water consumption.

How do you know if your horse has an impaction? First, he will start demonstrating typical signs of low-grade colic (pawing, lack of appetite, rolling, decreased manure production). At this point it is likely you will call your veterinarian out to evaluate him. Other signs to watch for include smaller or drier fecal balls, decreased water consumption, and change in normal attitude.

A veterinarian performing a rectal exam can palpate more than ten organs.The most important tool we use for diagnosis is our arm, which we use to perform a rectal palpation. Luckily, the most common area to become impacted is located far back near the pelvis, so it is easily detected. Our arm goes into the rectum, but we are actually feeling through the rectal wall and through the large colon wall to the impaction. Thus when we pull manure out, we are not relieving the impaction, we are only cleaning out the rectum so we have more room to feel. Once a diagnosis of impaction is made, our treatment is aimed toward rehydrating the horse and breaking up the feed material. We do this by administering large amounts of water and mineral oil (plus something like Epsom salts) via a tube into their stomach. If the blockage is particularly large or has been going on a long time, we will start the horse on intravenous fluids in order to “super-hydrate” him. We will also provide pain control as needed to keep him comfortable while the impaction passes.

Impaction colics are generally considered medical colics, i.e. they usually do not need to be cured surgically, but it can take a number of days and a lot of dollars to take care of them. The keys to preventing this condition are: make sure your horse has access to and is drinking plenty of water and be sure he is producing plenty of manure as the cold weather continues. It is also important to provide regular exercise to help stimulate intestinal motility.

You don’t need to whisper to your horse; you just need to listen to him.