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Impaction colic is most commonly found in the pelvic flexure of the colon. It usually consists of poorly digested food lodged where the colon turns back on itself and narrows (the pelvic flexure). This condition is easily diagnoses via rectal examination, an indispensable part of the physical exam when called on a colic case. This condition is most commonly seen when the horse is confined in a small space, not receiving enough exercise and is being fed a large volume of concentrated feed, pellets and/or grain. It can also occur if the animal’s teeth need floating or if there are other dental issues preventing normal chewing (mastication). It can also occur if the animal cannot take in adequate water.

Colonic impaction will almost always respond to medical treatment. Sometimes high enemas will resolve the issue when mineral oil pumped into the stomach is not sufficient to move the blockage.

In the Southeastern U.S. coastal Bermuda hay is commonly available and used to feed horses. This type of hay can result in an impaction of the terminal ilium, the portion of the small intestine where it joins with the cecum (a large blind sac where fermentation aids digestion of roughage) and the entrance into the colon (large intestine). Obstruction of the ilium can also be the result of ascarids (intestinal parasites) after the horse has been treated for the infestation and is passing large numbers of the dead parasites. It is most commonly seen in young horses following their first deworming. When equine tapeworms are an issue treatment can result from a blockage of these dead or stunned parasites in the small intestine. When this condition occurs, the animal will usually exhibit intermittent moderate to severe abdominal pain. Distended loops of small intestine can sometimes be found on rectal exam. Ultrasound diagnosis may be necessary to identify this type of colic. Severe cases may result in gastric reflux. This usually responds to nasogastric intubation and the release of the accumulated gases from the stomach. Cases that are non-responsive to routine treatment may respond to warm soapy water or carboxymethylcellulose enemas providing the site of impaction can be located and reached rectally.

Less commonly encountered is hypertrophy of the longitudinal and/or circumferential smooth muscle layers of the small intestine (ilium or jejunum). The condition may be idiopathic (of unknown cause), or neuronal dysfunction usually associated with parasitic migration, particularly of the larval stage of ascarids. It may also be the result of increased tone of the ileocecal valve. This leads to hypertrophy of the smooth muscle of the ilium because it has to push ingesta through a smaller orifice. This diagnosis is usually made during surgery and can occur following the removal of a portion of intestine and the anastomosis (rejoining of the bowel) resulting in stricture.

Sand colic can occur when horses are pastured on sandy or heavily over-grazed pastures or fed on the ground. When I practiced in Arizona (back in the 1960’s) it was relatively common for backyard horses kept in small corrals to be fed on the ground on loose dirt. The ingested dirt or sand mostly accumulates in the pelvic flexure but may also be found in the right dorsal colon or in the cecum. The sand or dirt will irritate the mucosa (lining) and can result in diarrhea. Examination of the manure will often reveal the presence of sand and/or dirt. Accumulation and the resulting weight and abrasion on the mucosa can also result in a lack of colonic motility rather than hypermotility and diarrhea and in severe cases, rupture and peritonitis.

The diagnosis is the result of careful observation of the conditions in which the animal is kept and fed, abdominal auscultation for the sounds of hyper or hypo motility (too much or too little) and gas accumulation. Radiographs or ultrasound may be required to make the diagnosis. Medical treatment with laxatives is often effective especially with the addition of psylliumhusk. Psylliumis the common name for several members of the plant genus Plantago. Commonly marketed products of this include; Metamucil, Pinch, Fybogel, Kansyl and Luelax. Mineral oil treatment alone is less effective since it will usually float on the surface of the accumulation without penetrating. Psylliumbinds to the sand and helps to remove it. Animals with this condition may also suffer from rapid overgrowth of Salmonellaor other bacteria so antibiotic added to the treatment may be indicated. If signs of severe colic do not respond to medical treatment within a few hours surgery is indicated. Where grazing or feeding on the ground cannot be avoided prophylactic treatment feeding a pelleted psylliumproduct may be recommended by your veterinarian.

Impactions of the cecum are uncommon. They can occur when horses ingest bedding or as a result of post-operative or other pain therapy involving the use of opioids resulting in GI stasis and constipation. Because of its function as a fermentation vat gas and fluid accumulation is rapid and can lead to rupture within a day or two, if not corrected surgically. The condition can usually be diagnosed on rectal exam but rupture can occur early in the progression of the condition.

Gastric impactions are rare. It can occur following ingestion of foods that swell after eating, ingestion of bedding or poor-quality roughage, dental problems, ingestion of a foreign object or disease that interferes with normal gastric function. Ingestion of persimmons form a sticky gel in the stomach and feeding haylage can be problematic. When I practiced in Arizona ingestion or feeding of mesquite beans was a problem. Feeding sugar beet pulp can also be problematic. Diagnosis using gastroscopy or ultrasound may be necessary. Gastric impactions will often respond to treatment with water or other fluids via nasogastric intubation.

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