Large colon impaction is a common cause of colic that doesn't respond to field treatments. Often, a horse with large colon impaction has been treated with routine field treatments and has returned to colic signs.

Rectal palpation reveals this classic problem- a firm hard mass palpable in the pelvic flexure of the colon, which a vet feels on the left side of the horse.

This hairpin, narrow turn is an area commonly affected and happens to be easily reachable on a rectal exam.

The problem is more commonly diagnosed in older horses and those with dental conditions that cause them to grind hay improperly. We tend to see this problem more commonly in the winter during cold periods. This is likely because horses are not drinking as much water. In addition, horses undergoing stresses of various kinds, and those with other health problems, are more likely to develop this problem.

Horses eating coarse feeds, those that are have other illnesses, those that are confined, and those that experience dehydration are also thought to more commonly acquire this problem.

Repeated incidents of this problem may indicate a colon motility disorder.

DIAGNOSIS is through rectal examination.

TREATMENT is usually medical- nasogastric and intravenous fluid therapy to soften the impaction, improve intestinal function, and hopefully allow the horse to break down the impaction and move it down the tract.