Wellness Wednesday: "Gut Rocks" in Horses

Digital x-ray of enterolith with foreign body (horse shoe nail) inside (Photo: Peterson and Smith Vet Notes, Feb 2013)

Enteroliths are one of the many causes of colic in the horse. The word comes from “entero” which means intestine or gut, and “lith” which means stone. They are actually concrete-like balls that form in the intestinal tract and eventually often cause obstruction of the gastrointestinal tract and have to be surgically removed.

The intestinal tract has rules about how big a particle can be to progress for- ward from the mouth to the rectum. The mouth is in charge of chewing things up into small enough pieces that they can be swallowed and then the stomach and intestine churn and add enzymes and chemicals to further break down food material into a thick liquid that the body can absorb nutrients from through the intestinal wall.

When the body encounters something such as a pebble, wire, nail, haystring, or nut, etc. that it cannot break down into a liquid, it regards the object as a threat. Its only available response to the threat to the body is to try and create a barrier between the object and the body. It does this by secreting a thin layer of a concrete like substance, which has minerals in it, around the object.

This is similar to how an oyster creates a pearl from a grain of sand. Over the course of months to years, more layers are secreted, creating enteroliths that can weigh up to 20 pounds. The enterolith does not move along the intestinal tract because it is too big, but at some time it gets big enough to block the area of the intestine that it is occupying or the propulsive movement of the intestine pushes it into a space that is too small for it. In either case when this happens, the horse has an obstruction to its intestinal tract and it usually has to be surgically corrected.

Enteroliths—one of which contains the horse shoe nail (Photo: Peterson and Smith Vet Notes, Feb 2013)

Fortunately, with advanced technology, we can take x-rays of a horse’s abdomen and often find the enteroliths. This re- quires a machine that is only available in a few hospitals and universities. We have used our machine to help diagnose enteroliths and severe sand accululation, since both are mineral densities. It has been tremendously helpful in the diagnosis and treatment of some colic cases.

There still are some mysteries about enteroliths. Some horses form them without having ingested a foreign object. By far they are most commonly found in horses from California, followed by horses from Texas and Florida. Research has been performed to attempt to make an association with water, soil, or feed type, but we have no definitive cause.