Young horses are more likely to eat foreign material due to their curiosity, although occasionally adult horses do the same.

Pieces of twine, fibers from lead ropes and feed sacks, and wire mesh from window screens are just some examples of foreign material I have personally found in the intestine of horses.

Often, this material passes through the intestine and is evacuated in manure uneventfully. However, in some cases it causes a blockage within the intestinal tract.

Foreign bodies can also remain within the intestine for weeks or months, without causing an apparent issue, but gradually accumulating a coating of hard mineral deposit. When this “fossilization” occurs, the resulting stone is called a “bezoar” or fecalith. These can grow quite large and heavy and usually end up blocking the lower part of the intestine, the small colon.

While small colon impaction can usually be diagnosed on rectal exam, the cause of the impaction is usually not known unless it is passed, or it is opened after surgery.

In some cases, the impaction can pass spontaneously or with medical treatment. Sometimes debris simply passes in the manure. But the more difficult obstructions will only be removed at surgery.