Enterolith - Horse

 See Colic Diagnosis in Horses

Medical Treatment of Colic in Horses

Also known as:

Intestinal calculi

Description

Enteroliths are mineralized concretions of magnesium ammonium phosphate (struvite) that form in the right dorsal colon of the horse. The enteroliths typically form in a concentric pattern around a central nidus such as a silicone stone. The pathogenesis of the disease is not fully understood but long-term ingestion of a diet rich in protein, phosphorus and magnesium (such as alfalfa hay) is thought to be a contributing factor. The relative hypomotility of the right dorsal colon is also thought to have a role in enterolith formation.

Signalment

All horses may be affected by enterolithiasis but certain breeds are predisposed including Arabians, Morgans and Miniature horses. Females are more likely to develop enteroliths than males. Thoroughbreds appear to be underrepresented. Middle aged horses are most affected in areas of endemic disease.

Clinical signs

Small enteroliths may pass through the gastrointestinal tract unnoticed. Clinical signs generally only occur if the enterolith is large enough to cause an obstruction. Obstruction most commonly occurs in the transverse or small colon. Affected horses often present with a history of being fed a large quantity of alfalfa hay or pellets in their diet.

Diagnosis

In most cases of enterolithiasis, passage of gas, faeces and lubricants such as mineral oil will still occur. In the case of obstruction, however, the passage of faeces will be blocked and defecation will no longer take place. Rectal examination rarely leads to the identification of an enterolith but may reveal distension of the large colon and tight mesenteric bands.