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

Horses with enterolithiasis generally have a history of being fed a large quantity of alfalfa hay or pellets in their diet. Small enteroliths may pass through the gastrointestinal tract unnoticed. Many horses with an enterolith have a history of chronic or recurrent colic, sometimes occurring over a period of weeks up to a year. Clinical signs in these horses may be non-specific including weight loss, anorexia, changes in demeanour and lethargy. Signs indicative of abdominal discomfort may also be present such as pawing, flank-watching, kicking or resentment of a girth.

If the enterolith is large enough to cause an obstruction (most commonly in the transverse or small colon), signs of acute, severe abdominal pain are usually seen.

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.