Changes

===Description===

===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.   

Enteroliths are mineralized concretions of magnesium ammonium phosphate (struvite) that develop 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, metal object, or rarely a piece of fibrous material such as baling twine. 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 major contributing factor. The relative hypomotility of the right dorsal colon is also thought to have a role in enterolith formation.   

===Signalment===

===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.

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; this is hypothesised to be due to the presence of prostaglandins in the serum leading to alterations in gut motility. Thoroughbreds appear to be underrepresented. Middle aged horses are most affected with enterolithiasis in horses less than four years of age rarely reported.

===Clinical signs===

===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.  

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. Horses with a partial obstruction of the right dorsal or transverse colon may display signs 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 mild 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.  

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. Other clinical signs such as tachycardia, tachypnoea, prolonged capillary refill time and bilateral abdominal tympany are frequently observed. If the integrity of the colonic wall has been compromised, signs reflecting endotoxaemia may develop.

===Diagnosis===

===Diagnosis===