On our last program we talked about the factors that predispose horses to colic.  Today we will discuss a specific cause of colic called enterolithiasis.  Enterolithiasis is the presence of a calculus, or stone, in the intestinal tract of the horse.  When the enterolith becomes lodged in the colon, it prevents movement of ingesta and as gas accumulates, severe colic develops. 

Enterolithiasis is a common cause of colic in certain areas such as California.  A study was done at the College of Veterinary Medicine at Texas A&M to determine the incidence of colic due to enteroliths in horses presented to the college and risk factors that affected the presence of enteroliths.  Only 1.7% of the horses presented for colic were due to enteroliths. 

In regard to breed susceptibility, horses with enteroliths were more likely to be Arabians or miniature horses.  Arabian horses were also shown to be more susceptible to enteroliths in California, but miniature horses were not.  The feeding of alfalfa also increased the risk of developing enteroliths, especially if grass hay was not fed concurrently.  It was postulated that the alfalfa predisposed the horses to the calculi formation due to the high concentration of magnesium in alfalfa and the ability of alfalfa to alkalinize the colon.  Horses kept outside had a lower incidence of enteroliths than those kept in a stall.  It was suggested that since outside horses have a greater opportunity to graze, the alfalfa in the intestine may have been diluted.  Also, horses that exercise more have greater digestibility then those kept in a stall.  Horses with colic due to an enterolith were determined to have longer duration of clinical signs, a higher rectal temperature, higher heart and respiratory rates, and were more dehydrated than horses that had colic for other reasons.  The diagnosis of enterolithiasis was made by rectal palpation, radiographs, and in some cases surgery.