Non-Infectious Diarrhea in the Adult Horse

By Lauren Lamb, DVM

Diarrhea in the adult horse can be caused by infectious and non-infectious diseases. Last month we talked about infectious causes of diarrhea; this month we will focus on the common cause of non-infectious diarrhea. The three most common cause of non-infectious diarrhea include sand accumulation in the colon, proliferative and inflammatory bowel disease, colon neoplasia (cancer), cantharidin toxicity (blister beetle) and parasite infection in the large colon.

Horses with sand accumulation in the colon frequently have a history of living in an area with sandy soil and being fed hay on the ground. Other common findings in the history include weight lose over a period of months to weeks, mild colic multiple times prior to developing a severe colic and intermittent or consistent diarrhea. Yes, I said that correctly, sand accumulation in the colon with cause colic as well as diarrhea.

A fecal sedimentation is a simple test that can be performed on a horse’s feces to confirm sand accumulation in the large colon. A fecal sedimentation can be performed by simply collecting a hand full of feces from the horse’s rectum and placing this feces in a plastic palpation sleeve. The palpation sleeve is then filled with one to two liters of water and hung up on the wall for 10 minutes.

After 10 minutes the fingers of the plastic palpation sleeve will be full of sand if your horse has sand accumulation in the large colon. Not all horses that have sand accumulation in the large colon will pass sand in their feces.

Abdominal radiographs of the lower abdomen can also be used to diagnose sand accumulation in the large colon. A powerful radiograph machine is needed to obtain diagnostic radiographs of the lower abdomen. Horses requiring an abdominal radiograph may need to be referred to a specialty equine medical center.

Read the July issue of OKFR to learn more about horse diarrhea.