Sand accumulation or impaction is a common diagnosis for horses living in sandy environments, and show signs of abdominal pain (colic), and/or have diarrhea.

Over time, ingested sand settles to the bottom of the intestine and accumulates there. The rate of accumulation exceeds the rate of passage. Over time, a large quantity of sand (up to 100 lbs+ in some cases) can accumulate inside a horse's intestine, resulting in pain and discomfort and, in some cases, blockage. Often horses don't show obvious signs until they have a large accumulation and blockage.

Whether a horse accumulates sand in their colon depends on grit size. Larger grit accumulates within the colon whereas smaller grit and clay soils move through the intestine and are expelled in the manure. Some horses in a group may have more of a tendency to accumulate sand than others because of habit or physiology.

Diagnosis is made by veterinary exam. Sometimes sand can be heard in the intestine with a stethoscope. It makes a very specific sound, often likened by veterinarians to water running over beach sand. It can also often be found using a sand sediment test of manure.

Abdominal radiography is a highly effective means of diagnosing sand in the equine abdomen. The sand lights up brightly as the x-ray beam cannot penetrate it. Unfortunately, most radiography systems are not sufficiently powerful to penetrate the abdomen of a horse.

Mild cases may be managed with stoppage of sand intake, pain relievers, laxatives and monitoring, whereas severe cases may require intensive care and even colic surgery.