The horse’s large intestine is composed of the cecum and the large colon. In an average horse, the cecum is a 3 foot long sock-shaped part of the large intestine that contains bacteria that digests plant fibers.

Ingesta (ingested material such as feed) from the small intestine empties into the cecum through a thickened muscular valve. Ingesta is mixed, and then emptied through a second valve into the large colon. The cecum's role overlaps that of the large colon. It is involved in the fermentation, digestion, and absorption of nutrients as well as water and electrolyte balance.

The cecum can distend with gas, twist, lose its blood supply, be impacted, accumulate sand, and telescope in on itself. Perhaps the best known cecal condition is impaction, which tends to occur in horses that are stall confined and rehabilitating from other injuries, particularly following orthopedic surgery.

One important aspect of cecal disorders is that the gastrointestinal tract can function (albeit poorly) with an ongoing obstruction of the cecum. This can make veterinary diagnosis difficult. Likewise, the external signs of cecal disorders look no different to the untrained eye from any other condition that causes signs of abdominal pain (colic).