Large bowel displacement is a fairly common cause of serious colic in horses. Displacement means the large bowel has moved out of it's normal position and includes:

• Left dorsal displacement also called renosplenic ligament entrapment
• Right dorsal displacement of the colon
• Volvulus or torsion (twisted) colon that varies from a slight twist to completely twisted (>360 degrees)
• Cranial displacement of the left colon (pelvic flexure)
• Herniation of the colon into the diaphragm, gastrosplenic ligament, and the mesentary connected to the colon (mesocolin)

The clinical signs of displacement are quite variable sometimes causing a chronic recurring low grade colic and other times starting off with mild signs of pain and progressively worsening. In the case of remarkable displacement the colic begins as severe pain and the horse rapidly degenerates. This article consists of a review of clinical signs, causes, diagnosis, treatment and prognosis of these diseases of the large colon.

The causes of large bowel displacement and torsion are difficult to study. We have no models which produce displacement in the horse and studying the horse after the torsion occurs provides few clues as to why it happened. The large colon of the horse is immense. Though only about 11 feet (3.4 meters) in length it holds 20 gallons (81 liters) of fluid. It is very mobile in the abdomen because it has very few mesenteric attachments. Together these properties predispose to displacement. Other factors associated with a higher incidence of displacement are:

• Age greater than 7 years old
• Large horses like warm and cold bloods
• Foaling and lactation: Broodmares comprised 79% of the total case load of surgical colics.
• Abrupt feeding changes
• Previous history of displaced bowel

This list illustrates the importance of a lot of space to move around. It has been suggested that feed changes may result in abnormal motility or changes in the character of the bowel contents that cause displacement. For instance if a lower section becomes very gassy it may float up and over more dorsal segments.