Right Dorsal Colitis in Horses - Causes, Treatment and Associated Conditions

Key takeaways

Right dorsal colitis (RDC) is an ulceration of part of the large intestine, the right dorsal colon, as a side effect of non-steroidal anti-inflammatory drugs (NSAIDs).

Although RDC is usually connected to high doses or prolonged ingestion of these drugs, some cases involve normal usage in inherently sensitive horses
Symptoms include soft feces or diarrhea, lack of appetite, and signs of abdominal pain
Diagnosis is made based on the history of NSAID administration, as well as physical exam, bloodwork, ultrasound and colonoscopy
Treatment includes discontinuation of NSAIDs and dietary changes, and in severe cases, surgery to remove scarred portions of the colon
Prognosis for horses with right dorsal colitis is guarded

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A closer look: Right Dorsal Colitis in Horses

The severity of RDC depends on the level of NSAID use, the sensitivity of the horse, and how long the condition develops before treatment.

NSAIDs are toxic to the mucous membranes that line the gastrointestinal tract of horses. Ulceration in other areas of the GI tract often occurs alongside RDC, commonly in the mouth and esophagus.

In cases where ulceration of the right dorsal colon is severe, bacteria and endotoxins can leak into the bloodstream and affect other bodily systems.

Horses that require NSAIDs benefit from ongoing monitoring for signs of RDC. Should signs appear, immediate veterinary care is required.

Risk factors

Right dorsal colitis is a rare condition in horses. Horses that are taking NSAIDs to control other conditions, particularly in the case of large doses or prolonged use, require close monitoring for symptoms of right dorsal colitis. If RDC symptoms occur, immediate veterinary attention is required.

Some horses are more sensitive to the side-effects of NSAIDs. In these cases, even conservative NSAID use causes RDC.

In some cases, horses develop chronic RDC.

Left untreated, RDC causes scarring to the right dorsal colon, causing ongoing, uncontrollable pain.

Possible causes

Right dorsal colitis is caused by prolonged or heavy use of non-steroidal anti-inflammatory drugs. These drugs interrupt the normal protective mechanisms of the colon, resulting in damage to the mucous membrane. The damage appears as ulcers in the right dorsal segment of the colon.

The drug most commonly associated with RDC is phenylbutazone. Whether this is because it is more widely prescribed than other NSAIDs or because it is the most toxic of them is unknown. Other NSAIDs that cause RDC include flunixin meglumine, and ketoprofen.

Main symptoms

Testing and diagnosis

Diagnosis is commonly made based on the history of NSAID use and physical examination. Other diagnostic tools include:

Blood work
Ultrasound
Colonoscopy
Gastroscopy
Colonic biopsy

Steps to Recovery

Treatment requires discontinuation of NSAIDs. In addition, treatments include:

Change of diet to include many small meals of complete pelleted feed and the elimination or restriction of roughage
IV fluids
Non-NSAID pain medications
Antibiotics
Blood transfusions
Ulcer medications
Intestine-specific anti-inflammatory medications

In the case of scarring of the colon, surgery may be required

Onset of symptoms occurs a few days to a few weeks after NSAIDs are administered. Recovery depends on the promptness of treatment, the severity of disease, and sensitivity of the horse. Due to the complexity of this condition, the prognosis is guarded. Early detection, long term monitoring, and prompt, careful treatment are required for the proper healing of the colon. Return to normal function and health takes 3 to 6 months.

Prevention

Avoiding use, and particularly overuse, of NSAIDs is the most direct route to preventing right dorsal colitis. In cases where that is not possible, monitoring of for symptoms of RDC during the period that NSAIDs are active in the body is required. Fecal consistency is the clearest sign that ulceration is occuring. Routine veterinary blood work for any horse on long-term NSAIDs is also beneficial.