What are hindgut ulcers?

Ulcers are caused by thinning of the lining of the digestive tract. Gastric ulcers can occur in the stomach. Also, ulcers can occur in the hindgut, specifically in the colon, which is referred to as colonic ulcers. Colonic ulcers are hard to diagnose. Hindgut ulcers that occur in horses are less common than gastric ulcers. But it has also been reported that it affects 44% to 63% of horses. There’s also a chance of both gastric and hindgut ulcers being present at the same time. 


What are the causes of hindgut ulcers?

Hindgut, colonic ulcers can be caused by stress, hindgut acidosis, use of non-steroidal anti-inflammatory drugs (NSAIDs), parasites, and other disturbances to the gut microbiome. 

  • Overuse of NSAIDs
  • Excess Grain Intake
  • Stress
  • Parasites


Overuse of NSAIDs - NSAIDs are used by horse owners for multiple conditions such as joint pain and lameness. The more common equine NSAIDs that are linked with toxicity and hindgut ulcer include Phenylbutazone (Bute), Flunixin meglumine (Banamine), Ketoprofen, Firocoxib and Meloxicam. NSAIDs should not be used longer than 5 to 7 consecutive days as overuse can lead to deterioration of the gut lining. Horses who are taking NSAIDs and do not acquire sufficient water may develop hindgut ulcers. 

Excess Grain Intake - If any horse consumes too much grain in a short span of time it can result in a buildup of lactic acid that kills good bacteria and promotes the growth of harmful bacteria. This is called hindgut acidosis. Hindgut acidosis in the colon is mainly caused by starch overload in a horse diet. Excessive grain intake and insufficient forage can result in insufficient forage and a significant drop in the pH level of the hindgut. To prevent this grain should always be fed in small amounts. 

Stress - Horses that are going through any form of stress are at a higher risk of both gastric and colonic ulcers. When horses are under stress the hormone cortisol is produced by the adrenal glands.  More common causes of stress in horses are from overtraining, frequent transport, or unnatural management conditions, such as routine stalling. 

Parasites - Parasites such as tapeworm, small strongyles plus many more types of parasites also cause ulcers at the site when they are attached to the intestinal wall. Parasite colitis occurs when a horse ingests parasites that become encysted in intestinal lining. Various bacteria, viruses, protozoans, and toxins may also lead to hindgut ulcer.   

The increased acidity in the hindgut damages the mucosa (gastric wall), allowing endotoxins to enter the general circulation. Endotoxins can provoke laminitis and trigger an inflammatory response.


Clinical Signs and Diagnosis of Hindgut Ulcers

Horses experiencing the hindgut ulcer can have different signs and symptoms. Some of these are the same as gastric ulcers. A sign of hindgut ulcers is mild, intermittent, or recurring colic, lethargy, and loss of appetite. As the condition increases more symptoms increase. These symptoms are Girthiness, Diarrhea, Sensitivity in the flank area, Chewing wood (cribbing) amongst others.

Horses even experience fever, depression, loss of appetite, colic, and/or watery diarrhea. 

While colonic ulcers in horses are more difficult to diagnose, they are still very real and can lead to even more damaging conditions.


Diagnosing of hindgut ulcers

It is harder to diagnose a hindgut ulcer than a gastric ulcer.  Transabdominal ultrasound is the only definitive method for hindgut ulcer diagnosis. In this type of ultrasound specialized equipment and skills are used. In case ultrasound shows a thickened colonic wall hindgut ulcers need to be diagnosed. 


Treatment and prevention

Hindgut ulcers may need to be treated medically or surgically. The odds of colonial ulcers are greatly increased if horses are fed diets and feed regimens that differ greatly from what they were designed for. But understanding and awareness of colonic ulcers are not as easy as gastric ulcers.

Fortunately, there are simple changes we can make to prevent ulcers from occurring.

  • Reduce the risk for right dorsal colitis by reducing or removing NSAIDs
  • Reduce concentrates (grains and processed feeds) 
  • Feed smaller meals throughout the day
  • Avoid situations that can cause stress


All of this will help ensure that carbohydrates are digested in the foregut. This keeps starches out of the horse hindgut so that the pH remains balanced.

If the ulcers are advanced, simple alterations to their diet are not adequate, Absucralfate is a medication known to alleviate symptoms. This medication will coat the ulcer that will help to prevent more damage. 

As always prevention is better than cure.