What are hindgut ulcers?

Hindgut or colonic ulcers are less understood than gastric ulcers but equally as damaging. Hindgut ulcers are found in the colon, predominantly affect performance horses and are frequently identified in horses already suffering from gastric ulcers. Equine gastric ulcers occur in the oesophagus, duodenum and stomach whilst colonic ulcers occur in the hindgut, specifically the colon. For more information on equine gastric ulcers please follow this link, read on for information on equine colonic/hindgut ulcers.

Horses are ‘hindgut fermenters’ – meaning they ferment food/forage in their colon which is then used to produce most of their energy. So this region is extremely important to a horse’s health.  The stomach is less than 10% of the total volume of the digestive tract, on the other hand, the hindgut (the cecum and colon) is huge.


What are the causes of hindgut ulcers?

Ulcers occur in the hindgut when its protective mucosal lining is compromised or damaged. Unfortunately, there can be various causes of this.


Right Dorsal Colitis

This is caused by the use of ‘non-steroidal anti-inflammatories’ or NSAIDs.

When injured, damaged tissues release chemicals called prostaglandins, which cause pain and inflammation. NSAIDs work by blocking the release of prostaglandins.

Unfortunately, normal healthy tissues also release prostaglandins, including those responsible for mucus production and blood flow regulation in the gut. When these ‘good’ prostaglandins are blocked it leads to a compromised hindgut lining. Most often leading to ulcer production in the horse’s right dorsal colon.



Previously parasites setting up in a horse’s hindgut were thought to be the main cause of hindgut issues – including colic. However, today’s anti-parasitic treatments are highly effective against the types of parasites that affect the hindgut, so that risk has all but been eliminated. In rare cases where there is parasitic involvement, the lesions that are created may open the door for ulceration.


Hindgut Acidosis

Hindgut acidosis is excessive acid in the horse’s hindgut most commonly caused by high grain/low forage diets. Modern equine diets include energy dense feeds like grains rich in starch. The small intestine digests starch but is easily overloaded when high levels of grain are fed at once. Undigested starch moves into the large intestine and when this is fermented the production of lactic acid increases.

In an acidic environment, bacteria critical to fibre fermentation are less efficient and can die off and release endotoxins. In comparison, lactic acid-producing and lactic acid–utilising bacteria increase in a more acidic environment. It is a vicious circle as the more acid these bacteria produce, the more acidic the hindgut becomes and the more they thrive.

The increased acidity in the hindgut damages the mucosa (gastric wall) which absorbs the endotoxins released, letting them enter the general circulation. Endotoxins initiate a series of inflammatory responses and can trigger laminitis, amongst other disorders.



Clinical Signs and Diagnosis of Hindgut Ulcers

The signs of digestive discomfort in horses are often the same, whether it’s gastric or colonic ulcers or something else. Watch for these signals that can signal a digestive issue, possibly colonic ulcers:

  • weight loss and/or general decline in body condition
  • resistance under saddle
  • irritability and other changes in attitude
  • lack of energy and stamina
  • loss of appetite
  • behavior indicating discomfort, such as pawing or laying down excessively
  • low-grade anemia

And because the hindgut’s large size and position, some symptoms often attributed to gastric ulcers are more likely a sign of colonic ulcers:

  • girthiness
  • sensitivity in the flank area
  • difficulty bending, collecting, and extending

If your horse is exhibiting any of these symptoms and testing shows that its manure pH is low, your horse is likely suffering from colonic ulcers.

Colonic ulcers in horses, while more difficult to diagnose, are still a very real threat that can lead to even more damaging conditions for your equine partner.


Treatment and prevention:

As discussed above, the current day horses have diets and feeding regimes that differ greatly from what they were designed to consume. And sadly, understanding and awareness of colonic ulcers is not as prevalent as that for 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) and increase forage in the diet
  • Feed smaller meals more frequently throughout the day


All of this will help ensure that carbohydrates are digested in the foregut where they belong. This keeps starches out of the hindgut so that the pH remains balanced and its acidity low.


If the ulcers are advanced and simple alterations to their diet are not adequate, sucralfate is a drug that can alleviate symptoms. It works by coating the ulcer which prevents further damage. If administered in conjunction with omeprazole (which control gastric acid secretion) this will help the ulcer to heal.


As always prevention is better than cure.