Anterior (Proximal) Enteritis in Horses

Key Takeaways

Anterior enteritis (AE), also known as proximal enteritis, is inflammation of the first two parts of the small intestine - the duodenum and the jejunum. 

• The cause of AE in horses is suspected to be clostridial infection, although currently causes are not completely understood 

• Symptoms include abdominal pain and fever

Horses with symptoms of abdominal pain require immediate veterinary attention

• Diagnostic tools include physical examination, rectal palpation, nasogastric intubation, bloodwork, and ultrasound

• Treatment includes repeated emptying of the stomach, IV fluids, pain medications, and antibiotics

• Prognosis with treatment is good unless further complications such as laminitis or peritonitis develop, in which case the prognosis is poor

• There are currently no proven preventative measures

A Closer Look: What is Anterior Enteritis in Horses?

The severity of anterior enteritis depends on the level of the inflammatory response and the rate at which fluid accumulates. Severe cases of anterior enteritis accumulate fluid rapidly, causing the stomach to swell and potentially leading to gastric rupture. Signs of colic increase in severity as abdominal pain increases.

Symptoms of severe colic include:

• Constant rolling 

• Sweating

Difficulty breathing

• Getting up and down repeatedly

• Unwillingness to stand

• Aggressively biting or kicking themselves to the point of causing injury

• Presence of a “toxic line”

Horses showing signs of colic require emergency veterinary attention.

Risk Factors

Anterior enteritis is uncommon in horses. Adult horses aged 5 to 10 are most at risk of developing AE. Horses showing symptoms of colic, particularly those with fever, require immediate veterinary attention. Horses whose symptoms improve within 72 hours are likely to recover. 

Left untreated, anterior enteritis can cause laminitis, a severe inflammatory condition of the hooves that can lead to permanent lameness.  Peritonitis, inflammation of the abdominal cavity lining, can also result and may be life-threatening. Laminitis and peritonitis are more likely to develop if the inflammation is not controlled quickly.

Possible Causes

The causes of anterior enteritis have yet to be completely characterized. There is some evidence that the bacteria species Clostridium is involved, but to what extent has yet to be determined. Some cases of anterior enteritis are associated with a recent diet change, particularly adding high-energy grains or lush pasture.

Main Symptoms

Anterior enteritis causes accumulation of fluid in the small intestine, which flows back into the stomach causing severe stomach distention. The symptoms of anterior enteritis include:

• Lethargy

Lack of appetite

• Reduced fecal production

• Grinding of teeth

• Flehmen response (inhaling through the mouth with the upper lip curled back)

• Groaning

• Rolling

• Signs of dehydration including sunken eyes, sticky or dry mucous membranes and skin tenting (the skin does not return quickly to its normal position when it is pinched)

• Presence of a “toxic line” - a bright pink or bluish-purple discolored line in the gums

Testing and Diagnosis

Diagnostic tools include:

• Physical examination

• Rectal palpation

• Nasogastric intubation

• Bloodwork

• Abdominal ultrasound

• Abdominocentesis (examination of fluid extracted from the abdomen)

Horses often have to be sedated for diagnostic examination.

Note: intubation of horses must be performed by a veterinarian. There is no safe way to intubate horses  at home.

Steps to Recovery

Most cases of anterior enteritis can be well managed with medication and supportive therapy. Severe cases may require surgical intervention. Treatments include:

• Repeated nasogastric intubation

• IV fluids

• Anti-inflammatory medication

• Pain medication

• Antibiotics

• Medications that stimulate small intestine movement

• Medications to prevent gastric ulcers

• Supportive care to prevent laminitis, including careful monitoring for signs of lameness and icing of the hooves

With treatment, the symptoms of AE usually improve in 3 days, however full recovery may take considerably longer. Horses are typically hospitalized for the duration of treatment. If gastric reflux is controlled quickly and fully, the prognosis is good. Severe cases that develop complications such as laminitis or peritonitis have a poor prognosis, and many horses in these cases are euthanized.


There are no proven preventative measures to avoid anterior enteritis. Early detection and treatment prevent further complications in most cases.

Is Anterior Enteritis Common in Horses?

Anterior enteritis is uncommon in horses.

Typical Treatment

• Nasogastric intubation

• IV fluids

• Anti-inflammatory medications

• Pain medication

• Antibiotics

• Small-intestine stimulators

• Gastric ulcer medications

• Supportive care

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