Proximal Enteritis (Proximal Duodenitis/Jejunitis, Anterior Enteritis)

Proximal enteritis is an inflammation of the first section of the small intestine and is a very serious cause of colic, or abdominal pain, in the horse. No one really knows what causes proximal enteritis. Some veterinarians suspect that there is a bacterial cause, but no single definitive cause has been defined.

Some veterinarians report geographic areas where proximal enteritis is more common. It may have to do with the types of bacteria that naturally occur in certain locations. More cases seem to be seen in the southeastern United States.

Older horses are more susceptible to proximal enteritis, but it is also seen in young horses one to two years of age.

The inflammation causes the affected part of the intestine to malfunction. The intestine ceases to absorb fluids, and instead, large amounts of fluid accumulate in the intestine. The fluid accumulation causes the horse to become extremely dehydrated. Although he is undergoing continual water loss, it is futile for him to drink, because he can't absorb the fluid.

Because horses are unable to vomit, the fluid causes the intestines, and eventually the stomach, to swell and become extremely painful. Eventually, if this fluid build-up is not relieved, the stomach or intestines may rupture.

Proximal enteritis is easily mistaken for a surgical cause of colic, such as twisted small intestine. Even with the best of diagnostic equipment and skills, your veterinarian may not be sure whether your horse requires colic surgery. The signs of colic, reflux, and distended small intestine may go with either problem.

Although there are some differences in some cases of proximal enteritis, such as fever, slightly less pain than with a surgical colic, and far more reduction of pain after reflux, not all cases follow the book.

What to Watch For


The most important diagnostic goal for your veterinarian is to determine if your horse can be treated medically or if the horse requires surgery. If your horse needs medical therapy, then your veterinarian will have to determine if therapy can be administered at home or if referral to an equine hospital is necessary.


Proximal enteritis can be a very expensive disease, due to the high cost of intravenous fluids and nutritional support.

Proximal enteritis refers to an inflammation of the duodenum and jejunum, which are the first segments of the horse's small intestine. It is a serious cause of severe abdominal pain, or colic and usually has a very acute onset – the horse is typically described as having been completely normal within the past 24 hours.

The cause of proximal enteritis is unknown. Certainly many clinicians suspect that there is a bacterial cause of proximal enteritis.

Proximal enteritis seems to have different levels of severity in various areas of the country, with the most severe cases being seen in the southeast of the United States. Certainly, each locale has its own resident population of normal bacteria, and it may be that for unknown reasons, these normal bacteria can become pathogenic under certain circumstances.

Although proximal enteritis is seen in all ages, it certainly seems to be more common in older horses.

In the normal horse, the contents of the intestines are continually propelled away from the mouth and toward the anus by peristalsis – a wave of worm-like contractions passing along the entire digestive system. In the normal condition, the small intestine also resorbs large amounts of fluid on a daily basis, both fluid that the horse drinks, and fluid that normally enters the intestines from the rest of the body. With proximal enteritis, whether the cause is bacterial or not, the ensuing inflammation causes damage to the intestinal walls. This causes the intestines to stop their peristaltic action – termed ileus – and to stop resorbing fluid. This in turn causes the horse to become extremely dehydrated, and causes the intestines to become severely distended. The distension causes the horse to experience abdominal pain that can be extremely severe, and thus results in signs of colic.

Because the walls of the intestines have become compromised, bacterial toxins, especially one called endotoxin, can seep into the body. Endotoxin can cause fever, high heart rate and pain.

The most important differential diagnosis for proximal enteritis is any other cause of small intestinal damage that requires surgical intervention. This may include a twisted or entrapped small intestine. Both proximal enteritis and surgical problems cause signs of colic, voluminous backed-up fluid in the stomach and small intestine, and distended small intestine on examination per rectum. However, small intestinal twists or entrapments usually cause the affected portion of the small intestine to die, thus requiring surgery, whereas the damage caused by proximal enteritis can usually be repaired by the body as long as supportive therapy is provided.

The horse with proximal enteritis has a good prognosis; however, this is usually a very expensive disease to treat.

Abdominocentesis can be performed with a needle or with a specialized instrument. It is a simple procedure but is mildly invasive. Normal peritoneal fluid is clear, and straw colored. It has a low protein count and a low number of white cells. In the prototypical case of proximal enteritis, the inflamed intestinal walls allow protein to infiltrate the peritoneal fluid, but the damage is rarely enough to let a high number of white cells seep into the peritoneal fluid. In the textbook surgical colic, the intestinal walls are more critically damaged, and both protein and white cells infiltrate the peritoneal fluid. In reality, either of these scenarios can be seen with either disease. It is a helpful test, but hardly definitive.

Home Care

Preventative Care