Proximal Enteritis in Horses: Duodenitis-Jejunitis Signs and Treatment

See your vet immediately if you think your horse has proximal enteritis. This condition is an emergency cause of colic. It affects the proximal small intestine, especially the duodenum and jejunum, and is also called duodenitis-jejunitis or anterior enteritis.

In proximal enteritis, the upper small intestine becomes inflamed and stops moving normally. Fluid then builds up in the stomach and small intestine, which can cause pain, dehydration, electrolyte problems, and reflux when your vet passes a stomach tube. Horses may start with obvious colic, then become quieter or depressed after decompression.

One of the biggest challenges is that proximal enteritis can look a lot like a small-intestinal obstruction that may need surgery. Because of that overlap, your vet may recommend repeated exams, referral, and close monitoring to decide whether medical care is appropriate or whether surgery is the safer next step.

Published veterinary references describe the condition as poorly understood. It has been reported in several regions, including the southeastern and northeastern United States and parts of Europe, and severity appears to vary by region and over time.

The exact cause of proximal enteritis is still not fully understood. Veterinary references describe it as a poorly understood inflammatory disease of the upper small intestine. In many horses, no single trigger is confirmed.

Possible contributors include infectious agents, bacterial toxins, inflammation of the intestinal lining, and motility disturbances that slow the normal movement of the small intestine. Some clinicians have suspected links with clostridial organisms or endotoxin-related inflammation, but this is not proven in every case.

Your vet will also think about conditions that can look similar, including small-intestinal strangulation or obstruction, peritonitis, enteritis from other causes, and other forms of colic. That is why diagnosis often focuses not only on identifying proximal enteritis, but also on ruling out surgical disease.

For pet parents, the key point is that this is usually not something you could have predicted at home. It is an internal inflammatory emergency that needs veterinary assessment rather than a wait-and-see approach.

Your vet diagnoses proximal enteritis by combining the history, physical exam, response to stomach decompression, and tests that help separate medical inflammation from a surgical small-intestinal lesion. Horses often have colic, increased heart rate, dehydration, and significant gastric reflux.

A workup may include nasogastric intubation, rectal exam, abdominal ultrasound, bloodwork, electrolyte testing, and abdominal fluid analysis. Merck notes that horses with proximal enteritis may have moderate to severe small-intestinal distension and sometimes increased protein in the peritoneal fluid with a normal white blood cell count, although that finding does not always clearly distinguish it from other small-intestinal disease.

Because the overlap with surgical colic can be substantial, diagnosis is often dynamic rather than one-time. Your vet may repeat exams over several hours, especially if pain persists, reflux continues, or ultrasound findings worsen. Referral to an equine hospital is common when the horse needs intensive fluids, around-the-clock decompression, or possible surgery.

In some horses, the final diagnosis becomes clearer only after close monitoring or exploratory surgery. That uncertainty is frustrating, but it is also why timely veterinary care gives your horse the best chance of getting the right level of treatment.

Because the exact cause is not fully known, there is no guaranteed way to prevent proximal enteritis. Still, good digestive management may help lower overall colic and intestinal stress. That includes steady forage intake, gradual feed changes, reliable access to clean water, regular dental and parasite care, and minimizing abrupt management changes when possible.

Work with your vet on a broader colic-prevention plan for your horse. That may include reviewing diet, turnout, travel stress, medication history, and any previous episodes of abdominal pain. Horses with any history of significant colic should have a clear emergency plan so treatment is not delayed.

Prompt attention matters too. Early veterinary assessment for colic can reduce the time a horse spends dehydrated or refluxing and may improve decision-making about medical care versus referral. Prevention is not always possible, but fast recognition and early treatment can make a meaningful difference.

After recovery, ask your vet whether your horse needs a gradual return-to-feed plan, hoof monitoring for delayed laminitis, or follow-up bloodwork. Prevention sometimes means preventing the next complication, not only the first episode.