English
Proximal Enteritis (also known as Anterior Enteritis) describes inflammation of the first two parts of the horse’s small intestine. Proximal Enteritis (PE) is a serious concern for horse owners, as it can block passage of food and water through the digestive system.
The causes of proximal enteritis are not yet fully understood, although its association with certain lifestyle and management factors is under investigation. These include the role of concentrates and pasture in the diet and exposure to bacterial agents and toxins.
The symptoms of proximal enteritis generally begin with mild or moderate colic that eases, followed by lethargy. Other symptoms include decreased mental alertness, heavy breathing, decreased stomach noises, and fever.
The inflammation caused by this condition can have serious repercussions for many other systems in the body including the hooves, lungs, liver, pancreas, and other organs involved in digestion.
The survival rate for horses with proximal enteritis is between 25 and 94%, with improvement usually seen by three days after starting treatment. Horses that develop laminitis or other disorders have a lower chance of survival. Prompt veterinary intervention provides the best chance of recovery.
Proximal Enteritis in Horses
Proximal enteritis is a serious inflammatory condition in which the first two parts of the horse’s small intestine, the duodenum and the jejunum, swell with fluids, effectively sealing off the passage of food and water through the digestive system. [1][2][3]
In severe cases, the pylorus, stomach and esophagus become inflamed as well. [4] The inflammatory fluid stretches the tissues, which is very painful for the horse. [1]
This condition is known by many names including: [2][3][4]
- Anterior enteritis
- Enteritis
- Duodenitis-proximal jejunitis
- Duodenitis
- Acute ileus syndrome
- Acute gastric dilation
- Cranial enteritis
- Fibrinonecrotic duodenitis
- Jejunitis
- Gastroduodenitis
- Hemorrhagic fibrinonecrotic duodenitis-proximal enteritis
- Hemorrhagic enteritis
Risk Factors
The risk factors for proximal enteritis are not fully understood at this time. [4] Studies show that proximal enteritis is more likely in horses being fed large quantities of concentrate or those who are grazing pasture. [1][4]
Changes in routine, particularly in diet, are also considered risk factors. [4]
There also appears to be geographic factors at play, with more reported incidences of proximal enteritis in Europe and North and South America, while there are fewer cases elsewhere in the world. [4][5]
The age range of affected horses is between five and ten years of age, with some exceptions reported. [4] It appears that mares are more at risk than geldings and stallions. [4] Stress, such as recent foaling also increases a horse’s susceptibility to proximal enteritis. [6]
There is some evidence that rates of occurrence are higher on individual farms. This suggests that once one member of a herd has had PE, the entire herd may be at risk of another occurrence. [6]
Causes
The causes of proximal enteritis in horses are not fully understood at this time. [4][7] Although there is an obvious inflammatory response involved in the disease, no specific agent has been identified in all cases. [8][9] Many theories are being tested. [4]
It is likely that PE is multifactorial, meaning there are multiple interactions and agents involved in the disease process, but the scope of these is not yet fully understood. [4]
Epidemiological data shows there are higher rates of incidence within the herd on individual farms. [6] This trend suggests that horses within the same herd are exposed to the same causal agent, which is consistent with the theory that lifestyle and management factors are at play.
The signs and physiological changes associated with PE suggest an infectious cause, but the presence of potentially infectious bacteria found in the intestines of healthy horses makes it difficult to prove any of these species are the causative pathogen.
The Role of Diet
One promising line of inquiry relates to dietary considerations. [3] Research shows that feeding large amounts of concentrate or providing access to pasture are associated with proximal enteritis, although the specific contribution of these factors to the disease has not been studied. [9]
Researchers speculate that toxin exposure while grazing, or management factors related to grazing may contribute to the development of proximal enteritis. [9]
Bacteria and Fungi
Two bacteria, Salmonella spp. and Clostridium spp., have been identified in the gastric juices from horses with proximal enteritis, which gives rise to questions about their association with the disease. [8] Evidence supporting Salmonella as a potential cause is weak. [4]
Newer research into the role of Clostridium difficile, a type of bacteria which was found in every case of proximal enteritis in one study, is more promising, although a causal link is far from being confirmed. [10]
Mycotoxins are another possible agent involved in proximal enteritis. [4] Mycotoxins are toxic compounds produced by certain types of fungi that grow on grains, nuts, grasses, or seeds. [1]
Further investigation into the link between this agent and proximal enteritis is required to confirm or eliminate it as a cause. [4]
Calcium Fluctuations
Hypocalcemia, a reduction in circulating levels of calcium in the blood, is common with proximal enteritis and likely contributes to poor gut motility. It is caused by large losses of chloride in refluxed stomach fluid. This causes a compensatory increase in bicarbonate, which binds to ionized calcium, making it unavailable. [10]
What's your top priority with your horse's health?
What's your top priority with your horse's health?
Symptoms
The symptoms of proximal enteritis vary widely in severity and in extreme cases can lead to death of the horse. [7]
The symptoms are also vague and non-specific, meaning no one symptom confirms a diagnosis of proximal enteritis, and all of the symptoms point to other possible conditions. [3]
This makes it challenging to differentiate proximal enteritis from other intestinal disorders that are caused by mechanical obstructions such as blockages caused by food getting stuck in the digestive system (impaction), or by the strangulation of the small intestine by a lipoma. [2]
Colic Signs
The first sign of proximal enteritis is typically mild or moderate colic (pain in the abdomen) that recedes, followed by depression or lethargy. [8]
The signs of colic in a horse include (listed in order of increasing severity): [2]
- Staring at the flank
- Pawing at the ground
- Kicking at the abdomen
- Lying down
- Intermittent rolling
- Persistent rolling
Severe Signs
As the disease progresses, more severe symptoms develop, including: [1][2][8]
- Decrease in mental alertness
- Decrease in responsiveness
- Fever
- Signs of dehydration including sunken eyes, loss of skin elasticity, decreased urination, dry feces, and tacky gums
- Decreased stomach noises
- Increased heart rate
- Heavy breathing or panting
- Lack of appetite
- Small speckles or bruises on the skin or mucous membranes
- Diarrhea
- Pale or blue gums
- Chilly ears or limbs
Complications of Proximal Enteritis
The inflammation associated with proximal enteritis disturbs nutrient absorption from the intestine into the horse’s bloodstream. [4] This can have serious repercussions for many physiological systems. [4]
Disorders that are associated with proximal enteritis include: [2][3][8]
- Pneumonia
- Blood clots (thrombophlebitis)
- Liver disorders
- Pancreatitis
- Laminitis
- Cardiac issues
- Gastritis (inflammation of the stomach lining)
- Ileitis (inflammation of the ileum)
- Typhlitis (inflammation of the cecum)
- Colitis (inflammation of the colon)
Diagnosis
Horses with symptoms of proximal enteritis require immediate veterinary care and hospitalization. [2][3][8]
The main challenge with diagnosing proximal enteritis is differentiating this disease from mechanical obstructions such as strangulating lipoma or gastric impaction, which have a wide overlap in symptoms. [1][3]
Diagnosis is based on physical examination, bloodwork, ultrasound, nasogastric decompression, abdominocentesis (withdrawing fluid from the abdomen with a syringe for study), and possibly exploratory surgery. [1]
The disease’s characteristic clinical finding is copious amounts of fluid upon gastric decompression. In this procedure, a veterinarian inserts a tube through the horse’s nostril into the stomach to release its contents. [3]
Confirmation of diagnosis is typically made by postmortem examination, surgical exploration, or by the easing of symptoms with nasogastric decompression. [5]
Treatment
Nasogastric decompression is used in both diagnosis and treatment of proximal enteritis. [1] During the procedure, the veterinarian inserts a tube through the nostril of the horse into the stomach to release gastric reflux (fluid from the stomach). [1]
The volume of reflux that is produced during this procedure is used as a criterion to diagnose proximal enteritis. Other conditions do not usually result in such a large volume of liquid in the horse’s body. [4]
The liquid retrieved is malodourous and typically reddish or orange-brown. [1] Horses with proximal enteritis also show relief from pain upon decompression, which differentiates this condition from mechanical obstructions where the horse does not show improvement. [6]
As a treatment, nasogastric decompression is typically required every two hours until signs begin to improve. [6] To facilitate treatment, your veterinarian may place a temporary indwelling nasogastric tube. [6]
Medical Management
Other treatments are aimed at supporting the horse’s overall health while the proximal enteritis resolves, including: [1]
- Intravenous fluids
- Electrolyte supplementation
- Nonsteroidal anti-inflammatory drugs
- Medications to increase gut motility
Horses with proximal enteritis typically require advanced monitoring of blood pressure and repeated abdominal ultrasounds to track the disease’s progress and monitor overall health. [1]
Surgical Intervention
There are some cases of PE where surgical intervention is necessary, including those where: [2]
- Medical management is not successful
- It is impossible to differentiate the diagnosis from other causes, such as intestinal obstruction
- The risk of waiting for the condition to resolve is high
The most common surgical procedure for treating PE is intestinal bypass, which redirects the excess fluid produced in the intestine into the cecum and colon. [3] This surgery relieves the painful pressure build-up caused by the fluid, but does not treat the underlying cause of disease. [3]
Supporting Gut Health
Aftercare for a horse recovering from proximal enteritis requires feeding a balanced, forage-based diet that supports optimal gut health. Work with an equine nutritionist to formulate a feeding program that helps maintain a healthy digestive system and minimizes the risk of recurrence.
- Feed good quality forage: High quality forages are usually more palatable for horses, which can improve appetite after a bout of enteritis. High quality forage is also usually more digestible, which may provide more readily available nutrients for the recovering tract.
- Feed frequent small meals: To avoid overloading the healing digestive tract, feed several small meals throughout the day.
- Limit grain-based concentrates: Reduce reliance on grain-based commercial feeds in the diet to minimize the risk of colic and hindgut disruptions.
- Provide fresh water: Ensure access to clean water at all times to prevent dehydration and support gut motility. Feed salt to increase water intake.
- Feed a digestive health supplement: To support nutrient absorption and hindgut function, provide a gut supplement that contains yeast, probiotics, digestive enzymes and toxin binders, such as Mad Barn’s Optimum Digestive Health.
Prognosis
Reported survival rates for horses with proximal enteritis vary between 25 and 94%. [2] Horses typically improve within 3 days of medical intervention, with more severe cases requiring care for a week or more. [6]
Horses that develop laminitis or other complications due to proximal enteritis have a lower chance of survival. [3]
The chance of recurrence once the horse has recovered is low. [3] Since the cause of PE is not well understood, there are no proven preventive measures available at this time.
Frequently Asked Questions
Here are some frequently asked questions about proximal enteritis in horses:
Proximal enteritis is a serious equine digestive condition where the first sections of the small intestine become inflamed and filled with fluid. This swelling can block the normal movement of feed and water through the gut. Affected horses often show colic signs at first, followed by dullness, fever, reduced gut sounds, dehydration, and heavy breathing.
Proximal enteritis does not have one confirmed cause, but diet, toxins, bacteria, and farm-level risk factors may all play a role. Research has looked at links with large concentrate meals, pasture access, sudden routine changes, Salmonella, Clostridium, and mycotoxins. Since the cause is not fully understood, prevention focuses on steady feeding practices and prompt care when signs appear.
Early signs of proximal enteritis often begin as mild or moderate colic that improves, followed by a horse becoming quiet, dull, or less responsive. Other warning signs can include fever, reduced appetite, decreased gut sounds, rapid breathing, dehydration, and pale or blue gums. Any colic, breathing trouble, or abnormal gum color should be treated as an emergency.
Proximal enteritis is a specific disease that can cause colic, while colic simply means abdominal pain with many possible causes. PE can look similar to intestinal blockages, which makes veterinary diagnosis important. One key clue is that horses with proximal enteritis often improve after gastric decompression, while horses with some mechanical obstructions may not.
Proximal enteritis is a life-threatening condition because fluid builds up in the small intestine and stomach, causing pain, dehydration, and major electrolyte losses. Severe cases can affect the hooves, lungs, liver, pancreas, heart, and other parts of the digestive tract. Reported survival rates vary widely, so fast veterinary treatment gives the horse the best chance of recovery.
Diagnosis of proximal enteritis usually requires a veterinary exam, bloodwork, ultrasound, stomach decompression, abdominal fluid testing, and sometimes exploratory surgery. A major finding is a large amount of foul-smelling reddish or orange-brown gastric reflux during nasogastric decompression. Veterinarians also need to rule out other serious causes of colic, including intestinal obstruction.
Treatment for proximal enteritis usually involves hospitalization, repeated nasogastric decompression, intravenous fluids, electrolytes, anti-inflammatory medication, and drugs to support gut movement. Decompression may be needed every two hours until the horse improves. Surgery may be considered when medical treatment fails or when veterinarians cannot safely rule out an intestinal obstruction.
Feeding practices may influence proximal enteritis risk, especially when horses receive large concentrate meals, sudden diet changes, or certain types of pasture access. Good-quality forage, gradual feed transitions, smaller meals, clean water, and limited grain-based concentrates can help support gut health. These steps cannot guarantee prevention, but they may reduce avoidable digestive stress.
Complications from proximal enteritis can extend beyond the small intestine and affect several body systems. Possible problems include laminitis, pneumonia, blood clots, liver strain, pancreatitis, gastritis, colitis, dehydration, and electrolyte imbalances. Horses that develop laminitis or other severe complications have a poorer prognosis, which is why close monitoring during treatment is so important.
Prognosis for proximal enteritis varies widely, with reported survival rates ranging from 25 to 94%. Many horses begin to improve within about three days of medical treatment, although severe cases may need a week or more of care. Recovery is less likely when laminitis or major complications develop, but recurrence after recovery appears to be low.
Summary
Proximal enteritis is a serious inflammation of the small intestine where swelling seals off the passage of food and water through the horse's digestive system. Immediate veterinary care and hospitalization are required for horses suspected of having proximal enteritis.
- The risk factors and causes of PE are not well understood but may include diet, bacterial agents, or toxins.
- Initial symptoms include mild to moderate colic followed by lethargy and depression. Other symptoms include fever, rapid heart rate, rapid breathing, dehydration, decreased appetite, decreased stomach noises, and decreased responsiveness.
- Proximal enteritis is often associated with other serious issues including laminitis, pneumonia, blood clots, and inflammation of other parts of the digestive system.
- Diagnosis is based on the volume and appearance of gastric reflux as well as bloodwork, ultrasound, abdominocentesis, and physical examination. Treatment includes ongoing gastric decompression, supportive care such as IV fluids and anti-inflammatory drugs, and in some cases, surgery.
- Survival rates vary, with horses that develop laminitis or other complications having a lower chance of survival.
References
- Feary, D. J., & Hassel, D. M. Enteritis and Colitis in Horses. Veterinary Clinics of North America: Equine Practice. 2006.View Summary
- Underwood, C. et al. Complications and Survival Associated with Surgical Compared with Medical Management of Horses with Duodenitis‐proximal Jejunitis. Equine Veterinary Journal. 2008.View Summary
- Reed, S. M. et al. Equine Internal Medicine. 3rd ed. Saunders Elsevier, St. Louis, Mo. 2010.
- Arroyo, L. G. et al. Equine Duodenitis-Proximal Jejunitis: A Review. The Canadian Veterinary Journal. 2018.View Summary
- Edwards, G. B. Duodenitis‐proximal Jejunitis Anterior Enteritis as a Surgical Problem. Equine Veterinary Education. 2010.
- Freeman, D. E. Duodenitis‐proximal Jejunitis. Equine Veterinary Education. 2000.
- Steward, S. K. T. Geographic Disparities in Clinical Characteristics of Duodenitis-Proximal Jejunitis in Horses in the United States. Journal of Equine Veterinary Science. 2020.View Summary
- Blikslager, A. T. et al., Eds. The Equine Acute Abdomen. Third edition. Wiley, Blackwell, Hoboken, NJ. 2017.
- Cohen, N. D. et al. Are Feeding Practices Associated with Duodenitis‐proximal Jejunitis. Equine Veterinary Journal. 2006.
- Arroyo, L. G. et al. Potential Role of Clostridium Difficile as a Cause of Duodenitis-Proximal Jejunitis in Horses. Journal of Medical Microbiology. 2006.View Summary
