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, exposure to bacterial agents and toxins, and fluctuations in calcium levels.

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 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 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] More recently, salmonella has been eliminated as a potential cause of PE. [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, 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

There may also be an interaction between calcium levels in the horse’s body that leads to a disruption in electrolytes within the tract, which may promote development of diarrhea. [3]

Prolonged diarrhea may be associated with inflammation and enteritis, but this interaction requires more study to be confirmed. [3]

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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 one structure by another structure. [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
Any instance of pale or blue gums, difficulty breathing, or colic is a medical emergency requiring immediate veterinary attention. Prompt medical intervention provides the best chance of survival.

 

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)
  • Typhilitis (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]

Nasogastric intubation should only be performed by a veterinarian. There is no safe way to intubate a horse at home.

 

Medical Management

Other treatments are aimed at supporting the horse’s overall health while the proximal enteritis resolves, including: [1]

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.

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  • Prebiotics, probiotics & enzymes
  • Support hindgut development
  • Combats harmful toxins in feed
  • Complete GI tract coverage

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.

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.

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References

  1. Feary, D. J., & Hassel, D. M. Enteritis and Colitis in Horses. Veterinary Clinics of North America: Equine Practice. 2006.View Summary
  2. 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
  3. Reed, S. M. et al. Equine Internal Medicine. 3rd ed. Saunders Elsevier, St. Louis, Mo. 2010.
  4. Arroyo, L. G. et al. Equine Duodenitis-Proximal Jejunitis: A Review. The Canadian Veterinary Journal. 2018.View Summary
  5. Edwards, G. B. Duodenitis‐proximal Jejunitis Anterior Enteritis as a Surgical Problem. Equine Veterinary Education. 2010.
  6. Freeman, D. E. Duodenitis‐proximal Jejunitis. Equine Veterinary Education. 2000.
  7. 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
  8. Blikslager, A. T. et al., Eds. The Equine Acute Abdomen. Third edition. Wiley, Blackwell, Hoboken, NJ. 2017.
  9. Cohen, N. D. et al. Are Feeding Practices Associated with Duodenitis‐proximal Jejunitis. Equine Veterinary Journal. 2006.
  10. 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