What are Enterolithiasis?
An enterolithiasis is a condition where mineral masses of struvite crystals made up of magnesium ammonium phosphate form in the intestine or colon of a horse. The stones usually begin their formations around an indigestible object such as a small rock or piece of cloth and grow as more minerals attach to it. Small enteroliths are generally passed in the manure, however, large enteroliths can get caught in the intestine and impair the passage of the contents of the gut and may ultimately get trapped in the digestive system, and the pressure and abrasion from the stone may cause the tissues to necrotize.
Enterolithiasis is a condition in which an enterolith, or large mineral mass, has formed around an indigestible object and gotten trapped in the horse’s digestive system.
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Symptoms of Enterolithiasis in Horses
Small enteroliths may not cause any symptoms as they pass through the digestive tract but larger enteroliths interfere with the digestive process and result in symptoms such as:
- Abdominal pain
- Abnormal behavior
- Loose stool
- Poor performance
- Rapid heart rate
- Reluctance to go downhill
- Reluctance to jump
- Small enteroliths or stones in manure
- Weight loss
This is an indigestible material that is coated in microscopic struvite crystals within the digestive tract. Also known as gut stones, these masses generally pass through the digestive system and are expelled with the feces, however, if the enterolith gets trapped in the digestive system it can continue collecting additional material until it reaches up to twenty pounds.
Symptoms of a trapped fecalith are the same as a trapped enterolith. The fecalith is made up of actual fecal matter rather than accumulations of crystals in the intestine. Fecaliths do not usually have the same spherical shape as enteroliths when viewed by x-ray.
Causes of Enterolithiasis in Horses
Several risk factors can encourage the development of the enteroliths that result in enterolithiasis.
- Dietary - A high pH diet has been linked to the formation of enteroliths, as is a diet lower in dry matter and diets high in minerals; alfalfa is high in calcium and protein, and diets that contain a high ratio of alfalfa create ideal conditions for enteroliths to form
- Exercise levels - Horses that are given a chance to exercise daily are less likely to develop stones than sedentary equines
- Gender - Females are more likely to develop this disorder than males
- Genetic predisposition - Arabian and Arabian crossbreeds are over-represented, as are Morgans, American Saddlebreds, donkeys, and miniature breeds; horses with siblings that develop enteroliths are more likely to develop enteroliths themselves
Diagnosis of Enterolithiasis in Horses
Your veterinarian will conduct a thorough physical evaluation, including a rectal exam. The symptoms and physical exam will most likely suggest an obstruction in the digestive system, but additional technology is required to determine what is causing the obstruction and where it is located. In many cases, radiography (x-ray) of the abdominal cavity after a twenty-four hour fast is useful for locating where the blockage is lodged. It is particularly helpful when the patient is physically small, and when the stone is lodged in the large colon.
Ultrasound imaging is useful for evaluating the health of the tissues in the digestive system and can be helpful in locating pockets of fluid or intestinal rupture. It is not uncommon for enterolithiasis to go undiagnosed until exploratory surgery is able to help uncover the cause of the obstruction. If the stone was not visible on the x-ray images, signs from the ultrasound may help to guide where exploratory surgery should take place.
Treatment of Enterolithiasis in Horses
In most cases, enteroliths that have expanded to the point that they are obstructing the digestion will have to be removed surgically. As stones grow, they can cause damage to the intestinal walls, particularly in the bowel. Abrasions and ruptures of the tissues that make up the digestive system can be very dangerous, and may negatively impact the outcome of surgery. After surgery, the feeding choices that are made can be a crucial component to the recovery of the patient.
Horses are usually fasted for twenty-four hours prior to surgery, and another twelve to twenty-four hours of fasting may be required after surgery to prevent the distention of any healing tissues. During this time, supportive fluids with electrolytes and sugars are often administered intravenously. Once the animal has returned home water should be made available at all times to help encourage proper digestion. The feed for the first 30 days post-surgery should include higher amounts of protein and phosphorus than normal, with decreased amounts of structural fiber.
Recovery of Enterolithiasis in Horses
Animals who have shown a predilection for developing enteroliths should have their diet adjusted to counteract this tendency. The amount of alfalfa and wheat bran in the diet should be reduced and offering ample opportunity for turn out will add valuable roughage from grazing. The addition of a cup or two of vinegar or apple cider vinegar has been shown to be useful for reducing the pH of the hindgut of equines, but it cannot dissolve stones that have already formed, and no studies have shown a definitive effect on the formation of gut stones as of yet. It is not harmful to supplement the equine diet with vinegar, however, and the reduction in the overall pH levels may be helpful.