Intestinal obstructions (blockages) are common in horses. Blockages can occur in any part of the digestive tract and can cause sharp and severe pain. These obstructions can stop the flow of food through the digestive tract and, in some instances, impair blood flow or cause damage to intestinal tissues. Obstructions can be mechanical (that is, they are due to a physical blockage, such as a foreign object) or functional (that is, lack of motility of the intestines stops the flow of food). Mechanical obstructions can occur due to abnormalities within the passageway of the intestine, within the intestinal wall, or outside of the intestine.
It is not always possible to determine the cause of an individual blockage. Feed impactions, parasite infections or migrations, abnormal dental conditions, inflammation of the intestines, electrolyte (salt) abnormalities, and changes in diet, daily activities, medications, or sudden stress may play a role in functional obstructions. Coarse feeds, reduced water consumption, and eating foreign objects are other common factors. Blockage may occur in a variety of locations within the intestines, especially where the intestines bend or become more narrow.
Twists (called torsion or volvulus), muscle tension changes, and changes in the position of various parts of the intestines can also bring on impaction or blockage. Altered intestinal movement and, possibly, strenuous exercise and rolling may cause or contribute to obstructions. Broodmares may be predisposed to obstructions, especially during pregnancy and shortly after giving birth. Standardbred stallions and colts develop inguinal and scrotal hernias that can trap an intestinal loop more commonly than other breeds. Lipomas (a benign tumor made of fat) and other types of intestinal tumors can constrict intestines from the outside. Intussusception is a condition in which part of the intestine gets stuck within an adjacent portion, similar to a closed telescope. Intussusceptions can cause an obstruction in horses.
Pain is the most common sign of intestinal obstruction in horses. The horse may pace, stretch, kick at its abdomen, and, upon occasion, roll or vocalize. Otherwise, the signs are the same as for colic. Intestinal obstructions are diagnosed based on the horse's history, signs, and physical and rectal examination findings. Ultrasonography and analysis of abdominal fluid may also help make the diagnosis. Some obstructions, however, require surgery to make a definitive diagnosis.
For functional obstructions in horses, the treatment is the same as for colic and may include medicine to relieve pain, fluid treatment, intestinal lubricants, and possibly laxatives. Mechanical obstructions, such as a twisted intestine, almost always require surgery to treat. If the obstruction is a foreign (nonfood) object that has penetrated the digestive system, care needs to be taken to locate and repair the injuries (there is often more than one injured site). This normally requires surgery. Antibiotics are usually prescribed before surgery to reduce infection. Additional supportive treatment may include fluids, electrolytes (salts), and calcium. Horses that require exploratory abdominal surgery to locate and correct an obstruction have an overall longterm survival rate of 50%, but early surgical intervention can improve that outlook.
Prevention of all—or even most—cases of intestinal obstruction is not possible. However, the likelihood is reduced if changes in diet and daily routines are gradual, adequate water is available at all times, dental care is regular and appropriate, and parasites are controlled. Access to coarse feeds, highly fermentable feeds (such as grains and lush grass), and foreign materials should be avoided or corrected.
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