Over the years, colic has become a broad term for a variety of conditions that cause horses to experience abdominal pain. Because it is such a broad term, it is used to refer to conditions that vary widely in cause and severity. Your veterinarian's understanding of your horse's digestive system structure and function is key to making a diagnosis and providing appropriate treatment for cases of colic (see Digestive Disorders of Horses: The Veterinarian's Examination of a Horse with Colic).

The most common signs of colic are pawing repeatedly with a front foot, looking back at the flank region, curling the upper lip and arching the neck, repeatedly raising a rear leg or kicking at the abdomen, lying down, rolling from side to side, sweating, stretching out as if to urinate, straining to defecate, distention of the abdomen, loss of appetite, depression, and a decreased number of bowel movements. It is uncommon for a horse with colic to exhibit all of these signs. Although these signs are reliable indicators of abdominal pain, they do not indicate which portion of the digestive system is affected.

A horse with colic may kick at the abdomen, stretch out, or lie down and roll.

Diagnosis and treatment occur only after a thorough examination of the horse, including a review of its history of any previous problems or treatments. Both the location and the cause of the colic should be determined. The list of possible conditions that cause colic is long (see Box). For that reason, your veterinarian may begin treatment based on the most likely diagnosis and then make a more specific diagnosis later, if necessary or possible. Information that you can provide includes the length and severity of the colic episode, as well as the horse's deworming history (schedule, treatment dates, drugs used), when the teeth were floated last, if any changes in the type or amount of feed or water supply have occurred, and whether the horse was at rest or exercising when the colic episode started.

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The Veterinarian's Examination of a Horse with Colic Type of Procedure Why It is Done Assessment of breathing and heart rate Increased heart rate or breathing rate can indicate pain. Examination of mucous membranes (inside of mouth) Paleness indicates poor oxygen level in blood; dryness indicates dehydration; discoloration indicates poor blood flow in the tissues. Insertion of tube through nose into stomach Because horses cannot vomit, the tube can allow release of gas or fluid that would otherwise result in stomach rupture. For this reason, passing a stomach tube may save the horse's life in addition to helping the veterinarian diagnose the condition causing the colic. Listening to various parts of the abdomen with a stethoscope Sounds (or lack of sound) may indicate the presence of fluid, gas, and/or obstruction. Sample of abdominal (peritoneal) fluid via needle Composition (protein and white blood cells) can reveal extent of intestinal damage. Rectal examination Allows the veterinarian to feel the intestines, their position, and their content. Ultrasonography Provides a view of certain abdominal organs, including the intestines. Some conditions (such as an inguinal hernia or an intussuception) can be seen.

Treatment

Horses with colic may or may not need surgery. Almost all horses will require some form of medical treatment, but only those with certain mechanical obstructions of the intestine need surgery. The type of treatment is determined by the cause of colic and the severity of the disease. If the horse appears to have only mild pain and the heart and circulatory system are functioning normally, the horse may be treated using medication or other nonsurgical methods and the response evaluated. Ultrasonography can be used to evaluate the effectiveness of nonsurgical treatment in some cases. If necessary, surgery can be used for diagnosis as well as treatment.

If the horse has severe pain and has signs indicating loss of fluid from the bloodstream (high heart rate and discoloration of the mucous membranes), the initial aims of treatment are to relieve pain, restore tissue blood supply, and correct any abnormalities in the composition of the blood and body fluids.

If damage to the intestinal wall is suspected, specific antibodies or medications may be administered to prevent or counteract the ill effects of bacterial toxins that leave the intestine and enter the bloodstream. If there is evidence that the colic episode is caused by parasites, one of the first goals of treatment would be to eliminate the parasites.

Pain Relief

Pain is mild in most cases of colic, and pain medication is all that is needed. This is the usual treatment if the cause of colic is believed to be a spasm of intestinal muscle or excessive gas in a portion of the intestine. If the pain is due to a more serious condition, such as an intestinal twist or displacement, some of the stronger pain medications may mask the signs that would be useful in making a diagnosis. For these reasons, whenever possible a thorough physical examination is performed before any medications are given. However, because horses with severe colic or pain may hurt themselves and become dangerous to people nearby, pain medication often must be given first. In addition, many horses with less severe problems may need pain relief until the other treatments have time to be effective.

Although pain relief usually is provided by medications, pain can be reduced in other ways. For example, the veterinarian's use of a stomach tube during diagnosis will also remove any fluid that has accumulated in the stomach because of an obstruction of the small intestine. The removal of this fluid not only relieves pain caused by distention of the stomach but also prevents rupture of the stomach.

Fluid Treatment

Many horses with colic benefit from fluid treatment to prevent dehydration and maintain blood supply to the kidneys and other vital organs. The fluids may be given either through a stomach tube or intravenous catheter, depending on the particular intestinal problem. Intravenous fluids may be needed for several days until intestinal function has returned, blood electrolyte (salt) concentrations are balanced, and the horse can maintain its fluid needs by drinking.

Protection against Bacterial Endotoxins

Endotoxins are a part of the outer coating of certain bacteria. Endotoxins are released when the bacteria die or multiply rapidly. Normally, endotoxins are contained within the intestines, but if the intestinal lining is damaged, they can escape into the abdominal cavity or bloodstream. Endotoxins then trigger an inflammatory response that can include fever, depression, reduced blood pressure, blood clotting abnormalities, and eventually death. One treatment is administration of antibodies or medications designed to neutralize the endotoxin. The effectiveness of this treatment is still being studied, however. In cases of colic, your veterinarian will be on the alert for damage to the intestinal lining and the possibility of complications due to endotoxins.

Intestinal Lubricants and Laxatives

A common cause of colic in horses is obstruction of the large intestine by dried digested food, sometimes mixed with sand. In most instances, lubricants or fecal-softening agents given through a stomach tube soften the impacted material, allowing it to be passed. Sometimes intravenous fluids are given during this procedure. The horse will normally need to be muzzled to prevent further impaction of feed while the obstruction is softening. Medications include mineral oil, dioctyl sodium sulfosuccinate (a soap-like compound), and psyllium hydrophilic mucilloid (an ingredient also found in some fiber products used by humans). When mixed with water, psyllium forms a gelatin-like mass that carries ingested food along the digestive tract. Horses that live in a sandy environment or that persistently develop impactions may be given psyllium powder in their feed, as directed by a veterinarian, to help prevent impaction.

Strong laxatives that stimulate intestinal contractions are not commonly used to treat impactions and, in fact, may worsen the problem. If an impaction does not start to break down within 3 to 5 days, surgery may be necessary to remove the impacted material.

Surgery

Usually, surgery is necessary only if there is a mechanical obstruction that cannot be corrected medically or if the obstruction also interferes with the intestinal blood supply. The latter condition causes death of the horse unless surgery is performed quickly. Occasionally, surgery is needed to diagnose the problem in horses with longterm colic that have not responded to routine medical treatment.

Specific Causes of Colic and their Treatment

Colic can be caused by several disorders of the stomach and intestines. The most common ones are discussed here.

Common Causes of Colic (Abdominal Pain) in Horses
The wall of the intestine is stretched excessively by gas, fluid, or partially digested food. There is tension on the tissue that supports the intestines (mesentery) due to the intestine moving out of its normal position. There is inflammation or ulceration in the stomach or intestine. Part of the intestine has reduced blood flow, most often as a result of passing through a hernia or severe twisting of the intestine. Inflammation develops which involves either the entire intestinal wall or the covering of the intestine. The intestine and/or its blood supply have become obstructed by feed, sand (if horses are fed on the ground where soil is sandy), parasites, or other foreign material. Enteroliths (rock-like concretions of material) have developed in the large intestine.

Distention and Rupture of the Stomach

Excessive gas or intestinal obstruction can lead to distention of the stomach. This may be caused by overeating fermentable feeds such as grains, lush grass, or beet pulp. If untreated, this can rapidly progress to a rupture of the stomach. Signs include severe abdominal pain, increased heart rate, and retching. Once the stomach ruptures, the horse may act relieved or depressed. The outlook for survival is excellent if the condition is recognized and treated soon enough, but stomach rupture is fatal.

Obstruction of the Small or Large Intestine

Signs of colic may occur if the small or large intestine is obstructed or inflamed. The outlook for these conditions is guarded, so rapid diagnosis and treatment are critical.

The most common condition that causes obstruction of the small intestine is impaction (blockage of the intestine by food or other materials that have been eaten). It has been linked to eating high-fiber hay and infection by the tapeworm, Anoplocephala perfoliata. Young horses may be affected by impaction of the small intestine with ascarid parasites following deworming. In the large intestine, obstruction has also been linked to coarse feed, insufficient water intake, and diseased teeth. In some areas sand may be the cause of intestinal obstruction and colic. This is especially true if there is not enough pasture and the horse is fed on the ground. The sand may accumulate in the large intestine and eventually cause a blockage.

Signs in horses with impaction of the small intestine include mild to severe abdominal pain, reduced intestinal sounds, stomach reflux, and increased heart rate. Because the horse's condition may remain stable and the pain may be mild at first, many horses with this condition are not immediately referred for surgery. The condition often requires surgery, although it may respond to treatment with fluids, pain-relieving drugs, and mineral oil if identified early. A lack of normal intestinal contractions may occur after surgery. Adhesions within the abdomen (see below) are another potential complication.

In contrast, horses with impaction of the large intestine rarely require surgery. Almost all respond well to administration of laxatives, fluids, and mild analgesics.

Adhesions

Adhesions are fibrous connections between organs within the abdomen. They generally affect the small intestine and usually constrict the inner opening of the intestine. Adhesions develop in response to abdominal injury such as surgery, longterm distention of the intestine, inflammation, or migration of larval parasites. Signs range from mild, recurrent colic to severe, continual pain. Treatment involves surgery to remove the fibrous tissue and the affected portion of the intestine. Medications are also given to try to reduce the formation of new adhesions. However, adhesions often recur and the longterm outlook for horses with extensive adhesions is poor.

Inflammation of the Small Intestine

Inflammation of the first part of the small intestine is a poorly understood condition of horses. It has been reported in the southeastern and northeastern US, as well as in England and continental Europe. There may be fluid or bleeding within the intestinal wall, or tissue death in more severe cases.

Varying degrees of abdominal pain are the most common sign of the disorder. Treatment may be either medical (such as fluids and pain medication) or surgical. About half of the cases are fatal. Laminitis, or inflammation of the hoof (see Bone, Joint, and Muscle Disorders in Horses: Laminitis (Founder)), is a common complication.

Lipomas

Colic caused by lipomas (benign fatty tumors) is sometimes seen in horses more than 10 years old. If the tumor is attached by a stalk to connective tissue in the abdomen, then it may wrap around a part of the intestine, shutting off its blood supply. Signs may include depression and severe abdominal pain, with rapid worsening of condition. Treatment requires removal of the tumor by surgery, along with any damaged sections of the intestine. If the problem is detected early, the outlook is good, but if surgery is not done before signs are advanced, the chances for recovery are fair to poor.

Twisting or Displacement of the Small or Large Intestine

Twisting of the intestines (volvulus) occurs when the intestine rotates around its attachment to the abdominal wall. This reduces the blood supply to the intestine, leading to colic. Horses with this condition are painful and have an increased heart rate. Dehydration is caused by movement of fluid into the stomach and intestine. The horse's condition may worsen rapidly. Displacement, without twisting, of the large intestine may occur and also leads to obstruction.

Treatment requires surgery to correct the positioning of the intestine. Removal of part of the intestine may also be required if it has been compromised by a lack of blood supply for too long. The outlook for recovery is good if the condition is detected and treated soon after it occurs. Adhesions (see Digestive Disorders of Horses: Adhesions) may be a complication, especially if the illness is prolonged.

Inguinal Hernia

Inguinal hernias (commonly referred to as scrotal hernias) occur when the intestine passes from the abdomen into the inguinal canal that connects the testes to the abdomen. They occur in male horses, generally after breeding, trauma, or a hard workout. If the inguinal opening is large enough, part of the intestine may become trapped, causing colic. Hernias appear to be most common in Tennessee Walking Horses, American Saddlebreds, and Standardbreds. If the condition has been present for more than a few hours, the horse's condition worsens rapidly. Surgery is the usual treatment and may require removal of the testicle on the affected side, along with a portion of the intestine if it has become too damaged. The chances for survival appear to be breed-dependent, with Standardbred horses having a good outlook and Tennessee Walking Horses a fair to poor outlook. Presumably, this is because Tennessee Walking Horse stallions with inguinal hernias show few signs of pain, which may delay recognition of the problem and treatment.

Enteroliths (Intestinal Stones)

Enteroliths are hard masses composed of magnesium ammonium phosphate crystals that form around a foreign object (such as a piece of wire, stone, or nail) in the large intestine of horses. Enteroliths may be seen singly or in groups and are commonly found in horses in certain parts of the United States, including California, the southwest, Indiana, and Florida. Most horses with enteroliths are about 10 years old; horses younger than 4 years old are rarely affected. A common factor associated with formation of enteroliths may be the consumption of alfalfa hay, which results in a higher pH and increased concentrations of calcium, magnesium, and sulfur in the large colon.

Many horses with this condition have a history of recurring colic, which may indicate that the enterolith(s) had caused partial or temporary blockage of the large intestine. Depending on the location of the enterolith, the horse may be in severe pain. Heart and respiratory rates increase, and the mucous membranes may be pale or pink. Generally, intestinal distention is evident to the veterinarian on rectal examination, but the mass cannot usually be felt. In areas where the problem is common, x-rays may be used to identify the enteroliths.

Treatment involves surgery to decompress the intestine and remove the stone(s). The outlook is excellent. Veterinary practices in areas where this condition commonly occurs report survival rates of 95%.

Last full review/revision July 2011 by Peter D. Constable, BVSc (Hons), MS, PhD, DACVIM; Gordon J. Baker, BVSc, PhD, MRCVS, DACVS; Joseph A. DiPietro, DVM, MS; Walter Ingwersen, DVM, DVSc, DACVIM; John E. Madigan, DVM, MS; James N. Moore, DVM, PhD; Michael J. Murray, DVM, MS; Sofie Muylle, DVM, PhD; Stanley I. Rubin, DVM, MS, DACVIM; Susan D. Semrad, VMD, PhD, DACVIM; Josie L. Traub-Dargatz, DVM, MS, DACVIM