Colic is a general term used to describe any painful condition involving the horse’s abdomen. Colic can result from problems affecting the gastrointestinal tract and abdominal organs (i.e. the liver, spleen, or kidneys). Colic involving the gastrointestinal tract may be separated into four main segments spanning from the head to the tail:

• Stomach.

• Small intestine.

• Large intestine.

• Small colon/rectum.

The focus of this article is on common causes, treatments, and prevention of colic originating in the gastrointestinal tract.

Signs
Colic can take on a variety of different appearances in a horse. Mild colic signs include the horse swishing its tail, pawing, laying down, and looking at its sides. Moderate colic pain is manifested as intermittent rolling, sweating, and striking at the abdomen. The violent pain of severe colic is evidenced by uncontrollable rolling, thrashing, and sweating. The degree of pain and the response of the animal to analgesics (pain relievers) are two of the criteria used to determine the severity of colic. Problems affecting the small intestine are typically evident by a shorter history of colic pain that progresses rapidly; whereas, problems involving the large colon (except a large colon twist) or small colon/rectum are manifested by a prolonged history of colic with a slower progression.

Clinical Assessment of Colic
Colic may be treated medically or surgically. The treatment is dependent on a number of clinical and laboratory findings. Clinical findings which help determine the severity of a horse’s colic include:

• Degree of pain.

• Temperature.

• Heart rate.

• Mucous membrane color.

• Bowel sounds.

Important diagnostics include:

• Rectal examination.

• Nasogastric intubation for reflux (spontaneous fluid collected from the stomach tube).

• Response to treatment with analgesics (pain relievers).

Additional diagnostic procedures include:

• Abdominocentesis (collection of abdominal fluid surrounding the intestines).

• Ultrasound examination.

• Gastroscopic examination.

• X-rays.

Laboratory blood tests may be needed in moderate to severe colic to assess the horse’s hydration, organ function, immune system, and electrolytes. Similarly, an abdominocentesis may be needed to evaluate the intestinal integrity and any compromise to the bowel’s blood supply.

If intestinal compromise exists, protein and white blood cells will leak into the abdominal fluid. If severe bowel damage has occurred, white blood cells will be damaged and bacteria and feed material may be found in the abdomen. All of the previously mentioned factors will be taken into account in moderate to severe colic that has not responded to basic field interventions with analgesics and fluids/laxatives through a stomach tube.

Ultrasound is used to visualize small intestinal movement, size, and position of abdominal contents or organs. It may also help image enteroliths (colon stones). The gastroscope provides pictures of the esophagus and stomach that are useful for diagnoses of ulcers, cancers, or obstructions. X-rays can be especially helpful for identifying enteroliths or sand impactions.

 The decision to treat a case of moderate to severe colic medically with aggressive intravenous fluids, feed withdrawal, laxatives, and analgesics versus surgery will depend on a balance of the factors outlined previously. Some factors that might send a horse to surgery for an abdominal exploratory to correct colic are uncontrollable pain, no improvement with intravenous fluids, extreme distension of the bowel on rectal examination, persistently elevated heart rate, abnormal abdominal fluid, or continuous gastric reflux.

Stomach
The most common causes of colic involving the stomach are associated with gastric ulcers and gastric distension caused by dietary indiscretion (i.e. grain or grass overload). Cancer and polyps are less common causes of colic in the stomach. Gastric dilation can result in severe colic pain. It may occur after rapid and excessive feed or grass consumption in horses of all ages. Gastric ulcers, however, are more common in foals and young horses than in older horses. Horses with gastric ulcer may have a history of grinding their teeth, excessive salivation, intermittent colic (often after eating), and poor appetite.

Treatment
Stomach ulcers and gastric dilation are treated with a balance between management and medications. Treatment of stomach cancers requires surgical intervention and carries a poor prognosis. Surgical correction of polyps carries a good prognosis.

The management changes for gastric ulcers involve removing any concentrates from the horse’s diet to avoid excessive stomach acid production. The horse should be allowed 24 hour access to good-quality hay or pasture. Since horses continuously secrete stomach acid, continuous feeding of forage results in less stomach acid build-up. Any environmental stressors should be removed, such as intense training, long transport, housing with dominant horses, etc. Medications, such as Cimetidine® or Ranitidine®, that help heal the stomach by reducing acid may be used as well as drugs that coat the stomach and improve blood flow, such as Sucralfate®. Any non-steroidal anti-inflammatory drugs (phenylbutazone, Ketofen®, and Banamine®) must be avoided, because they contribute to gastric ulceration.

Dietary indiscretion can result in colic of the stomach, small intestine, or large intestine. The treatment is similar regard-less of where the colic originates. Grain overload colic results from fermentation of excessive carbohydrates. In this case, all grain should be removed for a minimum of 24 hours or longer if complications develop. Colicky horses should be given mineral oil via stomach tube to help clear the grain and to reduce absorption of toxic by-products of grain fermentation. Anti-inflammatory drugs, such as Banamine, might be required to deal with the side effects of toxin absorption. These horses are at risk for colic, diarrhea, and laminitis (founder) following excess grain ingestion and should be carefully monitored.

Prevention
Gastric ulcers are difficult to prevent, as all factors that contribute to the development of ulcers are not known. It is preferable to allow stalled horses access to free-choice forages. If this is not possible, feed horses at least three times daily. Avoid feeding excessive levels of grain/concentrates. When non-steroidal anti-inflammatory drugs are needed to treat lameness or other problems, avoid high doses for an extended period of time, especially in foals and young horses.

To prevent accidental access to excessive quantities of grains, concentrates, or hay, ensure the feed storage area is securely enclosed. For additional nutritional management guidelines, refer to the sidebar “Nutritional Management: Preventing Equine Colic.”

Small Intestine
The small intestine can be affected by numerous conditions that can cause colic. It is easiest to divide these conditions into three major groups:

 Obstruction. Causes:

• Ascarid impaction (round worms found in young horses).

• Feed impaction.

• Foreign body.

• Stricture.

• Abdominal abscess.

• Cancer.

 Strangulation (compromised intestinal blood supply). Causes:

• Twisted intestine.

• Entrapment of intestines in abdominal structures.

• Diaphragmatic hernia (traumatic displacement of intestines into the chest).

• Inguinal hernia (stallions or recently castrated geldings with intestines in scrotum).

• Umbilical hernia (foals and young horses with intestines in navel).

• Lipoma (fatty tumor of older horses).

 Ileus (motionless intestine): Common cause is an infection of the small intestine.

Treatment
Treatment of the vast majority of small intestinal obstructions or strangulations requires immediate surgical intervention. These colics usually progress and the horse’s condition deteriorates rapidly. If surgical intervention is an option, maintaining a nasogastric tube is essential to the horse’s survival. If the stomach is not decompressed, it will rupture from small intestinal fluid back-up. Once the stomach ruptures, euthanasia is the only humane option.

Some feed impactions of the small intestine can be treated medically with laxatives, intravenous fluids, and analgesics. The prognosis for horses requiring surgical intervention depends on the severity of the bowel compromise and the degree of systemic deterioration. Minor problems not associated with cancer carry a good prognosis; whereas, major problems or cancer carry a guarded to grave prognosis.

Small intestinal infections or enteritis require aggressive medical treatment. Some bacterial types isolated from adult horses with enteritis are Salmonella sp. and Clostridium sp. Horses with enteritis require an indwelling stomach tube to allow for regular stomach decompression. They must be maintained on large volumes of intravenous fluids, since they cannot tolerate oral fluids and are loosing large volumes of fluids as stomach reflux and diarrhea. Horses may be given broad spectrum intravenous antibiotics as well as anti-inflammatory drugs because they may suffer from immune compromise and toxin absorption from the inflamed bowel.

Some compromised horses will require plasma transfusions to combat protein losses and toxin absorption from the damaged intestines. The prognosis for these horses is variable and is largely dependent on the duration of reflux and systemic compromise. These horses are prone to laminitis; therefore, foot support should be provided and comfort monitored closely.

Prevention
Unfortunately, the majority of small intestinal crises cannot be prevented. The only cause that can be prevented is ascarid impaction. Ascarid impactions occur in foals and young horses due to an excessive round worm parasite burden caused by a poor deworming schedule and/or a heavy environmental parasite load. It is recommended to start deworming foals at six to eight weeks of age and continue deworming every six weeks until six months of age. At this time, foals may be included in the farm’s deworming schedule, which typically involves deworming every eight to twelve weeks.

All pregnant mares should be dewormed one month prior to foaling to decrease the amount of parasites to which the foal is exposed. All incoming horses should be dewormed upon arrival. In addition, harrowing fields, rotating pastures, and picking up manure in the fields/paddocks on a regular basis will decrease the exposure of foals and adults to intestinal parasites.

Large Intestine
Disorders of the large intestine may be divided into four categories:

 Obstruction. Causes:

• Feed impaction.

• Sand impaction.

• Displacement (colon in wrong position).

• Enteroliths (mineralized stones).

• Cancer.

• Foreign body.

 Strangulation—Causes include intestinal torsion/volvulus (twisted colon) and diaphragmatic hernia.

 
Motility Alterations—Causes include excessive contractions of the intestines or excessive gas.

 Inflammation—Causes include:

• Infection: Common infectious causes of colitis involve bacteria (Salmonella or Clostridium), Erlichia risticii (potomac horse fever), and parasites (large strongyles and small encysted strongyles).

• Toxins: Toxic causes of colitis include excessive non-steroidal anti-inflammatory drugs, grain overload, blister beetle, and heavy metals.

Treatment
Most causes of colitis, as well as many feed impactions and some sand impactions, may be treated medically. The treatment of colitis is very similar to that outlined for enteritis under the small intestine section. Inflammation of the large and small intestines can have similar complications. However, chronic protein loss into the bowel and ill-thrift can develop with significant colon damage from parasites or toxins.

The treatment for impactions will vary from analgesics and fluids/laxatives in the field to intravenous fluids, feed withdrawal, laxatives, and analgesics in the hospital. Sand impactions require the addition of psyllium (a fiber source and laxative) to the treatment regime to help move sand out of the gastrointestinal tract. Some sand and feed impactions are so severe that the bowel must be surgically emptied.

All other large colon crises, except motility changes and nephrosplenic entrapment, require surgical intervention to correct the problem. Large colon torsion/volvulus (twist), diaphragmatic hernia, and cancers carry a guarded prognosis for survival. Nephrosplenic entrapment may, on occasion, be treated by anesthetizing the horse and rolling it in a specific manner.

Prevention
Feed and sand impactions (dietary indiscretion) are the easiest to prevent. To avoid feed impactions, assure the horse always has access to plenty of fresh water. Most horses drink 5-10 gallons of water daily. Make sure transitions to new feeds are made gradually, introducing 1/4 of the new hay or concentrate ration desired with 3/4 of the old ration at first and increase by 1/4 increments every 2-3 days until full transition to the new ration, which should take about 7-10 days. To help prevent impaction colic, a horse’s teeth should be checked annually and floated, if necessary, to ensure it can properly chew feedstuffs.

Sand impactions are best prevented by management. Do not place feedstuffs on the ground, use troughs or other feed containers. Avoid turn-out to sandy paddocks if the horse tends to eat sand. Provide the horse with a balanced diet and access to free-choice mineral to avoid inappropriate appetite for dirt and sand. If horses are kept on sandy pastures, prevention can be accomplished by feeding psyllium (one cup once daily for one week each month for a 1,000 lb horse).

The best prevention for toxic causes of colitis is to prevent exposure. Inspect alfalfa hay carefully for longitudinally black and yellow stripped blister beetles. Avoid heavy metal contaminated water and feed sources. Be careful to limit the use of unnecessary non-steroidal anti-inflammatory drugs. For additional nutritional management guidelines, refer to the sidebar “Nutritional Management: Preventing Equine Colic.” For guidelines regarding parasite control, refer to the previous section on preventing colic in the small intestine.

Small Colon/Rectum
Colic related to the terminal portion of the intestinal tract is usually caused by obstruction, strangulation, or injury. Obstructive lesions range from feed impactions, meconium impaction (newborn foal’s first manure), trichobezoars (hair balls), enteroliths (mineralized stones), polyps, cancer, nerve dysfunction, and prolapse. Strangulation of the terminal colon involves severe prolapses (rectum protruding from anus) and rarely lipomas (fatty tumors of older horses). Common injuries to the rectum include:

• A rectal tear caused by a rectal examination.

• A rectal tear in a mare due to misbreeding by a stallion.

• A rectovaginal tear resulting from a foaling accident.

Treatment
Obstructions of the terminal colon can be challenging to resolve with laxatives, enemas, intravenous fluids, and analgesics. However, most meconium impactions are easily resolved with warm soapy water enemas. Nerve dysfunction leading to recurrent impactions may be a chronic management issue that requires daily manual evacuation of the rectum along with enemas and a laxative diet. Strangulating lesions, foreign bodies, trichobezoars, enteroliths, cancers, and severe impactions require surgical correction.

Prevention
Prevention of impactions is outlined under the large intestine section. Some small colon impactions may be associated with a low grade colitis/proctatitis with Salmonella. If newborn foals are straining to defecate or have not passed their meconium, they may require an enema. The risk of small colon dysfunction due to equine herpes virus or equine rhinopneumonitis infection is difficult to prevent with regular herd vaccination. Nonetheless, all horses should be regularly vaccinated with equine herpes vaccine every two to three months starting at 12 weeks of age. When vaccinating pregnant mares, use killed virus vaccines to avoid abortion.

Conclusion
The equine intestinal tract is prone to a variety of different disorders that can result in colic. Some causes of colic can be avoided with sound management practices, such as:

• Provide an environment as natural as possible (pasture).

• Provide a balanced diet.

• Provide unrestricted access to cool, clean water.

• Maintain horse in optimum body condition.

• Regular deworming.

• Annual floating of the teeth.

• Gradual feed/ration transitions.

• Do not place feedstuffs directly on the ground.

• Use only the prescribed amount of a drug to control pain and swelling.

Unfortunately, there are many other causes of colic that cannot be prevented, but can be successfully treated. The key to treating colics is early detection and rapid intervention by a veterinarian.

Trademark designations:
Cimetidine is a registered trademark of Standard Products, Lederle, Pearl River, NY. Ranitidine (Zantac 300®) is a registered trademark of Glaxo Pharmaceuticals, Research Triangle Park, NC. Sucralfate is a registered trademark of Biocraft, Elmwood Park, NJ. Ketofen (Ketoprofen) is a registered trade-mark of Fort Dodge, Fort Dodge, IA. Banamine (flunixin meglumine) is a registered trademark of Schering-Plough Animal Health, Kenilworth, NJ.

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