Colic in Horses

Colic is a broad term used to describe abdominal pain in a horse. It is not a true disease, but a manifestation of an underlying disorder, usually involving the gastrointestinal tract. Colic is an emergency and warrants prompt veterinary care.

Colicky horses will often sweat profusely, appear restless, lie down and roll, and stare at their flanks. Diagnosis is based on a thorough physical examination and results of laboratory tests and procedural studies. These findings will help determine both the severity of the underlying condition and the appropriate treatment. A high percentage of colic cases are uncomplicated gastrointestinal disorders and will respond to early medical intervention. Failure of a horse to respond to initial therapy or finding indications of severe disease on physical examination usually indicates the need for surgery.

Prognosis varies according to the severity of the underlying disorder. Some colics may be prevented with proper nutrition, sound deworming protocols, and routine dental care.

A horse showing symptoms of colic (Source: www.centenarycollege.edu)

Clinical Signs:
Sweating and rolling are classic signs of colic. In milder cases a horse may only be restless or stare at its flank. Physical exam findings often reveal an increased heart rate, prolonged capillary refill time and, in severe cases, shock.

Description:
Colic is a manifestation of abdominal pain and not a true disease. There are numerous causes of abdominal pain. Many of these result in distension of the gut with fluid, gas, or ingested matter. The gastrointestinal distension may even cause decreased blood perfusion to an area within the abdomen. Traction on the root of the mesentery, which attaches the abdominal viscera to the body, produces abdominal pain, as does interruption of blood supply to the bowel.

Colicky horses will often sweat profusely, appear restless, lie down and roll, and stare at their flanks. Colic should be considered an emergency and warrants prompt veterinary care. A thorough physical exam will determine a course of action to treat the condition. While many causes exist that may trigger colic, most are uncomplicated and will respond to early medical intervention. A horse should be kept on its feet and walked while waiting for the veterinarian to arrive. However, the horse’s owner should use caution, as a painful horse may suddenly drop to the ground to roll. Rolling may turn an uncomplicated colic into a twisted or torsed bowel because gas in the intestines tends to rise. A gas cap may cause a loop of bowel to twist upon itself as the horse rolls over.

Failure to respond to initial therapy or poor findings during the physical exam calls for surgical intervention. Colic surgery is a major undertaking and should ideally be performed at a referral hospital. Surgery is a costly procedure and, depending on findings during surgery, may carry a guarded prognosis. Some colics may be prevented with proper nutrition, sound deworming protocols, and periodic dental care.

Diagnosis:
Diagnosis of colic is often established on clinical signs and symptoms alone. Determination of the underlying disorder, its severity, and appropriate treatment requires a thorough physical examination and occasionally procedural tests.

Examination may reveal increases in pulse and respiratory rates in the affected horse. A pulse rate greater than 60 beats per minute indicates severe disease and a guarded prognosis. Absence of peristalsis, or gut sounds, is not favorable for recovery. The mucous membranes may be poorly perfused in horses with diminished cardiovascular function and shock.

A peritoneal tap, or abdominocentesis, enables sampling of abdominal fluid via a needle or catheter inserted through the abdominal wall. This fluid is normally clear. A sample that is off-color, has blood in it, or contains feces indicates the need for surgery. The character of the white blood cells present and the level of protein in the fluid are important markers of the severity of the underlying disorder. Abdominocentesis is indicated for severe, recurrent, or chronic cases of colic.

Examination of aspirated fluid through a nasogastric tube will help to characterize the problem and evaluate the severity of the disorder. The stomach fluid retrieved can be evaluated for pH and color. Normal gastric fluids are acidic in character; an elevated, or alkaline, pH suggests a backflow of intestinal contents that may indicate some obstructive process. Gastric lavage fluids that are brown in color or resemble coffee grounds may contain blood, suggesting the possibility of gastric ulceration. Retained fluids often smell foul.

An elevated packed cell volume, or PCV, of blood indicates dehydration and poor perfusion. When PCV is elevated, the fluid fraction of blood has been reduced, thereby raising the relative level of red blood cells. Colicky patients that have a markedly elevated PCV are seriously ill, and have a poorer prognosis.

Rectal palpation is a useful adjunct to physical examination and laboratory testing. This exam permits the clinician to evaluate by feel the organs in the posterior section of the abdominal cavity. Palpation allows the veterinarian to detect distension or the presence of impaction, displacement or torsion of the intestines. When peritoneal inflammation is present, the surface of the intestines may become roughened, which is detectable by palpation. The presence or absence of feces and the character of the feces will be evident. Equine patients may resist rectal examination or strain excessively. Sedation, local anesthesia or nose twitching may be elected to permit safe examination and avoid the complication of a rectal tear.

Prognosis:
Most colic cases will respond to early medical intervention. These cases carry an excellent prognosis. Horses with significant clinical signs and serious physical exam findings will have a less favorable prognosis. Failure to respond to initial therapy or continuous uncontrollable pain offers a poorer prognosis also. Surgical cases, pending findings during surgery, rarely warrant better than a guarded prognosis. Horses surviving severe colic, with or without surgery, tend to develop laminitis, or founder, which also confers a poor prognosis for recovery.

Transmission or Cause:
The gastrointestinal system is the most common source for colic. Lesions of the stomach, small intestine or large intestine must be considered when assessing a patient with colic. Increased motility and spasm of the bowel are common self-limiting causes of colic; normal intestinal contractions are perturbed by many influences, including inflammation, intestinal parasites and moldy feeds. Gas distension of the large intestine frequently causes clinical signs of colic. This distension may result from abrupt changes in diet, poor quality diet, or heavy intestinal parasite burdens, with or without a recent history of deworming.

Obstructive processes of the large or small bowel can be characterized as simple obstructions or those that are strangulating obstructions, associated with substantial interruptions of blood supply. Impaction of the large intestine with feed or sand is a leading cause of colic in adult horses. Coarse feeds, poor dentition and dehydration may predispose a horse to the simple obstruction caused by feed impaction. Horses residing in sandy regions or animals fed hay grown in those areas may ingest more sand than is desirable, permitting obstruction of the bowel with sand.

There are several less common causes of intestinal obstruction. Enteroliths, or mineral concretions, that form in the bowel may cause obstruction (these are more common in eg. California, US where hay contains a high level of magnesium). Young patients especially may develop obstruction from eating foreign material, such as bedding or rope. Adhesions or tumors may cause obstruction, and rarely, strangulation of the bowel’s blood supply. Similarly, hernias of the abdominal wall, inguinal area or umbilicus can entrap a section of bowel, causing blockage and impaired blood circulation. Internal herniation, intussusception, or telescoping of the intestine, or torsion may occur as primary problems, or in response to any cause of altered motility, such as parasites or diet change.

Newborns may develop colic from fecal impaction or gastric ulcers associated with stress. Foals and yearlings may become impacted with Parascaris equorum, or roundworms, after deworming. In horses of all ages migration of the parasite Strongylus vulgaris and other large strongyles contribute to colic by stimulating inflammation in the gastrointestinal vessels along its migratory path. The blood vessels become occluded or obstructed with blood clots, depriving the gastrointestinal tissues downstream of oxygen. Diminished blood supply may alter motility, contributing to functional obstruction, and may even cause perforation of the bowel as those tissues become devitalized.

Inflammatory conditions of the small or large intestine may also cause substantial pain and functional obstruction. Enteritis and colitis must be discriminated from processes causing blockage or mechanical obstruction.

Reproductive problems such as uterine torsion, retained placenta, or tears of the uterus or cervix are common problems outside the gastrointestinal tract that produce signs of colic. Urinary tract disease, acute liver pain, or abdominal abscesses all are likely to produce signs of colic. Treatment:
Treatment is dictated by the severity of the clinical signs, physical exam findings, and response to pain-relieving medications such as flunixin meglumine or xylazine. Fortunately, most cases will respond to early medical treatment. This early treatment typically consists of controlling pain with injectable medications such as nonsteroidal anti-inflammatory agents, analgesics, and narcotics. Gastric decompression, or removal of stomach contents via a nasogastric tube, is an important early treatment of most colics. Patients with mechanical or functional obstruction will commonly experience progressive discomfort from distension of the stomach. Removal of the stomach contents relieves the pain.

Nasogastric intubation also permits fluid delivery for rehydration of dehydrated horses that have no apparent obstruction. Mineral oil is also commonly administered via a nasogastric tube to coat any irritated bowel segments and to ease the passing of fluid, gas, or ingesta. Many impactions and minor obstructions will be successfully treated with analgesics and mineral oil on an outpatient basis.

The patient’s fluid needs are assessed and addressed with nasogastric or intravenous fluid administration, as needed. Intravenous fluid therapy is indicated for horses with cardiovascular compromise. Most colic patients will receive laxatives or lubricants via a nasogastric tube.

If little or no relief occurs with such early, conservative treatment, or if clinical signs reappear within hours of treatment, more aggressive intervention is warranted, including the possibility of surgery. Anti-inflammatory agents such as flunixin meglumine may be indicated to counter the effects of bacterial toxins and reduce the risk of laminitis, a hoof problem that commonly occurs after endotoxemia, or bacterial toxins in the blood. Antibiotics are administered if bacterial infection is suspected or if surgery is planned.

Patients with a clinical diagnosis of strangulating obstruction must undergo prompt surgical exploration. Such patients are usually referred to a surgical facility, as colic surgery is a major undertaking.

Prevention:
While many cases of colic seem to appear sporadically and without reason, some are preventable. A horse's feed should never be abruptly changed or increased; doing so may lead to gaseous distension or impaction. A proper deworming schedule will prevent heavy parasite burdens, which may lead to colic. Good dental care allows a horse to properly chew its feed and prevents improper digestion.

Mops, ropes and foreign materials should be kept well out of reach of foals and indiscriminate eaters. In sandy areas horses should not be offered hay or feed from the ground. Feeding from elevated feed buckets and hayracks may reduce sand intake. Psyllium can be added to the diet on a regular basis to prevent recurrence of sand impaction; increasing dietary fiber will also reduce the risk of sand colic.