Chronic Colic in Horses: What to Consider

A horse that colics on a relatively regular basis is a frustrating problem for owners and veterinarians alike. Often these bouts of colic pop up unexpectedly with no obvious cause, resulting in lost training time, substantial veterinarian bills, mental anguish for the owner, and frustration for the veterinarian trying to diagnose the problem.

At the American Association of Equine Practitioners Focus on Colic Meeting, held July 24-26 in Indianapolis, Ind., Peter R. Morresey, BVSc, MACVSc, Dipl. ACT, ACVIM, internal medicine specialist at Rood & Riddle Equine Hospital in Lexington, Ky., presented on what veterinarians should look for when examining horses affected by recurrent colic.

"A horse that exhibits chronic, intermittent colic creates a situation fraught with difficulties for both the owner and veterinarian," Morresey began. "The owner may have sought many opinions--both lay and professional--prior to presentation. Considerable financial resources may have already been expended in attempting to secure a diagnosis or, in the absence of a diagnosis, a cure. Seemingly contradictory advice may have been given and followed, resulting in further frustration for the owner."

He reviewed some of the most important things to consider and employ when dealing with a horse affected by chronic colic.

The Horse's History: Morresey explained that a detailed history of colic episodes might be able to help an owner or veterinarian better understand the recurrent episodes. "Careful examination of the history may uncover seemingly unrelated events that may act as 'triggers,' " he said. Possible triggers include feed changes, medicines, exercise changes, transportation, social stress, and heat cycles, he added.

A Physical Examination: A thorough physical exam could uncover management issues or underlying medical conditions that might contribute to a horse's recurrent colic episodes, Morresey noted. For example, he explained that a horse consuming a high-quality diet that still struggles to gain weight or loses weight continually could be struggling with malabsorption (inability of the intestines to absorb nutrients), maldigestion (imperfect or impaired digestion), or catabolism (the process of breaking down body tissue to meet energy)--all three of which can trigger abdominal pain.

Diarrhea: "The presence of diarrhea could indicate an infectious, infiltrative, or inflammatory disease causing the colic signs," Morresey noted. Salmonellosis, excessive use of medications such as non-steroidal anti-inflammatory drugs, and inflammatory bowel disease can all cause abdominal pain and colic signs, he relayed.

A Rectal Examination: A veterinarian might be able to feel several potentially colic-causing ailments via rectal examination, Morresey noted, including the presence of extraneous masses, such as tumors, or changes in the shape, location, and consistency of organs. "Increased intestinal wall thickness might suggest infiltrative disease or, in the case of the ileum (a portion of the small intestine), abnormal muscular enlargement," he added. More so, he noted that roughening of the serosal surfaces (a membrane that lines the abdominal and chest cavities, enclosing their contents) can be telling of septic peritonitis (infection of the abdomen lining). All of these ailments can cause chronic abdominal pain in horses.

Ultrasonography: Morresey explained that an ultrasound examination can provide a veterinarian with a visual of the intestinal tract and organs, including their size, consistency, location, and architecture, which can help determine if a structural problem is causing the horse's chronic colic.

Gastroscopy: "Gastric ulceration, when present, can be a source of discomfort and chronic colic in affected horses," Morresey explained. "Gastric impactions, gastric masses, and the majority of the stomach ... can be evaluated with a three-meter scope." He added that a lack of ulcers seen on the scope doesn't mean they aren't still present in areas the gastroscope can't reach, such as in the colon or the cecum.

Complete Blood Count and Serum Chemistry: A few simple blood tests can potentially be very telling when it comes to chronic colic, Morresey explained. For example, an excess of white blood cells found in the blood could point to an abscess in the abdomen or peritonitis with subsequent scar tissue formation. Additionally, the elevation of specific enzymes in the blood serum can suggest inflammation, dysfunction, or lesions in the liver or kidney.

Fecal Examination: Although parasites might not be the first thing that springs to mind with a chronically colicky horse, Morresey encouraged veterinarians to consider a fecal test to confirm the absence of parasites and fecal eggs. A heavy parasite or egg burden has been known to cause abdominal pain in horses.

Abdominal Fluid Evaluation: "An evaluation of peritoneal fluid should accompany all chronic colic investigations," Morresey said. "The presence of increased protein, increased cellularity, or signs of sepsis suggest an inflammatory or infectious process within the abdominal cavity."

Absorption Studies: "Absorption studies are useful indicators of the integrity of the small intestinal wall, as inflammatory and infiltrative disease has been shown to delay or curtail absorption of sugars." Morresey explained. As mentioned previously, both types of disease can cause chronic abdominal pain.

Rectal Biopsy: A rectal biopsy can point to a few potential causes of colic, including intestinal tumors and some inflammatory or infiltrative diseases, Morresey explained. He cautioned, however, "This is a relatively low-yield diagnostic technique that requires a high degree of skill to perform, and this procedure is not without possible complications such as abscess formation, secondary full-thickness rectal perforation, and septic peritonitis."

Radiography: Radiographs (X rays) can help detect certain causes of chronic colic, such as sand and enteroliths (intestinal stones/concretions). Morresey noted that the drawback to this method is the power of the radiographic equipment as compared to the size of the horse: "The utility of radiology is constrained by the size of the horse, radiographic technique available, and scatter inherent in imaging a large dense area of the horse. Radiographic confirmation of an enterolith with field equipment is difficult, with the presence of enteroliths only suspected due to their vague outline contrasting against colonic gas."

Laparoscopy: Laparoscopy is a surgical technique using a tiny telescope (about 1 cm in diameter and approximately 50 cm in length) to view the abdominal cavity, perform surgery that can identify lesions in either standing or anesthetized horses, and identify abnormal structures. Morresey noted this is the least invasive surgical technique used in colic diagnosis.

Exploratory Celiotomy: When all else fails, an exploratory celiotomy (abdominal surgery) could be the best bet for the horse. "(This) is an invasive but useful technique allowing direct visualization of abdominal viscera (large internal organs) and harvesting of histologic samples from representative areas," Morresey noted. "Surgical correction of lesions and preventative measures for chronic large intestine displacement can be performed."

Treatment as a Diagnosis: "The intractable nature of some chronic colic horses often leads to the use of empirical treatments as a means of establishing a diagnosis," Morresey added. "In one retrospective study, 8% of the cases of chronic colic in horses examined did not have a definite diagnosis."

Healso  noted a few examples of how treatment can serve as a "diagnosis":

Morresey explained that horses evolved as grazers, but with domestication many now eat for only a few hours out of the day. For some horses with chronic colic, allowing the horse free choice access to forage helps resolve the issue. "Buffering of gastric acidity by maintaining hay within the stomach is beneficial in many horses," he noted.

Although it might seem counterintuitive, removing forage from the diet of some horses with chronic colic has been beneficial, Morresey noted. "The rationale ... is the curtailing of colonic fermentation and diminishing of volatile fatty acid (VFA) production within the colon," he explained. "The presence of VFA could be irritating in situations where pre-existing inflammatory changes of the intestinal wall are present."

Finally, treating a horse with corticosteroids in conjunction with larvicidal doses of a fenbendazole dewormer could help resolve chronic colic caused by encysted small strongyles.

Take-Home Message

"Evaluation of the horse that presents for chronic colic is a diagnostic ... challenge to the clinician and a potential source of frustration for the horse owner," Morresey concluded. "A stepwise approach to clinical investigation and the setting of realistic expectations is paramount to reaching the best possible outcome for all involved parties."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.