“We’ve all seen them, we’ve all dreaded them,” said Michelle Barton, DVM, PhD, Dipl. ACVIM. “They’re a different worry—will I be able to find a cause and treatment to prevent another recurrence, versus the situation with an acute colic episode, which is typically determining a single treatment plan.”
Nonetheless, veterinarians unravel complicated intermittent colic cases on a regular basis. At the American Association of Equine Practitioners’ Focus on Colic, held July 16-18, 2017, in Lexington, Kentucky, she described the steps veterinarians take in diagnosing chronic colic, along with some of the issues that can cause it. Barton is a professor, director of clinical academic affairs, Fuller E. Callaway Endowed Chair, and Josiah Meigs Distinguished Teaching Professor in the University of Georgia College of Veterinary Medicine’s Department of Large Animal Medicine, in Athens.
Barton said chronic colic typically causes mild to moderate discomfort over days, weeks, or months. It’s often owner-treated with veterinarian assistance and an open diagnosis, meaning nothing has been definitively diagnosed.
Complicating matters is the fact that signs of chronic colic are typically nonspecific, difficult to localize, and quite varied. “Sometimes chronic abdominal pain is manifested only as lethargy, decreased activity, anorexia, or weight loss,” she said.
Chronic colic’s underlying cause is usually intra-abdominal in origin, Barton said, and can include:
- Intestinal wall stretching (luminal distension) or inflammation;
- Impaired ingesta motility (movement through the gut);
- Partial obstruction; and
- Tension on a mesentery (a membrane that supplies blood to the intestines and connects them to the body walls) or an organ capsule.
Barton said veterinarians need to use a strategic approach when evaluating patients with chronic colic, including collecting the horse’s history, performing a thorough physical exam, and running diagnostic testing.
“Historical data that should be obtained include the horse’s signalment (age, breed, sex, etc.), use, work schedule, feed regimen, habitat, herd health, and a previous medical history,” she said. “Additional essential information includes the frequency, duration, and severity of colic episodes and the response to therapy.”
Specifically, she recommended veterinarians use open-ended questions to engage owners and help them describe the issues and treatments they’ve used. For example, how much does the chronic colic impact your horse’s use and quality of life? Can you describe the signs you’ve observed? How much Banamine have you given and how often? How does he respond to medication administration? These types of questions typically help the veterinarian gain more information than those with yes or no answers.
Next, Barton said, the veterinarian should conduct a thorough physical exam, ideally during a colic episode as it can make the affected area easier to identify. However, she conceded, this might be difficult to schedule during a mild active episode, and practitioners ultimately evaluate the horse in a comfortable state. The veterinarian should:
- Check the temperature, pulse, and respiration rate. A fever could be a sign of an inflammatory colic, while irregular heartbeats or murmurs could indicate an extra-abdominal colic cause, she said;
- Perform an oral exam. In addition to capillary refill time and mucous membrane color, Barton encouraged attendees to check horses’ teeth closely, as poor dentition could impact their chewing ability;
- Conduct a rectal exam. “Take your time,” she told attendees, adding that a dose of Buscopan (an anti-spasmodic drug) might be helpful in some horses. She encouraged attendees to evaluate the structures they normally would in an acute colic, but to check others, as well, such as the ovaries, uterus, inguinal rings (where the inguinal canal, an opening in the body wall through which the testes descend, meets the scrotum), nephrosplenic space (a “shelflike” space located on the left side of the body between the kidney and spleen), and the root of the mesentery, among others. Repeated rectal exams are beneficial to compare findings over time, and veterinarians should follow up the exam with transabdominal ultrasonography to check the intestinal thickness, she said.
- Pass a nasogastric tube. “Passage of a nasogastric tube can be both diagnostic and therapeutic in cases of acute small intestinal disease, as there may be a significant volume of gastric reflux,” Barton said. “However, nasogastric intubation may be less valuable in cases of chronic disease as these patients are less likely to have gastric reflux.” Still, it’s best to cover all the bases.
If a physical exam doesn’t produce substantial leads, diagnostic testing is the next step.
“Extensive diagnostic testing can become quite expensive,” Barton said, so she advised veterinarians to take a stepwise approach rather than conducting all the tests at once. She also cautioned that, in most cases, “the longer the horse has been colicking without identification of the cause, the longer it’s likely going to take to figure out the cause through stepwise diagnostic testing.” Prepare the owners in advance that a diagnosis might take a while to reach, and in some cases it is not reached.
Diagnostic testing options can include:
- A complete blood count, including fibrinogen and serum amyloid A (SAA) concentrations, both of which can suggest inflammation;
- A complete biochemical profile, including electrolyte, liver enzymes activity, and bile acids, and bicarbonate concentrations;
- A fecal exam to check for parasites and sand accumulation;
- Abdominocentesis (a belly tap);
- Abdominal radiographs (which can reveal enteroliths or sand in the digestive system);
- Thorough transabdominal ultrasonography; and
- Finally, investigation of “extra-abdominal” causes of colic, such as cardiac or pulmonary diseases.
In some cases, extensive diagnostic testing doesn’t reveal any substantial information. When veterinarians still don’t have answers, Barton offered a few options:
- An exploratory celiotomy (abdominal surgery) allows the veterinarian to get inside the horse and see what’s going on. It’s also expensive and isn’t without its own risks, such as those associated with general anesthesia;
- If the horse’s quality of life isn’t impacted significantly, continue on with the horse’s life, treating any episodes that arise, and/or make management changes to see if they reduce colic episodes. “In some instances, avoidance of all hay and maintenance on pasture or a low-bulk highly digestible diet, such as the senior complete feeds, is palliative,” Barton said; or
- If the horse’s quality of life is significantly diminished due to the repeated colic episodes, significant weight loss, and loss of use, consider euthanasia.
“Using a schematic approach, the cause of chronic colic can often be identified, though diagnosis may require several examinations,” Barton summed up. “However, in some cases, despite repeated evaluation and exhausting the list of diagnostic tests, including elective exploratory celiotomy, the exact etiology of chronic colic cannot be identified.”