A British study suggests that large intestinal impactions in horses are generally easier to resolve than blockages affecting the small intestine, but they pose diagnostic challenges that can lead to delays in treatment.
Large intestine impactions---block-ages of the cecum or large or small colon---are typically less painful and complex than impactions in the small intestine. “There is considerable room for distension in the cecum and large colon, and you often don’t get a large degree of distension with small colon blockages,” says Sarah Freeman, BVetMed, PhD, of the University of Nottingham. “The small intestine, in comparison, is small in diameter and secretes a lot of fluid, which means an obstruction quickly leads to the intestine reaching its maximum size, and because the horse cannot vomit, this backs up and distends the stomach.”
The mild degree of pain seen with many large intestinal impactions can, however, make diagnosis difficult, says Freeman, which sometimes means that vital veterinary care is delayed. “I personally have seen horses that developed ruptures from cecal impactions and died, but their signs of colic before the rupture were very low grade, with normal heart rate, etc. There are signs there, but they are often more subtle.”
Looking to understand more about large intestinal blockages, Freeman supervised graduate student Kyra Jennings in a review of the records of 120 horses with large intestine impactions seen by veterinarians in the field. The data revealed that most cases occurred during winter (42.1 percent) and after a recent change in management (59 percent). While neither of these findings was particularly surprising to researchers, another correlation they discovered was new: Forty-three percent of the study horses were not regularly being ridden at the time they colicked. “We only asked for current management at the time of the colic episode, so these numbers include both the horses who are retired from ridden work due to chronic musculoskeletal problems and those that were on rest due to an acute problem,” says Freeman. “This had not been identified as a risk factor previously, so we definitely need to do some more work to learn more.”
The tests that veterinarians used the most to diagnose large intestine impactions in the study were rectal examinations and nasogastric intubation.
“Rectal exams are undoubtedly the most useful test,” says Freeman. “You can’t differentiate between a cecal impaction, large colon impaction and small colon impaction without a rectal exam and, as their prognosis and the treatments vary, this is really important.”
Treatments of the study horses varied, due in part to the wide array of medication options available to veterinarians, says Freeman: “Most of the different treatments were variations on a theme. Most veterinarians use a painkiller [NSAID0] and oral fluids, but there are several different NSAIDs, and people add different things to their fluids. In addition, many people will give sedatives and/or a gut relaxant when performing tests such as a rectal exam. All of these treatments are probably effective, we just don’t have the evidence yet to say which are the best.”
Overall, the impactions resolved in 53 percent of horses after the initial treatment at the first veterinary visit, which is new and encouraging news, says Freeman: “We did know that this condition has a good prognosis for outcome, but most of the studies previously were from referral hospitals, so they reported on cases that were more difficult. We were lacking in data from the primary care stages before now, but this demonstrates that if you can pick them up early, they can be treated easily---and cheaply! Early diagnosis is the key.”
Reference: “Prospective survey of veterinary practitioners’ primary assessment of equine colic: clinical features, diagnoses and treatment of 120 cases of large colon impaction,” BMC Veterinary Research, July 2014
This article first appeared in EQUUS issue #446, November 2014.