Equine Postoperative Ileus Insights
When an owner sends a horse under the knife for colic surgery, he or she is first and foremost hoping the horse survives the operation. But just because he makes it through the procedure doesn't mean he's out of the woods: Many horses develop a dangerous complication called postoperative ileus—a lack of gut motility after surgery.
At the 2013 American College of Veterinary Internal Medicine Forum, held June 12-15 in Seattle, Wash., Neil P.H. Hudson, MA, VetMB, PhD, DEIM, DipVetClinStud, MRCVS, a senior lecturer at the University of Edinburgh's Royal (Dick) School of Veterinary Studies, provided insight on what we know, what we're still trying to learn, and what controversies surround postoperative ileus.
Equine Colic and Ileus
"Colic is reported by insurance companies and universities as the single greatest killer of horses," Hudson said.
Study results indicate four to 10 out of every 100 horses will colic each year. And while not all of those colics are surgical cases—meaning veterinarians can successfully manage some cases medically—Hudson noted that "all horses undergoing a laparotomy (i.e., exploratory colic surgery) for an acute abdominal crisis are at risk of developing postoperative ileus."
Researchers still aren't sure exactly what causes postoperative ileus in horses; however, studies have estimated that it occurs in 10-50% of surgical colic cases, Hudson said.
"Postoperative ileus has been described as being responsible for between around 9% and 40% of postoperative deaths," he explained. "Indeed, the fatality rate of postoperative ileus cases sadly can be high—ranges of 13-86% are described (in the literature)."
Researchers have frequently explored parameters for diagnosing postoperative ileus, and many have included the amount of nasogastric reflux (the horse's stomach contents being removed via a nasogastric tube) upon intubation (or the insertion of the tube through the horse's nasal passages and into the stomach) as an important criterion for confirming the condition, he said. A research editorial from the Equine Veterinary Journal recently suggested the following clinical criteria for confirming postoperative ileus:
Hudson cautioned that there is a school of thought that not all apparent cases are actually postoperative ileus. He cited one editorial that suggested some cases initially diagnosed as postoperative ileus might actually be due to mechanical obstructions or other surgical complications.
As previously mentioned, researchers still don't know exactly what causes postoperative ileus. However, scientists are exploring the disorder in a variety of species, trying to better understand its pathophysiology.
Traditionally, Hudson said, researchers believed ileus resulted from inhibited intestinal motor activity. More recent research suggests there is a significant inflammatory component to postoperative ileus, he said, possibly triggered by the surgeon's manual manipulation of the horse's intestines. And researchers have also learned that intestinal macrophages (specialized white blood cells that kill and "clean up" damaged tissue and cells) and mast cells likely play a role in developing and maintaining ileus, he said.
Treating and Managing Postoperative Ileus
Although postoperative ileus treatment generally involves one or more mainstays—including nasogastric decompression, fluid and electrolyte therapy, endotoxemia control, infection control, pain management, prokinetic therapy (administering drugs that make the bowel move contents faster), and inflammation reduction—Hudson said individual clinicians have their own treatment preferences.
Treatment methods most practitioners do agree upon include:
Although veterinarians have made strides in understanding and managing postoperative ileus, Hudson said, "there is still much we have to learn." He said questions still remain about the differences between healthy and diseased tissue behavior, inflammation's role in the disorder, and lidocaine's effects on postoperative ileus.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
Copyright © 2014 The Blood-Horse, Inc. All Rights Reserved.