Understanding Pedunculated Lipomas in Horses

Diseases of the small intestine account for approximately 34% of all colic cases treated at veterinary hospitals. Most (up to 85%) are caused by strangulations, which disrupt blood supply to the small intestine. The most common small intestinal strangulating diseases in adult horses are caused by pedunculated lipomas.
What is a Pedunculated Lipoma?
A pedunculated lipoma starts as a discrete plaque of fat within the mesentery of the small intestine. The mesentery is a broad but thin sheet of tissue that attaches the small intestine to the roof of the abdominal cavity and contains the critical arteries that provide life-sustaining oxygen to support normal intestinal function. As the horse gets older, the lipoma progressively enlarges and thereby stretches its attachment to the mesentery to form a long cordlike structure called a pedicle. The pedicle then wraps around a segment of nearby small intestine and its mesentery like a South American bola to strangulate these tissues until they die.
Lipoma development takes time, which explains why most affected horses are 10 years and older at the time of diagnosis. Old age is therefore an immediately recognizable diagnostic clue to strangulating lipoma. Unfortunately, affected horses are also victims of a diagnostic distraction: their own stoic attitude that blunts development of the more severe signs of colic.
One of the most dramatic observations in these cases is how the intestinal injury severity identified at surgery can exceed the vet’s expectations based on the preoperative condition and attitude of the horse. The only colic-related clues an owner picks up on might be a depressed attitude and abrasions about the head. Don’t ignore these abrasions, because they indicate the horse was rolling with sufficient intensity to rub his head repeatedly against the ground. If the horse is no longer rolling or showing other signs of pain, he has reached a state of shock and exhaustion.
Timely Intervention and Treatment
The lack of clear signs of colic means too many of these horses are treated at home, using a “watch-and-wait approach” and even given intravenous fluids to combat dehydration. All this does is delay the inevitable referral to a hospital for possible surgery. The delay can be not only fatal but also very expensive because it creates the need for a complicated surgery and intensive aftercare, both of which would be unnecessary if the horse were to go to surgery promptly to avoid resection of dead intestine. In fact, results from a recent study showed superior short- and long-term survival (up to 20 years) in horses that did not need removal of strangulated small intestine compared with those that had more advanced changes and needed removal by resection and anastomosis (joining the resected ends).
Unfortunately, the watch-and-wait approach is very attractive when horses have “manageable” signs of colic and their owners have financial constraints or doubt the benefits of surgery. Also, owners must consider many factors when selecting the surgical option, such as how many more years the horse will live—especially if he is nearing the end of a reasonable life span—and if he can continue to perform after surgery. Your horse might have other health problems unrelated to colic, making it time to say goodbye.
Delaying this decision can carry a high price and should not be justified by myths such as “the horse will never be the same” or “colic surgery does not work.” Some owners allow themselves to be lulled into the belief that if the pain is manageable, they can “kick the can down the road,” treat the horse at home, and pursue surgery if absolutely necessary. Surgery is by that point too late and far more expensive than if it had been done earlier.
Lipoma is not the only cause of colic in old horses, but it is the most common, which means if you own an older horse, consider how far you are prepared to go financially to save his life. Make this decision when the horse is healthy and free of life-threatening disease. Above all, be guided by the maxim that “an old horse with colic has a strangulating lipoma until proven otherwise.”

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