Recurrent Colic Q&A

My horse has recurrent colic that's usually fairly mild, but she had surgery last August due to a twist. She has done well until recently when she had another mild attack. A biopsy taken during surgery showed inflammation. No other problems were discovered.

Since the last attack, my veterinarian wants to treat her permanently with a low dose every other day of prednisolone. I would like to know what success this kind of treatment has had on recurring colic and what side effects could be expected from the prednisolone? I know from personal experience that prednisolone should not be treated lightly, and I would like to know more about the subject to make a more informed decision about possible courses of action.

Another veterinarian has suggested trying the five-day deworming program with fenbendazole for encysted larvae first. My mare is presently on a daily dewormer, and has been having these mostly mild colic episodes since she was about eight years old (she will be 15 this year). They mostly occur while she is on pasture, so at this time she is back on hay only.

Our veterinarian seems to not have much information on the long-term effects of prednisolone therapy and what the chances are that it would really help her problem. Also, we were trying to decide if it was worth taking biopsies before and after if we do decide to go with the prednisolone treatment. I have not been able to find any information so far about preventing colic with prednisolone; I appreciate any help you can give on the subject!                 V. Kent

I know the frustration you feel over your mare's colic episodes. Chronic or recurrent colic is one of the biggest diagnostic challenges we veterinarians have to deal with, and it's often just as difficult a problem to "cure."

Let's start with the biopsy. Inflammation from an intestinal biopsy can be acute or chronic. Acute means recently active, while chronic means ongoing or old. I suspect from your mare's history that the biopsy showed chronic inflammation. There are many reasons why we'd see chronic inflammation of the intestine lining. These can include past parasite damage, tumor, and granulomatous enteritis or other infiltrative bowel diseases.

Parasite damage can be old or ongoing. Even if we aren't sure that the inflammation is caused by parasites, one five-day treatment (as you mentioned) of fenbendazole can be very effective, and it is usually very safe, so there's no harm in trying it. Daily dewormer is something I try with a lot of problem cases, but I don't put all my faith in it--I usually do the five-day program and always do ivermectin at least every six months.

I doubt that a tumor is the cause of the inflammation in your mare, because the colic episodes have been going on for too long. The granulomatous, or infiltrative diseases, can behave like tumors in how difficult they are to treat. These conditions arise when, for some reason we really don't understand, the intestinal wall gets infiltrated by various types of inflammatory cells. This renders the horse's intestine wall unable to absorb nutrients properly, so usually the clinical signs include weight loss and soft manure. But I wouldn't be surprised at colic being the main sign either. This condition is very difficult to treat and usually we use some type of corticosteroid like prednisolone, which probably only buys the horse some quality time (same situation with tumors). With parasite problems, if aggressive deworming therapy doesn't help, we sometimes use steroids.

Now for your question about repeating the biopsy: If read your question correctly, I presume that the biopsy was taken from part of the intestine that was exposed when the horse was under general anesthesia (GA), and if that is the case then I doubt repeating GA is worth the risk for more biopsies, presuming the first one was "good." I understand your concerns for long-term use of prednisolone, a steroid, in your horse. From the information I have, there is no way I can comment on its appropriateness in your situation. But I have a very good feel for the position you and your veterinarian are in. Certainly there can be adverse effects from long-term use of steroids. However, I think that those risks are often rather small, especially with predisone and especially if the dose is reduced as much as possible for the long-term use. The biggest question I think is, what is your horse's quality of life right now and what is her long-term prognosis?

If her prognosis is not good without any treatment, then I might feel that it's well worth the risk of using some long-term medication. I have placed a number of old horses on daily phenylbutazone (Bute) for chronic arthritis and daily steroids for chronic heaves. We watched them carefully for adverse effects of the medications but realized we were improving the quality of life, even if just for a little while. This is where you are in the decision-making process, because I would venture to guess from what you've said that whatever in the world your mare has, we're probably going to have a hard time finding "a cure" and maybe need to accept that we are limited to treating the clinical signs and improving quality of life.

Sorry if I don't have any definitive answers for you. You are not alone though--these are always difficult cases. Good luck with your mare.

About the Author

Nancy Diehl, VMD, MS

Prior to attending veterinary school, Dr. Nancy Diehl completed a master’s degree in animal science while studying stallion sexual behavior. Later, she completed a residency in large animal internal medicine at the University of Pennsylvania’s New Bolton Center and worked in equine practices in Missouri and Pennsylvania. Diehl also spent six years on faculty at Penn State, where she taught equine science and behavior courses and advised graduate students completing equine behavior research. Additionally, Diehl has co-authored scientific papers on stallion behavior, early intensive handling of foals, and feral horse contraception. Currently she is a practicing veterinarian in central Pennsylvania.

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