The Breeders’ Cup Forum: Understanding Colic
From time to time, horses on and off the track make headlines if they undergo surgery for colic, which is a fairly common but complex illness in horses. Most recently, Grade 1 winner Dullahan showed symptoms of colic and died as a result of a ruptured colon, which prompted us to learn more about the illness.
Dr. Louise Southwood is an Associate Professor of Large Animal Emergency Medicine and Critical Care at Penn Vet's New Bolton Center. She is board certified in Veterinary Surgery as well as Emergency and Critical Care, and helped us learn more about colic.
What is colic?
Colic refers to the signs a horse shows when they're experiencing abdominal pain. The signs that they show include pawing at the ground, looking back at their flank, kicking at their belly; if they're more painful, they'll go down on the ground and roll.
Why would a horse be in abdominal pain?
Most of the time (about 90 percent), the signs of colic are caused by a gastrointestinal problem. Examples of a non-gastrointestinal cause of colic include uterine problems in the pregnant mare and urethral obstruction in geldings. The most common causes of colic are gas colic (~70-75% of horses with colic) and impaction which refers to a buildup of feed in the intestine which then causes an obstruction (~10-15% of horses with colic). Other causes include a large colon displacement (when the intestine is in the wrong position), a large colon volvulus or torsion (twisting of the gut which cuts off the blood supply), and small intestinal strangulations (which also cut of the blood supply to a segment the small bowel). There is a long list of causes of colic; however, it is important to recognize that the majority of horses are managed medically and make a full recovery.
Occasionally we hear about a horse like Dullahan, who died of a ruptured colon. How common are ruptures, and how do they happen?
It's uncommon. I can't speak to a specific case, but the ones I have seen might be the result of a large impaction in the colon and then a twist on top of that. Sand in the colon will sometimes predispose them to rupture because of the damage it causes to the intestinal lining (mucosa). Sometimes it may happen as a result of an underlying intestinal problem such as ulceration or an inflammatory disease, but that's less common.
We always worry about horses rupturing their stomach—if there's an upper GI obstruction (with the small, rather than the large intestine), the horse can't vomit so they can't relieve the pressure in their stomach and this can lead to rupture, which is why a veterinarian in the field will pass a stomach tube to relieve that pressure.
What are the risk factors for colic?
I think in a lot of cases, we don't know what caused it. Some of the things that are often associated with colic (but not necessarily known to be causes) are any change in diet, housing, or exercise regimen. The role of intestinal parasites in colic has long been debated; however, it is likely that they do play a role. Previously, regular, frequent deworming has been recommended. However, with the emergence of parasite resistance to commonly-used dewormers and a decrease in their efficacy, a more targeted approach under the guidance of a veterinarian is currently recommended. Appropriate deworming has been associated with a decreased risk of colic in some studies. In other studies, horses that don't have routine dental care seem to be more likely to experience colic. Inadequate water intake and quality of hay may also be a link.
Horses that spend more time at pasture walking around and grazing tend to have a lower risk for colic. This is tricky for racehorses and other performance horses, because they can't consume enough calories on pasture alone to support their athletic performance.
Can weather changes prompt colic?
There's one study I believe that looked at this, and I think they may have found an association between colic and weather change, but it was based on owner recall, which isn't the most reliable information source. I don't know the answer to this question. There is likely recall bias when we consider the association between colic and weather i.e. if there is a dramatic weather change and we see a lot of horses with colic then we take note…but we forget that we saw just as many horses with colic the week before when the weather was fine. I do know that spring and fall (which is when we see the most weather changes) we tend to see more horses with colic, but then, the way we exercise and feed horses and the types of pasture they have available to them changes at those times, too.
Is colic a sign that the horse isn't being managed or monitored properly?
No. I've had horses that are managed incredibly well and have still colicked.
So sometimes, it just remains a mystery?
Yes. There's still so much we don't know about why it happens.
How serious is colic?
The vast majority of the time (about 70 to 75 percent), horses that are showing signs of colic get better with either no treatment, or with one dose of an analgesic drug. In most cases it's probably caused by a gas build-up. Only about five percent of horses have a severe enough colic that they need to go to surgery. It's important to know though that in those five percent or so, the sooner we do surgery, the better. Typically if a horse doesn't respond to an initial treatment by a veterinarian in the field, it needs to be evaluated in the hospital.
Colic surgery sounds pretty serious.
Even as recently as 20 years ago, colic surgery was considered by many as a death sentence. In the 80's long-term survival rate for horses with strangulating obstructions of the small intestine (a twist of the bowel that resulted in a loss of blood flow to the intestine) was about 25 percent. Today the long-term prognosis is more like 80 percent or higher. I think the biggest reason for this improvement is that we are seeing horses with serious colic early. Early surgrical treatment for the small percentage of horses with colic that need it is absolutely critical.
We completed a study recently looking at the performance of racehorses that had colic surgery compared to their cohorts, and the vast majority (~ 70 percent return to racing) perform as well as the horses who didn't have colic surgery. Complications after colic surgery can occur, as with any surgery, but the occurrence and severity of these complications has decreased substantially in recent years.
Generally, the prognosis is good.