By Nora Grenager, VMD
Published in Bay Area Equestrian Network December 2007
Introduction
Colic. To some, it is a term that is unfortunately all together too familiar; to others, it is a word that causes fear with little understanding of what it is. While it is a situation we would all like to avoid, it is important to have a knowledge of what colic is, some of its causes, potential ways to minimize its occurrence, and how your veterinarian may deal with it.
Causes
Approximately 4 to 6% of horses in the United States will suffer from colic each year. This is a difficult statistic to interpret, because many mild episodes of colic likely go unnoticed. Of that percentage, only a very small amount require surgery. “Colic” is just a term that encompasses any abdominal pain – it is a clinical sign, not a specific disease. Horses have very extensive gastrointestinal tracts, and there are numerous possible causes of colic. There are many ways to categorize the causes of colic. One is to divide the causes into those that can be resolved by medical treatment alone versus those that require surgical intervention. Most horses with colic respond to medical treatment, and only a very small percentage have a cause that will not get better without surgery. A second useful way to categorize the causes of colic is based on whether the small intestine or large intestine is the source of the pain. This is beneficial because sometimes the veterinarian can differentiate between these two locations during the exam, and treatment and prognosis tend to depend on which part of the intestine is involved. A third way to categorize colic is based on whether it is a one-time occurrence or whether the horse has had multiple episodes of colic over time (i.e. it is a chronic situation). To list the specific causes of colic is beyond the scope of this article.
Clinical Signs
The clinical signs (a.k.a. “symptoms”) of colic vary from horse to horse, and can range from very mild to very severe. Some mild signs include a horse not being as interested in feed as normal, having decreased number of manure piles, or quietly laying down more than normal (or at an abnormal time, such as feeding time). A colicky horse may be looking at its side and showing evidence of having rolled (is covered in shavings). Moderate signs may include pawing, lifting the upper lip, looking at the flank, kicking at the belly, or stretching out. Severe signs can include repeated rolling or thrashing and sweating. Every horse is different, so knowing what behavior is normal for your horse is important so you can tell when something is amiss. Also, some horses are extremely stoic whereas others are very are more sensitive and quick to show signs of discomfort, which can make interpretation of signs tricky. It is therefore important to remember that the severity of colic signs you see may not always correlate very well with the severity of the underlying cause.
What to Do While Waiting for the Vet
If you are concerned that your horse is showing colic signs, you need to call your veterinarian immediately. If you are comfortable doing it, and the horse’s signs aren’t so severe as to prevent it, taking a heart rate and rectal temperature and evaluating the gums prior to calling your veterinarian may be helpful so you have more information for the phone call (ask your vet — (s)he may have a preference as to whether you do this or not). Next time your vet is out, have him or her show you how to take your horse’s heart rate and rectal temperature, and evaluate the gums. Normally a horse’s heart rate should be between 30 and 40 beats per minute. A normal rectal temperature is between 99°F and 101.5°F. The gums provide insight about how well hydrated the horse is and should be pink and moist. When you call your vet, (s)he may ask about the duration of colic signs, if the horse has colicked in the past, how uncomfortable the horse is, and if the horse is passing any manure.
There are different opinions on whether to walk a horse while waiting for the vet to arrive. If the horse is rolling and extremely uncomfortable, walking may help keep it quiet. Walking may help alleviate some gas, which can be a cause of colic. A horse should not be forced to walk, and laying quietly is generally okay.
Most veterinarians prefer that you do not administer any medications to a colicky horse unless they advise you to do so when you call. This is because a dose of Banamine or dipyrone (or whichever painkillers you have) can make evaluating the horse difficult for the vet. The horse may temporarily look better while the vet is there, only to become colicky again later; thus postponing necessary treatment by the vet and potentially making the situation worse. Situations in which the vet may advise you to administer medication are if it is going to be a long time prior to the vet seeing the horse, or if the horse is dangerously uncomfortable.
What to Expect from the Vet
Once the vet arrives, (s)he will likely examine the horse (take heart rate and respiratory rate, take the rectal temperature, evaluate the gums, and listen to the gastrointestinal sounds). If your horse is extremely uncomfortable, this exam may be brief and the vet will administer intravenous sedation/pain relief quickly. (S)he will then likely ask you a few more questions about duration of colic signs, any previous colic episodes, any recent changes in feed or management, or other medications recently given.
The most common initial workup for a colicking horse is for the vet to perform includes abdominal palpation per rectum and passing a nasogastric tube. The horse will likely be sedated for these procedures.
Abdominal palpation per rectum (a.k.a. “the rectal exam”) gives the vet information as to whether there is manure passing through, the appearance of that manure, and allows palpation of about the back third of the abdomen. Obviously horses are very large animals, and it is not possible to feel everything in the abdomen. However intestinal distention or impaction and some intestinal displacements can be palpated, so this is very informative. Sometimes this is not done if either the colic is very mild, or if the veterinarian does not feel safe doing the exam. There is obviously a degree of risk in standing directly behind a horse and performing a rectal exam, which is why at veterinary clinics this procedure is preferentially performed in the stocks.
Passage of a nasogastric tube has two distinct purposes. First, horses cannot vomit, so if the stomach is very full due to an obstruction of the intestine, it can get very distended. This is not only extremely painful, but it is fatal if the stomach ruptures. The quantity and quality of the reflux is useful information; it can help differentiate between small intestinal and large intestinal causes of colic. A normal horse may have 1 to 2 liters of nasogastric reflux, versus a horse with a small intestinal obstruction can have upwards of 20 liters of reflux. Second, a nasogastric tube is an excellent way to administer fluids and electrolytes to help rehydrate the horse. Horses with colic generally have some degree of dehydration. Additionally, your vet may add either mineral oil or detergent or epsom salts to the fluid to help soften the bowel contents.
If your horse becomes colicky again once the sedation and pain medications have worn off, or the initial colic is severe, your vet may recommend intravenous fluids and additional treatment. Depending on the horse’s condition, the vet’s preference, and the available facilities, this may be done at the farm or (s)he may advise taking your horse to a referral veterinary clinic.
At the Clinic
If your horse is referred to a veterinary clinic (or some vets may have resources to do some of this in the field), diagnostics such as abdominal ultrasound, abdominal radiographs, abdominocentesis (a.k.a., “the belly tap”), or gastroscopy may be performed. These are four different ways to evaluate different parts of the gastrointestinal tract and gather more information.
While every attempt is made to determine the cause of colic, the horse’s level of pain is the single most important deciding factor as to whether surgery is necessary. If a horse is repeatedly uncomfortable in spite of adequate pain medication and hydration, the cause of the colic is very likely something that is not going to resolve without surgery. If surgery is indicated, the vet will discuss with you his or her thoughts on the possible causes, tell you about the surgical procedure, and talk about the costs.
Possible Preventative Measures
Colic can be frustrating because, in a lot of situations, a reason for the colic episode is not determined. Possible causes that often are discussed include weather change (so the horse is not drinking enough water), change in feed, poor dentition, and parasites.
While it is probably not possible to prevent all episodes of colic, there are certainly some things owners can do to minimize the risk. Regular feeding schedules are very important for gastrointestinal health. If any feeding changes are to be made, they should be done slowly over a week or two. Horses were also designed to graze and therefore they are suited to more frequent smaller feedings when possible. It is important to make sure there is always access to fresh, clean water. Note how much water your horse drinks, and be cognizant of decreases if there is a weather change and try supplementing water in other ways at those times. For example, feeding a soupy mash or adding a few tablespoons of apple juice or Gatorade to the water to tempt the horse (obviously always have available both plain and flavored water).
Horses living on sandy soil should be fed in feeders with rubber mats underneath to minimize the amount of sand they ingest. Additionally, horses in sandy areas should be on a preventive psyllium program to help clear them of sand they take in. Studies have shown that horses in California (in particular, Arabians) that eat alfalfa are more likely to have enteroliths (stones that form in the colon that can cause colic and have to be removed surgically). Therefore, while alfalfa is a great feed source, it may be recommended to not feed it for more than 50% of your horse’s diet. Routine deworming is important for many reasons, and can help decrease the incidence of some types of colic. Routine dental care is critical, not only in older horses, because poor dentition can increase risk of impaction colics.
Conclusion
Certainly there are numerous causes of colic, but some of these can be avoided with routine good horse care and by being well-informed. Being armed with a little more information about colic can hopefully help to decrease the preventable risks and make a colic event less scary.