Ow, My Belly Hurts!

or

Equine Colic

   By Beth A. Pelletier, DVM

Colic. Anyone involved with horses knows the word, but what does it really mean?  One horse is fine after a dose of Banamine; another needs to be euthanized.  How can one word describe both of these situations?   Simple, the term "colic" merely means abdominal pain, which can range from simple gas discomfort to severe intestinal strangulation and necrosis.  The causes of colic are numerous and in some cases impossible to identify in the field.  However, we can sometimes infer a likely cause and thus determine prognosis based on a thorough history, physical examination and a few diagnostic procedures. 

As a horse owner it is important to be able to recognize colic signs and alert your veterinarian.  As a veterinarian, colic signs are an important indicator of the degree of pain and thus the severity of the underlying cause.  The more painful a horse is the more likely the damage is severe and potentially irreversible.  Some horses are less tolerant of pain than others (ie. wimpy drama queens), but in general, the following signs are a good judge of colic severity (from least to most severe): 

            Lying down for long periods of time or getting up and lying down repeatedly

            Decreased or no appetite

            Restlessness

            Quivering of the upper lip

            Looking at the flank (turning the head to the side)

            Repeated stretching as if to urinate

            Kicking at the abdomen with hind feet

            Crouching as if about to lie down

            Sweating

            Rolling on the ground or thrashing

If a horse has several abrasions, especially on its head or face, you should be suspicious of recent rolling and thrashing, even if this has not been witnessed.  Regardless of the severity of the signs, you should contact your veterinarian immediately; mild signs could rapidly progress to severe signs depending on the cause.  Be prepared to provide a full history including: duration and progression of current colic signs, any prior colic events, diet, exercise, environment, parasite control, behavioral changes or habits, reproductive status or other medical issues. In any case of colic, the horse should be walked and prevented from rolling while you wait for your veterinarian to arrive.  Walking facilitates movement of gas or ingesta through the intestines, and in mild cases, may be enough to resolve the issue.

Being able to identify a horse with colic is essential for an owner but you may also be wondering, "Why is my horse acting this way?"  In order to better understand colic, it is important to know a few things about the anatomy and function of the equine gastrointestinal tract.  Refer to the images below. 

The equine stomach and small intestines are similar to those of the human - with one very important difference.  Horses are unable to vomit.  Any build up of fluid, excess food, toxic substance or foreign object, once in the stomach can not be purged by the horse.  The accumulation of fluid in the stomach can be secondary to several other causes of colic but in itself, can drastically increase the severity of pain experienced by the horse. 

Beyond the small intestines, the equine gastrointestinal tract becomes very specialized in order to ferment and extract nutrients from the tough plant materials that they have adapted to eat.  For example, their cecum, which is a fermentation vat that functions at the junction of the small and large intestine, is 1 meter in length and holds approximately 33 liters of material!  The equine large intestine is also very developed and is comprised of several loops that wind their way back and forth across the abdomen in a horseshoe shape.  As ingesta moves through the body, it must traverse several bends as well as areas where a large lumen narrows into a tight space.  You know how congested the highway gets when 4 lanes of traffic suddenly narrow into 2 lanes? Then you'll understand how easy it is for ingesta to become impacted (packed in tightly to the point of being immobile, such as a car in a traffic jam) at any of these locations, especially if it is dehydrated, contains a foreign object or motility is decreased.  Impactions are one possible and common cause for equine colic.

Another important aspect of the large and small intestines that contributes to colic is that several of the loops are freely mobile.  There are no bands of tissue or ligaments anchoring them to their location as there are in most other parts of the abdomen.  Occasionally, a section of bowel folds over on itself, twists or becomes trapped around other organs causing severe pressure, occlusion of blood supply and ultimately death of the tissues.  As you can imagine, this is extremely painful.  A specific type of bowel entrapment more commonly found in older horses is a "strangulating lipoma", where a long, dangling fat deposit wraps around a piece of intestine, cutting off the flow of ingesta and blood to that region.  Any type of colic where bowel is twisted or entrapped is usually a surgical emergency.  Unfortunately, many horses are euthanized with these types of colic due to poor prognosis or expense of surgery.

Besides these mechanical disruptions, there are several other causes of colic including inflammation (enteritis), infection, parasites, tumors and decreased motility.  These are just a few examples of the more than 70 identified causes of colic.  In addition, these causes can be triggered by numerous and varied factors, including: sudden changes in the weather, change in feed, poor quality or moldy feed, parasites, overexertion, chilling, sand or foreign object ingestion, laminitis or infections elsewhere (such as pneumonia or dermatitis).

When your veterinarian arrives to identify colic, they will start with getting a complete history while assessing your horse's attitude and behavior.  If the horse is too painful to perform a full examination, it may be necessary to provide pain medication or sedation first.  However, it is best to make a full assessment before medications are administered.  As was mentioned earlier, the behavioral signs and mental status of the horse are key indicators of the severity of pain and thus the underlying cause of colic. 

Next, the horse's vital signs are evaluated.  Mucous membrane (gum) color and capillary refill time indicate blood flow and presence or absence of toxins in the blood (which can occur if there is leakage from damaged intestines).  Heart rate and respiratory rate tend to increase proportionately with pain intensity.  However, some horses become very nervous during their examination and this alone causes their values to rise.  This is one reason why it is important to know the individual horse's resting heart and respiratory rates through yearly wellness exams.  Temperature during colic typically remains normal unless there is an infectious cause or severe inflammation.  Gut sounds are often decreased with colic as motility is impeded, whether primarily or secondarily.  In cases of impending diarrhea, gut sounds may become increased or splashy. A lack of gut sounds is generally a poor sign.

A rectal examination can be helpful in identifying impaction, displacement or distention of abdominal contents.  The organs palpable per rectum include the edge of the spleen and left kidney, pelvic flexure (an area where the large colon makes a sharp turn), cecum and the small colon with fecal balls.  If the small intestine is distended, it may be palpable extending into the back of the abdomen.

Another diagnostic aid is nasogastric intubation (with an NG tube).  A tube is passed through the nose into the esophagus and the stomach.  This allows your veterinarian to assess if there is any excess fluid buildup (reflux) and release it if necessary.  Greater than 2 liters of reflux is considered abnormal.  Reflux occurs if there is lack of motility, severe inflammation or obstruction of the small intestine.  If a large amount of reflux is present, removing it will reduce distension and discomfort of the stomach and small intestine.  If no reflux (or less than 2 liters) is removed, warm water and laxatives (typically mineral oil) can be administered to facilitate hydration and movement of ingesta.  Please note that passage of a nasogastric tube can cause a nose bleed and this should not be cause for concern, although it can be alarming to you as an owner.  The bleeding should resolve within 15 minutes of removing the tube.

After the initial evaluation, unless surgery is immediately indicated, pain medication, such as Banamine or Equioxx, can be administered.  These are effective gastrointestinal pain relievers in many cases.  If one of these NSAIDs is not enough to relieve signs or if sedation is needed to pass the nasogastric tube, stronger pain medications with sedative properties can be tried.   If the horse's pain is refractory to heavy pain medication, meaning it continues to try to roll or the heart rate is still elevated, the condition requires referral to a surgery clinic or sadly, euthanasia.  If surgery is an option and the veterinarian determines it may be necessary, it is better to send the horse to the referral clinic sooner rather than later.

Every case of colic is different and the individual circumstances will dictate exactly how to proceed.  It is not possible to absolutely ensure that your horse will never experience a problem; however, you can try to prevent the factors mentioned above and take immediate action if signs do occur.  Colic can be a frightening event for the horse and the owner, but thankfully the vast majorities of episodes are mild and respond well to symptomatic treatment.