One word that can mean so many different things and, with many myths and misconceptions, a lot of misunderstanding among horse owners. To clear confusion let us take some time to review the many avenues one diagnosis can take.
Any disruption of the gastrointestinal tract that causes discomfort.
Equine Gastrointestinal Tract
Before we can understand how colic can cause pain, we must first understand the normal digestive system. The stomach receives water and food boluses from a long muscular tube called the esophagus which attaches the back of the mouth to the stomach. After mastication (chewing), the stomach is where the first part of digestion takes place: gastric acid is mixed with food to break it into smaller particles before it passes into the small intestine. The small intestine has three distinct sections: duodenum, jejunum, and ileum. Next comes the large intestine which can also be broken down into three sections: cecum, large colon, and small colon. In total, the digestive tract is approximately 115 feet long and takes approximately 36- 72 hours for food stuffs to make it from mouth to anus. For a fantastic visual representation of the different components of the digestive tract check out this great video
Types of Colic
Irritation/Ulceration– most frequently encountered in the stomach but also possible in a specific section of the large colon. Typical presentation is recurrent mild colic around feeding time.
Strangulation– most often a problem of the small intestine. Horses (some breeds more commonly than others) can grow fatty tumors on stalks in the abdomen that can then wrap around portions of intestine and cut off their blood supply. Typical presentation is acutely painful horse that may respond to initial pain control but continues to have increasing discomfort.
Impaction/Obstruction– typically feedstuffs (but occasionally foreign material) can either partially or completely obstruct a section of the digestive tract. Obstructions of the small intestine are often very painful while impactions of the large intestine may present more mildly.
Volvulus/Torsion– twisting of the intestine which results in loss of blood supply to the affected section. Pain not controlled by medication and increases in severity with time.
Displacement– movement of the large colon from its normal position to an abnormal position. Displacements can occur with or without torsion, the latter being much more severe.
Gas Distention– normal digestion in the equine hindgut produces gas as gut flora (good bacteria) break down the feedstuffs. In some situations, this gas can be over produced or can accumulate abnormally and cause a stretching of the intestine, thus causing varying degrees of pain.
Spasmodic– food and water move from the stomach through the gastrointestinal tract because of synchronized muscular contractions called peristalsis. If peristalsis is disrupted it can result in mild cramping or, if left untreated, continue into displacement or volvulus/torsion.
The above listed of types of colic are intended to be informative of the most common types of colic but should not be considered inclusive of the extensive list of all types of colic.
Even though there are many different types of colic, horses are only able to show us they are uncomfortable in a limited number of ways. Not eating is a very common way horses express discomfort; aside from colic, horses with a fever, tooth pain, or esophageal obstruction (choke) may also present with temporary anorexia.
Pawing may be exhibited by a horse due to agitation. Rolling/Getting Up and Down frequently in a short period of time. Stretching out and making frequent attempts to urinate with little or no urine stream produced.
Medical vs Surgical Colic
When a horse first starts exhibiting signs of colic it is not always readily apparent what type of colic is at play. More often than not, an on farm examination by the veterinarian is the first step. The veterinarian will take a heart rate, as heart rate is an indicator of pain and can give us clues as to the severity of the colic. We will look at mucous membranes to asses hydration and perfusion. A careful auscultation of gut sounds (borborygmi) is also part of the initial exam. After examination the veterinarian will likely administer an injection of banamine for pain and a mild sedative to facilitate a rectal examination. Rectal examination allows to the practitioner to feel for twists, displacements, impactions, gas distention, and a variety of other conditions. It is extremely important to note that each portion of the exam is just a piece of the puzzle and no single diagnostic test can tell us exactly what is going on; rather, we must take all the history and exam findings into consideration when deciding what to do next. Often a nasogastric tube is passed up the patient’s nose, down the esophagus, and into the stomach. Horses are unable to burp or vomit and passing a tube allows pressure on the stomach to be released if necessary. It also allows the veterinarian to administer fluids or mineral oil. The majority of horses will begin to look better after the above described treatment and are considered mild colics. If they again start exhibiting pain signs again then further treatment is warranted.
At this stage we will often discuss sending the patient to a hospital for further workup and monitoring. Some types of colic—strangulating lipomas, large colon volvulus, etc—will only be corrected with surgery. One of the main indications to take a horse to surgery is pain that cannot be controlled with medication. We will often utilize abdominal ultrasound and abdominocentesis (sampling fluid within the abdominal cavity) to gain more information about what is happening inside the abdomen. If surgery is necessary to correct the problem, the
sooner it is performed the better. Swift surgical intervention when indicated can dramatically improve the prognosis vs. a horse that has been colicking for many hours prior to the decision to go to surgery.
– Should I handwalk my horse?
o Short periods (20-30 minutes) of hand walking at the onset of colic can be very helpful. A veterinarian should always be contacted at the onset of colic signs to help direct on farm treatment. Excessive handwalking (walking for hours on end) is not recommended.
– Will letting my horse roll lead to a displacement or torsion?
o No. Displacements and torsions are caused by disruption in peristalsis and a horse does not need to roll to lead to a displacement or torsion.
– My horse pooped while walking—does that mean everything is ok now?
o While passing a bowel movement is a great sign, a single bowel movement doesn’t necessarily mean everything is ok. The gastrointestinal tract is very long and the passage of manure happens at the very end, so it is possible the problem is further up and may not be corrected even though the horse passed a pile of manure.