09/06/2025
Colic in the Horse (Part 1)
Brian S. Burks, DVM
Diplomate, ABVP
Board Certified in Equine Practice
Veterinarians are often asked about treating colic. This is a little like asking how to treat a limp. There are many causes of colic, enough to fill volumes. Most simply, colic means abdominal pain, from whatever the cause in the immediate case. There are many misconceptions about colic.
• Rolling causes the colon to twist
• Passing manure means that the horse is getting better
• Trailer rides will fix the colic
• Horses colic with changes in weather
These misconceptions can lead to delays in treatment and possibly even death. The question, then, should be: What is the diagnosis that is causing the colic? To answer this question, one must understand the anatomy and physiology of the equine digestive tract.
THE EQUINE GASTROINTESTINAL TRACT
The equine digestive tract is unique in its ability to digest cellulose and other structural carbohydrates. This process is known as fermentation, which requires a special and complicated digestive tract. Fermentation yields copious amounts of gas due to the microfauna (bacteria and yeasts) required for digestion. This works well for what horses were meant to do- range over many acres, but it does not translate well into being stall kept and fed meals twice daily.
The digestive tract begins in the mouth. Prehension and mastication are important aspects here. Very sharp teeth may affect mastication and cause injury to the inside of the mouth. Food must be taken in in small bites, chewed well, and this stimulates saliva production, beginning digestion. Saliva contains many digestive enzymes and buffers to break down food and buffer acids in the stomach. From the nose to the stomach is about one and a half meters; a three-meter endoscope is required to examine the stomach in its entirety. The stomach normally holds around three to five gallons, and it exits, via the pylorus, into the small intestine which is around 80 feet. The small intestine is divided into three parts: duodenum, jejunum, and ileum. The jejunum is the longest portion of small intestine. The small intestinal mesentery (ligamentous attachment of the intestine to the body wall) is connected to the top of the abdomen (toward the spine) near the first and second lumbar vertebrae at the site known as the “root of the mesentery.”
Within the root of the mesentery exists the large cranial mesenteric artery. The mesentery is wide and fan-shaped and carries numerous vessels and nerves to the intestines. It is attached to the small intestine along its entire length, but because of its fan shape and singular attachment, it is highly mobile and permits the small intestine to move freely in the abdomen.
The small intestine exits into the cecum (appendix), a 3.5-foot blind sac which holds around 5-7 gallons of ingesta. This is essentially a blind pouch, with an entrance and an exit lying in proximity. The cecum mixes the ingesta, ferments feed material via microbial digestion, and absorbs water. Next comes the large colon which has several turns, including an upward hairpin curve. It is designed as a double stacked horseshoe. The large colon is about 15 feet long and varies greatly in diameter, from 8cm to as large as 50cm in the right dorsal colon.
The sequence of the limbs and flexures of the ascending colon is as follows: Right Ventral Colon passes out of the cecocolic or***ce on the right side of the abdomen and continues cranially to the xiphoid region; Sternal Flexure, passes across the midline from right to left, Left Ventral Colon, which has a diameter of about 20cm, runs caudally on the left ventral abdominal floor; Pelvic Flexure, which has a diameter of about 8cm, turns dorsally just cranial to the pelvic inlet and then runs cranially to the diaphragm as the Left Dorsal Colon, parallel and dorsal to the left ventral colon; Diaphragmatic Flexure, turns right at the diaphragm; Right Dorsal Colon, with a diameter of 50cm, continues caudally on the right. It is the shortest limb of the ascending colon.
The transverse colon continues from the right dorsal colon as the right dorsal colon turns medially. The right dorsal colon is attached by a mesentery to the dorsal abdominal wall, the base of the cecum, the root of the mesentery and the pancreas. This anatomical arrangement of mesentery allows the left ascending colon to twist and is a common cause of colic (colonic torsion).
The large colon in turn empties into the 10-foot-long small colon, where f***l balls form before exiting the re**um and a**s. All told, the equine digestive tract secretes and absorbs about 100 liters of fluid every day. All the twists and turns of the equine GIT are to slow movement, cause mixing of the contents, and allow microbial digestion, making Volatile Fatty Acids, the major source of energy in the horse.
SIGNS OF COLIC
Horses are very sensitive to abdominal pain and may present differently than other species. Signs in horses range from mild to severe and include anorexia, lethargy, ‘ain’t doin’ right’, lip curling, teeth grinding (bruxism), flank watching, stretching as if to urinate, pawing, kicking at the abdomen, rolling, thrashing, and more.
CONDITIONS CAUSING COLIC
Colic signs may emanate from any point of disturbance in the gastrointestinal tract. It may be confused with pain from other areas of the body, for example chest pain.
There are many causes of colic, depending upon the site affected. There may be gas, simple obstruction, or strangulation. Examples include the stomach with gastric ulceration or feed impaction, the small intestine can twist at the root of the mesentery (volvulus), the large colon may have gas, impaction of feed material, or may have a torsion. Any part of the intestinal tract may be affected by inflammatory diseases or bacterial infections. There are many other potential causes.
What is causing the pain experienced during colic episodes?
• Tension on attachments to the body wall (mesentery)
• Distention or muscular spasm of colon
• Irritation to the intestinal lining- gastric/colonic ulcers
• Loss of blood supply (ischemia) from mesenteric volvulus or colon torsion
BREAKING THE PAIN CYCLE
Many times, horses may recover quickly and on their own. They may colic in the night or when you are gone, and you may never know that your horse had a mild belly ache. Where colic is identified, many resolve with time and an injection of flunixin meglumine, a potent anti-inflammatory and pain reliever; however, it is critical to understand what this medication may accomplish. For minor causes of colic, it may be fine. For more severe forms of colic, it may take away the pain while the internal process continues, delaying diagnosis and treatment. It could even cost the horse its life. Never give any medication without consulting a veterinarian first. Some drugs may do irreversible harm if given in the wrong situation.
Anything that blocks normal movement of ingesta from the stomach to the re**um may result in gas and/or fluid build-up, stretching the intestine, causing increasing amounts of pain as the condition worsens. Pain relief may stop this cycle in milder forms of colic. More severe forms of colic such as a twist, displacement, or impaction will require more aggressive forms of treatment, including surgery, especially in the former two causes listed here.
Simple observation is not enough to distinguish mild and severe cases, although more severe signs of pain that continues is more likely to be life-threatening, but this is not always the case. An experienced veterinarian can identify the cause of colic based on signalment, history, physical examination findings, re**al palpation, and other diagnostic modalities such as abdominal ultrasound.
COLIC OCCURRENCE
Roughly 5-10% of horses will experience colic each year. This happens in all groups, herds, breeds, and geographic locations. There are specific conditions that are more common in certain age groups, i.e., Ascarid impactions and intussusceptions are more common in younger horses. Colon torsion is common in broodmares post foaling. Stall kept horses experience more colic than those with regular exercise and those that are fed more concentrates than forage (hay or grass).
Dr. Brian Burks, Dipl. ABVP is the owner/veterinarian at Fox Run Equine Center, a 24-hour medical-surgical center near Pittsburgh, Pennsylvania. He is board certified by the American Board of Veterinary Practitioners (Equine Practice). This certifies him as an expert in all categories of equine practice. He enjoys the diagnostic and treatment challenges of internal medicine and intestinal disorders.
Fox Run Equine Center
www.foxrunrequine.com
724-727-3481
