Impaction Colic in Horses
Updated December 9, 2024 | By: Andris J. Kaneps, DVM, PhD, DACVS, DACVSR
What is Impaction Colic in Horses?
Colic is a general term for any type of abdominal pain. Impaction colic is an obstruction of the digestive tract that can occur anywhere from the stomach to the rectum. It prevents normal movement of fluid, gas, and ingested feed from passing through the intestinal tract.
Where in the digestive tract can impactions occur?
The equine gastrointestinal system is 50 to 75 feet long, so there are many possible sites for an impaction. The most common cause of impaction is reduced moisture of the ingested feed leading to dry, firm intestinal contents and obstruction. These types of obstructions most commonly occur in the large colon where the intestine makes a sharp bend or abruptly becomes smaller in diameter.
Examples of these sites are the pelvic and diaphragmatic flexures and the transverse colon. Impactions may also occur in the stomach and small intestine, commonly at the ileum.
Specific Causes of Impaction Colic in Horses
In general, impaction colic occurs more commonly in the winter and following changes in management such as new hay, feed, or reduced level of activity [4]. Understanding the potential causes of this type of colic could be helpful in lessening the chances of an impaction. Things that may cause an impaction colic include:
- Reduced water intake or dehydration.
- Poor access to clean, fresh water.
- Common in fall and winter if ice freezes the water source.
- Change in feed or regular activity.
- Switch from grazing on pasture much of the day to feeding only hay.
- Abrupt change from regular athletic activity to stall-restricted activity that slows gut motility and lowers water consumption.
- Ingesting coarse forage can be difficult for horses to chew and for the large colon to digest.
- Poor dentition.
- Sharp enamel points, irregular chewing surfaces, painful teeth, or mouth issues.
- Parasite infection.
- Round worms (Ascarids) in young horses may obstruct the small intestine.
- Ingestion of foreign material.
- Sand can accumulate in the colon and lead to an impaction.
- Eating bedding, such as shavings and straw.
- Inadvertently eating objects such as a lead rope, plastic bag, twine string from a hay bale, or nylon webbing.
- Inflammation of the intestinal tract, which slows gut motility.
- Enteritis (inflammation of small intestine wall).
- Colitis (inflammation of wall of the colon or small colon).
- Blockage of the intestine by a stone (called enteroliths in horses) that gradually enlarges over time in some horses.
How Common is Impaction Colic?
Impaction colic is among the most common types of colic in horses. In a review of medical records of 604 horses presented for colic to Western College of Veterinary Medicine, the most common causes of colic were large colon impaction (20.8%), large colon displacement (16.5%), spasmodic colic (11.7%) and large colon volvulus (twist) (7.3%). Of the medically treated cases, large colon impaction (38.4%) and spasmodic colic (22.5%) were the most common. Recovery rate for the medically treated cases was 93.6%. Recovery rate for surgical cases was 73.5% [1].
In a compilation of 1,032 colics in Great Britain, 216 were impactions, of which 168 were left ventral colon or pelvic flexure impactions. Of the 216 impactions, other anatomical sites affected were: small intestine (17), cecum (7), small colon (6), rectal (5), gastric (2) [2].
In a review of 1,100 colics in America, 147 were due to large colon impaction with 70% of the impactions located at the pelvic flexure. Only 16% required surgery. Medical care successfully resolved the impactions in 1 to 6 days [3].
Identifying Signs of an Impaction Colic
Initial signs of impaction colic in horses may include:
- Mild discomfort and intermittent signs of pain.
- Loss of interest in feed.
- Reduced water consumption.
- Less manure production or especially dry manure.
- Reduced gut sounds are identified in 76% of horses with impaction colic when first examined.
Even with mild signs of discomfort, contact your veterinarian. More severe colic signs can occur as the impaction gets worse, which may look like:
- Pawing, looking at the flank, curling the upper lip, stretching out as if to urinate.
- Laying down and getting up frequently, rolling.
Read this article to learn all the potential signs of colic in horses.
Veterinary Diagnostics for Impaction Colic
A complete veterinary evaluation involving a physical examination, rectal palpation, passage of a stomach tube, and possibly blood work will help determine if your horse’s colic is due to an impaction or some other cause of abdominal discomfort. Further diagnostics for an impaction colic may include ultrasound examination and X-rays of the abdomen.
Impaction colic of the colon or small intestine may often be diagnosed on rectal examination. If the small intestine is involved, then distended small intestine may be palpated or evident with an abdominal ultrasound. The stomach tube is generally passed to determine if the stomach has excess fluid or gas that could be associated with an obstruction. If the stomach is not filled to capacity, the tube may be used to administer fluids to the digestive tract.
Treatment Options for Impaction Colic
Most cases of impaction colic in horses are successfully treated without surgery. Feed is withheld to prevent further filling of the obstructed digestive tract. Pain relief using non-steroidal anti-inflammatory drugs, such as flunixin meglumine, is often necessary.
Hydration and lubrication of the digestive tract is undertaken using a stomach tube. Water with electrolytes or Epsom salt will stimulate intestinal motility and help draw body fluids into the gut to soften the impaction. Mineral oil is commonly used as a lubricant to help move the impaction through the gut. The oil also acts as a marker. Oil found passing from the anus or in the manure is a sign that the impaction is resolving. Horses that are clinically dehydrated may require intravenous fluids [4].
If the impaction is not clearing and your horse’s condition worsens with a high heart rate, poor capillary refill time and other clinical signs of significant pain, your horse may require surgery. Surgery is most commonly necessary for impactions involving the small intestine, stomach, and obstructions due to enteroliths.
Strategies for Preventing Impactions
The most important factor in preventing an impaction colic is consistency in the management of your horse. This applies to their nutrition, hydration, dental health, parasite control program, and exercise.
Maintain a consistent diet and slowly introduce new sources of hay or changes in grain.
Always provide easy access to clean, fresh water. This is especially important in colder weather. Horses cannot drink frozen water. Daily water requirements may range from 5 to 20 gallons (20 to 70 liters) of water per day depending on exercise level, diet, and climate conditions.
Provide regular dental care. Your horse should have an oral examination every 6 to 12 months. Abnormalities of dentition and other issues within the mouth may then be identified and appropriately treated.
Parasite control is critical for preventing any type of colic. Your veterinarian can advise on and recommend an appropriate deworming program for your horse.
If your horse’s activity level suddenly decreases for reasons such as an injury or a stretch of inclement weather, steps can be taken to reduce the impact on your horse. If a horse must be restricted to a stall or small paddock, you should assure that they’re consuming enough water every day. You may also add water to their grain to increase water content in the gut. When possible, hand walking for 15 to 20 minutes twice daily will help maintain some activity.
Supplements That May Support Normal Digestion in Horses
In conjunction with smart management practices, providing ingredients in supplements to support a heathy stomach and digestive processes may be helpful.
Firstly, adding salt or electrolytes to your horse’s feed could help stimulate water intake to ensure adequate hydration [5]. Probiotics are beneficial microorganisms that help break down food, while prebiotics serve as food for the gut’s good bugs and may help reduce disruption in the hindgut. Enzymes could assist in proper digestion of starch in the horse’s foregut.
Yeast may help the body digest fiber and better adjust to feed changes. DVEquine™ Postbiotic is an ingredient that contains hundreds of bioactive metabolite compounds that are created from fermentation of the yeast Saccharomyces cerevisiae. These bioactive compounds may support immunity and gut health among other bodily processes.
Lastly, psyllium supplements may assist in fecal sand clearance if your horse lives in a sandy environment.
Video on Impaction Colic Prevention
In this Ask the Vet video, Dr. Lydia Gray answers a question on whether impaction colics build up over time, and she explains some tips for preventing impaction colic.
Evidence-Based References
- Abutarbush, Sameeh M et al. “Causes of gastrointestinal colic in horses in western Canada: 604 cases (1992 to 2002).” The Canadian veterinary journal = La revue veterinaire canadienne vol. 46,9 (2005): 800-5.
- Jennings, Kyra et al. “Prospective survey of veterinary practitioners' primary assessment of equine colic: clinical features, diagnoses, and treatment of 120 cases of large colon impaction.” BMC veterinary research vol. 10 Suppl 1,Suppl 1 (2014): S2. doi:10.1186/1746-6148-10-S1-S2
- Dabareiner, R M, and N A White. “Large colon impaction in horses: 147 cases (1985-1991).” Journal of the American Veterinary Medical Association vol. 206,5 (1995): 679-85.
- Hallowell, G.D. “Medical management of large colonic impactions.” Equine Vet Educ (2017) 29: 385-390. https://doi.org/10.1111/eve.12530
- Margraves, Madison. “How Much Water Do Horses Require Daily and Why Is Water Important?” Michigan State University Extension, 18 July 2018.