Gastric Impaction in Horses: A Review

Colic and its causes are part of most owners' horse care vocabulary--an intestinal twist, sand accumulation, or gas buildup might be among the familiar events leading to equine abdominal pain. But owners might not be aware of another, less-frequent cause of colic: gastric impaction. A team of researchers recently found that these impactions of the stomach, if treated promptly, can result in a good prognosis.

To gain a better understanding of gastric impactions, the research team (based in Finland) performed a retrospective study in which they examined 20 gastric impaction cases and their associated clinical signs, diagnosis, prognosis, and treatment.

"Gastric impaction in horses is a condition characterized by excessive accumulation of ingesta in the stomach that does not clear after an appropriate fasting period," lead author Kati Vainio, DVM, Dipl. ACVIM, and ambulatory equine practitioner based in Inkoo, Finland, explained in the study. She added that the condition is caused by a variety of factors including the consumption of certain feeds that swell after ingestion, dental problems that diminish the horse's ability to chew feed properly, inadequate water supply, excessively rapid eating, and pathophysiological disturbances (changes in the horse's normal mechanical, physical, and biochemical functions).

Vainio and colleagues recently reviewed the medical records of 6,097 horses admitted to the Hyvinkää Horse Hospital between October 2005 and December 2008. They narrowed their focus to 20 horses diagnosed with a gastric impaction.

The horses diagnosed with gastric impactions (12 mares, seven geldings, and one colt, ages 8 months to 25 years) had been presented at the hospital with a variety of clinical signs. The most common signs were a lack of appetite, acute colic, and recurrent colic. Other less common clinical signs included difficulty swallowing, decreased fecal output, fever, lethargy, and excessive salivation.

Prior to hospital admission, all 20 horses were fed either hay or haylage, and only one had access to pasture. Vainio noted that although specific information regarding the type of forage the horses were fed was not available, in her experience most horses in the surrounding areas were fed haylage as opposed to hay.

Treating veterinarians made a correct diagnosis on Day 1 of hospital stay in 11 of the 20 horses and on Day 2 in the remaining horses. Vainio explained that the treating veterinarians' diagnostic method of choice was gastroscopy (an endoscopic examination of the stomach) because "the presence and extent of ingesta accumulation could be directly confirmed."

In many causes, veterinarians used ultrasound in conjunction with gastroscopy during the diagnostic period, although they occasionally used ultrasound alone. She noted that rectal examinations aren't useful in diagnosing gastric impactions due to the stomach's location in relation to the rectal passage.

The veterinarians treated all of the affected horses enteral (via the gastrointestinal tract) fluids, and Vainio noted that this proved very successful for resolving impactions. The team believes the enteral fluids aided in softening impactions and allowing them to pass through the rest of the digestive tract.

Vainio noted that in some cases veterinarians administered analgesics (pain relievers) to combat horses' discomfort; however, the medications did not appear to impact the horses' recovery.

Of the 20 case horses, 18 survived and were discharged from the hospital after an average stay of five days. The other two were euthanized (one due to a presumed gastrointestinal tract rupture and one that did not respond to treatment; neither horses were necropsied after euthanasia).

Of the 18 discharged horses, only two suffered gastric impaction recurrence. One was euthanized after not responding to treatment and the other was treated again successfully.

The researchers were able to obtain follow-up reports on all the surviving horses. All but two had recovered and were still alive when the study was completed (one horse had been euthanized due to an unrelated orthopedic disease, and one was euthanized for unknown reasons).

"Based on the present study ... gastric impaction has a good prognosis," Vainio said. "The short-term survival rate was 90% and the long-term survival rate was 75%."

Although there are no surefire preventive techniques, Vainio suggested that routine dental care might reduce the chance of a gastric impaction by allowing the horse to chew his food more completely (thus lessening the amount of large or unchewed matter in the stomach). Additionally, she suggested limiting or withholding feed from horses suffering from colic, as the decreased gastrointestinal motility could lead to impaction.

"Gastric impaction is one differential diagnosis for a chronic or recurrent colic," she added. "If colic signs do not resolve within a day or so and there is no obvious cause for the colic, the owner should consider taking their horse to a clinic where it can be gastroscoped."

The article, "Primary gastric impaction in horses: a retrospective study of 20 cases (2005-2008)," was published in Equine Veterinary Education in April 2011. The abstract is available online.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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