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Stomach
Food engorgement
This is a life threatening condition, with a great risk of gastric rupture, and also of secondary laminitis. It is caused by excess food intake, for example, a horse that has broken into a food store.
Gastric/pyloric spasm
This commonly affects racehorses, immediately after racing, and is known colloquially as 'racehorse colic'. Typically, the animal will have had access to cold water, but this is not always the case. Although the signs of colic seen may be very violent, this condition is not associated with any risk of gastric rupture. Spasmolytic drugs are ineffective in treatment, however, naso-gastric intubation is immediately curative.
Inappropriate feed/poor mastication
Either of these may lead to a condition where the stomach is unable to efficiently empty. A common example is feeding of unsoaked sugar beet, which then expands within the stomach.
Neurological atony
A chronic motility dysfunction, leading to a slow filling of the stomach with ingesta. Inhibition of gastric outflow is not normally a feature, and therefore gastric rupture is not a risk. A mild colic may be seen, but far more common is poor condition and reduced performance. Warmblood horses are more commonly affected than other breeds, leading to the suggestion that there may be a genetic component to the disorder.
Ulceration
Equine Gastric Ulcer Syndrome (EGUS) is a common cause of mild to moderate colic, and is more prevalent than had been appreciated. In racehorses, the prevalence is as high as 90%. In other performance horses, prevalence ranges from 40-60%. In foals, prevalence is approximately 25%, and probably higher in those being hospitalized for other reasons.
In adult horses, ulceration commonly occurs in the non-glandular portion of the stomach, unlike in humans, where peptic ulcers are far more common. While the bacterium Helicobacter pylori is a common cause of ulcers in humans, equine gastric ulcers are not typically infectious in origin. It is thought that EGUS is often stress-related, such as after travelling or confinement, and gastric ulceration is a known potential side-effect of treatment with non-steroidal anti-inflammatory drugs. A diet consisting of a high proportion of concentrates is also considered a risk factor. In affected horses, pain is often associated with eating, and the horse typically takes one or two bites of food, then no more. A definitive diagnosis requires endoscopy. Treatment is usually effected using H2 receptor antagonists, such as Cimetidine, or proton pump inhibitors, such as Omeprazole.
Neoplasia
A malignant squamous carcinoma can effect the cardia and upper squamous regions of the stomach, resulting in a persistent mild colic, commonly seen soon after feeding. Weight loss and general ill health are usually seen, and the prognosis is very poor, due to the high risk of metastasis.