Equine Gastric Ulcer Syndrome

Ulceration of the stomach lining in the equid is a syndrome rather than a disease state itself, as numerous disease entities exist which contribute to the emergence of such lesions. This distinction becomes increasingly critical as the evidence grows for multiple pathophysiologies accompanied by varying and distinct risk factors, presentations, and treatment responses. Thus, Equine Gastric Ulcer Syndrome (EGUS) has become the accepted parent term to describe gastric ulceration symptomatic of a more specific underlying condition.

While ulceration of the squamous portion of the equine stomach has been long recognized and understood, evidence is growing surrounding glandular ulceration as well. Because ulceration of the squamous vs. glandular regions of the stomach is often unrelated, has different causative factors, and responds differently to omeprazole therapy, it is critical to distinguish between the two. Learn more about:

Presentation and Symptoms of EGUS

Equine Gastric Ulcer Syndrome is far and away the most common disease condition affecting the stomach of the horse. In symptomatic horses, inappetance, difficulty maintaining weight or weight loss, recurrent colic, changes in hair coat, changes in behavior, and underperformance may result. Additionally, sterotypies such as cribbing or wood chewing have been linked to gastric ulceration, as increased saliva or inflation of the stomach may temporarily relieve irritation from gastric acids.

Note that pain on girthing, flank sensitivity, and diarrhea have oft been misattributed to gastric ulceration, when they are more likely indicative of hindgut disorders. Due to the physical location of the stomach relative to the position of saddle and girth, more pressure is directly applied over the colon on the ventral, right side of the horse’s abdomen. And because diarrhea results when normal fluid absorption in the colon is disrupted, it always indicates a problem beyond the stomach. If diarrhea is present when gastroscopy confirms stomach ulceration, a hindgut condition is also at issue.

It’s critical to remember that clinical experience among practitioners shows many horses to be asymptomatic even in the face of severe gastric ulceration, and their symptoms are more readily overlooked.

Differential Diagnosis of Equine Gastric Ulcer Syndrome

Gastroscopy continues to be the only reliable method for the differential diagnosis of gastric ulceration in horses. A complete and thorough examination of the stomach is essential to differentiate between squamous and glandular ulceration (or identify if the problem is instead something else entirely, such as parasitic infection or neoplasia). Keep in mind that the presence or absence of ESGUS does not predict the accompanying presence or absence of EGGUS – or of ulceration or inflammatory pathologies of the hindgut – and score each region separately.

For most horses, a fasting period of at least 12 hours prior to endoscopy is recommended, as even small amounts of residual food impact the ability access the pyloric antrum. It may be helpful, but not mandatory, to also remove water 4 hours prior to the procedure.

Some studies have revealed a potential drawback to gastroscopy for diagnosing gastric ulceration as some horses may develop low-grade ulceration in less than 12 hours when feed is withheld.

Grade Squamous Mucosa Glandular Mucosa
0 The epithelium is intact and there is no appearance of hyperkeratosis (yellow appearance to the mucosa) The epithelium is intact and there is no hyperemia (reddening) of the mucosa
1 The mucosa is intact, but there are areas of hyperkeratosis The mucosa is intact, but there are areas of hyperemia
2 Small single, or multifocal lesions Small single, or multifocal lesions
3 Large single, or multifocal lesions, or extensive superficial lesions Large single, or multifocal lesions, or extensive superficial lesions
4 Extensive lesions with areas of apparent deep ulceration Extensive lesions with areas of apparent deep ulceration

Treating Equine Gastric Ulcer Syndrome

Omeprazole therapy to suppress the production of gastric acid has long been used successfully. It has essentially become the ‘gold standard’ treatment protocol for equine gastric ulceration, particularly in the squamous region of the stomach. While acid suppression does not contribute directly to healing, it does create an environment conducive for healing to occur.

While highly effective for treating ESGUS, the rate of healing with omeprazole drops significantly for incidents of EGGUS, so additional therapies are recommended when glandular ulceration is present.

While some may recommend therapeutic trial with omeprazole when gastroscopy is unavailable, this can be problematic. First, it doesn’t differentiate between glandular and squamous ulceration. Second, a negative response to therapy reduces the likelihood of EGUS but doesn’t remove it, as some horses are slower to respond and symptoms may not alleviate until complete healing is achieved.

Alternate, nutritional approaches may be equally, if not more effective in the treatment of gastric ulceration long-term. Recent studies have shown that a dietary supplement may be just as effective in treating gastric ulcers as the omeprazole.