Gastric Ulcer Syndrome

Equine Gastric Ulcer Syndrome (EGUS) refers to ulceration of the squamous (non-glandular) or glandular mucosa of the stomach. It is one of the most common conditions in horses, with prevalence up to 90% in Thoroughbred racehorses in training.

Squamous ulceration:

• Non-glandular mucosa lacks protective mechanisms
• Exposed to gastric acid during exercise (increased intra-abdominal pressure squeezes acid onto squamous mucosa) and when stomach is empty
• High-concentrate diets increase volatile fatty acid production, which damage squamous mucosa

Glandular ulceration:

• Less common than squamous; different pathophysiology
• Results from breakdown of mucosal defense (mucus, bicarbonate, prostaglandins) rather than acid exposure
• Associated with NSAID use, stress, Helicobacter-like organisms (controversial)

Risk factors: High-grain/low-forage diet, intermittent feeding (gastric pH drops when empty), intense exercise, transport, stall confinement, NSAIDs (especially phenylbutazone), concurrent illness.

Clinical signs: Often vague — poor performance, attitude changes, mild colic after eating, poor appetite, weight loss, bruxism, cribbing, dorsal recumbency in foals.

Gastroscopy — gold standard:

• 3-meter video endoscope required (stomach is 3–4 meters from nares in adult horses)
• Horse fasted 12–16 hours (withhold hay; water OK)
• Visualize cardia, squamous mucosa, margo plicatus, glandular mucosa, pylorus

Squamous ulcer grading (EGUS Council):

• Grade 0: Normal
• Grade 1: Mild — small single/multiple lesions
• Grade 2: Moderate — larger lesions, multifocal
• Grade 3: Severe — extensive lesions, coalescing
• Grade 4: Very severe — deep/extensive lesions with bleeding

Glandular ulcers: Described as present/absent and by location (pyloric, body, cardia); no standardized grading

Other diagnostics:

• Fecal blood tests (sucrose permeability) — poor sensitivity/specificity; not recommended as sole diagnostic
• Trial treatment with omeprazole — if signs improve, supports diagnosis; less reliable than scoping

Pharmacologic treatment:

• Omeprazole: 4 mg/kg PO q24h x 4 weeks (squamous); may need 8 weeks for severe cases. First-line, gold standard.
• Sucralfate: 20–40 mg/kg PO q6-8h (binds to ulcer crater, stimulates prostaglandins; especially useful for glandular ulcers)
• Misoprostol: 3–5 mcg/kg PO q6-8h (prostaglandin analog; for glandular ulcers refractory to omeprazole; expensive, can cause colic/diarrhea)

Environmental/Dietary management:

• Forage-first: Free-choice hay or pasture; stomach needs continuous saliva production (bicarbonate) to buffer acid
• Reduce concentrates: High-starch diets increase acid and VFAs
• Frequent small meals: Avoid long periods with empty stomach
• Pasture turnout: Natural grazing behavior; reduces stress and provides continuous forage intake
• Decrease NSAIDs: Use lowest effective dose; consider COX-2 selective NSAIDs (firocoxib)
• Pre-exercise feeding: Small amount of hay 30 min before exercise reduces acid splash onto squamous mucosa