Gastrointestinal: Gastric Ulcer
Understanding Equine Gastric Ulcer Syndrome (EGUS): Pathophysiology and Management
Equine gastric ulcer syndrome (EGUS) encompasses a spectrum of mucosal pathophysiological changes affecting the terminal esophagus, nonglandular and glandular regions of the stomach, and proximal duodenum. This condition, prevalent among performance horses and foals, presents with vague clinical signs, necessitating prompt diagnosis and targeted treatment to alleviate discomfort and prevent complications.
Risk factors for EGUS development in horses include participation in performance disciplines, high-concentrate diets, intermittent feeding, environmental stressors, and illness. While racehorses in active training exhibit a high prevalence of EGUS, non-racing performance horses also face substantial risk. Additionally, neonatal foals, with their underdeveloped gastric mucosa, are predisposed to EGUS, with clinical manifestations ranging from subclinical to severe.
The pathogenesis of EGUS involves a complex interplay of factors. Equine squamous gastric ulcer disease arises from repeated exposure to acidic gastric contents, exacerbated during exercise-induced pressure changes. Dietary composition, particularly high-grain, low-roughage regimes, promotes fermentation, leading to mucosal acidification and ulcer formation. In contrast, equine glandular gastric disease etiology remains less defined, with proposed mechanisms including breakdown of mucosal defenses, bacterial colonization, and stress-induced inflammation.
Diagnosis and clinical signs:
Clinical presentation varies with age and severity of ulceration. Foals may exhibit lethargy, colic, and poor nursing habits, while adult horses often display nonspecific signs such as poor performance and abdominal discomfort. Diagnosis relies on gastroscopic visualization of lesions, with endoscopy serving as the gold standard for definitive evaluation. Grading systems aid in lesion severity assessment, guiding treatment decisions and monitoring efficacy.
Treatment:
Supportive care and dietary management play integral roles in the treatment of equine gastric ulcers. Omeprazole, a proton pump inhibitor, stands as the treatment of choice with minimal reported adverse effects.Supportive care involves dietary adjustments, such as feeding low-starch grains and alfalfa hay, which serve to buffer stomach contents. The primary goal of treatment is to suppress gastric acidity and maintain a pH of ≥4. Various medications have been explored for this purpose, including surface-coating agents, antacids, histamine type-2 receptor antagonists like ranitidine and cimetidine, and omeprazole.
Sucralfate, while binding to the gastric mucosa, has not shown significant efficacy when used alone but may aid healing when combined with omeprazole. Antacids, though administered frequently, have not been proven effective in ulcer management. Ranitidine has demonstrated effectiveness in healing equine squamous gastric ulcer disease lesions when horses are removed from training. However, cimetidine has not shown efficacy in treating gastric ulcers.
Omeprazole, by blocking hydrogen ion secretion, effectively promotes ulcer healing. It is the only FDA-approved medication for treating and preventing recurrence of equine gastric ulcers. Misoprostol, a synthetic prostaglandin analog, either alone or in combination with sucralfate and omeprazole, has shown effectiveness in treating equine glandular gastric disease. Esomeprazole, the S-enantiomer of omeprazole, has demonstrated success in treating equine squamous gastric ulcer disease, although its efficacy for glandular gastric disease remains uncertain.
In conclusion, EGUS poses significant challenges to equine health and performance. A comprehensive understanding of its pathophysiology and tailored treatment protocols are essential for mitigating morbidity and optimizing long-term outcomes in affected horses. Through multidisciplinary collaboration and ongoing research efforts, the veterinary community continues to refine diagnostic and therapeutic approaches, advancing the management of this prevalent equine condition.
