Vetnews | Desember 2025 44 « BACK TO CONTENTS Gastrointestinal (GI) ulcers are a significant concern in small animal practice, often presenting a diagnostic and therapeutic challenge for veterinarians. While the true incidence in dogs and cats remains unknown, GI ulceration is recognised as more common in dogs and can lead to serious complications if not promptly identified and managed. This article explores the aetiology, pathophysiology, clinical presentation, diagnosis, and treatment of GI ulcers in small animals, providing practical insights for veterinary professionals. The Gastric Mucosal Barrier: Nature’s Defence The stomach and proximal duodenum are constantly exposed to a harsh chemical environment, including gastric acid, bile acids, and digestive enzymes. To protect itself, the GI tract relies on a sophisticated mucosal barrier. This barrier consists of tightly joined epithelial cells, a thick bicarbonate-rich mucus layer, and robust local blood flow. Tight junctions between epithelial cells prevent leakage of luminal contents, while the mucus layer neutralises acid and traps harmful agents. High mucosal blood flow not only clears any acid that penetrates the epithelium but also supports rapid cell turnover and repair. Locally produced prostaglandins E2 and I2 further enhance mucosal defence by increasing mucus and bicarbonate secretion, maintaining blood flow, and stimulating epithelial regeneration1. Pathophysiology: When the Balance Tips Under normal conditions, the aggressive factors in the gastric lumen are balanced by the mucosal barrier’s defences. However, this equilibrium can be disrupted by various drugs and diseases, leading to mucosal injury and ulceration. When the barrier is compromised, hydrochloric acid, bile acids, and proteolytic enzymes penetrate the epithelium, causing cellular damage, inflammation, and apoptosis¹. This initiates a self-perpetuating cycle: inflammation leads to further acid secretion (often mediated by histamine release from mast cells), decreased mucosal blood flow, ischemia, and reduced secretion of protective mucus and prostaglandins. The result is progressive mucosal damage, with ulcers exposing the submucosa or deeper layers to the corrosive luminal environment. Aetiology: Common Causes in Dogs and Cats Dogs • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): NSAIDs are a leading cause of gastroduodenal ulceration in dogs. They cause direct topical injury and, by inhibiting cyclooxygenase-1 (COX-1), reduce the synthesis of protective prostaglandins. Even COX-2-selective NSAIDs, though considered safer, can still cause ulceration and perforation. • Neoplasia: Tumours such as lymphoma, adenocarcinoma, leiomyoma, and leiomyosarcoma can induce ulceration through local tissue effects. Paraneoplastic syndromes, especially from mast cell tumours and gastrinomas (e.g., Zollinger-Ellison syndrome), can increase gastric acid production and promote ulcer formation. • Hepatic Disease: Acute hepatic injury and portosystemic shunts are associated with GI ulceration, possibly due to altered acid secretion and mucosal blood flow. • Other Causes: Major trauma, spinal disease, renal disease, hypoadrenocorticism, GI inflammation (e.g., inflammatory bowel disease, foreign bodies), systemic inflammation (pancreatitis, sepsis), and extreme exercise (such as in sledge dogs) are also implicated. Corticosteroid therapy remains controversial, but combining corticosteroids with NSAIDs is contraindicated due to a markedly increased risk. Cats In felines, GI ulceration is most often linked to neoplasia (lymphoma, adenocarcinoma) and inflammatory conditions (lymphoplasmacytic or eosinophilic inflammation)1. Clinical Presentation: Nonspecific but Important Clues Most small animals with GI ulcers exhibit nonspecific signs such as vomiting, anorexia, abdominal pain, and weight loss1. Hematemesis (vomiting blood) and melena (black, tarry stools) may occur but are variable, especially in cats, where overt GI bleeding is rare. Severe ulceration or perforation can lead to acute abdominal pain, weakness, pallor, shock, and signs of sepsis. Notably, some animals may show no clinical signs, underscoring the importance of vigilance in at-risk patients. Understanding Gastrointestinal Ulcers in Small Animals: Aetiology, Pathophysiology, and Clinical Management Dr. Julian Kampman (BSc)(BVSc)(MRCVS)
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