A stoma is an opening in a body surface, natural or surgically created, that connects an internal cavity or hollow organ to the exterior. In equine anatomy the term applies to two distinct contexts: the microscopic pores on the visceral peritoneum through which lymphatic vessels absorb fluid from the abdominal cavity, and the surgically fashioned openings used in gastrointestinal surgery, most commonly a typhlostomy (into the caecum) or a colon stoma, to decompress or bypass a diseased segment of bowel.
Natural stomata in the horse are passive structures; their clinical significance arises when peritoneal inflammation or neoplasia obstructs lymphatic drainage, contributing to ascites. Surgical stomata are created under general anaesthesia when intestinal resection is not feasible or when temporary faecal diversion is required to protect an anastomosis; they carry a guarded prognosis and are managed with wound care to prevent soiling and stricture. The term appears in equine surgical literature and in pathology reports; it is not a diagnosis but a structural descriptor.