Concurrent small intestinal neoplasia and large colon volvulus in a standardbred yearling.

Large colon volvulus is a common, life-threatening cause of colic in horses. Gastrointestinal neoplasia is a rare cause of abdominal pain in young horses. A 1-year-old Standardbred colt presented with acute colic unresponsive to medical treatment. An exploratory laparotomy identified extensive gastrointestinal pathology, and euthanasia was elected due to a poor prognosis. Necropsy revealed a 360-degree volvulus of the caecum and large colon with adhesions, enterotyphlocolitis, and a well-circumscribed mesenteric mass arising from the small intestine. Histopathology in combination with immunohistochemistry confirmed the mass as a soft tissue sarcoma (leiomyosarcoma). This case describes the coexistence of intestinal neoplasia and acute colic in a juvenile horse.