Thrombosis resulting in rectal perforation in a horse.

A 12-year-old Quarter Horse gelding was admitted to the veterinary medical teaching hospital with a 2-day history of signs of abdominal pain. Initial findings on physical examination included signs of lethargy, dehydration, diarrhea, and gastric reflux. Results of laboratory testing indicated that the horse had panleukopenia with neutrophilic toxic changes, was dehydrated, and was hypocalcemic. During the first 48 hours of hospitalization, 1 abdominal palpation per rectum and 3 analyses of peritoneal fluid were performed; abnormalities were not detected. A preliminary diagnosis of enterocolitis was made. Salmonella anatum was isolated from the feces. The horse's condition improved during a 5-day period, although left jugular thrombosis did develop. On day 8 of hospitalization, the gelding was found dead. Necropsy revealed acute severe fibrinous peritonitis as the result of vasculitis and thrombosis of the caudal mesenteric artery and its cranial rectal branch with rectal infarction and perforation. Immediate classification of rectal tears and perforation as iatrogenic should be avoided. Ischemic vascular disease is a consideration, and horses with thromboembolic disorders may be at risk for rectal perforations.