Colonic Volvulus in a Cynomolgus Monkey (Macaca fascicularis)

A five-year-old male cynomolgus monkey (Macaca fascicularis) with loose stool from two days before dying was observed with dark blood-like watery diarrhea. The animal was not used in the toxicology study as its body weight (4.5 kg) was lower than that of male monkeys of the same age. Gross examination revealed a clockwise rotation of the colon accompanied by a dark-reddish change and distention. After fixation, a pink, small, distorted and semi-hard foreign body was found in the lumen of the colon along with dark blood-like watery contents. Examination of the cage revealed that the foreign body was the one of the pieces of the hard rubber chew toy, which is given to monkeys as an environmental enrichment device in our facility. Microscopic examination revealed severe congestion and hemorrhage accompanied with distended veins mainly in the mucosa in the colon. There were no regenerative or proliferative lesions such as a granulation tissue or hypertrophic smooth muscle between the proximal and distal regions of the colon and the rectum. Therefore, the animal was pathologically diagnosed as having colonic volvulus of an unknown cause. This is the first case of colonic volvulus in a cynomolgus monkey. When spontaneous occurring intestinal volvulus in monkeys given environmental enrichment devices are experienced in future, it is necessary to recognize the possibility that environmental enrichment devices, wherein it is possible to chew and ingested part of the device, may be a risk factor concerning colonic volvulus in cynomolgus monkeys.