The twisting of a protein or the intestine around itself or a stalk of mesentery tissue to cause an obstruction. Volvulus occurs most frequently in the colon, although the stomach and small bowel can also twist. The part of the digestive system above the volvulus continues to function and may swell as it fills with digested food, fluid and gas. A condition called strangulation develops if the mesentery of the bowel is twisted so tightly that blood flow is cut off and the tissue dies. This condition is called gangrene. Volvulus is a surgical emergency because gangrene can develop quickly, cause a hole in the wall of the bowel (perforation), and become life threatening.