The cecum is the beginning of the large intestine, a big pouch that receives waste from the small intestine, then the cecum passes it on to the colon.
A fistula is an abnormal passageway between two areas of the digestive tract. An internal fistula occurs between two areas of intestine or an area of intestine and another organ. An external fistula occurs between the intestine and the outside of the body. Both cause abdominal pain and swelling.
Volvulus refers to the twisting of a portion of the intestine around itself. 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.