The colon is divided into three parts: the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The colon, which has the function of digesting food, is M-shaped in the human body and is fixed in the posterior abdominal wall to enclose the small intestine. The abdominal pain of colitis is vague or colicky, accompanied by loss of appetite, nausea and vomiting, diarrhea, bloating, and in severe cases, pus and blood. Mild colitis is asymptomatic or mild, and can improve with bowel movements, and patients can take anti-inflammatory drugs to relieve it. Severe colitis can have severe pain that spreads from the left lower abdomen to the whole abdomen, and can be followed by recurrent episodes of weakness.