If the anus feels painful with gas and arch, mainly consider the following reasons: First, caused by internal hemorrhoids, because internal hemorrhoids occur above the dentate line of the anal canal, when internal hemorrhoids have obvious vascular varices or edema of the hemorrhoid nucleus, seriously blocking the anus, it will lead to obvious swelling and painful sensations in the anal area, and impede the discharge of gas in the intestine, causing patients to have painful anus with gas discharge and arch The symptom of the pain. Second, perianal abscess, perianal abscess is the result of the spread of anal gland infection to the skin around the anus, and easy to form a special fistula around the anus, which leads to the leakage of pus and gas from the fistula, causing anal distension and pain. Thirdly, some rectal tumors cause, if the rectum internal tumor, easily lead to intestinal obstruction, which will prevent the normal exhaustion and defecation of the anus, causing anal distension and pain.