Anal swelling and wanting to have a bowel movement and stomach pain may be caused by anal and intestinal inflammation, perianal abscess, rectal cancer and other reasons. 1. Anal and intestinal inflammation: such as proctitis, due to the stimulation of inflammation, the intestinal mucosa is congested and edematous, which can cause anal distension and pain on the left side of the abdomen. 2. Perianal abscess: the loose fat connective tissue of rectal-anal tube and the surrounding interstitial space is infected and forms abscess, the inflammatory redness, swelling, heat and pain can cause anal swelling and stomach pain. 3. Rectal cancer: Cancer growth stimulates and oppresses the intestinal tract, accompanied by ulceration, erosion, infection, etc., which can cause anal swelling and stomach pain. It is recommended that patients should go to the hospital in time for consultation to clarify the cause of the disease and carry out standardized treatment under the doctor’s guidance to avoid delaying the condition.