The pain in the stomach and anal swelling may be caused by rectal inflammation, hemorrhoids, etc. In a broad sense, rectal inflammation refers to the inflammation that occurs in the rectal area, the milder the inflammation of the rectal mucosa, the more severe the involvement of the submucosa, muscle layer, and even the tissue around the rectum. The symptoms of constipation alternate. In addition, men with prostatitis and women with pelvic inflammatory disease may also experience pain in the lower abdomen along with anal cramping.