The inflammatory disease of the intestinal tract, most commonly ulcerative colitis, is not the only cause of distension in the lower left abdomen, and is more common in young people. Patients may present with abdominal distension and vague pain, as well as blood in the stool or mucopurulent stool, which may gradually resolve after the stool, but the history of the disease is usually long, and repeated attacks may also induce the formation of anemia. Colonoscopy can reveal local ulcer formation, congestion and edema in the mucosa of the intestinal canal. The disease mainly occurs in the rectum and sigmoid colon, so the patient will have significant distension and pain in the left lower abdomen. Oral immunomodulatory drugs should be taken, and regular follow-up examinations, mainly colonoscopy, should be performed.