Colonic distention is a common cause of ulcerative colitis (UC), an inflammatory disease of the rectum or colon of unknown origin. It mainly involves the rectum, sigmoid colon and descending colon and is characterized by mucosal congestion, edema, multiple superficial ulcers, advanced wall thickening and luminal narrowing with polyp formation. The disease is characterized by persistent diarrhea, mucus stools, bloody or purulent stools, abdominal pain and urgency, and may be accompanied by extraintestinal manifestations such as fever, anemia, arthritis, skin lesions and liver disease. The onset of the disease is rarely acute, but most of them have a slow onset and a long course, often with recurrent episodes of variable length, also known as chronic non-specific ulcerative colitis. In the early stages, abdominal pain, diarrhea and bloody stools may occur. Abdominal pain of varying degrees is caused by spasm of the colonic muscles, distension of the colon and inflammation stimulating local sensory nerves. Abdominal distension is mostly confined to the left lower abdomen or lower abdomen, with paroxysmal mild pain. When the lesion is severe, it may present as colic. The main symptoms: diarrhea or constipation, the symptoms are mild at the beginning of the disease, there is mucus on the surface of the stool, later the number of bowel movements increases, in severe cases 10-30 times a day, the stool is often mixed with pus and blood and mucus, can be paste-like soft stool. Blood in the stool is a common symptom, mainly due to local ischemia of the colonic mucosa and an increase in the activity of fibrinolysis. It is usually a small amount of blood in the stool, but in severe cases, it can be a large amount of blood in the stool or bloody water-like stool. The abdominal pain is mostly confined to the left lower abdomen or lower abdomen, or may not be present in mild cases, but may increase with the development of the disease and may be relieved after defecation. The posterior urgency is due to inflammatory irritation of the rectum, and there is often sacral discomfort. Indigestion often manifests as anorexia, fullness, belching, epigastric discomfort, nausea, vomiting, etc. Systemic manifestations are seen in patients with acute fulminant severe disease, with fever, water-electrolyte imbalance, vitamin and protein loss, anemia, and weight loss. Signs: pressure pain in the left lower abdomen or the whole abdomen, the descending colon, especially the sigmoid colon, can be felt in the form of a hard tube with pressure pain, sometimes abdominal muscle tension, anal sphincter spasm can be found on anal examination, mucus or bloody mucus secretion in the finger sleeve, and tenderness in the rectum. In some cases, a large liver can be palpated, which is associated with fatty liver. Differential diagnosis: ① chronic bacteriophageal dysentery Often there is a history of acute bacillary dysentery, fecal culture can isolate Bacillus dysenteriae, the positive rate of culture of mucopurulent secretions taken during colonoscopy is high, and antibacterial drug therapy is effective. Chronic amoebic dysentery The lesion mainly invades the right colon, but can also involve the left colon, the colonic ulcer is deeper, the edge is submerged, and the mucosa between the ulcers is mostly normal. Amoebic trophozoites or cysts can be found in the fecal examination, and amoebic trophozoites can be more easily found by colonoscopy by taking the exudate of the ulcer for intestinal examination. Anti-amoebic treatment is effective. Colon cancer is usually seen in middle age or above, and often a mass can be palpated by rectal examination. Colonoscopy and X-ray barium enema examination are valuable for differential diagnosis, and attention must be paid to differentiate it from colon cancer caused by ulcerative colitis. Schistosomiasis: History of exposure to epidemic water, often with hepatosplenomegaly, and positive for schistosome eggs and hatching trichurias on stool examination; mucosal yellow-brown granules on proctoscopy in the acute stage, and schistosome eggs on biopsy of mucosal pressure or histopathological examination. (5) Irritable bowel syndrome with generalized neurosis, mucus but no pus and blood in the stool, only a few white blood cells on microscopic examination, and no evidence of organic lesions on colonoscopy. (6) Other diseases such as intestinal tuberculosis, ischemic colitis, pseudomembranous enteritis, Clostridium difficile enteritis, radiation enteritis, colonic polyposis, and colonic diverticulitis should be differentiated from this disease.