Crohn’s disease: Due to fibrosis and scar formation at the site of the lesion, intestinal stricture may occur in 25-30% of patients. In those cases where clonorchiasis involves the rectum, the lesion is mostly above the dentate line and, in a few cases, in the anal canal. This stricture is mostly tubular and gradually migrates toward the normal intestine, unlike congenital and injurious circumferential strictures. If anorectal strictures are accompanied by abscesses or fistulas, they should be given high priority for further follow-up. Intestinal tuberculosis: In patients with proliferative intestinal tuberculosis, the intestinal canal is narrowed due to extreme proliferation of tuberculous granulomas and formation of masses. Ulcerative intestinal TB, if adherent to the mucosa, may pull or compress the intestinal canal; if the ulcer heals, fibrous hyperplasia and scar contracture may narrow the intestinal canal. However, most of these patients have a previous history of tuberculosis or other extraintestinal tuberculosis, and have systemic manifestations of tuberculosis toxemia, such as hot flashes, night sweats, and emaciation. Anti-TB treatment is effective. Schistosomiasis: In the late stage of chronic schistosomiasis, the rectal wall can form masses of different sizes due to egg deposition, granuloma formation and fibroplasia, some of which are fused into clusters, hard and uneven, easily confused with tumors. These patients have a history of exposure to epidemic water, and local mucosal biopsies of schistosome eggs found in the feces can confirm the diagnosis. Rectal tumors: those with strictures caused by tumors generally have a short history, progressive aggravation, and a history of dark red bloody stools or pus-blood stools. Early stage rectal cancer is mostly asymptomatic and occasionally has a history of bloody stool, so it is difficult to detect. For those who have formed stenosis, they are already in advanced stage of disease. If the location is low, the lump can be palpated by finger diagnosis, irregular, uneven, hard, painful, and stained with blood on the finger sleeve. If the location is high, sigmoidoscopy or fiberoptic examination should be performed, and a rectal mass with an intact intestinal mucosa should be seen endoscopically. Biopsy can confirm the diagnosis. Stenosis after low anastomosis or other anal preservation surgery for rectal cancer, multiple biopsies must be performed to exclude the possibility of local recurrence. Venereal lymphogranuloma: Patients are predominantly female, with a history of exposure to venereal disease and lesions mainly in the genital and inguinal lymph nodes, which are viral infections. Difficult bowel movements are often accompanied by anal irritation. Mucopurulent and bloody stools can be complicated by anal fistula. The stenosis is mostly located above the dentate line, with a hard and smooth surface, pale color, and an open anal opening. Frye test, complement binding test and viral test are positive. Chronic ulcerative proctitis: Multiple ulcers in the rectum can form extensive granulomas and extensive scarring during the healing process resulting in rectal strictures. Such patients often have a history of chronic recurrent colitis.