The indications of colonoscopy in a patient with ulcerative colitis are all of the following except

.Colonoscopy is of value to rule out carcinoma. It is easiest and most direct method in establishing the diagnosis. Colonoscopy shows mucosal nodules or ulcers; caecal and ileal strictures; deformed ileo caecal valve; mucosal oedema and pseudopolyps and occasionally diffuse colitis. Biopsy can be taken to confirm the diagnosis Contraindication-Acute ulcerative colitis. ref:SRB&;S manual of surgery,ed 3,pg no 514