<prompt> Which of the following is the earliest sign of ulcerative colitis on double-contrast barium enema study -Mucosal granularityLoss of haustrationsCollar - button ulcerLead pipe colon  <response>: Earliest radiological change of UC on barium enema is blurring of the mucosal lining and a fine granularity when mucosa is seen enface due to edema.Earliest radiological change of Crohns disease Aphthous lesions Bulls eye or Target lesions. 