LAUSR

Hokoma et al. describes the dragon sign in ulcerative colitis, where there is a slightly tortuous, thick-walled sigmoid colon with hyperaemic mesenteric vessels. Hokoma et al. also coined the appearance of this radiological pattern as ‘the reverse question mark sign’. The gold standard for assessing ulcerative colitis is colonoscopy. CT has a reported sensitivity of 74%. Loss of haustration, rigid bowel wall and bowel wall thickening are moderately correlated with the severity of ulcerative colitis. Imaging plays a greater role in assessing complications, such as strictures and perforation. Importantly, an abdominal x-ray is the standard first line investigation for diagnosing toxic megacolon. This is defined as the mid transverse colon having a diameter of greater than 5.5 cm.