PET/CT colonography: a novel non-invasive technique for assessment of extent and activity of ulcerative colitis

Extent of involvement and activity of ulcerative colitis (UC) is best evaluated by colonoscopy. Colonoscopy however carries risk during acute exacerbation. We investigated the utility of PET/CT colonography for assessment of extent and activity of UC. Within a 1-week window, 15 patients with mild to moderately active UC underwent colonoscopy and PET/CT colonography 60 min after injection of 10 mCi of F-18-fluorodeoxyglucose (FDG). PET activity score based on the amount of FDG uptake and endoscopic mucosal activity in seven colonic segments of each patient was recorded. The mean maximum standardized uptake value (SUVmax) of seven segments was compared with activity in liver. A PET activity grade of 0, 1, 2 or 3 was assigned to each region depending upon their SUVmax ratio (colon segment to liver). The extent of disease was left-sided colitis in five and pancolitis in ten. The mean Ulcerative Colitis Disease Activity Index (UCDAI) was 7.6. The number of segments involved as per colonoscopic evaluation and PET/CT colonography was 67 and 66, respectively. There was a good correlation for extent evaluation between the two modalities (kappa 55.3%, p = 0.02). One patient had grade 0 PET activity, nine had grade 2 and five had grade 3 PET activity. In six patients, there was one to one correlation between PET activity grades with that of endoscopic grade. One patient showed activity in the sacroiliac joint suggesting active sacroiliitis. PET/CT colonography is a novel non-invasive technique for the assessment of extent and activity of the disease in patients with UC.