Background: Positron emission tomography (PET) using 18-fluorodeoxyglucose (18-FDG) is a noninvasive, functional imaging modality most often used to assess cancer. The aim of this study was to perform PET/computed tomography (CT) on patients with quiescent ulcerative colitis (UC) to understand the limits of this technology for assessing inflammatory activity.
Methods: We identified patients diagnosed with UC in a strictly defined remission state. PET/CT was performed in standard fashion, using approximately 10 mCi of 18-FDG with a 60-minute uptake delay. Uptake in each of 4 colonic segments (recto-sigmoid [r-s], descending, transverse, and ascending), and distal small bowel were scored on a 3-point scale (0 = no uptake or uptake <or=liver; 1 = uptake somewhat >liver; 2 = uptake much greater than liver).
Results: Ten patients participated in this study, 6 male. Eight had pancolitis, 1 had extensive colitis, and 1 had procto-sigmoiditis, with a median disease duration was 32 years. A PET scan was performed mean 37 days after endoscopy. Six patients had no increased 18-FDG uptake, 3 had increased uptake in the r-s region, 1 patient with r-s uptake also had ascending colon uptake, and 1 had ileal uptake with no colonic signal.
Conclusions: In this study, PET demonstrated inflammatory activity in the colon despite negative endoscopic, histologic, and symptom assessment. This has important implications in the understanding of UC disease quiescence. Further exploration of this highly sensitive modality should be performed.