PET/contrast-enhanced CT detection of incidental colonic 18F-FDG uptake: Correlation with uptake patterns combined with CT findings and histopathology

Objectives To evaluate the incidental colonic FDG uptake in the patients without colorectal carcinoma who underwent PET/contrast-enhanced CT for other purpose, FDG uptake patterns combined with contrast-enhanced CT findings are compared with histopathology.

Methods The files of 8,855 patients referred for 18F-FDG PET/contrast-enhanced CT were retrospectively reviewed. The patients showing incidental FDG uptake without colorectal cancer history were selected. Limited subjects who underwent FDG PET/contrast-enhanced CT and colonoscopy within 6 months were evaluated to confirm histopathology. Subgroups were classified by focal or diffuse uptake, and these groups were analyzed by histopathologic type and contrast-enhanced CT findings.

Results Fifty nine of the subjects demonstrated 43 focal uptake and 16 diffuse uptake in colon incidentally. Contrast-enhanced CT findings revealed the mass, wall enhancement or wall thickening in the 31 cases and histopathologic confirmation through follow up colonoscopy determined 11 adenocarcinomas, 16 adenomas, and 4 benigns. Whereas, in the no mass lesion on the contrast-enhanced CT, histopathologic results showed that no adenocarcinoma, 7 adenoma and 5 benign. However, in sixteen cases showing diffuse colon, 8 cases showing mass lesions on the contrast-enhanced CT was classified by 2 adenocarcinomas, 1 adenoma, and 5 benigns, and 8 cases without mass lesion was divided by 1 adenocarcinoma, 4 adenomas, and 3 benigns.

Conclusions Incidental FDG uptake evaluation is very important in most patients. Mass lesions detected by contrast-enhanced CT represented cancerous lesion rather than benign lesions. These findings should help to guide the follow up procedure and treatment in the patients with incidental colon FDG uptake