Clinical Significance of Incidental Colonic Focal Lesions Detected by FDG PET/CT

Objectives The aim of the study were: (i) to evaluate the focal incidental colorectal uptake of 18F-fluorodeoxyglucose (FDG) and to correlate it with colonoscopy and histological findings; (ii) to evaluate the relationship between the presence ⁄ absence of neoplastic disease and clinical data and the anatomical site of FDG uptake; and (iii) to compare our results with those reported for incidental colorectal uptake of FDG in the literature.

Methods The database of 6500 patients referred for FDG positron emission tomography ⁄ computed tomography (PET-CT) to our institution from January 2010 to December 2014 were retrospectively reviewed for incidental colorectal uptake of FDG. Lesions which appeared neoplastic on colonoscopy were confirmed with histopathology obtained after biopsy or surgery. Colonoscopy and pathology findings were considered as gold standard.

Results Incidental colorectal uptake of FDG was seen in 102 (1.5%) patients, of whom 44 (0.6%) had focal uptake; 35 out of these 44 patients underwent colonoscopy, which showed malignant tumours in 8 (22.8%), premalignant lesions in 13 (37.1%), non-neoplastic lesions in seven (20%) and lesions not confirmed by colonoscopy in 7 (20%). Our data agreed with previously published data. Statistical analysis did not show any significant relationship between the presence ⁄ absence of neoplastic disease and patient sex or age, type of primary disease and anatomical site of FDG uptake.

Conclusions Focal incidental colorectal uptake of FDG is observed in 1.5% of PET ⁄ CT studies and carries a high risk of neoplastic disease. İt allows an accurate localization of the lesions and justifies a colonoscopy to detect (pre-)malignant lesions. PET/CT is a useful tool to differentiate pathologic from physiologic FDG uptake.