Incidental focal colonic lesions found on 18Fluorodeoxyglucose positron emission tomography/computed tomography scan: further support for a national guideline on definitive management

Aim  18Fluorodeoxyglucose (18FDG) positron emission tomography/computed tomography (PET/CT) is an established part of staging in a wide variety of malignancies. Incidental abnormal uptake of 18FDG of unknown significance is frequently encountered. Therefore, we investigated patients with abnormal colonic uptake of 18FDG, determined by PET/CT images, using colonoscopy. Method  The radiology reports of all patients referred to a tertiary referral centre for a PET/CT scan were reviewed retrospectively. Patients with abnormal colonic uptake of 18FDG were identified and the PET/CT findings were correlated with colonoscopic findings. Results  Of 555 consecutive patients identified over a 26-month period, 53 had abnormal colonic uptake of 18FDG, as determined by PET/CT images. Twenty-nine were not investigated following discussion in a specialist multidisciplinary (MDT) meeting, according to local protocol. Twenty out of 24 patients investigated by endoscopy had a colonic lesion correlating to the site identified on the PET/CT image: 16 patients had tubulovillous adenomas (nine of which were > 10 mm), two had invasive adenocarcinomas, two had diverticular disease and one had collagenous colitis; no colonic lesion was detected in three. These findings were incidental and not related to the primary diagnosis for which the scan was being performed. Accordingly, a positive predictive value of 83% is associated with the finding of abnormal uptake of 18FDG on PET/CT images. Conclusion  Incidental abnormal colonic uptake of 18FDG, determined by a PET/CT scan requires definitive colonic investigation in patients suitable for further treatment because significant colonic pathology is frequently identified. The benefit of this approach should be discussed in specialist MDT meetings and tailored to each patient; however, national guidelines for management are required.