Incidental focal colonic uptake in studies 18 F-FDG PET/CT.

OBJECTIVES: To assess the frequency of focal colonic uptake as an incidental observation in 18 F-FDG PET/CT studies, and to correlate this finding with histopathological results.

MATERIAL AND METHODS: Out of a total of 3,176 PET/CT studies with 18 F-FDG systematic analysis was carried out on 30 studies in which colonic focal uptake was observed. Patients with known colorectal neoplasia were excluded. The maximum standardised uptake values (SUVm) and the morphological findings provided by the CT were recorded. The studies were reported by a radiologist and a nuclear medicine doctor. The findings were compared with endoscopy and pathology findings.

RESULTS: Of the 30 patients with focal hypermetabolic lesions of the colon (0.94%), 15 were men and 15 were women with ages between 27 and 73 (mean 55 years). The reasons for PET/CT were bronchopulmonary cancer (4), breast cancer (4), tumour of unknown origin (4), melanoma (3), renal carcinoma (3), cervical neoplasia (2), adenocarcinoma of ovary (2), and others (8). Of the 23 colonoscopies performed, 10 patients (43.4%) had malignant lesions, 6 (26.1%) had pre-malignant lesions, and in 7 patients (30.4%) no lesion was identified or was benign. No endoscopy was performed on 7 patients for various reasons (patient refusal to perform the study, advanced oncological disease). An analysis was performed with the SUVm, with no statistically significant differences being found between malignant-premalignant lesions and benign lesions.

CONCLUSIONS: Focal uptake in the colon of 18 F-FDG has clinical relevance, and is mainly associated with morphological lesions in CT. It should be evaluated, as it may be a second tumour or a pre-malignant lesion. It is recommended that all focal uptakes of the colon be evaluated with endoscopy.