The incidental discovery of colonic polyps, colonic malignancy, diverticulitis and inflammation during PET scanning is well described.
This study is a retrospective review of the incidence and follow up of incidental focal FDG uptake in the colon detected during routine PET scanning. PET scan reports over 12 months were reviewed for the reporting of incidental colonic uptake and then clinical follow up performed in available patient records for the incidence of further colonic investigation and results.
In 2008, 1985 PET scans were reported at the Royal Adelaide Hospital for the staging and detection of malignancy. Review of the results show that incidental focal colonic uptake was seen in 27 cases, (11 female aged 56-83 years). Follow up colonoscopy was performed in 8 cases and in 4 cases showed tubulovillous adenomas, 7-9 mm in size, in the region of abnormal FDG uptake, 1 had diverticulae and another focal inflammation. Two colonoscopies revealed no abnormality (25% false negative rate). One patient with Head and Neck cancer did not have colonoscopy but the colonic lesion resolved on a post therapy PET scan. Of the 18 cases that did not have colonoscopic follow up 5 were reported on the PET scan to have diffuse probably physiological caecal activity but 13 had focal lesions in the large bowel. Although incidental colonic lesions were detected in only 1.3% of studies, of those having colonoscopy 75 % had significant findings.