OBJECTIVETo investigate the value of water enema (18)F-fluorodexyglucose positron emission tomography and computed tomography((18)F-FDG PET-CT) in incidental finding of hypermetabolism focus in the colon and rectum for differential diagnosis of benign or malignant lesions.

METHODSFrom June 2010 to December 2012 in our hospital, 77 patients were found incidentally with uncertain hypermetabolism focuses in the colon and rectum during PET-CT examination. Water enema (18)F-FDG PET-CT was performed to classify the lesions. According to the pathological examination and clinical follow-up, these cases were divided into malignant disease (including advanced colorectal adenoma), benign adenoma, inflammation and physiological uptake. Radioactive uptake level (SUVmax) and change of water enema imaging (retention index, RI) of hypermetabolism focus were compared between groups.

RESULTOf these 77 cases, 23 were malignant diseases, 16 benign adenoma, 7 inflammation and 31 physiological uptake. The difference of average SUVmax was not statistically significant between benign and malignant lesions as well as physiological uptake(P>0.05). But the difference of RI was statistically significant between neoplastic lesions and inflammation(P<0.05). The accuracy of water enema (18)F-FDG PET-CT in diagnosing non-neoplastic uptake was 100%, and the sensitivity, specificity and accuracy in differentiation of malignancy form benign lesions were 95.6%, 96.3%, and 96.1% respectively.

CONCLUSIONSThe incidental focal colorectal (18)F-FDG uptake in PET-CT may indicate potential colorectal malignant lesions and adenoma. Water enema can effectively differentiate the physiological uptake and predict benign lesions or malignancy in the colon and rectum colorectum with good accuracy.