Incidental finding of focal FDG uptake in the bowel during PET/CT: CT features and correlation with histopathologic results

OBJECTIVE. The purpose of this study was to identify and characterize the clinically significant lesions associated with incidental detection of focal uptake of 18F-FDG in the bowel at PET/CT. MATERIALS AND METHODS. Among 2,250 consecutively registered patients with various nongastrointestinal malignant diseases who underwent FDG PET/CT as part of their care, patients with the incidental finding of focal bowel uptake of FDG were included in the study. All patients underwent an endoscopic or surgical procedure for characterization of the lesions. The location, intensity of uptake, and appearance of the lesions on PET/CT images were recorded and compared with the endoscopic and surgical pathologic results. RESULTS. Twenty-one of 25 foci of intense uptake in the bowel were associated with endoscopic or surgical abnormalities (positive predictive value, 84%). Seven lesions were malignant (two primary, five secondary); 13 were premalignant (nine tubovillous adenoma, four tubular adenoma); and one lesion was benign (hyperplastic polyp). Eleven lesions detected with endoscopy were not FDG avid, and all 11 were smaller than 1 cm in diameter. There was no statistically significant difference in the maximum standardized uptake values of the benign and malignant lesions. CONCLUSION. The incidental finding of focal FDG uptake in the bowel justifies further investigation of these foci and should not be dismissed as physiologic uptake. Premalignant lesions, such as adenoma, are often found, and early treatment may prevent the development of carcinoma.