Unexpected FDG-PET uptake in the gastrointestinal tract:Endoscopic and histopathological correlations

AIM:To investigate the nature and significance of unexpected positron emission tomography with fluorodeoxyglucose(FDG-PET)uptake within the gastrointestinal tract(GIT).METHODS:Patients with unexpected FDG-PET findings in the GIT were evaluated.All patients had a previous confirmed malignancy,either solid or lymphoproliferative.The radiologic reports were performed by experienced radiologists with an exclusive PET expertise.Endoscopy,i.e.,esophagogastroduodenoscopy(EGD)and colonoscopy,and histopathological evaluation of all findings was performed in all patients in accordance to the FDG-PET results.The findings from each of these modalities were compared to each other.Both clinically significant and insignificant findings were assessed.RESULTS:Seventy-two patients were endoscopically evaluated.Twenty-seven patients(37.5%)had primarily a lymphoproliferative tumor and 45(62.5%)had solid tumors.In 50 patients(69.4%)the endoscopic examination revealed lesions in the same anatomical areas as the FDG-PET findings.Among these 50 patients,malignant and premalignant lesions i.e.,adenomatous polyps were found in 16(32%)and 9(18%)patients,respectively.Inflammation was noted in an additional20 patients(40%).Compared to primary solid tumors,a background of primary lymphoproliferative malignancy was more likely to reveal an additional primary malignancy(15.6%vs 33.3%,respectively,P<0.01).EGD compared to colonoscopy,revealed altogether 11(25.6%)new malignancies compared to 5(17.2%),respectively,P=0.12.No GIT clinically significant findings were overseen by the FDG-PET.CONCLUSION:Unexpected FDG uptake in the GIT is commonly encountered and may contain significant findings.Endoscopy evaluation is justified in order to detect these additional findings.