18F-FDG uptake in the normal appendix in adults: PET/CT evaluation

Objective This study aimed to determine the level of 18 F fluorodeoxyglucose ( 18 F-FDG) activity in the normal adult appendix using positron emission tomography/computed tomography (PET/CT). Materials and methods We performed a retrospective review of PET/CT images using 18 F-FDG in 563 consecutive asymptomatic adult patients without appendiceal pathology. We excluded 257 patients for an undetected or obscured appendix and three patients for appendicitis found on CT imaging. FDG uptake in the appendix was qualitatively and quantitatively assessed. The maximum standardized uptake value (SUV max ) was calculated for quantitative analysis with SUV max of the normal liver for comparison. A total of 303 patients (200 males, 103 females, mean age of 66 years) were included in this study. Medical charts and histories were evaluated for patients who showed positive FDG accumulation. Pearson’s correlations between appendiceal SUV max and age, body mass index, and blood glucose levels were analyzed. Results The mean appendiceal SUV max was 1.14 (range 0.52–5.12) with an appendix-to-liver SUV max ratio of 0.34 (range 0.06–1.28). Three patients qualitatively showed a positive FDG accumulation with appendiceal SUV max greater than 3.00. There were no correlations between appendiceal SUV max and age, body mass index, or blood glucose levels. Conclusions FDG in the normal adult appendix shows a low activity level and is lower compared with normal liver. However, the normal appendix can rarely show high FDG accumulation. In such cases, differentiation from appendiceal pathology solely by PET/CT images would be difficult.