Clinical significance of incidental 18 FDG PET uptake in the gastrointestinal tract: a retrospective cohort study.

Abstract

Incidental gastrointestinal tract (GIT) uptake is found in up to 6.3% of patients undergoing positron emission tomography (PET). This may be physiologic or pathologic and requires endoscopic assessment. To determine the diagnostic yield of endoscopy in this setting and characterise PET avidity as a predictor of clinically significant findings. We retrospectively reviewed all consecutive patients undergoing upper endoscopy or colonoscopy for incidental 18 FDG PET positivity in the GIT. A total of 255 patients (62% male, median age 67 years) underwent colonoscopy or sigmoidoscopy for 276 separate areas of PET avidity in the colon. Malignancy was found in 44 cases (16%), and a significant polyp was found in an additional 103 cases (37%). Neoplastic change was found more often in the case of intense compared with non-intense PET avidity (odds ratio (OR) 3.40, 95% confidence interval (CI) 1.95-5.93, P < 0.001), and in focal compared with diffuse uptake (OR 5.97, 95% CI 2.9-12.2, P < 0.001). Upper GIT endoscopy was performed in 75 patients (46 male, median age 63 years) for 77 isolated areas with PET avidity. Malignancy was found in 16 cases (21%), and all were new primary lesions. Numerically, malignant findings were more common in intense (29.7%) than non-intense (12.5%) PET avidity (OR 2.96, 95%, CI 0.92-9.57, P = 0.069). Both focal and intense colonic 18 FDG uptake correlate strongly with a high-risk polyp or malignant lesion. Up to 21% of all gastroscopies performed for evaluation of incidental PET uptake diagnosed a new primary malignancy. These referrals need appropriate triaging and timely endoscopic assessment.