Colonic Uptake Patterns of F-18-FDG PET in Asymptomatic Adults: Comparison with Colonoscopic Findings

Pai, Moonsun; Cho, Yoo Kyung; Jung, Sung Ae; Shim, Ki Nam; Lee, Hong Soo

Abstract

PURPOSE
Physiologic intestinal FDG uptake is frequently observed in asymptomatic individuals for cancer screening FDG PET. Colonic FDG accumulation is a well-known confusing findings that interfere true cancer detection or cause false positive. The aim of this study was to evaluate the pattern and intensity of colonic uptake in whole body FDG PET in asymptomatic healthy adults and to correlate them with colonoscopic findings. MATERIALS AND METHODS: We reviewed retrospectively 64 subjects (age: 27-87, M: F = 31: 33 ) who underwent both FDG PET and colonoscopy for cancer screening. FDG uptake patterns were classified as focal, segmental and diffuse. Maximum SUV were measured. The PET results were compared with colonoscopic and histologic findings. RESULTS: In 13 patients FDG bowel uptake was interpreted as focal, in 17 patients as segmental and in 34 patients as diffuse uptake. Six adenomas (17.6%, average diameter =5.0 mm) were found in diffuse pattern, 7 adenomas (41.1%, 5.6 mm) in segmental and 4 adenomas and 1 adenocarcinoma (38.5%, 16.4 mm) in focal uptake pattern. In patients with focal uptake, four were non-adenomatous pathologic lesions (30.8%, 2 intestinal tuberculosis, 2 mucosal ulcer). There is no difference of mean SUV between patients with adenoma and with negative colonoscopic results in each group of intestinal FDG pattern (Diffuse: 1.7 +/- 0.1 vs. 1.9 +/- 0.5, Segmental: 4.8 +/- 3.6 vs. 4.2 +/- 1.2, Focal: 6.5 +/- 4.7 vs. 3.5 +/- 1.3). Large adenomas (> 1 cm) can be detected more in the focal uptake pattern (4 out of 5) rather than in segmental (1 out of 7) or diffuse uptake (none) and had higher SUV (6.3 +/- 4.8) than small adenomas (3.5 +/- 3.0) (statistically insignificant). CONCLUSION: Focal FDG uptake is associated more often with large adenoma and other pathologic findings in colonoscopy. Segmental uptake cannot discriminate presence of adenoma from negative results, while diffuse pattern may have more chance to be normal.