Aim: We assessed the pattern of metabolic activity in the colon of subjects who received oral contrast and had no known or suspected colonic disease.
Methods: Positron emission tomography/computed tomography (PET/CT) with [F-18]-fluorodeoxyglucose was performed in 50 patients with cancer and no known or suspected colonic pathology. Studies with intense focal or segmental colonic activity (in comparison to liver reference activity), which are known to be predictive of colonic pathology were excluded. Retrospectively, colon was divided into cecum, ascending, transverse, descending, and rectosigmoid partitions, and the corresponding volumetric regions of interest were drawn on all relevant CT images. Partitioned colonic maximum standardized uptake values (SUVmax) were compared using Wilcoxon rank-sum test. Frequency of occurrence for the various colonic uptake rank orders was also tabulated.
Results: For colonic partitions, range and median SUVmax, respectively, were in decreasing order: rectosigmoid (1.5-9.9, 2.9), cecum (1.2-6.3, 2.6), ascending (0.7-4.0, 1.8), transverse (0.4-4.1, 1.2), and descending (0.6-3.1, 1.2). The SUVmax at different colonic partitions were significantly different from each other (P<0.001), except for the SUVmax between descending and transverse colonic segments (P=0.77). Combining the latter segments, the uptake rank order of "rectosigmoid>cecum>ascending" was demonstrated in 50% and "cecum>rectosigmoid>ascending" in 30% of subjects.
Conclusions: Rectosigmoid and cecum tend to demonstrate higher metabolism than other colonic segments in the majority subjects who receive oral contrast during [F-18]-fluorodeoxyglucose positron emission tomography/CT and have no known or suspected colonic pathology.