Effect of oral hypotonic water and isotonic saline on physiological intestinal 18F-FDG uptake in PET/CT imaging.

PURPOSE: Hydration of patients before the PET/CT examination may lead to non-specific FDG accumulation in the intestine. This study aims to explore the influence of isotonic saline and hypotonic water on physiologic intestinal 18F-FDG uptake in PET/CT imaging. METHODS: 185 patients were included, 82 patients were randomized to receive oral administration of isotonic saline and 103 patients received oral administration of hypotonic water before examination. About 32 patients in the isotonic group and 19 patients in hypotonic group underwent repeated PET/CT with pre-administration of hypotonic water, and the intra-individual comparative analysis was performed for the first and second examinations. Segmental uptake patterns were documented and volumetric regions of interest were delineated. The SUVmax of intestinal segment and the SUVmean of liver were recorded. RESULTS: No significant differences existed in baseline characteristics between the two groups. The isotonic group demonstrated lower physiological uptake incidence and target-to-background ratio (TBR) in all segments except jejunum and ascending colon (p < 0.05). Physiological uptake incidence in jejunum showed no intergroup difference, whereas the TBR of isotonic group showed lower tendency. Notably, the isotonic group exhibited higher physiological uptake incidence (p < 0.001) in the ascending colon, though no significant difference existed in TBR between two groups. These results were similar in intra-individual comparative analysis of the first and second examinations. Moreover, constipation was positively associated with FDG uptake in the ileum, diarrhea was positively associated with FDG uptake in the transverse colon, ascending colon and rectum. Bone tumors and gynecological tumors were positively correlated with FDG uptake in the ascending colon and transverse colon. BMI was negatively correlated with FDG uptake in the duodenum, ileum, jejunum, and sigmoid colon. CONCLUSION: Pre-administration of isotonic saline resulted in lower physiologic 18F-FDG uptake in different intestine segments (except ascending colon), which is helpful for accurate assessment of gastrointestinal diseases.