Association between diffuse renal uptake of F-FDG and acute kidney injury.

Objective: The aim of this study was to investigate the clinical characteristics of patients with diffuse renal uptake (DRU) of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG), with particular focus on renal function.

Methods: We retrospectively analyzed 40 patients who showed DRU on FDG PET/CT and the same number of matched controls. The clinical features, imaging parameters (the mean SUVmax of the kidneys and the kidney size), and laboratory data including renal function parameters (Cr, the serum creatinine level; estimated glomerular filtration ratio (eGFR); Cr-ratio, Cr divided by the baseline; max-Cr-ratio, the maximum serum creatinine level within 30 days divided by the baseline) and C-reactive protein (CRP) were compared between the two groups. In the DRU group, follow-up FDG PET/CT scans were additionally evaluated to determine the presence of DRU.

Results: No significant differences were observed in the clinical features except for antibiotic administration, Cr, and eGFR. Significantly more patients underwent antibiotic administration within 30 days in the DRU group (p = 0.002). The mean SUVmax of the kidneys was significantly higher (p < 0.001) and the kidney size was significantly larger in the DRU group (p = 0.003). Cr-ratio and max-Cr-ratio were significantly higher in the DRU group (p = 0.005 and p < 0.001, respectively). CRP was significantly higher in the DRU group (p < 0.001). Eighteen of the 40 patients in the DRU group underwent a second FDG PET/CT scan, and 16 of them did not show DRU. Six of the 18 patients showed acute kidney injury (AKI, i.e., Cr-ratio ≥ 1.5) at the time of the initial scan and recovered before the second scan. None of the six patients showed DRU on the second scan.

Conclusion: DRU indicates the presence of AKI, could be a reversible finding, and may disappear as renal function improves.