Hepatic and splenic 18F-FDG blood clearance rates (Ki) in hepatic steatosis and diabetes mellitus

Aim The study aim was to investigate the relationships of blood glucose level (BGL) with hepatic and splenic blood FDG clearances (Ki) in patients with diabetes mellitus (DM) and/or hepatic steatosis (HS). Methods This was a retrospective study of 238 patients, including 92 with type 2 DM (DM2) and 11 with type 1 DM (DM1), having routine whole body FDG PET/CT. Patients with lymphoma were excluded. Patients were divided into the following groups: HS-DM-, HS-DM2+, HS+DM-, HS+DM2+ and 2 DM1 groups (hypoglycaemic and hyperglycaemic). ROI were placed over liver and spleen for measurement of SUVmax, and left ventricular cavity (LV) for measurement of SUVmean. Tissue SUVmax was divided by LV SUVmean. This division, giving Z, eliminates bias from the whole body metric used to calculate SUV and renders SUVmax a closer surrogate of Ki. HS was diagnosed when hepatic unenhanced CT was <= 40 HU. Results In all patients, individual hepatic Z and individual splenic Z correlated significantly with individual BGL. Highest mean hepatic Z and highest mean BGL were recorded in HS+ DM2+ group and lowest in hypoglycaemic DM1 group. Patients with DM1 and hyperglycaemia showed low hepatic Z in relation to BGL. Hepatic and splenic Z correlated inversely with CT density in patients without DM but not in those with DM2. Conclusion As BGL increases, hepatocyte glucokinase is up-regulated. This includes patients with HS and DM2 but not DM1. We speculate that in HS and DM2, up-regulation results from insulin resistance and hyperinsulinaemia. The data also support a hepato-splenic metabolic axis.