Objective To evaluate hepatic functional reserve and investigate the clinical value through measuring hepatic functional blood flow by D-sorbitol clearance rate and liver volume changes with CT. Methods Ninety-two patients with portal hypertension due to posthepatic cirrhosis were investigated (cirrhosis group). Twenty healthy volunteers were used as control group. D-sorbitol was infused intravenously at a steady rate. Blood and urine were collected and recorded once before infusion and at 120, 150 and 180 min after infusion, and their concentrations of D-sorbitol were examined by enzyme spectrophotometry. From pharmacokinetic equations, hepatic clearance rate of D-sorbitol (CLH) was calculated. Total hepatic blood flow (QTOTAL) was measured by Doppler sonography, intrahepatic shunt rate (RINS) was obtained. The liver volume change rate was obtained in patients with cirrhosis through the abdominal CT scan. The relations among the indicators, Child classification and postoperative complications were studied. Results After D-sorbitol was infused intravenously for 120 min, the plasma concentration was at the steady state. The plasma concentration was (0.189±0.05) mmol/L in control group and (0.358±0.06) mmol/L in cirrhosis group (Plt;0.01). CLH was (1 248.3±210.5) ml/min in control group and (812.7±112.4) ml/min in cirrhosis group (Plt;0.01). Although QTOTAL in cirrhosis group was declined, compared with the control group 〔(1 280.6±131.4) ml/min vs. (1 362.4±126.9) ml/min〕, Pgt;0.05, while RINS increased markedly 〔(36.54±10.65)% vs. (8.37±3.32)%, Plt;0.01〕. In cirrhosis group, the mean liver volume of Child A, B and C patients were (1 057±249) cm3, (851±148) cm3 and (663±77) cm3 respectively. There were significant differences among the mean liver volume (Plt;0.05). The liver volume was significantly smaller in Child B and C patients than that in Child A (Plt;0.05, Plt;0.01). When CLH was less than 600 ml/min, and liver volume decreased by more than 40%, postoperative complications increased significantly. CLH and the liver volume change rate were not in absolutely good accordance with Child classification. Conclusion The hepatic clearance of D-sorbitol and the quantitative determination of the liver volume with CT can be an objective evaluation of the liver metabolism of the inherent capacity and the hepatic functional blood flow changes. It contributes to the correct understanding of the hepatic functional reserve and lay the foundation for determining a reasonable treatment plan, surgical methods and time.