Changes in portal blood flow following acute exercise in liver transplant recipients

The aim of this study was to investigate the impact of acute exercise on portal blood flow in liver transplant recipients compared to healthy subjects since it is known that transplantation produces a denervated liver and intrahepatic vascular tube. Twelve liver transplantation recipients and 12 age-gender-matched subjects were included in the study. All patients were at least 6 months posttransplant and in stable condition with normal liver biochemistry values. Measurements of portal vein blood flow were performed before starting exercise and immediately after its completion. The exercise program consisted of 40 minutes of treadmill running or walking with at least 20 minutes at 75% of maximal heart rate. The portal vein flow in the controls decreased by 74% after 40 minutes of exercise (absolute flow, 730 +/- 160 to 190 +/- 35 mL x min). Among the liver transplant group, following exercise the portal vein cross-sectional area also decreased to a lesser degree. However, statistical significance was only reached for blood flow. In this group the absolute flow was 940 +/- 165 mL x min at rest and 460 +/- 135 mL x min at 40 minutes (P <.01 by ANOVA). This flow pattern was more resistant to exercise, thereby protecting the liver from an exercise-induced low-flow state. Exercise and physical conditioning should be recommended without hesitation for liver transplant recipients.