Hemodynamics and oxygen variables, plasma cytokines, and histological features of a liver tissue sample obtained by transvenous biopsy were evaluated during 65 episodes of acute rejection. The hepatic venous pressure gradient was significantly higher in patients with acute rejection than in those without (5.1+/-0.3 vs. 3.1+/-0.2 mmHg, P<0.01). The increase in pressure gradient was related to the severity of rejection lesions. Hepatic blood flow was significantly lower in patients with than in those without acute graft rejection (1.28+/-0.11 vs. 1.75+/-0.13 L/min, P<0.05). Plasma interleukin-6 levels were significantly increased in patients with acute rejection and positively correlated with pressure gradient values. In patients with acute rejection, a significant decrease in hepatic venous oxygen content (-16%) was associated with a significant increase in hepatic oxygen consumption (+24%), whereas hepatic oxygen transport did not change significantly. In treated patients with a favorable response, the pressure gradient decreased significantly by 46%, but it remained elevated in patients who later developed chronic graft rejection. In conclusion, this study confirms that acute graft rejection may induce an increase in portal pressure, which is related to the severity of rejection lesions. It also shows that acute rejection decreases hepatic blood flow and increases hepatic oxygen consumption. In addition, it suggests that the hepatic venous pressure gradient might be useful to determine the outcome of rejection.