Portal pressure and portal-systemic collateral circulation after orthotopic liver transplantation have not been investigated. We studied systemic and splanchnic hemodynamics in 17 patients with cirrhosis before and 205 +/- 146 days after orthotopic liver transplantation. Among the 17 orthotopic liver transplantation patients, 12 had undergone hemodynamic study in the 6 mo before orthotopic liver transplantation. Controls were 50 patients with normal liver architecture. Cardiac index remained elevated in orthotopic liver transplantation patients compared with controls (3.6 +/- 0.9 vs 3.1 +/- 0.4 L/min.m2; p < 0.05). Azygos blood flow, which was elevated before orthotopic liver transplantation (585 +/- 402 ml/min), remained elevated after orthotopic liver transplantation (553 +/- 343 ml/min). In transplant patients, hepatic blood flow was higher than it was in controls (2.26 +/- 0.86 vs. 1.38 +/- 0.57 L/min; p < 0.05). Elevated hepatic blood flow correlated with cardiac index (r = 0.647, p < 0.025). In patients with normal graft function, hepatic venous pressure gradient was normal (2 +/- 1 mm Hg). In a patient with acute rejection, a sharp elevation in the hepatic venous pressure gradient was observed; it returned to normal 45 days after treatment. We conclude that despite normal portal pressure, portal-systemic collateral blood flow remains elevated after orthotopic liver transplantation. Possibly because of persistent collateral circulation, which may keep portal tributary blood flow elevated, hepatic blood flow is increased after orthotopic liver transplantation. Elevated splanchnic blood flow, in turn, contributes to the high cardiac index in liver recipients. Finally, a sharp elevation in portal pressure, which may be observed during acute rejection and subsides after treatment, merits further study.