Portal and hepatic vein flow-velocity profiles were examined by pulsed Doppler in 66 patients with tricuspid regurgitation (color Doppler grading: severe: 37, moderate: 18; mild: 11) and 20 normal subjects to determine if portal vein flow analysis is useful in the evaluation of tricuspid regurgitation. Portal vein flow was defined as one of the following categories: subcontinuous (dependent on respiration), pulsatile systolic (not inverted), inverted after systole, and continuous (not dependent on respiration). An index of portal vein flow pulsatility was also calculated. Standard classification of hepatic vein flow pattern was performed. Portal vein flow was pulsatile in 20% of normals subjects, and in 27.3% 44.5% and 51.3% of patients with respectively mild, moderate and severe tricuspid regurgitation; portal vein flow was inverted after systole in further 32.4% of patients with severe tricuspid regurgitation. Portal vein pulsatility index correlated with color Doppler grading of tricuspid regurgitation (r:0.63; p < 0.001) and right ventricle-atrium pressure gradient (r:0.39; p < 0.01). However, when compared with hepatic vein flow, both sensitivity and specificity of quantitative portal vein flow analysis was less reliable in diagnosing and grading tricuspid regurgitation. In particular, in patients with severe tricuspid regurgitation, the portal vein flow pattern was quite variable (pulsatile in 19 patients, inverted after systole in 12, and continuous in six). Liver biopsy was performed in nine patients, four of them with severe tricuspid regurgitation and continuous portal vein flow. Histology showed severe liver fibrosis in all four.(ABSTRACT TRUNCATED AT 250 WORDS)