To understand hepatic vein (HV) and portal vein (PV) duplex waveforms and their normal and respiratory variations, HV and PV duplex sonography with simultaneous electrocardiograpy was performed on 11 volunteers. Absolute velocities of the waveforms' components and their ratios were determined at mid· in· spiration, full inspiration, full expiration, and Valsalva maneuver. The normal HV waveform was variable in shape and component velocities and ratios but essentially consisted sequentially of (1) an antegrade systolic wave resulting from movement of the tricuspid annu• lus toward the cardiac apex and occurring shortly after QRS; (2) a retrograde v-wave resulting from atrial overfilling and occurring immediately after the T · wave; (3) an antegrade diastolic wave resulting from opening of the tricuspid valve and occurring shortly after the T-wave; and (4) a retrograde a· wave resulting from N ormal hepatic vein (HV) and portal vein (PV) duplex Doppler waveforms show cyclic phasicity that is more prominent in the HV. The nature of these waveforms is not well understood by most radiologists, and it is unclear even in the sono~ graphic literature whether this phasicity is cardiac or respiratory in origin.,_, It also has been shown that tricuspid regurgitation and diffuse hepatocellular disease can affect the shape of these duplex Doppler atrial contraction and occurring immediately after the P-wave. The ratio of the maximum systolic velocity to maximum diastolic velocity varied from 1.0 to 2.8 (mean 1.4). Systolic-to-diastolic ratio decreased during inspiration but was always greater than 0.6 and increased during expiration. The Valsalva maneuver di~ minished waveform pulsatility. PV waveforms were more triphasic than biphasic but less pulsatile, flow was totally antegrade, and respiratory changes were less remarkable than HV waveforms. All normal HV and most normal PV waveforms showed multiphasic· ity that corresponded to cyclic cardiac changes. The shapes of these waveforms were variable and were modified by respiratory movements. KEY WORDS: Liver, duplex; Hepatic and portal veins, Doppler flow varia· tions.waveforms by changing the velocities of their various components and their velocity ratios.M Because liver dysfunction can be the initial manifestation of some of these diseases, radiologists are in a position to make a specific diagnosis from the changes that occur in the shape and velocity ratios of these waveforms. However, they must first be familiar with the various components of the normal waveforms, their ratios, and their normal and respiratory variations.The purposes of this study were (1) to illustrate the Received October 2 .• 1991; from the Department of Radiology, nature of the various components of the normal HV