Flow measurement using duplex Doppler ultrasound: haemodynamic changes in patients with colorectal liver metastases.

Duplex Doppler ultrasound has been used to make measurements of liver blood flow. The relationship between time average velocity as measured using pulsed Doppler and the true mean velocity was determined using a flow phantom. Correction factors were applied to measured time average velocities of blood in the hepatic artery and portal vein. Blood flow was calculated from the product of corrected velocities and the cross-sectional area of the vessels. There was no significant difference in total liver blood flow for patients with colorectal liver metastases when compared with controls. However, the ratio of the hepatic arterial flow to the sum of the portal and hepatic arterial flows (Doppler perfusion index, DPI) was markedly elevated (P < 0.0001) in the patients with metastases when compared with the controls. The DPI values for a third group of subjects who had undergone resection for colonic cancer but who had no proven liver metastases overlapped the values for the other two groups. When attention is paid to technique, the procedure can detect and quantify the changes in liver blood flow which occur in the presence of metastases.