Influence of respiration and portal pressure on transabdominal duplex Doppler ultrasound measurement of portal blood flow: A porcine model for experimental studies

Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for m easuring hepatic blood how (HBF) in clinical practice. Flow velocity and th e cross-sectional area (CSA) of vessels are obtained separately and used to compute blood how. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these pa rameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshi re pigs (20.7-25.1 kg) were used for the study. TDDU determination of porta l blood flow was carried out using CSA of the portal vein obtained at inspi ration (maximal) and at expiration (minimal) for computation, and the diffe rences obtained were compared. Determination of HBF was carried out simulta neously on the same animals casing diisopropyliminodiacetic acid (DISIDA) c learance. A physiological increase in portal pressure was then created by 5 0% hepatectomy and TDDU measurement similarly carried out on the second pos toperative day, Computing portal blood flow in the intact Fiver using maxim al and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033), T he respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in por tal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using max imal CSA more accurately reflects HBF. (C) 2000 Academic Press.