Doppler sonographic portal vein parameters are used for the noninvasive evaluation of portal hypertension in cirrhosis. The patency of a paraumbilical vein is a rather frequent finding in cirrhosis, which may affect hepatic hemodynamics and function. We evaluated portal and hepatic arterial parameters in 184 cirrhotic patients with and without a patent paraumbilical vein and the relationships with paraumbilical blood flow. A patent paraumbilical vein was found in 33.7% of patients. The prevalence was higher (56.8%) in Child C patients. Portal blood flow velocity (PBV) (10.8 t 2.2 vs. 9.8 t 2.4 cdsec; P < .01) and volume (PBF) (995.0 2 383.8 vs. 811.6 2 318.7 d m i n ; P < .001) were significantly higher, and effective portal liver perfusion (PLP) (portal blood flow paraumbilical blood flow) (621.3 ? 420.8 vs. 811.6 t 318.7 d m i n ; P < .001) was significantly lower in patients with a patent paraumbilical vein than in those without. These differences were more evident in Child C patients (10.7 t 2.0 vs. 8.3 t 2.3 cdsec; 935.7 t 378.3 vs. 680.6 2 239.4 mIJmin; 369.0 ? 282.0 vs. 680.6 t 239.4 d m i n ) . Portal vein diameter, the congestion index (CI) of the portal vein, hepatic arterial resistance indexes, and the severity of esophageal varices did not differ between the two groups. In patients with a patent paraumbilical vein, the Child-Pugh score and the prevalence of ascites were significantly higher than in those without. In conclusion, the evaluation of PBV and PBF in cirrhotic patients can provide misleading results if a paraumbilical vein is patent, underestimating the degree of portal hypertension. The CI and hepatic arterial resistance indexes are not influenced by the paraumbilical vein patency. (HEPATOLOGY 1995;22:1689-1694.) In patients with cirrhosis, portohepatic hemodynamics can be evaluated, noninvasively, by duplex Doppler ultrasonography (DDU). Parameters evaluated by DDU are mainly related to the presence, direction, and velocity of Abbreviations: DDU, duplex Doppler ultrasonography; PUV, paraumbilical vein blood flow mean velocity; PUF, paraumbilical vein blood flow volume; PBV, portal blood flow mean velocity; PBF, portal blood flow volume; PLP, portal liver effusion; CI, congestion index; PI, pulsatility index; RI, resistive index.