The aim of this study was to determine if the addition of pulsed Doppler imaging to conventional sonography allows discrimination between true paraumbilical veins of portal hypertension and the apparent vein sometimes seen in the ligamentum teres in normal subjects. Conventional sonography and Doppler sonography of the ligamentum teres were performed in 33 normal subjects and in 39 patients with portal hypertension due to chronic liver disease. An apparent ligamentum teres vessel (i.e., hypoechoic channel) was identified on sonograms in 32 (97%) normal subjects (diameter 0.6-1.9 mm) and in 35 (90%) patients with portal hypertension (diameter 1.1-22 mm). In the portal hypertension group, the apparent vessel had a diameter of greater than 3 mm in only 20 patients (51%), but in 32 patients (82%) it was shown on Doppler examination to be a patent paraumbilical vein (i.e., hepatofugal venous signal). A patent paraumbilical vein on duplex Doppler sonography is therefore a specific sign of portal hypertension. The addition of Doppler imaging to conventional sonographic examination significantly increases the sensitivity for the diagnosis of portal hypertension by demonstration of a paraumbilical vein.