Currently, portal pressure is measured by the standard method known as hepatic venous pressure gradient (HVPG). But it is an invasive procedure; therefore, an alternative noninvasive technique to estimate portal pressure is required to monitor portal hypertension. In this work, a 3D portal vein model is developed to study the acoustic interaction with microbubbles in the portal vein. Ultrasound scattering by ultrasound contrast agent (UCA) is modelled and analyzed using finite element analysis in order to estimate portal pressure. It was found from the analysis that the subharmonic component dropped by 1.5 dB as the portal pressure raised from 0 mmHg to 10 mmHg. Over the same pressure range, the fundamental component reduced by only 0.2 dB. The results suggest that the subharmonic component from the nonlinear response of microbubble is strongly affected by the ambient pressure, and the proposed model may be used to estimate portal pressure noninvasively. Copyright © 2020 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved