Hepatic fibrosis causes an increase in the liver stiffness, a parameter measured by elastography and widely used as diagnosis method. This study aims at determining the extent to which a portal occlusion due to concomitant portal vein thrombosis can also affect these mechanical properties. Portal vein occlusion was generated by progressive inflations of a balloon catheter in the portal vein of four swines. The portal flow and liver stiffness were investigated using 4D-flow MRI and MR-Elastography. This vascular mechanism is shown to be sufficient to attenuate the increase in stiffness due to moderate fibrosis and may lead to false-negative diagnosis.