Doppler ultrasound in the evaluation of portal hypertension.

Doppler ultrasound has become a powerful diagnostic tool in evaluating the portal system. It can provide a great deal of information about the morphology and hemodynamics of portal hypertension. Together with CT and MRI, it has partly relegated the role of angiography from diagnostic towards preoperative evaluation. The diagnosis of portal hypertension can be made and the cause of the elevated pressure can be located before, in, or after the liver parenchyma. Spontaneous shunts can be identified. On the basis of their location and direction of flow, portohepatic collaterals can be differentiated from portosystemic collaterals. The presence of portohepatic collaterals may be the first indication of portal thrombosis or stenosis. Portosystemic collaterals can be either collaterals towards the SVC, with consequent risk of bleeding, or collaterals draining into the IVC, which do not carry such risk. The latter may mimic surgically created shunts in their large volume-flow capacity. The hemodynamic conditions leading to encephalopathy are identifiable by looking at the size of the collaterals in conjunction with the direction of flow in the major portal vessels. Patency of surgically created shunts can be established. Flow patterns may be quantified by performing volume flow estimations, and the presence of a hyperdynamic circulation can thus be identified. By providing insight into portal hemodynamics, Doppler ultrasound can help to select optimal individualized treatment and is well suited for follow-up of medical and surgical therapy.