Radionuclide hepatic perfusion index and ultrasonography: assessment of portal hypertension in clinical practice.

The final value of portal blood flow pressure depends on the degree of vascular obstruction, then on the resistance in collateral vessels and, last, on splanchnic blood flow. The iniciating cause of portal hypertension most often lies in advancing anatomical damage leading to increased resistance and, consequently, to a reduction of portal blood flow, and simultaneous reciprocal development of extrahepatic collaterals. The determination of a true portal flow is a necessity particularly when deciding about a shunt surgery and its type, but it also supplies valuable information on the degree of portal flow restriction and, in this way, on the progress of pathophysiological changes, their extent and advance.