A case of liver cirrhosis with large portacaval shunt from the superior mesenteric vein is reported. The portal blood flow was diagnosed as reversed on admission, but normalized with treatment. Blood flow was measured noninvasively and repeatedly using an ultrasonic Doppler duplex system. The reversed portal flow led to the superior mesenteric vein, right (and some left) internal inguinal vein, and inferior vena cava. This rare collateral pathway was clearly demonstrated by percutaneous transhepatic portalgraphy. A link between shunt and an appendectomy carried out 22 yr ago is considered, and the possibility of the temporarily reversed portal blood flow on admission being due to deteriorated hepatic hemodynamic conditions is discussed.