Much confusion regarding the hemodynamics following interposition mesosystemic shunts prevails. Many authorities have claimed that portal venous perfusion continues following interposition mesocaval shunts. In 1971, a prospective, randomized trial comparing the distal splenorenal shunt with a variety of interposition mesosystemic shunts (primarily mesocaval or mesorenal) was begun. Visceral angiography was utilized to assess the early and late postoperative hemodynamic changes following both selective and nonselective shunts. None of the patients with patent interposition shunts retained portal perfusion present preoperatively. Searching for an explanation for this hemodynamic discrepancy, we examined two patients of the randomized trial angiographically. Both patients had excellent portal perfusion preoperatively, yet following interposition shunting (one mesocaval and One splenocaval), neither maintained portal perfusion of the liver. Celine artery injections produced opacification of the entire splenoportal axis; however, it is shown that such portal venous opacification occurred in a retrograde direction by selective hepatic arterial injections demonstrating hcpatofugal portal venous flow. Additionally, two nonrandomized patients received interposition mesorenal shunts and exemplify this phenomenon, entitled “portal pseudoperfusion.” The explanation for conflicting literature reports lies in the misinterpretation of venous phase celiac and non-selective SMA arteriography in determining the direction of portal flow. A narrative of preoperativc and postoperative angiograms of four patients will clarify the mechanism of “portal pseudoperfusion” and demonstrate that interposition shunts totally siphon portal venous perfusion. Clues to the detection and techniques to avoid this phenomenon will be presented.