Pyelovenous back flow is the name that was applied in 19231 to the phenomenon of drainage into the venous system from the renal pelvis under certain conditions of back pressure.
In routine injection methods for demonstrating renal circulation, 2 a cast of the renal pelvis is often made to demonstrate the relationship of its outline to the arterial blood supply, and it was a frequent occurrence to have extrapelvic extravasation even with moderate pressures. This had been a frequent observation of others in injection methods. From the experimental side, as early as 1856, Gigon, 3 using potassium iodide and starch, demonstrated the passage of fluid by way of the venous plexus on the surface of the calices from the pelvis in both cadaver and living kidneys. Both Poirier4 in 1891 and Tuffier 5 in 1894 noted a marked difference of absorption with and without ureteral obstruction. A lethal