Relative frequencies of portosystemic pathways and renal shunt formation through the "posterior" gastric vein: portographic study in 460 patients. Percutaneous transhepatic portography was carried out in 460 patients with portal hypertension to study various collateral routes. Besides the left gastric vein, which was the most frequent collateral route and feeder of esophageal varices, a distinct vein located between the left gastric vein and the short gastric vein constituted a major collateral route in 191 patients (42%). In terms of frequency, this vein was more significant than the short gastric (34%) and the paraumbilical vein (24%) as a collateral route. We propose that this previously anonymous vein be called the "posterior gastric" vein because it runs posterior to the stomach. This vein also formed a renal shunt, a common cause of encephalopathy, in 43 (23%) of the 191 patients; the relative frequency of renal shunt formation by this vein was significantly greater than that by the left gastric vein (12%) and the short gastric vein (18%). 