In portal hypertension, the coronary and short gastric veins drain into the azygos vein and subsequently the SVC via the esophageal venous plexus, thereby bypassing the portal system. Reversal of flow coupled with increased hydrostatic pressure opens collateral circulation and produces venous dilation (varices).
In splenic vein obstruction, splenic venous return is diverted through the short gastrics and fundal plexus allowing blood to drain into the portal venous system via the left gastric vein.
