This document discusses collateral pathways in portal hypertension. It describes various veins that enlarge to drain blood away from the portal system and into the systemic circulation when portal pressures are elevated. These include esophageal varices, gastric varices, splenorenal shunts, paraumbilical veins, and retroperitoneal varices. The document explains the anatomy and venous drainage patterns of these various collateral pathways and how they develop as alternatives for blood flow.