Portosystemic collateral pathways

Portosystemic collateral pathways (also called varices) develop spontaneously via dilatation of pre-existing anastomoses between the portal and systemic venous systems. This facilitates shunting of blood away from the liver into the systemic venous system in portal hypertension, as a means for reducing portal venous pressure. However, these are not sufficient for normalizing portal venous pressure.

The main sites of portosystemic collateral pathways are:

• left gastric
  • left gastric (coronary) vein and short gastric veins to distal esophageal veins
  • located between medial wall of gastric body and posterior margin of left hepatic lobe in lesser omentum
  • usually accompanied by esophageal/paraoesophageal varices (see below)
• esophageal: dilated submucosal venous plexus of distal esophagus
• paraoesophageal
  • coronary vein to azygos and hemoazygos veins and vertebral venous plexus
  • located posterior to esophagus in posterior mediastinum
• perisplenic: splenic vein to left renal vein, traversing splenocolic ligament; may eventuate in spontaneous splenorenal shunt
• retrogastric
  • left gastric (coronary) vein or gastroepiploic vein to esophageal or paraoesophageal veins
  • located in posterior/posteromedial aspect of gastric fundus
• retroperitoneal-paravertebral: colic or mesenteric branches of superior mesenteric vein to retroperitoneal/lumbar veins to the inferior vena cava
• paraumbilical : left portal vein to paraumbilical veins in anterior ridge of falciform ligament
• anterior abdominal wall: paraumbilical and omental veins to subcutaneous periumbilical veins and superior and inferior epigastric veins; collaterals appear to radiate from the umbilicus (caput medusae)
• mesenteric: dilated branches of superior mesenteric vein
• anal canal: superior rectal vein (from the inferior mesenteric vein) to upper anal canal veins (hemorrhoids)

Differential diagnosis

Dilatation of splenic veins at the splenic hilum mimicking splenic hilar varices without splenomegaly may occur in situations such as increased perfusion of splenic tissue associated with an immune response ⁴.