PORTAL-SYSTEMIC COMMUNICATION (ANASTOMOSES)
Netter 312 or MD 306
A system in which the portal venous system communicates with the systemic venous
system:
 When portal circulation through the liver is diminished or obstructed, blood from
the lower regions can still reach the right side of the heart through the IVC by way
of these collateral routes. These alternate routes are available because the portal
vein and its tributaries have no valves; hence blood can flow in a reverse direction
to the IVC.
 However, when the collateral pathways must convey large volumes, potentially
lethal esophageal varices may develop (blood in the esophagus).
Gastroesophageal region
 Between the submucosal Esophageal veins draining into either the Azygos
vein (systemic) or the Left Gastric vein (portal); when dilated these are
esophageal varices
Rectal region
 Between the Inferior and Middle Rectal veins draining into the IVC,
which is posterior/superior to rectum (systemic) and the Superior Rectal
vein, continuing as the Inferior Mesenteric vein (portal)
Paraumbilical region
 Paraumbilical veins (portal) anastomose with Small Epigastric veins of the
anterior abdominal wall (systemic), which go to the IVC
Retroperitoneal region
 On the posterior aspects (retroperitoneal viscera or the liver), where twigs
of visceral veins—for example, the Colic vein, Splenic veins, or the Portal
vein itself (portal system)—anastomose with retroperitoneal veins of the
posterior abdominal wall or diaphragm (systemic) and go to the IVC
RENAL AND SUPRARENAL VEINS
The left gonadal and suprarenal veins drain into the left renal vein, which crosses under
the superior mesenteric artery to the IVC (the one that can cause varicose veins in the left
testes due to the pressure of the SMA-20% of men). The right renal vein is shorter
because it drains directly into the IVC. The right gonadal and suprarenal veins also drain
directly into the IVC.