Clinical - Porto-Systemic Anastomoses Flashcards
what is the porto-systemic anastomosis?
a connection between the veins of the portal venous system, and the veins of the systemic venous system
what are the major sites of the porto-systemic anastomoses?
oesophageal
rectal
retroperitoneal
paraumbilical
what is the oesophageal anastomoses between?
the oesophageal branch of the left gastric vein and the oesophageal tributaries to the azygous system
what is the rectal anastomoses between?
the superior rectal vein and the inferior rectal veins
what is the retroperitoneal anastomoses between?
the portal tributaries of the mesenteric veins and the retroperitoneal veins
what is the paraumbilical anastomoses between?
the portal veins of the liver and the veins of the anterior abdominal wall
what can cause obstruction to the portal system?
e.g due to cirrhosis, portal vein thrombosis, or external pressure from a tumour
what happens when blood flow through the portal system that is obstructed?
the pressure within portal system increases
what is defined as portal hypertension?
A portal venous pressure in excess of 20mmHg
what happens in portal hypertension?
blood may be re-directed through the porto-systemic anastamoses
why may blood be re-directed through the porto-systemic anastomoses?
these are now under a lower pressure
If a large volume of blood passes through these anastamoses over a long period of time, what can happen?
the veins around the anastomosis can become abnormally dilated
what are the abnormally dilated veins known as?
varices
what can happen if the oesophageal or rectal varices rupture?
can result in fatal blood loss
