Ascites

Write about Ascites here.


Causes Include:

Heart failure

• IVC thrombosis

• Hepatic vein thrombosis

• Pathology at the level of the hepatic sinusoid (e.g. cirrhosis)


Obstruction within the portal vein, or external pressure on the vein (e.g. from nodes in the porta hepatis) do NOT cause ascites:


Because:


• Blood flows into the liver from the hepatic artery and the portal venous system.

• The former delivers blood at a higher pressure than the latter.  

• Any process that impedes the normal exit of blood from the liver via the hepatic vein (heart failure, IVC obstruction, hepatic vein occlusion or disease within the hepatic sinusoid) triggers a striking rise in portal vein pressure and the development of ascites.


• In chronic portal vein thrombosis, there is no transmission of pressure from the hepatic arterial system to the portal vein, and there is a minimal rise only in the portal vein pressure.

• It is not usually sufficient to produce ascites

Acutely however, portal vein thrombosis may trigger a transient ascites

• It is not usually sustained, and the subsequent fall in portal venous pressure to near normal values presumably occurs as a results of the opening of the small anastamotic channels to the systemic venous system

Varices (very large anastamotic channels between the portal and systemic venous systems) are seen when a patient has much higher portal vein pressure (cirrhosis etc.)