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Pathophysiology of ascites in Cirrhosis

There are numerous causes of ascites, the most common causes are
1. Malignant disease.
2. Cirrhosis.
3. Heart failure. 

Primary disorders of the peritoneum and visceral organs can cause ascites, and they should be considered even in those patients with chronic liver disease (CLD).
The main cause of ascites in cirrhosis is Splanchnic vasodilatation.It is mediated by vasodilators especially nitric oxide.These vasodilators are released when there is shunting of blood into the systemic circulation due to portal hypertension.As cirrhosis advances systemic arterial pressure falls due to severe splanchnic vasodilatation. 

This in turn leads to 
1. Activation of the RAS (renin–angiotensin system) with secondary aldosteronism.
2. Increased sympathetic nervous system activity.
3. Increased atrial natriuretic hormone secretion.
4. Altered activity of the kallikrein–kinin system.

These systems will try to normalise the arterial pressure but they result in salt and water retention.Combination of splanchnic arterial vasodilatation and portal hypertension tend to alter the intestinal capillary permeability, resulting in accumulation of fluid within the peritoneal cavity.