Thursday, April 2, 2009

Ascites :Causes,pathophysiology and prognosis

This post is also for medical students, I'll try to explain the pathophysiology of ascites in liver failure and portal hypertension, and other causes of ascites.

In liver cell failure, the liver is cirrhotic and cells are damaged so the liver can't form enouh albumin cirrhosis will also lead to obstruction in the liver sinusoids , so :

Pathophysiology of ascites
in liver failure can be summed up in :

  • Hypoalbuminemia:
    Ascites developes when serum albumin drops below 3 gm %.

  • Portal hypertension:
    Together with lowered albumin level , portal hypertension localizes the transudate to the area of drainage of the portal vein producing ascites.

  • Lymphatic extravasation:
    Lymphatics dilate in cases of post-sinusoidal obstruction leading to extravasation of lymph into the peritonium. Also known as "lymphorrhea".

  • The hypoperfusion of liver cells leads to increased production of ADH and alsosterone by the kidneys resulting in salt and water retention, thus aggravating ascites.

  • In T.B peritonitis or if SBP develope, ascites becomes more and more resistant to diuretics and other means of treatment.

Causes of ascites:

1-Portal hypertension: as in liver failure, portal vein obstrucion/compression, IVC obstruction, etc.

2-Generalized hypoalbuminemia: as in nephrotic syndrome.

3-Exudation: as in:
  1. Tuberculous peritonitis.
  2. Malignant ascites : with malignant cells in ascitic fluid and rapid ascites formation.
  3. pseudomucinous and pseudomyxomaperitonii.
4-Chylous ascites: this is caused by obstruction of the thoracic duct, in this case, the ascitic fluid is milky white, stains orange with Sudan III and rich in fats.

5-Haemorrhagic ascites: in blood diseases and some malignancies.

6-Ovarian fibroma wit ascites (Meig's syndrome).

Bad prognostic criteria of ascites:
It's really important to treat the actual cause of ascites to get results. In many hepatic patients, alcohol restriction, diuretics and tapping of ascites are very effective. Prognosis depends mainly on the cause of ascites.
  • Development of hepatic encephalopathy.
  • Prothrombin time more than 6 seconds.
  • Malignant ascites has a very poor prognosis.
  • Ascites resistant to treatment (maybe due to wrong diagnosis or patient non compliance or failure of treatment of the cause.

I hope that this helped a little in understanding the pathophysiology and causes of ascites. There are new theories that develope every while about how ascites occurs but I tried to cover the main causes and the most popular mechanisms.

Feedback is always appreciated.