[Dynamics of ascitic fluid in decompensated cirrhosis]

The ascitic fluid in decompensated liver cirrhosis constitutes a continuously circulating pool which carries on sustained water exchanges with plasma and extracellular fluids through the whole peritoneal membrane. The actual ascites volume results therefore from the steady-state between the formation and reabsorption transperitoneal water flows. The ascitic reabsorption concerns both the "iso-osmotic" (i.e. the portion bound to the ascitic proteins and solutes) and the "free-water" (i.e. the amount exceeding the osmotic bounding ability of the peritoneal solutes) fractions of total ascitic water. By means of a simple dilution test, it is possible an in vivo estimation of both the ascites volume and the rate of transperitoneal free-water reabsorption, which is the actual free-water peritoneal clearance (CPAL) and an evaluation of the total intra-abdominal pressure (PIA). PIA results from the sum of the ascitic hydrostatic pressure, and the tension of the abdominal wall. Diuretic administration is able to significantly reduce CPAL, inducing a negative sodium balance and thus leading to a readjustment of ascites steady-state. This fact may cause reductions of ascites volume and PIA only after several days of diuretic treatment. An acute diuretic treatment by itself, even if intensive and resulting in a rapid diuresis and a significant modification of CPAL, does not appear able to determine rapid and detectable modifications of PIA. CPAL has an intrinsic prognostic value in patients with decompensated cirrhosis, since the cumulative mortality was reported to be significantly higher in the patients with lower CPAL levels. The peritoneal clearance ability may be regarded as a compensatory mechanisms of portal hypertension, and its estimate may be a reliable index of patient's aptitude to a lower hydro-retentive trend, which is in turn correlated to a greater cirrhosis severity and a worse prognosis.