Patients with liver cirrhosis are at risk for development of renal failure, usually after a precipitating event such as infection or bleeding. This form of renal failure has a high morbidity and mortality and may be partly caused by increased intra-abdominal pressure secondary to ascites. Recent studies have shown that paracentesis (and the resulting decreased IAP) can increase urinary output and decrease renal arterial resistive index in patients with hepatorenal syndrome (a very pronounced form of renal failure in cirrhosis patients). The aim of this study is to evaluate the influence of Paracentesis on intra-abdominal pressure and kidney function in critically ill patients with liver cirrhosis and ascites across a wider range of kidney function. Kidney function will be evaluated using several estimates of glomerular filtration rate and measures of kidney injury i.e. cystatin C, serum NGAL, creatinine clearance, urinary output and renal arterial resistive index.