TENSE ASCITES IN CIRRHOTICS: A NEW DEFINITION?

The investigators have attempted to define tense as‐cites on the basis of the observed failure of cirrhotics with tense ascites to achieve increased diuresis in the supine position. They tested the hypothesis that functional inferior vena cava (IVC) obstruction by tense ascites prevents the central shift of fluid. Patients with cirrhosis and mild or moderate ascites (n = 11) or tense ascites (n = 2), and others with membranous IVC obstruction (n = 2) were given a water load. Diuresis (urinary volume), natriuresis (urinary sodium excretion) and glomerular filtration rate (creatinine clearance) were determined in the sitting, supine, and 10° head‐down tilt positions before and after the water load. Improved diuresis, natriuresis, and creatinine clearance were observed in the mild‐to‐moderate ascites group, in the supine and head‐down positions. In the tense ascites group, these parameters showed improvement in the head‐down position but not in the supine position. The patients with membrane IVC obstruction showed improved diuresis, natriuresis, and creatinine clearance in the supine position and further improvement in the head‐down position; both these positions gave additional benefit when studied after membranotomy. This disproved the authors′ initial hypothesis that it was functional IVC obstruction alone which was responsible for failure of postural shift of blood into the chest and, hence, increased diuresis, in tense ascites. The authors therefore postulated compression of collateral vessels, in addition to the IVC, by the increased intracavitary pressure and radius of the cavity (Laplace's law) as a probable cause of failure of patients with tense ascites to increase diuresis in the supine position. They suggest defining ascites as “tense” if it is severe enough to compress the IVC and collaterals, as determined by failure to increase diuresis in the supine position