Gamma-variate plasma clearance versus urinary plasma clearance of Cr-EDTA in patients with cirrhosis with and without fluid retention.

In patients with fluid retention, the plasma clearance of Cr-EDTA (Cl obtained by multiexponential fit) may overestimate the glomerular filtration rate (GFR). The present study was undertaken to compare a gamma-variate plasma clearance (Cl with the urinary plasma clearance of Cr-EDTA (Cl ) in patients with cirrhosis with and without fluid retention. A total of 81 patients with cirrhosis (22 without fluid retention, 59 with ascites) received a quantitative intravenous injection of Cr-EDTA followed by plasma and quantitative urinary samples for 5 h. Cl was determined from the injected dose relative to the plasma concentration-time area, obtained by a gamma-variate iterative fit. Cl and Cl were determined by standard technique. In patients without fluid retention, Cl , Cl and Cl were closely similar. The difference between Cl and Cl (Cl - Cl  = ΔCl) was mean -0·6 ml min  1·73 m . In patients with ascites, ΔCl was significantly higher (11·8 ml min  1·73 m , P<0·0001), but this value was lower than Cl - Cl (17·5 mL min  1·73 m , P<0·01). ΔCl increased with lower values of GFR (P<0·001). In conclusion, in patients with fluid retention and ascites Cl and Cl overestimates GFR substantially, but the overestimation is smaller with Cl . Although Cl may underestimate GFR slightly, patients with ascites should collect urine quantitatively to obtain a reliable measurement of GFR.