Total plasma clearance versus urinary plasma clearance of ⁵¹Cr-EDTA in patients with cirrhosis with and without fluid retention

Abstract

Background and aim. In patients with fluid retention, the total plasma clearance of ⁵¹Cr-EDTA (Cl_P) may overestimate the glomerular filtration rate (GFR). The present study was therefore undertaken in order to compare Cl_P with the urinary plasma clearance of ⁵¹Cr-EDTA (Cl_U) in patients with cirrhosis with and without fluid retention. Material and methods. A total of 136 patients with cirrhosis (24 without fluid retention, 112 with ascites) received a quantitative intravenous injection of ⁵¹Cr-EDTA followed by plasma and quantitative urinary samples for 5 hours. Cl_P was determined from the injected dose relative to the plasma concentration-time area, extrapolated to infinity. Cl_U was determined as urinary excretion relative to the plasma concentration-time area up to voiding. Results. In patients without fluid retention, the difference between Cl_P and Cl_U (Cl_P − Cl_U = Cl_Δ) was mean 4.5 mL/min/1.73 m². In patients with ascites, Cl_Δ was significantly higher (17.6 mL/min/1.73 m², p < 0.0001). Cl_Δ increased with lower values of GFR (r = − 0.458, p < 0.001). Repeated measurements of Cl_U in a subgroup of patients with fluid retention (n = 25) gave almost identical values. Different types of corrections of one-pool clearance were almost identical with Cl_P, except for higher clearance values, which were somewhat underestimated by the former. Conclusion. In patients with fluid retention and ascites Cl_P and corrected one-pool clearance overestimates GFR substantially. Although Cl_U may underestimate GFR slightly, patients with ascites should collect urine quantitatively in order to obtain a reliable measurement of GFR.

Key Words::

• Ascites
• corrected one-pool clearance
• delayed indicator distribution
• glomerular filtration rate
• peritoneal clearance

Acknowledgements

The authors wish to express their gratitude to Ms Georgina T. Narvaez, BsC, for skillful handling of the paper. This work was supported by The John and Birthe Meyer Foundation and Savværksejer Jeppe Juhl og Hustru Ovita Juhls Mindelegat.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.