Estimation of creatinine clearance in end-stage liver disease.

Background: Estimation of renal function in patients with end-stage liver disease (ESLD) is complicated by several factors.

Objective: To develop a practical and relatively inexpensive method for estimating creatinine production and clearance in patients with ESLD.

Methods: Serum creatinine concentrations and urinary excretion of creatinine were measured in 27 patients with moderate-to-severe liver disease with the goal of developing equations to predict creatinine clearance from serum creatinine. Subjects were studied during an initial evaluation for a liver transplant program. Two 24 hour urine specimens were collected along with 3 serum samples over a 2 day evaluation period. Serum and urine creatinine concentrations were determined using both a modified Jaffé (autoanalyzer) method and an HPLC method. The data were analyzed using nonlinear mixed-effects modeling.

Results: Considering both statistical criteria and physiological conventions through allometric scaling theory, creatinine clearance (mL/min) in males can be estimated as (80/serum creatinine) x (actual body weight/70)0.75. For females, the same equation is valid, but the result is multiplied by 0.661. A simplified equation without the exponent is presented, along with equations that are appropriate when an HPLC assay is used for greater specificity.

Conclusions: These equations offer potential for improved estimation of creatinine clearance in patients with liver impairment; however, they need further validation using an independent group of subjects.