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.
Nix
David E
DE
Department of Pharmacy Practice & Science, College of Pharmacy, University of Arizona, AZ 85721-0207, USA. nix@pharmacy.arizona.edu
Erstad
Brian L
BL
Nakazato
Paul Z
PZ
Barletta
Jeffrey F
JF
Matthias
Kathryn R
KR
Krueger
Todd S
TS