THE CREATININE APPROACH TO ESTIMATE SKELETAL-MUSCLE MASS IN PATIENTS WITH CIRRHOSIS

The creatinine-method to estimate muscle mass is frequently used in cl inical studies, although the validity of this approach is uncertain in patients with cirrhosis. In this study 102 patients with cirrhosis di ffering in cause, clinical state, liver, and renal function were inves tigated to determine whether reduced liver or renal function may expla in in part the low levels of urinary creatinine excretion frequently o bserved in these patients. Muscle mass assessed by 24-hour urinary cre atinine excretion was compared with anthropometrically obtained muscle mass calculated hom arm muscle area (AMA), and with body cell mass (B CM) estimated by bioelectrical impedance analysis and total body potas sium counting. In cirrhosis, the 24-hour urinary creatinine excretion was 10.4% and AMA was 19% lower than predicted values. The differences between the results obtained by different methods did not show any re lation to parameters of liver function (ICG-t1/2, caffeine-t1/2, MEGX- test, cholinesterase) or the severity of liver disease (i.e., Child-Pu gh score). In contrast, renal function was strongly correlated with th e differences between creatinine- and anthropometric-muscle mass (r =. 64, P <.001). At the same time, patients with normal renal function (6 2% of the whole population) had significantly higher creatinine (29.1 +/- 8.5 vs, 15.8 +/- 6 kg, P <.001) and anthropometric-muscle mass (22 .4 +/- 6 vs, 17.9 +/- 5.3 kg; P <.01) than patients with reduced renal function (38% of the patients). In addition, significantly higher dif ferences between measured and predicted values of urinary creatinine e xcretion (-0.389 +/- 0.33 vs. 0.06 +/- 0.31 g/24 h; P <.001) and of AM A (13.2 +/- 12 vs. 7.2 +/- 12 cm(2); P <.03) were found in the subgrou p with impaired renal function. In conclusion, renal dysfunction but n ot reduced liver function systematically affects the urinary creatinin e method for the estimation of skeletal muscle mass in cirrhosis.