Creatinine excretion and total body potassium in renal failure

Total body potassium (TB K) and daily urinary creatinine excretion were measured in 12 patients with mild chronic renal disease (CCr/1.73 m2 BSA greater than 40 ml/min, Group I) and 12 patients with severe renal disease (CCr/1.73 m2 BSA less than 19 ml/min, Group II). Creatinine excretion as a function of total body potassium was significantly lower in the males and females of Group II as compared to males and females in Group I. TB K was linearly related to creatinine excretion in both groups of patients. Mean TB K was not significantly different from mean predicted normal values (TB Kp) in both groups. The decreased creatinine excretion observed in severe renal failure cannot be due to a significant loss of lean body mass because TB K was not significantly decreased below predicted normal values. Decreased creatinine biosynthesis, alternate routes of excretion, metabolic reutilization, or conversion of creatinine to other metabolites may have contributed to the decreased creatinine excretion noted in this group of patients with renal failure.