Creatinine, Creatinine Clearance
Creatinine is a degradation product of creatine phosphate which serves as a fast energy supplier in muscle tissue. Creatinine as a urinary substance is filtered exclusively in the glomerulus, the determination of its (physiological) clearance of 95-150 ml/min is therefore suitable as a functional test to assess the filtration performance () of the kidney.
Since the determination of creatinine clearance depends on various factors (muscle mass, age, skin colour, serum creatinine, sex), different formulas have been developed to allow an approximate determination.