Renal clearance ratio

Diagram showing the basic physiologic mechanisms of the kidney

The renal clearance ratio or fractional excretion is a measure of the speed at which a constituent of urine passes through the kidneys. It is defined by following equation:

clearance\ ratio\ of\ X = \frac{C_x}{C_{in}}

Creatinine is sometimes used instead of inulin as the reference substance.

See also