filtration fraction

The filtration fraction is a medical measurement that indicates the proportion of blood plasma flowing through the kidneys that is filtered by the glomeruli. It is calculated by dividing the glomerular filtration rate (GFR) by the renal plasma flow (RPF).1

In healthy individuals, the filtration fraction is approximately 20%, meaning about one-fifth of the plasma entering the glomeruli becomes filtrate, while the remaining four-fifths continues into the efferent glomerular arterioles. This fraction can change in various clinical conditions, such as hypertension.1

Tests like inulin clearance are used to estimate the GFR, which is the rate at which substances are filtered from the plasma. Renal plasma flow can be estimated using substances like para-aminohippuric acid (PAH). These quantitative tests are crucial for evaluating kidney function and diagnosing kidney disorders.12