Filtration fraction

Filtration Fraction is a term used in Nephrology to describe the proportion of the renal plasma flow that is filtered by the kidney. It is a key concept in understanding the function of the kidney and its role in maintaining homeostasis in the body.

Definition

The Filtration Fraction (FF) is defined as the ratio of the Glomerular Filtration Rate (GFR) to the Renal Plasma Flow (RPF). It is usually expressed as a percentage and typically ranges from 15% to 20% in a healthy individual.

Formula

The formula for calculating the Filtration Fraction is:

FF = GFR / RPF

Where:

• GFR is the Glomerular Filtration Rate, which measures the amount of blood filtered by the glomeruli per minute.
• RPF is the Renal Plasma Flow, which measures the volume of plasma that reaches the kidneys per minute.

Clinical Significance

The Filtration Fraction is an important parameter in assessing kidney function. Changes in the Filtration Fraction can indicate various kidney diseases and conditions. For example, a decreased Filtration Fraction may indicate glomerulonephritis, while an increased Filtration Fraction may suggest renal artery stenosis.

See Also

• Glomerular Filtration Rate
• Renal Plasma Flow
• Kidney Function Tests

References

• Smith, H.W. (1951). The Kidney: Structure and Function in Health and Disease. Oxford University Press, New York.
• Brenner, B.M., Rector, F.C. (2008). Brenner and Rector's The Kidney, 8th ed. Saunders Elsevier, Philadelphia.