PAH clearance

PAH Clearance is a medical term referring to the process by which Para-Aminohippuric acid (PAH) is removed from the body, specifically the kidney. This process is often used in medical research to measure the renal plasma flow, which is the volume of blood that is cleared of PAH per unit time.

Overview

PAH clearance is a method used to estimate the renal plasma flow. PAH is filtered and secreted by the renal tubules, but not reabsorbed, making it an ideal substance for this purpose. The clearance of PAH is nearly equal to the renal plasma flow because PAH is both filtered and secreted in the renal tubules.

Process

The process of PAH clearance involves the following steps:

1. PAH is injected into the bloodstream.
2. The kidneys filter out some of the PAH, and the rest is secreted into the renal tubules.
3. The amount of PAH in the urine and in the blood is measured.
4. The renal plasma flow is calculated using the formula: (Urine PAH concentration * Urine flow rate) / Plasma PAH concentration.

Clinical Significance

PAH clearance is used in clinical settings to measure renal plasma flow, which can be useful in diagnosing and monitoring kidney diseases. It can also be used to assess the effect of drugs on kidney function.

Limitations

While PAH clearance is a useful tool, it does have some limitations. It assumes that all PAH is cleared from the blood in a single pass through the kidneys, which is not always the case. Additionally, the method is invasive and requires the injection of PAH into the bloodstream.

See Also

• Renal function
• Renal physiology
• Glomerular filtration rate