PAH is completely removed from blood that passes through the kidneys (PAH undergoes both glomerular filtration and tubular secretion), therefore the rate at which the kidneys can clear PAH from the blood reflects total renal blood flow.
The renal extraction ratio of PAH in a normal individual is approximately 0.92, and thus not exactly 1.0. Thus, this method usually underestimates RPF by approximately 10%. This margin of error is generally acceptable considering the ease with which eRPF is measured.
- Reubi FC (September 1953). "Glomerular filtration rate, renal blood flow and blood viscosity during and after diabetic coma" (PDF). Circulation Res. 1 (5): 410–3. PMID 13082682.