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Effective Renal Plasma Flow Calculator (PAH Clearance)

· Last updated：2026-08-21

This tool is for informational purposes only and does not constitute medical, financial, or legal advice; consult a qualified professional for advice.

Estimate ERPF from PAH clearance (C = U·V/P, normal ~500–700 mL/min), plus true RPF, renal blood flow from Hct, and filtration fraction from GFR. Not medical advice.

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Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Health
Input types
number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Effective Renal Plasma Flow Calculator estimates ERPF using para-aminohippuric acid (PAH) clearance calculated from urine PAH, plasma PAH, and urine flow rate. It also computes true renal plasma flow (RPF) via the extraction ratio, total renal blood flow (RBF) using hematocrit, and the filtration fraction (FF) alongside glomerular filtration rate.

When to use

  • Calculating effective renal plasma flow (ERPF) and clearance from urine and plasma PAH concentrations.
  • Deriving true renal plasma flow (RPF) and renal blood flow (RBF) with extraction ratio and hematocrit adjustments.
  • Evaluating the renal filtration fraction (FF) by comparing glomerular filtration rate against calculated plasma flow.

How it works

  1. 1Enter urine PAH concentration, plasma PAH concentration, and urine flow rate to calculate PAH clearance as C_PAH = (U · V) / P.
  2. 2Provide the PAH extraction ratio (default 0.90) to compute true renal plasma flow as RPF = ERPF / Extraction Ratio.
  3. 3Input hematocrit (fraction) to determine total renal blood flow as RBF = RPF / (1 - Hct) and enter GFR to compute filtration fraction as FF = GFR / RPF.

Use cases

  • Renal physiology education: Demonstrating clearance formulas, tubular secretion, and hemodynamic relationships.
  • Experimental laboratory analysis: Quantifying kidney perfusion parameters from measured animal or human clearance data.
  • Physiological research: Assessing alterations in renal blood flow and filtration fraction under various hemodynamic states.

Examples

1. Baseline Renal Perfusion Calculation

Physiology Educator

Background

A physiology instructor is demonstrating renal clearance equations with standard normal physiological parameters.

Problem

Calculate ERPF, true RPF, RBF, and filtration fraction for a healthy adult baseline dataset.

How to use

Enter urine PAH = 6.5 mg/mL, plasma PAH = 0.01 mg/mL, urine flow = 1 mL/min, extraction ratio = 0.90, hematocrit = 0.45, and GFR = 125 mL/min.

Outcome

Computes an ERPF of 650.0 mL/min, true RPF of 722.2 mL/min, total RBF of 1313.1 mL/min, and a filtration fraction of 0.173.

2. Reduced Perfusion Scenario Analysis

Nephrology Researcher

Background

A researcher is evaluating clearance data indicating decreased renal plasma delivery.

Problem

Evaluate the shift in RBF and filtration fraction given elevated plasma PAH and lower extraction efficiency.

How to use

Set urine PAH = 6.5 mg/mL, plasma PAH = 0.02 mg/mL, urine flow = 1 mL/min, extraction ratio = 0.85, hematocrit = 0.40, and GFR = 100 mL/min.

Outcome

FAQ

Why is PAH clearance used to estimate effective renal plasma flow?

PAH is freely filtered at the glomerulus and actively secreted by the proximal tubule, clearing almost all PAH from renal arterial plasma in a single pass.

What is the normal ERPF range in healthy adults?

Normal effective renal plasma flow typically ranges between 500 and 700 mL/min for a standard adult body surface area.

How does true RPF differ from ERPF?

ERPF assumes 100% extraction, whereas true RPF accounts for the actual PAH extraction ratio (typically around 0.90) using RPF = ERPF / E.

How is renal blood flow calculated from plasma flow?

Renal blood flow (RBF) accounts for cellular blood volume by dividing true RPF by the plasma fraction: RBF = RPF / (1 - Hematocrit).

What does the filtration fraction represent?

The filtration fraction (FF = GFR / RPF) represents the proportion of plasma entering the kidney that is filtered across the glomerulus, normally around 0.20.

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Calculates a reduced ERPF of 325.0 mL/min, true RPF of 382.4 mL/min, RBF of 637.3 mL/min, and an increased filtration fraction of 0.262.