Renal Reabsorption Rate Calculator
Calculate tubular reabsorption of substances like Glucose or Sodium.
mL/min
mg/mL
mL/min
mg/mL
Please enter valid positive numbers for all fields.
Filtered Load:
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Excretion Rate:
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Net Reabsorption Rate:
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Reabsorption Percentage:
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Status:
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How to Calculate Reabsorption Rate in Renal Physiology
Understanding reabsorption rate is fundamental to nephrology and renal physiology. It measures the amount of a substance that the kidneys filter from the blood but then reclaim back into the bloodstream, preventing it from being lost in urine. This process is vital for retaining necessary nutrients like glucose, amino acids, and electrolytes.
The Reabsorption Formula
The calculation is based on the principle of mass balance. To find the amount of a substance reabsorbed, you must first determine how much was filtered and subtract how much was excreted in the urine.
Reabsorption Rate = Filtered Load – Excretion Rate
Where:
- Filtered Load: Glomerular Filtration Rate (GFR) × Plasma Concentration (Px).
- Excretion Rate: Urine Flow Rate (V) × Urine Concentration (Ux).
Mathematically:
Reabsorption = (GFR × Px) – (V × Ux)
Step-by-Step Calculation Example
Let's calculate the reabsorption rate for Glucose in a healthy individual:
- Determine Filtered Load: If GFR is 125 mL/min and Plasma Glucose is 1.0 mg/mL, the Filtered Load is 125 × 1.0 = 125 mg/min.
- Determine Excretion Rate: If Urine Flow is 1 mL/min and Urine Glucose is 0 mg/mL (healthy kidneys reabsorb all glucose), the Excretion Rate is 1 × 0 = 0 mg/min.
- Calculate Reabsorption: 125 mg/min (Filtered) – 0 mg/min (Excreted) = 125 mg/min.
In this scenario, the reabsorption rate is 100%, meaning the kidney successfully reclaimed all glucose from the filtrate.
Net Reabsorption vs. Net Secretion
The calculator determines the net handling of a substance:
- Positive Reabsorption: The substance is filtered and then taken back into the blood (e.g., Glucose, Sodium).
- Negative Reabsorption (Secretion): If the Excretion Rate is higher than the Filtered Load, the result will be negative. This indicates Net Secretion, meaning the kidney actively added more of the substance to the urine from the blood capillaries (e.g., Penicillin, PAH).
Why This Metric Matters
Calculating the reabsorption rate helps clinicians and researchers evaluate tubular function. A decrease in the reabsorption rate of substances that should be fully retained (like glucose or protein) indicates tubular damage or that the transport maximum (Tm) has been exceeded (as seen in diabetes mellitus).