RENAL CLEARANCE
RENAL CLEARANCE
- Substance clearance is volume of plasma that is completely cleared of substance by kidney pet unit time.
- Also referred as “Plasma clearance”.
Calculation:
- Clearance = U * V / P
- U – Urinary clearance of substance.
- V – Urinary flow rate.
- P – Plasma concentration of substance.
Clearance measurement methods:
- PAH clearance – Used as measure for renal plasma flow.
- Inulin & creatinine clearance methods – Estimates GFR.
- Inulin clearance more accurate measure than creatinine clearance.
- Because small amount of creatinine is secreted by tubules.
- Hence creatinine excreted is slightly exceeding amount filtered.
| Substance | Clearance |
| Glucose | 0 |
| Sodium | 0.9 |
| Chloride | 1.3 |
| Potassium | 12.0 |
| Phosphate | 25.0 |
| Urea | 88.0 |
| Inulin | 125.0 |
| Creatinine | 140.0 |
- Substances which are reabsorbed (not secreted) with Tm: Glucose.
- Substances which are secreted (not reabsorbed): PAH.
- High doses of PAH – Results in low renal plasma flow.
- Drug has more renal clearance than GFR
- Substances which are neither reabsorbed/secreted): Inulin.
Exam Important
- PAH clearance – Used as measure for renal plasma flow.
- Inulin & creatinine clearance methods – Estimates GFR.
- Inulin clearance more accurate measure than creatinine clearance.
- Clearance value for glucose is 0.
- Clearance value for urea is 88.
- Clearance value for inulin is 125.
- Substances which are reabsorbed (not secreted) with Tm: Glucose.
- Substances which are secreted (not reabsorbed): PAH.
- High doses of PAH – Results in low renal plasma flow.
- Substances which are neither reabsorbed/secreted): Inulin.
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