RENAL-GFR MEASUREMENT

SUMMARY

1. Creatinine clearance: using 24 hour urine collection. But difficulties with accurate collection.

2. Exceeds true GFR by 10 to 20% due to tubular secretion.

3. Tubular secretion increases with drop in GFR: up to 50% in Near End Stage Renal Failure (NESRF).

4. Equations using serum creatinine: Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI).

5. More accurate that MDRD and Cockcroft-Gault equations in normal or near-normal GFR but MDRD better for low levels of GFR.

6. Isotopic measurement of GFR using a radioactive tracer (DTPA nuclear medicine test): accurate but cumbersome and expensive. Used mostly in transplant donor workup.

Reference(s)

Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education