Biomarkers of Kidney Function: Creatinine Clearance

Optimal Takeaways

Creatinine clearance is a urine test that assesses kidney function, determining how effectively the kidneys can filter out creatinine, a waste product from muscle metabolism. Low creatinine clearance can indicate reduced kidney function, renal artery atherosclerosis, decreased muscle mass, aging, or conditions like dehydration, shock, and cirrhosis with ascites. On the other hand, high creatinine clearance can occur during pregnancy and with high meat intake. This assessment is derived from a 24-hour urine sample, which, while accurate, can be influenced by factors such as age, obesity, malnutrition, paralysis, and pregnancy and requires diligent collection to ensure reliability.

Standard Range: 75.00 – 125.00 mL/min             

The ODX Range: 85.00 – 125.00 mL/min

Low creatinine clearance can be seen with decreased kidney function, renal artery atherosclerosis, decreased muscle mass, cirrhosis with ascites, dehydration, shock, aging (Pagana 2021), slower gait speed, and reduced muscle density (Roshanravan 2015).

High creatinine clearance can be seen with pregnancy and a high meat intake (Pagana 2021).

Overview

Creatinine clearance is a 24-hour urine test that evaluates the ability of nephrons to filter out creatinine, which the kidney must excrete entirely. Creatinine clearance is directly proportional to the glomerular filtration rate (GFR). It depends not only on nephron competence but on the amount of blood being filtered, which can be decreased in dehydration, shock, or atherosclerosis of the renal artery. Age, obesity, malnutrition, paralysis, and pregnancy may confound estimating glomerular filtration rate. Creatinine clearance assessment depends on a 24-hour urine collection which can be time-consuming and may be compromised if a complete 24-hour sample is not obtained (Pagana 2021).

Although creatinine clearance can overestimate the glomerular filtration rate by 10-20%, it may still be used to estimate and monitor kidney function. Normal creatinine clearance may range from 100-150 mL/min, depending on gender and age (Shahbaz 2022).

References

Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.

Roshanravan, Baback et al. “Creatinine clearance, walking speed, and muscle atrophy: a cohort study.” American journal of kidney diseases : the official journal of the National Kidney Foundation vol. 65,5 (2015): 737-47. doi:10.1053/j.ajkd.2014.10.016

Shahbaz, Hassan. and Mohit Gupta. “Creatinine Clearance.” StatPearls, StatPearls Publishing, 25 July 2022.