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Objective:

Determine the significance and clinical use of measuring Creatinine Clearance in clinical practice

 

Lab Test Name:

Creatinine Clearance – CrCl

 

Description:

Healthy kidneys remove creatinine from the blood. It then passes out of your body through urine. Creatinine is created in the body as a byproduct from normal wear and tear on muscles and protein in your diet.

Creatinine Clearance is a test that compares the level of creatinine in the blood against the level in the urine and evaluates Glomerular Filtration Rate. Hydration, blood volume status, blood pressure, and the state of the glomeruli impact GFR. 

Remember that GFR is the amount of blood cleaned each minute by tiny filters in your kidneys called glomeruli.

An increase in CrCl indicates an increase in GFR.

 

Indications:

The creatinine clearance test is done when your healthcare provider thinks that the eGFR result given with your blood creatinine level may not be accurate. This would be in patients who have diabetes, those with HF, those with kidney disease, and is sometimes evaluated in those with hypertension.

• Kidney Function
  • GFR
• Diabetes
• Heart Failure
• Hypertension

 

Normal Therapeutic Values:

Normal – Creatinine clearance rates go down as you age

• Male: 97 to 137 mL/min 
• Female: 88 to 128 mL/min 

For every decade after age 40, a normal test result is 6.5 mL/min less than the numbers above.

Collection:

• Plasma separator tube for serum
• Urine is collected for 24 H in a plastic container
• First void is flushed
• Date and time recorded, and urine collected and stored at room temperature
• Processed once collection is complete

 

What would cause increased levels?

Increased Creatinine Clearance→ Increased GFR

• Pregnancy- higher blood volume
• Large protein intake
• Exercise

 

What would cause decreased levels?

The kidneys are solely responsible for removing Creatinine from the blood. If kidney function is declining, the creatinine level increases in the blood, but less creatinine is excreted into the urine.

Decreased Creatinine Clearance→ Decreased GFR

• Abnormal kidney function
• Poor perfusion
• Dehydration
• Bladder obstruction
• Nephrotoxic medications