The creatinine clearance test is done to evaluate kidney function, which is done by comparing the creatinine concentration in the blood with the creatinine concentration present in the person's 24-hour urine sample. Thus, the result informs the amount of creatinine that has been taken from the blood and eliminated in the urine, which is made by the kidneys. Changes in results may be indicative of kidney problems, for example.
Generally, creatinine clearance is required when there is a change in blood creatinine concentration, when a high concentration of protein in the urine is noted and to aid in the diagnosis of renal and cardiac diseases. In addition, creatinine clearance may also be required to monitor the evolution of some diseases, such as Congestive Heart Failure and Chronic Renal Insufficiency, for example. Understand more about what creatinine is.
When the exam is requested
In addition to being required when excess blood creatinine or a high concentration of protein in the urine, also called proteinuria, is checked, the creatinine clearance test is also usually requested when symptoms appear that may indicate kidney problems such as:
- Swelling in the face, wrists, thighs or ankles;
- Urine with blood or foam;
- Significant decrease in the amount of urine;
- Constant pain in the region of the kidneys.
Thus, this test is also regularly ordered when you have kidney disease, to assess the degree of disease progression and to understand the level of kidney function.
How to take the exam
To do the creatinine clearance test one must collect urine for 24 hours and have a blood test at the beginning or end of that time. Both blood and urine collected are sent to the laboratory for creatinine dosing in both materials. Here's how to do the 24-hour urinalysis.
The value of creatinine clearance is given by a mathematical formula that considers, in addition to the creatinine concentration in blood and urine, the weight, age, and sex of each person.
How to prepare
Although there is no specific preparation to perform the creatinine clearance test, some laboratories recommend fasting for 8 hours or just avoiding the consumption of cooked meat, since the meat increases the creatinine levels in the body.
What are the reference values
Normal values for creatinine clearance are:
- Children : 70 to 130 mL / min / 1.73 m²
- Women : 85 to 125 mL / min / 1.73 m²
- Men : 75 to 115 mL / min / 1.73 m²
When clearance values are low they may indicate kidney problems such as kidney failure, heart failure, such as heart failure, or even be a poor consequence in meats, such as the vegetarian diet, for example.
High creatinine clearance values usually occur in pregnant women after physical activity or even after eating large amounts of meat.
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