Significance of Creatinine Urea Testing

What Is a Creatinine Urine Test?

As the name suggests, the creatinine urine test aims to measure urine creatinine levels. It also gives the doctor an idea about the functioning of the kidneys. This is because the kidneys filter and expel creatinine from the body. Normally, creatinine is released in the urine. In addition to measuring creatinine levels, this test helps diagnose kidney disorders or other medical conditions that can elevate the creatinine levels in the body. It is a simple procedure wherein the doctor uses the urine sample obtained from the patient. Sometimes, the doctor might recommend a 24-hour urine sample. Creatinine levels can vary based on the patient's diet, hydration, and exercise. So it is essential to get it checked at regular intervals. The procedure is non-invasive and does not cause any pain.

Why Is a Urine Creatinine Test Done?

A urine creatinine test provides insight into the condition of the patient's kidneys. The test is usually done for the following purposes:

• To make a diagnosis for patients with kidney diseases.

• It can be used as a screening test for patients suffering from diabetes, high blood pressure, and other conditions that increase the risk of kidney diseases.

• To evaluate the treatment of kidney diseases and the improvement in the patient's condition after the treatment.

• To evaluate the adverse reactions of the drugs, including kidney damage or alterations in kidney function.

• To check whether the transplanted kidney is functioning normally.

How Should the Patient Prepare for the Urine Creatinine Test?

Creatinine tests can be done by two methods: the blood test and the urine test. A blood test is a simple procedure wherein the doctor draws a small amount of blood from the patient's arm. The blood is collected in a container known as the vacutainer and is sent to the laboratory. Once the reports are available, the doctor can check the creatinine levels in the blood. If the levels are high, it can be concluded that the kidneys are diseased and have lost their ability to filter the blood. The other method is the 24-hour urine test. It is a procedure wherein the creatinine levels are directly checked with the patient's urine. The patient must do the following before the test:

• Female patients must inform the doctor if they are pregnant or planning to conceive, as it might be inconvenient for them to take the test.

• The patient must inform the doctor about the drugs, including prescription, over-the-counter, multivitamins, and other supplements he has been taking. This is because some drugs might interfere with the test results and show a false positive or negative result.

• The patient must consult the doctor and avoid food and beverages as advised.

• Listen to the doctor's instructions carefully and check whether the test has to be started at a particular time of the day.

• The patient must send the container to the laboratory immediately after completing the test.

How Is the Urine Creatinine Test Performed?

The urine creatinine test, or 24-hour urine test is initiated by collecting the urine in a sterile container. The patient must follow all the instructions because any mistakes in following the instructions can alter the test results. The steps of the urine creatinine test are listed below:

• First, the patient must note the time of urination. The urine should be collected at the same time the next day.

• Collect the urine for 24 hours in a container and store the container in a refrigerator.

• On the following day, urinate at the same time in the container.

• Once the 24 hours are over, place the lid on the container and send it safely to the laboratory.

• The patient must inform the doctor if the instructions cannot be followed and if any amount of urine is spilled from the container.

What Is the Significance of the Test Results?

Creatinine levels vary according to the patient's age and body mass. The more the musculature of the patient, the more creatinine build-up would be observed in his body. In addition, the test results vary according to the laboratories and the method of urine collection. Normally, the creatinine levels range between 955 to 2936 mg (milligram) per hour for males and 1689 mg per hour for females. The creatinine values beyond the previously mentioned range are suggestive of the following:

• Kidney failure.

• Kidney infections or pyelonephritis.

• Urinary tract obstruction due to kidney stones.

• Muscle dystrophy.

• Myasthenia gravis.

Sometimes patients with diabetes who consume a diet rich in meat or proteins might have varying creatinine levels. If the results vary, the doctor might order a serum creatinine test to confirm the diagnosis.

What Are the Serum Creatinine Levels?

Creatinine enters the bloodstream at a constant rate and passes to the kidneys. Usually, the creatinine levels in the blood should be stable because fluctuations are usually suggestive of kidney disorders. The range of serum creatinine levels for males and females is listed below:

• For Males - 0.74 to 1.35 mg per dL.

• For Females - 0.59 to 1.04 mg per dL.

Serum creatinine levels also help measure the glomerular filtration rate of a patient, but the results usually vary according to a person's kidney function. Glomerular filtration rate (GFR) is calculated based on serum creatinine levels and other factors, including age and sex. A GFR below 60 is usually a sign of kidney disease progression.

What Is Creatinine Clearance?

Creatinine clearance is the amount of creatinine cleared by the kidneys in 24 hours. Therefore, it can be determined by measuring the creatinine levels in the 24-hour urine sample. The range of creatinine clearance for women is listed below:

1. 18 to 29 Years - 78 to 161 mL per minute per BSA (body surface area).

2. 30 to 39 Years - 72 to 154 mL per minute per BSA.

3. 40 to 49 Years - 67 to 146 mL per min per BSA.

4. 50 to 59 Years - 62 to 139 mL per min per BSA.

5. 60 to 72 Years - 56 to 131 mL per min per BSA.

Conclusion:

A creatinine urine test is an important diagnostic procedure that helps the doctor know about creatinine levels and kidney function. Patients and doctors prefer this test as it can be easily done at home, and a hospital stay is not required. So, the patients must not ignore the symptoms of kidney disease and consult a urologist at the earliest.