Kidneys play many important roles in maintaining the health of the human body. The most important function of the kidney is to filter waste products from the blood and remove them with urine. A kidney function test (KFT) is performed to measure the functions of the Kidney.
The kidney Function Test (KFT) is also known as the Renal Function test (RFT).
The kidney also helps maintain the level of water and many essential minerals in the body.
Apart from this, the kidneys are also considered very important for producing the following in the body:
- Vitamin D
- Red blood cell
- Hormones that regulate blood pressure.
There can be many reasons for the kidneys not working effectively. A kidney function test helps the doctor to check the kidney functions and monitor them over time.
Several types of blood and urine tests can provide information about kidney function to the doctor. The kidney function test is also known as the renal function test and the urea and electrolytes test.
What is Kidney Function Test (KFT)
A kidney function Test or Renal Function Test is done to know whether all the parameters of kidney function are functioning properly within the normal range.
With the help of kidney function tests, the level of blood urea, creatinine, uric acid, and other minerals can be detected.
The main tests are the following:
- Creatinine level in the blood
- Estimated Glomerular Filtration Rate (eGFR)
- Blood Urea Nitrogen (BUN)
Some other tests may include:
- Urine test to measure products of metabolism
- Testing for electrolytes in the blood – usually sodium, potassium, chloride or bicarbonate,
- Complete blood count test.
What is the purpose of the Renal Function Test (RFT)
There are many reasons why kidney function tests may be needed, such as:
- As a general health check
- To evaluate kidney function and to diagnose and test kidney diseases
- To keep an eye on increasing kidney failure
- If the level of urea increases, if you are suspecting that there is a lack of water in the body
- If you suspect kidney failure due to which the kidneys are unable to function properly and to check for high levels of urea and creatinine in the blood
- Before and after starting treatment with any medicine, as there are some medicines whose side effect affects the kidney. Hence kidney function is checked before and after starting these medicines.
Before Kidney Function Test
- If you take any kind of medicines, herbal or supplements etc., then tell the doctor about all of them before getting the test done. Because the consumption of some medicines can also be asked to stop for some time.
- Do not consume large amounts of meat before the creatinine clearance test and do not exercise vigorously before taking a urine sample for the test.
- A diet high in meat can increase serum creatinine and creatinine clearance levels for a short period of time.
- A high-protein diet or dehydration can increase blood urea nitrogen (BUN) levels.
- Exercising can increase creatinine clearance levels.
- There are certain drugs that can affect BUN levels, serum creatinine, and creatinine clearance.
During Kidney Function Test
During the test, technicians remove a sample of blood from the patient’s body, in the process first a bandage or elastic band is tied on the patient’s upper arm.
The area where the injection needle is to be injected is then cleaned with an antiseptic and then the needle is inserted into the vein from under the skin.
The blood sample is then drawn through the needle, which is collected in a syringe, vial or tube attached to the needle and taken to the laboratory for analysis.
When the needle is inserted, a slight prick or pain may be felt. After removing the needle, the doctor places a piece of cotton wool or a bandage on that place, so that the bleeding is stopped.
There may be a blue mark on the needle site for a few days, although it does not cause severe and long-term pain.
After Renal Function Test (RFT)
- After the test, you are taken out of the testing facility.
- Medicines and food items that were stopped before the test are started again as per the instructions of the doctor.
- Blood may collect or a blood clot may form at the needle site, this condition is called a ‘hematoma’. It is a harmless condition and gets better on its own. If the size of the hematoma increases, or it increases swelling and other problems, to get relief from it, apply ice for the first 24 hours and then compress it with a warm and damp cloth. By doing this the clots start disappearing.
What are the risks of renal Function Test?
The risks associated with taking a blood sample for the test are quite minor. Taking blood samples can be a little more difficult in some people than in others.
The risks associated with taking a blood sample are minor, but may include:
- Bleeding
- Fainting or spinning
- Hematoma (blood accumulation under the skin)
- Infection (the needle can cause minor infections at the site)
KFT Result and Normal Range/Value
The reference table for the Kidney function test is given in below –
| Parameters | Normal Range |
|---|---|
| Serum Creatinine | Men: 0.2 – 1.3 mg/dl Women: 0.6 – 1.1 mg/dL |
| Serum urea | 10 – 45 mg/dl |
| Blood urea nitrogen (BUN) | 6 to 20 mg/dL |
| BUN / SR. Creatinine Ratio | 9:1 – 23:1 |
| Calcium | 8.8 – 10.6 mg/dl |
| Serum Sodium | 136 – 149 m. eq./l |
| Serum Potassium | 3.5 – 5.2 m. eq./l |
| Est. Glomerular filtration rate (eGFR) | > = 90 mL/min |
Note: If your testing facility has not provided GFR or eGFR report, please use this link to calculate your GFR with the help of the Serum Creatinine value observed in the report.
Urine test
Appearance: Normal urine should be light yellow or colorless
Chemical: Results should be negative for ketones, leukocytes, bilirubin and nitrate. The level of glucose in urine should not exceed 130 mg/dL and protein should not exceed 150 mg/dL.
Microscopic: The urine sample should not contain any crystals, bacteria and yeast. The red blood cell level should be less than 2 RBCs and the white blood cell level should be less than 2-5 WBCs/HPF.
Imaging Tests: A CT scan and SG of the kidney provide detailed information about the type and size of all the organs of the urinary system. It also includes the right and left kidneys, ureters, bladder, and urethra.
Your blood and urine samples are sent to the laboratory for analysis. The doctor looks at the test results to rule out kidney disease or other abnormalities.
1. Blood Test
Serum Creatinine – Creatinine is a waste product that comes from dietary meat proteins and from normal muscle breakdown. The level of creatinine in the blood can vary and each laboratory has its own normal range.
The normal range in many laboratories is 0.6 to 1.2 mg/dl (mg/dl). The level is higher than this means that the kidney is not working properly. As kidney disease progresses, the level of creatinine in the blood starts increasing.
Blood Urea Nitrogen (BUN) – Urea nitrogen is also formed in the body by the breakdown of proteins of foods. Normal blood urea nitrogen levels are 7 to 20 milligrams per deciliter (mg/dl). As kidney function declines, blood urea nitrogen levels begin to rise.
Estimated Glomerular Filtration Rate (eGFR) – Estimated glomerular filtration rate (eGFR) provides guidance for kidney function. Although the level of creatinine in the blood also guides kidney function, the estimated glomerular filtration rate gives a more accurate result. Calculate your GFR here.
The normal value of eGFR is 90-120 mg per minute, its value below 60 mg per minute indicates kidney damage. The lower its value falls, the greater the severity of kidney damage.
Serum electrolytes (Dissolved salts) – The regular measurement of sodium, chloride, potassium and bicarbonate is the serum electrolyte. Sometimes these are referred to as electrolytes. Abnormal levels of any of these can be caused by a kidney problem.
2. Urine Test
Color of urine:
Discolored urine can be a sign of some kind of underlying infection. Red or brown in the color of urine can be a sign of urinary infection or chronic kidney disease.
The orange color of urine is also seen in some people, in general, this condition can be due to the consumption of TB medicines like rifampicin.
| Color | Observation |
|---|---|
| Discolored | Underlying infection |
| Red or brown | Urinary infection or CKD |
Chemical:
A positive ketone test results in a patient is considered a sign of a serious disease called diabetic ketoacidosis. In this situation, tests like serum sodium, potassium, calcium and chloride are recommended.
The presence of leukocyte esterase and nitrites in urine indicates a bacterial infection.
High levels of glucose in the urine can be seen in diabetes mellitus and during pregnancy.
A higher than normal level of protein in urine can be a sign of diabetes mellitus, fever, nephrotic syndrome, multiple myeloma and some other diseases.
Microscopic
The presence of RBCs can be a sign of sickle cell anemia, renal cell carcinoma, prostatic hyperplasia, kidney stones, and other problems.
An increase in the amount of WBC indicates that the body is fighting an infection. At the same time, the presence of crystals can be a sign of gout or kidney stones.
Imaging Test
Through imaging tests, it is easy to know about problems like tumors, stones, and poor blood supply to the kidney.
When to get Renal Function Test
If you are experiencing some signs and symptoms associated with kidney problems, then you should get a kidney function test done.
Signs and symptoms associated with kidney problems can be as follows:
- High Blood Pressure
- Blood in urine
- Frequent urination
- Having trouble urinating initially
- Pain to urinate
- Swelling of hands and feet due to fluid buildup in the body
Feeling one symptom does not indicate a serious condition, but if more than one symptom is felt at the same time, then they may indicate kidney failure and in this case, KFT can help determine the original medical condition.
Kidney function test (KFT) cost/price
Renal function test (RFT) or Kidney Function test (KFT) cost may vary from lab to lab. However, in most of the cities, its price remains between 350 – 700 INR.
