Renal / Kidney Function Test (RFT / KFT)

A Renal / Kidney Function Test (RFT / KFT) test is used to diagnose the overall function of the kidneys. It helps diagnose inflammation, infection or damage in the kidneys. The test measures Calcium, Uric Acid, Creatinine, BUN and BUN/Creatinine Ratio in the blood to determine the health condition of the kidneys.

Kidneys play a crucial role in filtering waste products from the blood and discarding them in the form of urine. They also remove excess water from the body. Any damage to the kidneys can prevent them from functioning properly. Kidney-related diseases can result in a toxic waste build-up in the body and can also lead to excess water in the body, causing inflammation.

The doctor prescribes a renal function test for the early detection of any kidney disease. In addition, people who have diabetes, hypertension, heart disease and a family history of kidney disease should undergo regular renal function tests to monitor kidney health.

Diabetes, heart disease and kidney disease form a triad where one condition often leads to another. For example, people suffering from diabetes or hypertension or any form of cardiac disorder are at risk of developing kidney disease.

Other Names of Renal Function Test

• Kidney function panel
• Renal function panel
• Kidney function test
• Renal function test
• KFT
• RFT

What does the test detect/measure and who is this prescribed for?

Renal function test measures multiple components that help understand the status of the kidneys. The RFT test procedure is usually prescribed by the doctor when there are signs and symptoms of kidney damage or kidney disease. The common kidney disorders are Acute Renal Failure (ARF), Chronic Kidney Disease (CKD) and glomerulonephritis.

The common signs and symptoms of loss of kidney function are:

• Changes in urine like appearance, quantity and frequency.
• Swelling in the body due to an unknown cause. Swelling is usually seen on the face and feet.
• Muscle pain and cramps.
• Unexplained weight gain or weight loss.
• Nausea or vomiting.

 Apart from these symptoms, a renal function test is also advised in people with other chronic diseases like diabetes, high blood pressure and cardiac disease like coronary artery disease. In addition, the doctor might prescribe this test as a routine evaluation blood test in case of a family history of renal disease.

Diabetes, renal disease and cardiac disease are three diseases that are closely interlinked. One disease can lead to another and the worsening of one disease can have a negative effect on the other. Therefore, people with diabetes and cardiac disease are advised to do renal function tests as part of their routine blood tests.

The prevalence of Chronic Kidney Disease (CKD) is rapidly increasing worldwide. CKD can lead to a complication called End-stage Renal Disease (ESRD). Men are more susceptible to developing ESRD after CKD than females.

A renal function test is a group of tests that requires a sample of blood to assess kidney functions.

Test Preparation

A renal function test requires a blood sample to check for the various components and fasting is not required before giving the blood sample. Inform your doctor about all ongoing medications, vitamins and supplements before taking the test.

Test inclusions: What parameters are included?

Renal function test measures a multitude of parameters. The components of renal function tests differ based on the laboratories and the prescriptions. Some of the components measured in a renal function test are:

• Serum creatinine – Creatinine is a waste product formed due to the normal activity of the muscles in the body. An increased creatinine level may mean that the kidneys are not functioning optimally.
• Blood Urea Nitrogen (BUN) – It measures the amount of urea in the blood. Urea is formed as a result of the breakdown of proteins in the body. It is also referred to as urea nitrogen, a waste product excreted by the kidneys. High levels indicate kidney damage.
• Calcium - A mineral vital for the bones, teeth, muscles, heart and nerves. Both low and high levels indicate health conditions that require attention.
• BUN (Blood Urea Nitrogen): Creatinine ratio – BUN and creatinine are waste products of the body. This test helps differentiate the cause of abnormal levels due to kidney damage or problems in another part of the body.
• Estimated Glomerular Filtration Rate (eGFR) – Glomerular Filtration Rate (GFR) is an evaluation of kidney function. It measures the quantity of blood filtered by the kidney in a minute.
• Urea/Creatinine Ratio
• Urea (Calculated)
• Uric Acid

Other measurements that may be included in a renal function test are:

• Total protein – Apart from albumin, there are various other proteins in the blood. The total protein is a test that measures the overall amount of protein in the blood.
• Sodium – An electrolyte that maintains fluid balance in the body. Low sodium levels indicate a fluid imbalance and suggest kidney-related disease.
• Potassium – Like sodium, it is also an electrolyte that maintains healthy fluid balance and acid-base balance in the body.
• Chloride - An electrolyte that works in combination with other electrolytes to maintain fluid balance in the body.
• Phosphorus – Mineral is present in bones, teeth and muscles. Phosphorus is excreted by the kidneys. A high level of phosphorus can be due to kidney disease.
• Serum albumin – Albumin is a type of protein produced in the liver. Healthy kidneys do not let albumin pass in the urine. Less albumin in the urine means the kidneys are functioning well.
• Glucose – It is also known as blood sugar. Excess sugar is a common finding in diabetes. Persistent high levels of glucose can damage kidney cells over a period of time.

Acute kidney disease, Chronic kidney disease, Diabetic nephropathy, Renal failure

The normal values, parameters, and reference ranges of the tests may vary from lab to lab. Please refer to the ranges mentioned in the report and consult a doctor to understand the interpretation of lab reports.

If the values of the RFT tests are higher or lower than the normal range, it means that there is an underlying renal disease condition. The results of each test help the doctor to get a better picture of the overall health of the kidneys. Having an abnormal RFT value in just one of the components of the renal function test may not confirm a kidney disease. The test results of RFT are to be matched with the patient's medical history and health status.

eGFR value is of high significance to understanding the functioning of the kidneys. If the eGFR is less than 90 but more than 60, it suggests mild kidney disease. But, if the eGFR is below 60, it is a sign of damage to the kidneys. An eGFR of less than 15 means a high risk of kidney failure and may require dialysis or a kidney transplant.

Depending upon the test results and the health condition of the patient, the doctor may order more tests to confirm a diagnosis. There are many conditions that can lead to the loss of kidney function. The doctor will do thorough testing before establishing a diagnosis and starting a treatment plan.