Kidney Function Test

What is the Function of a Kidney?

The primary function of the kidney is balancing homeostasis. The kidney manages fluid levels, electrolyte balance and others which keep the internal environment of our body stable. The kidney excretes water-soluble wastes from our body. It removes two significant compounds Urea and Uric Acid, which help to purify our blood. The kidney also reabsorbs essential nutrients from the blood and sends them as per need. The reabsorbed products are glucose, amino acids, bicarbonate, sodium, phosphate, chloride, magnesium, potassium, ions etc. The kidney maintains the pH level of the human body, which helps proteins and enzymes not to break down. Beside these, the kidney regulates blood pressure and secretes active compounds such that Erythropoietin, Renin, Calcitriol.


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What Is KFT Test?

KFT test full form is a kidney function test. KFT test means the determination of renal disorders. KFT test is a test to check kidney function. Kidney function test includes urine examination, serum urea, blood urea nitrogen (BUN), calcium, serum creatinine, dilution test.


How To Test Kidney Function?

After collecting the blood sample, we have to compare the urea, creatinine, calcium, nitrogen level with the kidney function to test typical values. Beside this imaging tests can also help. Kidney renal function test is done by the following steps.

  • Urine Examination – In this process, a physical examination is done, which records the colour, odour, quantity, specific gravity of the urine. A microscopic exam of urine is done to determine any element which should not be present in urine.

  • Serum Urea – Urea is formed as an end product of protein catabolism. By urea cycle, it is produced from the amino group of the amino acids in the liver. Urea is filtered at the glomerulus, and it is secreted and reabsorbed at the tubular phase. Urea level increases only for the reduction of glomerulus function by 50%. The rise of serum urea level is considered as glomerular dysfunction, which causes renal dysfunction. The standard serum urea value is 20-45 mg/dL. But this value can also be affected by a high protein diet and other non-renal disorders, hepatic injuries. So, determination of serum urea level is not a good detector of kidney disorders. Still, it is one of the most suggested tests for renal dysfunction.

  • Blood Urea Nitrogen (BUN) – BUN can be determined from serum urea level. By calculating the molecular weight and the contribution of nitrogen in serum urea, we can get the blood nitrogen level. Increase in blood nitrogen level detects Azotemia.

  • Calcium – By this test, we measure the amount of calcium in blood cells. Usually, calcium is for building and fixing of bones and teeth. It also helps nerves to work and makes the construction of muscles. Calcium helps every body’s cells to work correctly. High calcium level causes headaches, nausea, sore eyes, itchy skin, aching tooth etc.

  • Serum Creatinine Level – Creatinine is a tripeptide of muscles. Unlike urea, it is a marker of renal function. The problem of glomerular filtration can cause high serum creatinine level. Serum creatinine level can determine glomerular dysfunction. Creatinine level depends on muscle mass and muscle wear. It is a vital part of the kidney function test.

  • Dilution Test – Dilution test measures the working of tubules. For less reabsorption of tubules, urine becomes diluted. In this test, the patient fasts overnight, and in the morning, drinks 1200 ml of water over 30 minutes. Then urine samples are collected every 4 hours. Urine’s specific gravity of 1.033 or more than that indicates tubular dysfunction.

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Solved Examples

A 53 years old woman is selected for a kidney function test. She didn’t take anything before the test but drank water. A patient would fast for 8-12 hours before the KFT Test.


Now we get From the Kidney Function Test –

Calcium- 11.3 mg/dL, Creatinine- 1.7 mg/dL, Potassium- 6.1 mEq/L, Sodium- 153 mEq/L, Uric Acid- 6.8 mg/dL, BUN- 22 mg/dL.


From the result, the symptoms we get are high blood pressure, blood in urine, frequent urges to urinate, difficulty in beginning urination, painful urination. These symptoms indicate that the kidneys aren’t working correctly. The patient should take treatment accordingly.


Did You Know?

As a result of kidney disease, the risk factors are diabetes, high blood pressure etc. If kidney disease gets worse, it may lead us to kidney failure. It can also cause heart problems, blood vessel disease and many other health problems. People who have these risk factors should check-up regularly. Simple ways to protect our kidneys keep blood sugar, blood pressure, cholesterol under control, eat healthily, do exercise, don’t smoke, and limit alcohol.

FAQ (Frequently Asked Questions)

1. What is the Blood Test for Kidney Function?

Answer: As a part of the KFT test, the blood test is GFR. The full form of GFR is Glomerular Filtration Rate. In this process, creatinine is determined, which comes from muscle tissue. In kidney problems, they fail to remove creatinine from the blood, and thus creatinine level becomes higher. Creatinine level depends on age, sex etc. GFR number detects that our kidneys are working correctly or not. Apart from GFR, there are some other blood tests which can determine renal disorders. In the kidney function test, we also measure calcium, potassium, nitrogen, sodium by blood test. But GFR is the first blood test.


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2. How will I Know if I have Kidney Disease?

Answer: In kidney disease, there may not be any symptoms at the first stage. Symptoms come gradually, and in advanced stages, for it causes nausea, nocturia, vomiting, stomatitis, anorexia, fatigue, pruritus, lassitude, water retention, peripheral neuropathies etc. If these symptoms are present, then a KFT test is a must. Laboratory-based diagnosis of renal functions and renal biopsy is necessary. More tiredness, less energy, sleeping trouble, dry and itchy skin, feel of urinating more often, blood in urine, foamy urine, swollen ankles and feet, poor appetite, cramping muscles are also symptoms of kidney problems. The Kidney problems must be cured as soon as possible.