Renal Function Test (RFT): Importance of Test Results

Renal function tests, also referred to as kidney function tests, are diagnostic procedures that involve analyzing blood and urine samples to assess the performance of the kidneys. These tests evaluate the glomerular filtration rate (GFR), and levels of creatinine in the blood, and identify the presence of proteins, blood, or bacteria in the urine. This test plays an important role in the early detection and diagnosis of kidney problems.

Functions of the kidneys

The kidneys perform the following functions:

• Filter waste material
• Regulate fluid levels
• Regulate blood pressure
• Regulate salt concentration
• Produce hormones to make red blood cells
• Metabolism of vitamin D
• Acid-base balance

Purpose of renal function test (RFT)

RFT is done to rule out kidney diseases; it may be used for

Diagnosis: To detect the disease condition after the onset of symptoms. If physicians think a kidney problem is causing symptoms, they may order RFT.

Screening: To detect the issue at an early stage, screening tests, including RFT, are conducted prior to the manifestation of any symptoms.

Monitoring: To determine whether the kidney disease is improving or getting worse over time. After the kidney disease treatment, an RFT test is conducted to track kidney function.

Symptoms of kidney diseases

Common symptoms of kidney problems are:

• Tiredness
• Swelling of hands, legs, and face
• Sleep problems
• Frequent urination
• Poor appetite
• Muscle cramping
• Itchy and dry skin
• Confusion

Who should undergo the renal function test?

The renal function test is a valuable tool in the diagnosis and treatment of conditions that impact the proper functioning of the kidneys. Individuals who are 60 years of age or older are advised to undergo RFT due to the potential risks of high blood pressure, kidney stones, diabetes, a family history of kidney diseases, any unusual findings in the imaging results, or abnormalities in the structure of the kidneys. Additionally, individuals who are overweight or obese, as well as those who take medications that may harm the kidneys, should consider undergoing RFT. Furthermore, individuals who smoke and have other cardiovascular diseases are also encouraged to undergo this test.

What does a renal function test measure?

A renal function test analyzes proteins and waste products in blood and urine samples. This includes:

Estimated Glomerular Filtration Rate (eGFR): This test measures the filtration rate of kidneys based on protein levels, age, gender, height, weight, and race.

Serum creatinine: Creatinine is the waste product that the kidneys remove from the blood and excrete as urine. It is filtered from the blood by the kidneys and carried out of the body through urine. Kidney diseases are indicated by an increase in blood creatine levels.

Blood urea nitrogen (BUN): Urea nitrogen is a waste product formed after the breakdown of proteins and excreted out of the body through urine. A normal urea nitrogen level depends on age and other health conditions; high levels may indicate kidney disease.

Microalbuminuria: This test measures the presence of albumin protein in the urine. It also detects the risk of developing kidney disease because of diabetes or high blood pressure.

Albumin-Creatinine Ratio: This test detects kidney damage by measuring the presence of albumin and creatinine in urine.

Creatinine clearance: This test measures the level of creatinine in the urine compared to that in the blood. A urine sample is collected for 24 hours to measure creatinine clearance levels.

Urinalysis: This test includes microscopic analysis of urine samples to detect colour, appearance, pH, and other chemical and microscopic findings that may be indicative of disorders of the kidney, urinary tract infections, and diabetes.

Test preparation

For a blood test, a healthcare provider will tie a band around the upper arm to take a blood sample from a vein. After that, an antiseptic wipe will be used to clean a small area of skin. Then, the needle will be inserted into the vein, and a small amount of blood will be drawn.

The 24-hour urine test requires the patient to collect their urine sample continuously for a full day using the provided container. The patient should begin by urinating normally upon waking up, then proceed to collect all subsequent urine samples in the container throughout the day, including the first morning urine the following day.

Interpretation of RFT test results

A deviation from normal levels indicates the following:

• The eGFR range below 60 can indicate different stages of kidney functionality and damage.
• Having higher-than-normal serum creatinine and BUN levels in the blood increases the risk of kidney disease.
• Having higher-than-normal levels of urine albumin and albumin-creatinine ratios can increase the risk of kidney disease and other disorders like diabetes and high blood pressure.
• Having dark or amber-coloured urine is usually a sign of kidney disease.
• High or low pH levels in the urine are an indication of urinary tract infections.
• The presence of crystals in the urine can be an indication of kidney stones.
• The presence of blood in urine can indicate infection, and the presence of protein indicates kidney disease.
• The presence of bacteria, white blood cells, or red blood cells in the urine indicates urinary tract infections and other kidney diseases.

The renal function test determines how well an individual’s kidneys are working. The kidneys are responsible for eliminating waste materials from the body by excreting them through urine. By identifying medical conditions like diabetes and hypertension that impact the kidneys, these tests are crucial for early detection and diagnosis of kidney issues.