As a nephrologist, part of my practice involves ordering blood and urine tests to assess the functionality of your kidneys. These tests help determine if your kidneys are effectively removing waste and excess fluid from your body, as well as if there are any signs of kidney damage, such as abnormal protein leakage. Here’s a concise overview of the various tests used to evaluate kidney function.
Blood tests
1. Serum Creatinine
Creatinine, a waste product resulting from muscle wear and tear, is measured in the blood. Elevated creatinine levels typically signify impaired kidney function.
2. Estimated Glomerular Filtration Rate (eGFR)
eGFR, calculated from serum creatinine levels, considers age and gender. A normal eGFR varies with age, declining as one gets older. An eGFR below 60 indicates insufficient kidney function, and levels below 15 suggest a high risk of kidney failure.
3. Blood Urea Nitrogen (BUN)
BUN levels reflect urea nitrogen from protein breakdown in food. While normal levels range from seven to 20, an increase often correlates with decreased kidney function.
Urine tests
Urine tests vary from simple to more extensive assessments, with some requiring a 24-hour urine collection. These tests provide insights into kidney function and protein leakage:
1. Urinalysis
This test involves microscopic examination and dipstick testing of a urine sample. It detects abnormalities like excess protein, blood, bacteria and sugar, aiding in diagnosing kidney and urinary tract disorders.
2. Urine protein
An excess of protein in urine, termed proteinuria, indicates kidney damage. A positive dipstick test should be confirmed with a quantitative measurement like the urine protein-to-creatinine ratio.
Imaging tests
1. Ultrasound
Utilizing sound waves, ultrasound offers images of the kidneys to identify abnormalities, such as size, position or obstructions like stones or tumors.
2. CT Scan
This imaging method employs X-rays to visualize the kidneys for structural anomalies and obstructions. Contrast dye may be used, but caution is advised for individuals with kidney disease.
Other tests
1. Glomerular Filtration Rate (GFR) Scan
A GFR scan assesses kidney function and blood flow using a radioactive tracer. It’s a safe procedure conducted in the Nuclear Medicine Department and lasts about four hours.
2. Kidney Biopsy
In this procedure, small kidney tissue samples are extracted using a thin needle for microscopic examination. It’s performed to diagnose specific diseases, assess damage or investigate issues with kidney transplants.
It is important to note that these tests aren’t all conducted simultaneously and should only be performed when deemed necessary by your physician.
