How is kidney failure diagnosed?

There are several tests your doctor can use to diagnose kidney failure. These include:

Urinalysis

Your doctor may take a urine sample to test for any abnormalities, including abnormal protein or sugar that spills into the urine. Your doctor may also perform a urinary sediment examination. This measures the amount of red and white blood cells, looks for high levels of bacteria, and searches for high numbers of cellular casts.

Urine volume measurements

Measuring urine output is one of the simplest tests to help diagnose kidney failure. For example, low urinary output may suggest that kidney disease is due to a urinary blockage, which can be caused by multiple illnesses or injuries.

Blood samples

Your doctor may order blood tests to measure substances that are filtered by your kidneys, such as blood urea nitrogen (BUN) and creatinine (Cr). A rapid rise in these levels may indicate acute kidney failure.

Imaging

Tests such as ultrasounds, MRIs, and CT scans provide images of the kidneys themselves, along with the urinary tract. This allows your doctor to look for blockages or abnormalities in your kidneys.

Kidney tissue sample

Tissue samples are examined for abnormal deposits, scarring, or infectious organisms. Your doctor will use a kidney biopsy to collect the tissue sample. A biopsy is a simple procedure that’s usually performed while you’re awake. You’ll have a local anesthetic to eliminate any discomfort. The sample is collected with a biopsy needle inserted through your skin and down into the kidney. X-ray or ultrasound equipment is used to locate the kidneys and assist the doctor in guiding the needle.