A kidney biopsy is done using a long thin needle put through the back (flank) into the kidney. This is called a percutaneous kidney biopsy. A tissue sample is taken and sent to a lab. It is looked at under a microscope. The sample can help your doctor see how healthy your kidney is and look for any problems.

The two kidneys are found on either side of the spine, in the lower back. They help the body balance water, salts, and minerals in the blood. The kidneys also filter waste products from the blood and make urine.

A kidney biopsy may be done to check for kidney problems. It may also be done after other tests for kidney disease, such as blood and urine tests, ultrasound, or a computed tomography (CT) scan, show a kidney problem. If kidney cancer is suspected, a biopsy may not be done because of the chance of spreading the cancer.

Why It Is Done

A kidney biopsy is done to:

• Find kidney disease when there is blood or protein in the urine or when the kidneys are not working well.
• Check kidney problems seen on an ultrasound or a CT scan.
• Watch kidney disease and see if treatment is working.
• See whether a transplanted kidney is working.

How To Prepare

Tell your doctor if you:

• Are taking any medicines. If you are taking aspirin, nonsteroidal anti-inflammatory medications (NSAIDs, such as ibuprofen or naproxen), or blood thinners (such as Coumadin, heparin, or Plavix), your doctor may tell you to stop taking these medicines for several days before the biopsy.
• Are allergic to any medicines, such as those used to numb the skin (anesthetics).
• Have had bleeding problems or take blood thinners, such as aspirin or warfarin (Coumadin).
• Are or might be pregnant.

Do not eat or drink for 8 hours before the biopsy. You will empty your bladder before the biopsy.

Arrange to have someone take you home after the biopsy because you may be given a medicine (sedative) to help you relax.

You will have blood tests done before the kidney biopsy to see whether you have any bleeding problems or blood clotting disorders. You may also have an ultrasound test or CT scan of the kidney to show the best place in your kidney to put the biopsy needle.

For a kidney biopsy, you will be asked to sign a consent form. Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).