What is a Kidney Biopsy?

A kidney biopsy involves taking one or more tiny pieces (samples) of your kidney to look at with special microscopes. The microscopes make it possible to see the samples in greater detail.

The biopsy sample may be taken in one of two ways:

  1. Percutaneous (through the skin) biopsy: a needle placed through the skin that lies over the kidney and guided to the right place in the kidney, usually with the help of ultrasound.
  2. Open biopsy: the kidney sample is taken directly from the kidney during surgery.
    The kidney sample is then sent to a doctor (pathologist) who looks at it with microscopes. He or she will check for any signs of disease.

What are the reasons for doing a kidney biopsy?
Some kidney problems can often be found with blood and urine tests, a sonogram (an image made by ultrasound) or other special x-rays, and a physical exam rather than a biopsy. But in some patients with certain types of kidney disease, and those with a kidney transplant that is not working well, a correct diagnosis can only be made with a kidney biopsy.

Specific reasons to do a kidney biopsy include:

  • Blood in the urine (hematuria) or protein in the urine (proteinuria)
  • Abnormal blood test results
  • Acute or chronic kidney disease with no clear cause
  • Nephrotic syndrome and glomerular disease (which happens when the filtering units of the kidney are damaged)

A kidney biopsy may also help to find:

  • If a disease is getting better with treatment or if it is getting worse. It may also show a problem that cannot be cured, but can be slowed down by other therapy.
  • How much permanent damage has happened in the kidney.
  • Why a transplanted kidney is not working well and helps your doctor decide on further treatment.
  • A kidney tumor.
  • Other unusual or special conditions.
  • If a certain treatment is hurting your kidneys

Your healthcare provider should explain the reasons for the kidney biopsy. You should know why it is necessary, the benefits, and any risks. You will be asked to sign a consent (permission) form to make sure you are aware of any risks. Be sure you understand the risks before you sign the consent form. You may want to write down a list of questions about the biopsy.

What are the possible risks of kidney biopsy?
The risks of kidney biopsy are very small, but they should be discussed with your healthcare provider. As in other medical and surgical procedures, certain complications may happen even though every effort is taken to prevent them. A blood transfusion may be needed if serious bleeding occurs. Rarely, surgery may be needed to fix a blood vessel that is damaged during the procedure.

How should you prepare for the biopsy?
For two weeks before the biopsy, you should not take aspirin, over-the-counter pain medicines such as aspirin, ibuprofen, naproxen, Advil®, Nuprin®, or other medicines that may cause thinning of the blood. These medicines can change the way the blood clots and raise the risk of bleeding. For the same reason, you should stop taking some supplements such as fish oil. Blood and urine samples are usually taken before the kidney biopsy to make sure you do not have an infection or other condition. Your doctor may also want you to change other medications before the biopsy. You may be told to not eat or drink for eight hours before the procedure.

How is the biopsy done?
A kidney biopsy is usually done in a hospital. An overnight stay may be needed to watch for any problems. You may be awake with only light sedation, or asleep under general anesthesia. You will be lying face down with a pillow under your rib cage. If the biopsy is done on a transplanted kidney, you will be lying on your back.

Percutaneous biopsy:
The kidney is found using a sonogram, x-ray images, or both. Sometimes, an injection of dye into your veins may be needed to help the doctor find the kidney and important blood vessels. Once the biopsy site is found, your skin is marked, and cleaned where the biopsy needle will be inserted. You will receive a local anesthetic to numb the area where the biopsy needle enters. You will be asked to take in a deep breath and hold it as the doctor puts in the needle. When the needle pushes through the skin to the kidney, you may feel a "pop" or pressure. It is important to stay still and to hold your breath (about 45 seconds or less). Sometimes two needle passes are needed to get enough of the kidney sample for diagnosis. When enough is taken, the needle is removed and a bandage is placed over the needle puncture site. The entire procedure, from start to finish, usually lasts about one hour. Sometimes the biopsy may take longer than an hour.

Open kidney biopsy:
Some patients should not have a percutaneous biopsy because they may have a history of bleeding problems. For these patients, an open operation may be done where the surgeon can actually see the kidney to get a good sample to study.

After the test
You may need to rest in bed for 12 to 24 hours after the biopsy, as directed by the doctor. Staying still on bed helps to heal the site where the kidney sample was taken and lessen the chance of bleeding. Your blood pressure and pulse are checked often to look for any signs of bleeding inside your body, or other problems. Blood tests are also done. You may eat and drink fluids after the biopsy. If your blood tests, blood pressure and pulse are stable, you should be allowed to leave the hospital the next day.

Your doctor will talk to you about physical activity and things to watch for after going home from the hospital. Heavy lifting, strenuous exercise, including contact sports, and sexual intercourse should be avoided for two weeks after the biopsy. If you had an open biopsy, be sure to ask your doctor for any specific instructions you need to follow after the surgery.

Test results
After the kidney sample is taken, it is sent to specially trained pathologists who will read and interpret your kidney biopsy. It often takes three to five days to get the full biopsy results. In some cases, you may have a partial or full report within 24 hours or less.

THINGS TO REMEMBER
Before the biopsy:

  • Talk with your health care provider to make sure you understand the need for a biopsy and the risks and benefits.
  • Tell your doctor about any allergies you have and medicines you take.
  • Avoid blood thinning medications and supplements.
  • Avoid food and fluid for eight hours before the test.

After the biopsy:

  • Follow your doctor's instructions.
  • Rest in bed for 12 to 24 hours.
  • Avoid blood thinning medications.
  • Report any problems, such as:
    • Bloody urine for more than 24 hours after the biopsy
    • Unable to pass urine
    • Fever
    • Worsening pain at the biopsy site
    • Feeling faint or dizzy

Additional information
The following additional information on kidney biopsy is available from the National Kidney Foundation:

If you would like more information, please contact us.

© 2014 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.