A kidney biopsy, also called renal biopsy, is a procedure to remove a small piece of kidney tissue so that it can be examined under a microscope for signs of damage or disease. Your doctor may recommend a kidney biopsy if blood tests, urine tests or imaging techniques don't provide enough information to diagnose a kidney problem. A kidney biopsy may also be used to determine the severity of kidney disease or to find out if treatment for kidney disease is working. You may need a kidney biopsy if you've had a kidney transplant that's not working properly.

Most kidney biopsies are performed by inserting a thin needle through the skin. In this procedure, an imaging device helps guide the needle into one of your kidneys to remove tissue.

A kidney biopsy may be done to:

• Diagnose a kidney problem that can't otherwise be identified
• Help develop treatment plans based on the kidney's condition
• Determine how quickly kidney disease is progressing
• Determine the extent of damage from kidney disease or another disease
• Evaluate how well treatment for kidney disease is working
• Find out why a transplanted kidney isn't working properly

Your doctor may recommend a kidney biopsy based on the results of blood or urine tests. Some common reasons for kidney biopsy include:

• Blood in the urine (hematuria)
• Protein in the urine (proteinuria) that's excessive, rising or accompanied by other signs of kidney disease
• Problems with kidney function, leading to excessive waste products in the blood

Not everyone with these problems needs a kidney biopsy. The decision is based on your signs and symptoms, test results and overall health.

n general, percutaneous kidney biopsy is a safe procedure. Possible kidney biopsy risks include:

• Bleeding. The most common complication of kidney biopsy is blood in the urine (hematuria). The bleeding usually stops within a few days. Bleeding that's serious enough to require a blood transfusion affects a very small percentage of people who have a kidney biopsy. Rarely, surgery is needed to control bleeding.
• Pain. Pain at the biopsy site is common after a kidney biopsy, but it usually lasts only a few hours.
• Arteriovenous fistula. If the biopsy needle accidentally damages the walls of a nearby artery and vein, a fistula, or abnormal connection, can form between the two blood vessels. This type of fistula usually causes no symptoms and closes on its own.
• Others. Rarely, a collection of blood (hematoma) around the kidney becomes infected. This complication is treated with antibiotics and surgical drainage. Another uncommon risk is development of high blood pressure related to a large hematoma.

How you prepare

Before your kidney biopsy, you'll meet with your doctor to talk about what to expect. This is a good time to ask questions about the procedure and make sure you understand the risks and benefits.

Medications
When you meet with your doctor, bring a list of all medications you take, including over-the-counter medications, vitamins and herbal supplements. Before your kidney biopsy, you'll be asked to stop taking medications and supplements that can increase the risk of bleeding. These include:

• Blood-thinning medications (anticoagulants), such as warfarin (Coumadin)
• Aspirin, ibuprofen (Advil, Motrin, others) and other nonsteroidal anti-inflammatory drugs (NSAIDs)
• Fish oil
• Ginkgo

Your doctor or nurse will let you know when to stop taking these medications and supplements, and for how long.

Blood and urine samples
Before your biopsy, you'll have blood drawn and provide a urine sample to make sure you don't have an infection or another condition that would make the biopsy risky.

Diet
You may be asked not to drink or eat for eight hours before the kidney biopsy.

What you can expect

Kidney biopsy

A kidney biopsy is done at a hospital or outpatient center. Your health care team will review your medical history, including the medications you take. Just before your biopsy, you'll undress and put on a hospital gown. You may be given a light sedative to help you relax during the procedure.

During the procedure
During a kidney biopsy, you'll be fully awake and lying on your stomach, so your kidneys are positioned near the surface of your back. If the biopsy is for a transplanted kidney, you'll lie on your back instead. A percutaneous biopsy takes about an hour for the entire process and follows this sequence:

• You'll have an ultrasound of your kidney so your doctor knows exactly where to insert the needle. Ultrasound uses sound waves to create images of your internal organs and tissues. In some cases, a CT scan may be used instead of ultrasound.
• Your doctor marks your skin on the site where the needle will be inserted, cleans the area and applies a numbing medication (local anesthetic).
• The doctor then makes a small incision where the needle will go in. An ultrasound device is used to guide the needle into the correct place in your kidney.
• You'll be asked to take a deep breath and hold it as the doctor uses a spring-loaded instrument to insert the biopsy needle into the kidney. When the needle pushes through your skin to the kidney, you may feel a "pop" or pressure and hear a sharp clicking noise. You'll remain still and hold your breath for the time it takes to collect the tissue — 30 to 45 seconds. Your doctor may need to insert the needle three or four times (often through the same incision) to get enough tissue.
• A small bandage will be placed on the incision.

Other kidney biopsy procedures
Percutaneous kidney biopsy isn't an option for some people. If you have a history of bleeding problems, have a blood-clotting disorder or had a kidney removed, your doctor may use a laparoscopic biopsy. In this procedure, your doctor makes a small incision and inserts a thin, lighted tube with a video camera at its tip (laparoscope). This tool allows the doctor to view your kidney on a video screen and remove tissue samples.

After the procedure
After the biopsy, you can expect to:

• Be taken to a recovery room where your blood pressure, pulse and breathing will be monitored. In addition, a urinalysis and complete blood count will be done to check for bleeding and other complications.
• Rest quietly on your back — or your stomach if you have a transplanted kidney — for several hours. You can eat and drink after the procedure.
• Be given written instructions about your recovery.
• Feel some soreness or pain at the biopsy site for a few hours. You'll be given medications to relieve pain.

Most people can leave the hospital the same day. Some people need to rest in bed for 12 to 24 for hours after the biopsy, as directed by their doctor. Your health care team will let you know about any restrictions you need to follow after the biopsy. For example, you should avoid heavy lifting and strenuous exercise for two weeks.

Your kidney tissue goes to a laboratory to be examined by a doctor who specializes in diagnosing disease (pathologist). The pathologist uses microscopes and dyes to look for unusual deposits, scarring, infection or other abnormalities in the kidney tissue.

Call your doctor if you experience:

• Significant bright red blood or clots in your urine more than 24 hours after the biopsy
• Inability to pass urine
• Fever
• Worsening pain at the biopsy site
• Fever over 100.4 F (38 C)
• Faintness or weakness