A kidney biopsy is a procedure to remove a small piece of kidney tissue that can be examined under a microscope for signs of damage or disease.

Your doctor may recommend a kidney biopsy — also called renal biopsy — to diagnose a suspected kidney problem. It may also be used to see how serious a kidney condition is, or to monitor treatment for kidney disease. You may also need a kidney biopsy if you've had a kidney transplant that's not working properly.

Most often, a doctor performs a kidney biopsy by inserting a thin needle through the skin. This is called a percutaneous kidney biopsy. An imaging device helps the doctor guide the needle into the kidney 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
• Monitor the health of a transplanted kidney or 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 that show:

• Blood in the urine originating from the kidney
• 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.

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

• Bleeding. The most common complication of a kidney biopsy is blood in the urine. 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, an abnormal connection (fistula) 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.

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 benefits and risks.

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, such as warfarin (Coumadin, Jantoven), rivaroxaban (Xarelto), dabigatran (Pradaxa) or enoxaparin (Lovenox)
• Drugs that keep blood platelets from excessively sticking together, such as clopidogrel (Plavix)
• Aspirin
• Ibuprofen (Advil, Motrin IB, others) and other nonsteroidal anti-inflammatory drugs (NSAIDs)
• Certain dietary supplements, such as omega-3 fatty acids

Your doctor or nurse will let you know when to stop taking these medications and supplements, and for how long. Often, these medications are stopped seven days before the procedure and then started again seven days after the procedure.

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.

You'll have a kidney biopsy at a hospital or outpatient center. An IV will be placed before the procedure starts. Sedatives may be given through the IV.

During the procedure

During the biopsy, you'll be awake and lie on your abdomen or your side, depending on which position allows best access to your kidney. For a biopsy of a transplanted kidney, most people lie on their backs.

A percutaneous biopsy includes these steps:

• With an ultrasound probe, your doctor identifies exactly where to insert the needle. In some cases, a CT scan may be used instead of ultrasound.
• Your doctor marks your skin, cleans the area and applies a numbing medication (local anesthetic).
• Your doctor makes a small incision where the needle will go in and uses the ultrasound device to guide the needle into your kidney.
• You may be asked to hold your breath as your doctor collects a sample using a spring-loaded instrument. You may feel a "pop" or pressure and hear a sharp clicking noise.
• Your doctor may need to insert the needle several times — often through the same incision — to get enough tissue.
• Your doctor removes the needle and places a small bandage 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 have only one kidney, your doctor may consider 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:

• Spend time in a recovery room where your blood pressure, pulse and breathing will be monitored.
• Have urinalysis and complete blood count tests done to check for bleeding and other complications.
• Rest quietly for around four to six hours.
• Receive 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, about 12 to 24 hours after the procedure. Once home, your doctor will probably recommend that you rest for another day or two. Your health care team will let you know about any activity restrictions, such as avoiding heavy lifting and strenuous exercise.

Your kidney tissue goes to a lab 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
• Changes in urination, such as an inability to pass urine, an urgent or frequent need to urinate, or a burning sensation when urinating
• Worsening pain at the biopsy site
• Fever over 100.4 F (38 C)
• Faintness or weakness

It may take up to a week before your doctor has your biopsy report from the pathology lab. In urgent situations, a full or partial report may be available in less than 24 hours.

Your doctor will usually discuss the results with you at a follow-up visit. The results may further explain what's causing your kidney problem, or they may be used to plan or change your treatment.