A renal biopsy is a procedure used to extract kidney tissue for laboratory analysis. The word “renal” describes the kidneys. A renal biopsy is also called a kidney biopsy.
The test helps your physician to identify the type of kidney disease you have, how severe it is, and the best treatment for it. A renal biopsy can also be used to monitor the effectiveness of kidney treatments and see if there are any complications following a kidney transplant.
There are two different ways to perform a renal biopsy.
The most common type of renal biopsy is called a percutaneous biopsy, or a renal needle biopsy. For this procedure, a doctor inserts a thin biopsy needle through the skin to remove your kidney tissue. He or she may use an ultrasound or computed tomography (CT) scan to direct the needle to a specific area of the kidney.
In an open biopsy—or surgical biopsy—your doctor makes a cut in the skin near the kidneys. This allows the physician to look at the kidneys and determine from which area the tissue samples should be taken.
A renal biopsy can identify problems that are interfering with your normal kidney function. Healthy individuals have two kidneys that perform many functions. It is the kidneys’ job to:
- remove urea—or liquid waste—from the blood by producing urine
- maintain a balance of chemicals, such as sodium and potassium, in the blood
- supply the hormone erythropoietin, which supports red blood cell growth
- control blood pressure by producing the hormone renin
- provide the hormone calcitriol, which regulates calcium absorption and calcium blood levels
If your routine blood and urine tests indicate that your kidneys are not doing their job properly, your doctor may decide to perform a renal biopsy. Your doctor might also order this test to:
- find the reason for an abnormal level of waste products in the blood
- see if a kidney tumor is malignant or benign
- gauge how well a transplanted kidney is working
- investigate the cause of hematuria (blood in your urine) or proteinuria (a high level of protein in your urine)
- see the severity of progressive kidney failure and how quickly the kidneys are failing
- create a treatment plan for a diseased kidney
A renal biopsy usually is performed as an outpatient procedure at a hospital. However, it can also be done in a radiology department if an ultrasound or CT scan is necessary during the procedure.
Typically, a percutaneous, or renal needle, biopsy is done by a doctor and takes about an hour.
Just before the procedure, you’ll change into a hospital gown. Your doctor might give you a sedative through an intravenous (IV) line in your hand or arm to help you relax. However, you will not receive general anesthesia for this procedure, meaning you will be awake throughout.
You will be positioned so that you are lying on your stomach. This will keep your kidneys easily accessible from your back. You may be given a pillow or towel, since you will have to remain still and stay in this position for about 30 minutes. If you have already had a kidney transplant, you will be told to lie on your back.
Next, a doctor will inject a local anesthesia into the entry site to numb the area and make a small incision there. He or she will insert the needle through the incision and into your kidney. Your doctor might use an ultrasound or a CT scan to direct the needle.
You will have to take a deep breath and hold it as your physician takes the tissue sample. This may take about 30 to 45 seconds. You may feel some discomfort when the tissue sample is being extracted.
If more than one tissue sample is needed, the process will be repeated several times. Each time, the needle will be inserted through the same incision. You will have to hold your breath while each sample is retrieved.
There are two main types of percutaneous biopsies. The type of procedure your physician uses will determine the instrument required to remove the tissue.
In a fine needle aspiration biopsy, your physician extracts a small tissue sample from your kidney using a small, thin needle that is attached to a syringe.
For larger tissue samples, your physician may use a needle core biopsy. In this procedure, the physician removes a larger sample of kidney tissue using a spring-loaded needle. If you are having a needle core biopsy, you will hear a loud clicking or popping sound when the tissue sample is being removed.
After the sample is retrieved, pressure will be applied to the biopsy site until any bleeding has stopped and a bandage will be applied over the incision site.
Depending on your physical condition and medical history, your doctor may recommend an open biopsy. Usually, you will have this type of biopsy if you have had problems with bleeding or blood clotting in the past, or if you have only one kidney.
If you are having an open biopsy, you will receive general anesthesia. This means you will be asleep throughout the procedure. Your doctor will make an incision and surgically remove a tissue sample from your kidneys while you are unconscious.
Some surgical biopsies require an incision up to five inches long. Often, however, surgical biopsies can be performed laparoscopically. For this procedure, your doctor will make a small incision and use a laparoscope, which is a thin, lighted tube, to perform the biopsy. The laparoscope has a video camera at the end, which sends images of the kidney to a video monitor. Using a laparoscope, your physician can observe the kidney and extract the larger tissue sample through a smaller incision.
After your renal biopsy, you will need time for recovery and observation before you are released from the hospital. The timing of your release will vary, depending on your overall physical condition, your doctor’s practices, and your reaction to the procedure.
Generally, you will be taken to a recovery room for rest and observation. During this time, you will lie on your back—or on your stomach if you have had a kidney transplant—for about six to eight hours.
A nurse or doctor will keep track of your vital signs, including blood pressure, temperature, pulse and breathing rate. A complete blood count test and urine test will be done to see if there is any internal bleeding or other problems. You will also be given medication to reduce pain at the biopsy site.
When your vital signs are stable, you will be released from the hospital to go home. It is normal to have bright red blood in your urine up to 24 hours after the biopsy. If this condition lasts more than a day however, you should report it to your doctor.
Typically, you can go back to eating your normal diet when you feel hungry. Your doctor may ask that you rest in bed for 12 to 24 hours after your biopsy and avoid strenuous activity and heavy lifting for two weeks. You should also avoid jogging, aerobics, or any other activity that involves bouncing for two weeks after your biopsy. You may want to take a pain reliever for any discomfort you have at the biopsy site.
A renal biopsy can provide valuable information that allows your doctor to diagnose kidney abnormalities and decide on appropriate treatments.
Post-procedure infection is a serious potential risk. However, this rarely occurs. Always be on the lookout for symptoms that could indicate an infection after your renal biopsy. Contact your doctor if you:
- have bright, red blood or blood clots in your urine for longer than 24 hours after your biopsy
- cannot urinate
- have chills or a fever
- experience pain at the biopsy site that increases in intensity
- have redness, swelling, bleeding, or any other discharge from the biopsy site
- feel faint or weak
In addition to infection, a renal biopsy—like any invasive procedure—carries the risk of potential internal damage to the targeted organ or nearby areas.
Typically, you do not need to do much to prepare for a renal biopsy.
Be sure to tell your physician about any prescription drugs, over-the-counter medications, and herbal supplements you are taking. You should discuss with him or her whether you should stop taking them before and during the test, or if you should change the dosage.
Your doctor may provide special instructions if you are taking medications that could affect the results of the renal biopsy. These medications include:
- anticoagulants (blood thinners)
- nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin or ibuprofen
- any medications that affect blood clotting
- herbal or dietary supplements
Tell your physician if you are pregnant, or think you might be pregnant, so that your fetus is not harmed.
Before your renal biopsy, you will have a blood test and provide a urine sample. This will ensure that you do not have any pre-existing infections.
You will need to fast from food and drink for at least eight hours prior to your kidney biopsy. If you are given a sedative to take at home before the biopsy, you will not be able to drive yourself to the procedure and will have to arrange for transport.
The tissue sample that was retrieved during your renal biopsy will be sent to a laboratory for examination. A pathologist, who is a doctor who specializes in disease diagnosis, will examine the tissue.
Your sample will be analyzed with microscopes and reactive dyes. The pathologist will identify and assess any deposits or scars that appear. Infections and other abnormal conditions also will be detected.
The pathologist will compile the results and make a report to your doctor. He or she should call you with the results in about a week.
If the kidney tissue shows a normal structure that is free of deposits and other defects, the results are considered normal.
The results of a renal biopsy are considered abnormal if there are changes in the kidney tissue. There are numerous causes for this result. Sometimes, diseases that begin in other parts of your body can cause damage to the kidneys as well.
If your results were abnormal, it could indicate:
- infection of the kidneys
- restrictions or weaknesses in the flow of blood to the kidneys
- connective tissue diseases
- rejection of a kidney transplant
- kidney cancer
- complicated urinary tract infection
- any of numerous other diseases that have a negative effect on kidney function
Your doctor may decide to order additional tests in order to plan treatment. He or she will go over your results and your condition in depth with you, and discuss all the next steps following your renal biopsy.