A renal biopsy is a procedure used to extract kidney tissue for laboratory analysis. The word “renal” describes the kidneys, so a renal biopsy is also called a kidney biopsy.
The test helps your doctor 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 ways to perform a renal biopsy:
- Percutaneous biopsy (renal needle biopsy). This is the most common type of renal biopsy. For this procedure, a doctor inserts a thin biopsy needle through the skin to remove your kidney tissue. They may use an ultrasound or CT scan to direct the needle to a specific area of the kidney.
- Open biopsy (surgical biopsy). For this procedure, your doctor makes a cut in the skin near the kidneys. This allows the physician to look at the kidneys and determine the area from which the tissue samples should be taken.
A renal biopsy can identify what is interfering with your normal kidney function. Healthy individuals have two kidneys that perform many functions. It’s the kidneys’ job to:
- remove urea (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
- help activate the hormone calcitriol, which regulates calcium absorption and calcium blood levels
If your routine blood and urine tests indicate that your kidneys aren’t 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 the urine)
- determine the cause of proteinuria (high level of protein in the urine)
- see the severity of progressive kidney failure and how quickly the kidneys are failing
- create a treatment plan for a diseased kidney
Usually, a renal biopsy 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 needed during the procedure.
- A percutaneous biopsy is the most common type of renal biopsy. A doctor inserts a thin biopsy needle through the skin to remove kidney tissue.
- In an open biopsy, a doctor makes a cut in the skin near the kidneys to determine the area from which to take the tissue samples.
Read on to learn about how these two methods of renal biopsy differ.
Typically, a percutaneous 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 won’t receive general anesthesia for this procedure, meaning you’ll be awake throughout.
You’ll be positioned so that you are lying on your stomach. This keeps your kidneys easily accessible from your back. You may be given a pillow or towel, since you have to remain still and stay in this position for about 30 minutes. If you’ve already had a kidney transplant, you’ll be told to lie on your back.
Next, a doctor will inject a local anesthetic into the entry site to numb the area. They will make a small incision there and 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’ll 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 is inserted through the same incision. You’ll have to hold your breath while each sample is retrieved.
Types of percutaneous biopsies
There are actually two types of percutaneous biopsies. The procedure your doctor uses will determine the instrument required to remove the tissue:
- Fine needle aspiration biopsy. In this procedure, your doctor extracts a small tissue sample from your kidney using a small, thin needle that is attached to a syringe.
- Needle core biopsy. For larger tissue samples, your physician may use a needle core biopsy. In this procedure, the doctor removes a larger sample of kidney tissue using a spring-loaded needle. If you’re having a needle core biopsy, you’ll hear a loud clicking or popping sound when the tissue sample is being removed.
After the sample is retrieved, pressure is applied to the biopsy site until any bleeding has stopped. 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 have this type of biopsy if you’ve had problems with bleeding or blood clotting in the past or if you have only one kidney.
If you’re having an open biopsy, you’ll receive general anesthesia. This means you’ll be asleep throughout the procedure. While you’re unconscious, your doctor makes an incision and surgically removes a tissue sample from your kidneys. Some surgical biopsies require an incision up to five inches long.
This procedure can also 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’ll need time for recovery and observation before you’re 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’ll be taken to a recovery room for rest and observation. During this time, you’ll lie on your back — or on your stomach if you’ve had a kidney transplant — for about six to eight hours.
A nurse or doctor keeps track of your vital signs, including blood pressure, temperature, pulse, and breathing rate. A complete blood count test and urine test is done to see if there is any internal bleeding or other problem. You’ll also be given medication to reduce pain at the biopsy site.
When your vital signs are stable, you’ll be released from the hospital to go home. This usually happens 12 to 24 hours after the procedure. It’s normal to have bright red blood in your urine up to 24 hours after the biopsy. But if this condition lasts more than a day, 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.
Developing an infection after the procedure is a serious 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
- can’t 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 don’t need to do much to prepare for a renal biopsy.
Be sure to tell your doctor about any prescription drugs, over-the-counter medications, and herbal supplements you’re taking. You should discuss with them 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’re taking medications that could affect the results of the renal biopsy. These medications include:
- anticoagulants (blood thinners)
- nonsteroidal anti-inflammatory drugs, including aspirin or ibuprofen
- any medications that affect blood clotting
- herbal or dietary supplements
Tell your doctor if you’re pregnant or think you might be pregnant. Also, before your renal biopsy, you’ll have a blood test and provide a urine sample. This ensures that you don’t have any preexisting infections.
You need to fast from food and drink for at least eight hours prior to your kidney biopsy.
If you’re given a sedative to take at home before the biopsy, you won’t be able to drive yourself to the procedure and need to arrange for transportation.
The tissue sample that was retrieved during your renal biopsy is sent to a laboratory for examination. A pathologist, a doctor who specializes in disease diagnosis, examines the tissue.
Your sample is analyzed under microscopes and with reactive dyes. The pathologist identifies and assesses any deposits or scars that appear. Infections and other abnormal conditions will also be detected.
The pathologist will compile the results and make a report to your doctor. Results are usually ready 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.
If results are abnormal, it could indicate:
- kidney infection
- 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
- numerous other diseases that have a negative effect on kidney function
Your doctor may decide to order additional tests to use to help make a treatment plan. They will go over your results and your condition in depth with you and discuss all the next steps following your renal biopsy.