A biopsy is often used to diagnose cancer. During a biopsy, a small sample of tissue is taken from the area in question and sent to a laboratory for further investigation under a microscope. Kidney cancer doesn’t always require a biopsy. Sometimes imaging tests such as a computed tomography (CT) scan, magnetic resonance imaging (MRI) and ultrasound may be sufficient to identify kidney tumors and determine whether they’re benign (noncancerous) or malignant (cancerous).
Why kidney biopsies are performed
A doctor may order a kidney biopsy if:
- Small, slow-growing tumors are being monitored
- Imaging tests are not as conclusive as the doctors would like
- The patient is a candidate for treatments other than surgery
- Following surgery, the doctors want to see how well the patient is doing and whether the cancer has returned
A kidney biopsy may also be ordered to evaluate the following conditions.
- Hematuria: Blood in the urine may be a sign of a problem with kidney function. A biopsy may help diagnose hematuria.
- Albuminuria: Albumin is a protein. Albuminuria happens when an abnormal amount of protein has been detected in the patient's urine. A kidney biopsy may be needed to diagnose this issue.
- Changes in kidney function: A biopsy may be ordered to determine why a patient's kidneys aren’t functioning properly and waste products are building up in the blood.
If doctors suspect that cancer has spread to other tissue, they may perform a biopsy of that site rather than of the kidney.
During a percutaneous biopsy
- The patient will likely be asked to lie on his or her stomach on the examination table. A firm pillow or sandbag may be placed under the stomach to provide support and push the kidneys closer to the skin.
- The patient will receive a sedative through an intravenous (IV) line.
- The health care team uses an ultrasound or X-ray to locate the kidney. The patient may be given a contrast material through his or her veins to make the kidney and important blood vessels light up and easier to see.
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The doctor may mark the skin once the spot is identified. The patient's skin is then sterilized.
- The patient will be asked to stay still and hold his or her breath as the doctor puts the needle through the skin. The patient may feel some pressure or a “pop” where the needle is inserted in the kidney.
- If the doctor isn’t using ultrasound to guide the needle insertion, the patient may be asked to breathe in and out with deep breaths. This helps the doctor know that the needle was properly placed.
- The doctor may need to pass the needle through the skin up to four times to be sure a large enough sample is taken. Each time, the patient may be asked to hold his or her breath.
- Pressure is applied to the site where the needle was inserted to stop any bleeding.
A percutaneous biopsy should take about an hour. The biopsy alone may take about 15 minutes to a half-hour.
During an open biopsy
- The patient is given general anesthesia, so he or she won’t feel anything during the procedure.
- The surgeon makes a small incision above the kidney.
- The surgeon identifies the area of the kidney that’s of concern and removes a small sample.
- The surgeon closes the incision with sutures.
Afterward, the patient will likely be given medicine to help alleviate any pain from the surgery, and may also be given fluids by mouth or an IV.
The staff will monitor the patient's urine for heavy bleeding.
How to prepare for a kidney biopsy
Preparing for a kidney biopsy is usually simple, and typically involves following these steps:
- The patient should speak with a doctor about the procedure, the reasons for it, and what the results could mean. This may help relieve stress and make him or her feel prepared.
- Arrange for a ride to and from the procedure. Patients can’t drive home after general anesthesia.
- The patient should tell the doctor about any medications they’re taking, and whether they’ve been prescribed or bought over the counter. Include any vitamins and supplements. Ask which, if any, should be taken before or the day of the procedure. The patient should be sure to mention if they're taking blood thinners and ask when to stop them. Doctors may advise halting blood thinners up to two weeks before the biopsy.
- Inform the doctor of any allergies to medications or foods.
- Don’t eat or drink for at least eight hours before the procedure is scheduled.
- The patient may take a bath or shower before the biopsy, but don’t use lotion, perfume or deodorant. Avoid nail polish as well.
- Leave jewelry at home, including piercings.
- Arrive 90 to 120 minutes before surgery is scheduled to allow enough time to fill out the necessary paperwork, undergo needed blood tests and receive IV fluids and sedatives. The patient's blood and urine will be tested for bleeding issues or high blood potassium that would make it too risky to undergo a kidney biopsy.
Post-biopsy care
Under observation, the patient should remain lying on his or her back for four to six hours after the procedure. The patient may be in the hospital afterward for a minimum of 12 hours. Patients should be allowed to leave once their blood pressure and pulse are stable.
- Follow the directions provided for the care of the wound. Patients may need to keep the bandage on for at least one to two days.
- Expect some soreness where the needle was inserted or where the incision was made for the next couple of days. Don’t take aspirin to relieve the pain, as it acts as a blood thinner and may cause bleeding.
- Don’t lift objects that weigh more than 10 pounds for at least two weeks after the biopsy. Avoid activities that may injure the kidney (such as contact sports) until recovery is complete. The doctor should say when the patient may resume previous physical activities.
- Moving may help during recovery. Start with walking, going a little longer and farther each day. Moving helps improve circulation.
- Expect to hear from the doctor with the results in three to five days, but it may be sooner.
- Patients should be able to resume a normal diet.
Fuhrman grade tumors
The pathologist who examines the tissue sample cells will grade it as a 1, 2, 3 or 4 using the Fuhrman system for kidney cancer. According to this system, the more abnormal the cells, the higher the grade.
The grade is used to help determine the most appropriate cancer treatment.
Risks of kidney biopsy
While risks are rare, a kidney biopsy is a surgical procedure, which means there’s a possibility of complications. Some risks include:
- Damaged blood vessel: Surgery may be needed to fix it.
- Serious bleeding: The patient may need a transfusion as a result of blood loss.
- Infection: As with any surgery, infection is always a risk, but it’s rare when undergoing a kidney biopsy. If the patient develops an infection, he or she will be given antibiotics to treat it.
Because doctors only take a tiny sample of the kidney, it’s possible they miss the actual cancer—that the area they take the sample from doesn’t have cancer. It’s also possible for the biopsy needle to spread the cancer.
Patients with high blood pressure (greater than 140/90) are at greater risk of complications during the procedure. The doctor may try to control the patient's blood pressure with medications before performing a biopsy.
Discuss the risks and benefits with the care team before undergoing a kidney biopsy.
When to call the doctor
Patients should call their doctor immediately if any of these issues occur following kidney biopsy:
- Inability to urinate
- Frequent urination and/or constant urge to go
- Burning sensation when going to the bathroom
- Dark red or brown urine
- Blood or pus seeping from under the bandage
- Fever
- Faintness
