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Kidney Biopsy What is the test? A kidney biopsy obtains a sample of your kidney tissue so that it can be examined under a microscope. Kidney biopsy is useful for deciding what the cause of kidney failure is and for making decisions about how it would be best to treat the kidney. A kidney biopsy can also be used to diagnose cancer in the kidney. How do I prepare for the test? You will have blood tests done to help your doctor know if you are at extra risk for bleeding after the procedure. You will be asked to sign a permission or "consent" form allowing your doctor to perform this test. Tell your doctor if you have ever had an allergic reaction to the medicine lidocaine or the numbing medicine used at the dentist's office. You will be asked not to eat or drink anything after midnight the night before the test — this is a safety precaution in case you are one of the rare patients who has a complication that might require surgery on the same day as the procedure. You should continue to take your medicines with sips of water even though you are not eating a meal, however. This is particularly important for blood pressure medicines — if your blood pressure is too high on the day of the test, your doctor will probably not do the procedure. If you have diabetes and take insulin, discuss this with your doctor before the test. If you take aspirin, non-steroidal anti-inflammatory drugs, or other medicines that affect blood clotting, talk with your doctor. It may be necessary to stop or adjust the dose of these medicines before your test. You should plan on spending one night in the hospital after this test so that you can be monitored for complications such as bleeding. What happens when the test is performed? On the day of the test, you will provide a urine sample that will be tested for signs of a bladder infection. If you have an infection in the urine, you will need to get treatment before you are able to have the biopsy done. Your blood pressure will be measured. You will have an IV (intravenous) line placed in case you need any fluid during the procedure. You will lie on your stomach with a pillow under your abdomen to support you. Some clear jelly will be squirted onto your back on both sides and an ultrasound will be done. An ultrasound is a painless test that uses sound waves to find the kidney. The ultrasound will make sure you have two kidneys and will show the location of the one that will have a sample taken. The ultrasound sensor that is held against your back resembles a microphone. While the ultrasound sensor is showing your doctor where the kidney is, you will be asked to take in a deep breath, a shallow breath, and a normal breath and to hold each one. This allows the doctor to see what amount of breathing makes the kidney move closest to where it is easy to biopsy. Some numbing medicine will be injected under your skin and into the muscle that the biopsy needle will go through. The ultrasound sensor will continue to show the kidney while this medicine is being injected. You will feel some brief stinging from the numbing medicine. A special sampling needle will then be pushed gently into the area that has been numbed by the medicine. The doctor will push this needle forward until it is just at the edge of the kidney. This specialized needle has a spring-loading mechanism that your doctor can then release. The spring-loading allows this needle to move a short distance into and out of the kidney very quickly to collect the sample. Some patients do feel some discomfort from each biopsy, but because the needle moves so quickly it will last only for a second. Your doctor will ask you to hold a large or small breath (as you practiced earlier) during the part of the test when the kidney is being sampled. The specialized needle is removed so the sample can be put aside for testing. A second sample is taken from the same kidney using the same technique. You will have a bandage placed on your back where the needle was inserted. Another look will be taken with the ultrasound to see that you do not have any bleeding around your kidney. What risks are there from the test? The most serious risk from this test is bleeding. Many patients have a small amount of bleeding into the space around the kidney, but in a few patients this can be significant enough to require a transfusion and, in rare cases, even surgery. Somewhere between 1 and 3 patients out of every 1000 have serious bleeding that requires a transfusion. Almost all patients have some bleeding into their urine that can be seen with urine tests under the microscope. About 1% of patients have enough bleeding into the urine that the color of urine changes from yellow to a red color. The bleeding into the urine is almost always temporary. It is not very likely that you would develop a kidney infection after this test, but this is a possibility. Most patients have a small amount of soreness in their back for a day or two where the needle was placed. Must I do anything special after the test is over? You will likely spend the night in the hospital so that you can have a blood test done to check for bleeding and so that your urine can be reevaluated after the test to make sure any blood in the urine is clearing up over the day. You will be asked not to walk around for 3 hours after your biopsy. How long is it before the result of the test is known? Your kidney samples must be treated with special stains and treatments before they can be viewed under the microscope and under a special high-power "electron microscope." The report of your results may require a full week or more.
From Harvard Medical School Family Health Guide by Harvard Medical School. Copyright © 1999 by President and Fellows of Harvard College. Reprinted by permission of Simon & Schuster, Inc.
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