Kidney biopsy

What is the test?

A kidney biopsy is a procedure to obtain a sample of your kidney tissue so that it can be examined under a microscope. A kidney biopsy is useful in patients with kidneys that are not functioning properly, to determine the cause of the problem and the most appropriate treatment.

How do I prepare for the test?

Your doctor will review your medications and order blood tests to find out if you are at extra risk for bleeding after the procedure. If you take a medicine that affects blood clotting, talk with your doctor. It may be necessary to stop or adjust the dose of these medicines before your test.

You will be told when to stop eating and drinking prior to 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. However, you should continue to take your medicines with sips of water even though you are not eating a meal.

You may need stay one night in the hospital after this test.

What happens when the test is performed?

On the day of the test, you provide a urine sample to be tested for signs of a bladder infection. If you have an infection in the urine, you need to get treatment before you are able to have the biopsy done. Your blood pressure is measured. You will have an IV (intravenous) line placed in a vein in case you need any fluid during the procedure.

You lie on your stomach with a pillow under your abdomen to support you. You then have an ultrasound or CT scan to locate the kidney from which the samples will be taken. You are asked to take a deep breath, a shallow breath, and a normal breath and to hold each one. This allows the doctor to see what type of breathing moves the kidney into a position where it is easy to biopsy.

Some numbing medicine is injected under your skin and into the muscle that the biopsy needle is to go through. The ultrasound sensor or CT imaging continues to show the kidney while this medicine is being injected. You will feel some brief stinging from the numbing medicine.

A special sampling needle is then pushed gently into the area that has been numbed by the medicine. The doctor pushes this needle forward until it is just at the edge of the kidney. Your doctor then releases a special spring-loaded mechanism on the needle that quickly moves the needle a short distance into and out of the kidney to collect the sample. Some patients feel some discomfort from each biopsy, but because the needle moves so quickly, this lasts only for a second. Your doctor asks you to hold a large or small breath (as you practiced earlier) when the kidney is being sampled. The needle is removed and the sample put aside for testing. A second sample is taken from the same kidney using the same technique.

A bandage is placed on your back where the needle was inserted. The doctor takes another look 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.

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 possible, but unlikely, that you will develop a kidney infection after this test. 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 may 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 checked to make sure any blood in the urine is clearing up. You will be asked not to walk around for at least three hours after your biopsy.

How long is it before the result of the test is known?

Your kidney samples will be viewed under the microscope and under a special high-power electron microscope. The report of your results may require a full week.