Kidney biopsy

A medical kidney biopsy, also called a renal biopsy, takes a few thin strips of kidney tissue so a kidney pathologist can study them. It is used when the kidney itself is not working properly, not to sample a lump.

Each kidney has about a million tiny filters called glomeruli. Blood and urine tests can show that these filters are leaking protein or blood, or that kidney function is dropping. Only a biopsy can show why. The pathologist looks at the tissue with a regular microscope, with special stains for immune proteins and with a very powerful electron microscope.

What we see

The result often changes treatment. It can show whether steroids or other immune medicines will help, how much permanent scarring there is and what to expect over time. For a transplant, it can separate rejection, which needs stronger anti-rejection medicine, from drug side effects or infection.

When you arrive, a nurse starts an IV and draws blood to check your blood count, clotting and kidney function. See before your procedure for more.

1. 1
   Getting ready

   In the interventional suite at El Camino Hospital, you lie on your stomach, often with a pillow under your belly. For a transplant kidney, which sits in the lower belly, you lie on your back. You receive moderate (twilight) sedation.

2. 2
   Finding the kidney

   We find the kidney with ultrasound or CT, clean the skin and numb it and the path down to the kidney.

3. 3
   Taking the samples

   We ask you to hold your breath for a few seconds while a spring-loaded needle takes each sample. You hear a click and feel a push. A pathology technologist checks under a microscope that the samples contain enough filters.

4. 4
   Finishing up

   We remove the needle, press on the site, check the kidney for bleeding on ultrasound and apply a small bandage.

For a kidney biopsy, I aim for the outer rim at the lower tip of the kidney and stay away from the center, where the larger vessels run. I work closely with the pathology technologist so we stop as soon as we have enough filters, not one pass more. I also check your blood pressure myself before we start, because good control is one of the best ways to prevent bleeding.

Fabio Komlos, MD, interventional radiologist · About Dr. Fabio Komlos

1. First 4–6 hours
   Strict bed rest, lying flat. Nurses check your blood pressure, the site and your urine often. You can eat and drink, and family can visit.
2. Overnight
   You stay in a hospital room for observation. Pink urine for a day or two is common.
3. Next morning
   A blood test compares your blood count with the day before. If it is stable and you feel well, you usually go home before noon.
4. First week
   No heavy lifting, hard exercise, contact sports, baths or swimming. Light activity and desk work are fine.

Mild soreness in the back is normal for 2 to 3 days. An ice pack and acetaminophen (Tylenol) usually help. Avoid ibuprofen and naproxen. Ask your kidney doctor when to restart blood thinners.

Kidney biopsies need several kinds of testing, including electron microscopy, so the full report usually takes 1 to 2 weeks. A preliminary result may come sooner if treatment is urgent. Your kidney doctor will go over the results and the treatment plan with you.

The kidney has a rich blood supply, so bleeding is the main risk. A small bruise around the kidney is common and usually causes no problems. Visible blood in the urine happens in about 1 in 20 to 1 in 30 people and usually clears within a day or two. About 1 in 100 people need a blood transfusion, and fewer than 1 in 100 need a procedure to seal the bleeding artery (embolization). Losing the kidney is extremely rare.

Other risks, such as infection or a small abnormal connection between an artery and a vein, are rare. Most such connections close on their own.