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    Michael L. Aaronson, MD
    Kidney Doctor and High Blood Pressure Specialist
    7401 O Street Lincoln, NE 68510
    Phone: 402-484-5600

    Saturday, January 12, 2019

    The Kidney Biopsy in a Nutshell

    Figure: kidney biopsy demonstrating a condition called focal segmental glomerulosclerosis (abbreviated fsgs) in a patient who was spilling grams of protein in her urine. The picture shows a glomerulus, or filter, of the kidney. There is scarring of the filter at 3 o'clock.

    Your nephrologist may tell you that you need to have a kidney biopsy to help figure out why your kidneys are failing. The purpose of the procedure is to diagnose the cause of the kidney disease and determine the appropriate treatment.

    Some examples of people who might need a biopsy of their kidneys include:

    • sudden worsening of kidney function -- reasons unknown, and we are trying to figure out the cause.
    • chronic kidney disease of unknown etiology.
    • high levels of protein spillage from the kidneys.
    • bleeding from the kidneys.
    • medication allergy affecting the kidneys, so-called acute interstitial nephritis. Medications that can do this include 
      • acid suppressant medications such as omeprazole
      • non-steroidal anti-inflammatory medications such as ibuprofen.
      • certain antibiotics
    • some patients with lupus may need a kidney biopsy to stage the severity of their disease. 
    • and finally, people who have had kidney transplants who are noted to have worsening function may need a kidney biopsy to evaluate for rejection.
    • note: there are many other reasons your nephrologist might suggest you get a kidney biopsy. But this list presents many common indications.
    Is it safe? Getting a kidney biopsy today is much safer than it used to be. The procedure is performed with the help of an ultrasound machine or a CT scanner, so the doctor performing the biopsy knows where to go.

    Figure: this kidney biopsy is performed under ultrasound guidance. At 2 o'clock you can see the needle going into the kidney, getting a piece of the kidney to later be analyzed by a pathologist.

    I have been asked if one should worry about losing filters if a patient's kidney function is declining. Shouldn't we preserve all the ones we have to keep us off kidney dialysis? The normal kidney has approximately 1 million filters present. And if a person has 2 kidneys, that person has 2 million filters. Of the one million filters in the biopsied kidney, a "good" kidney biopsy takes approximately 10-15 filters from the patient. 10-15 glomeruli (or filters) out of one million is a very small number to lose. Consider the benefit versus the risk: if the filters are collapsing, or dying, and the cause is not identified, there eventually will be no filters left to function, and you might end up needing kidney dialysis. So in my opinion, although there is some risk, you should not worry about losing 10-15 filters if the result is saving hundreds of thousands with proper diagnosis and treatment.

    Please note: not everyone needs a kidney biopsy. Only some people do.

    And there are some situations when a person might benefit but should not get biopsied. Examples of contraindications to kidney biopsy include:
    • a person who is unwilling to do it and is going to move and risk a bleeding event.
    • pregnancy
    • those at high risk for bleeding should not get a kidney biopsy because the risk may be greater than the benefit. Note that a needle is used to get a piece of the kidney to obtain the tissue required for analysis. A few "passes" may be required to get an adequate sample for analysis. Check out this link on YouTube to learn more about the needle used during a kidney biopsy.
    • infection in the kidneys.
    • very high blood pressure.
    • use of certain medications: such as anticoagulants.
    • small kidneys
    • 1 kidney
    • Note: everything is relative. Some centers might consider performing a renal biopsy in a pregnant patient or in a patient with 1 kidney. It just depends....
    Prior to consenting to kidney biopsy, it is important to have a conversation with your nephrologist to discuss the risks and benefits of a kidney biopsy when indicated. Personalize the situation to your circumstances to get the best nephrology care possible.