A kidney biopsy is a medical procedure where a small piece of kidney tissue is removed for microscopic examination. This diagnostic tool helps understand and identify underlying kidney conditions, damage, or disease.
Reasons for a Kidney Biopsy
Healthcare providers recommend a kidney biopsy for several diagnostic purposes when other tests do not provide a clear answer. It is often performed to determine the cause of unexplained kidney failure or dysfunction. Persistent protein (proteinuria) or blood (hematuria) in the urine can also necessitate a biopsy.
The procedure helps diagnose specific kidney diseases, such as glomerular diseases, which damage the kidney’s filtering units. For individuals who have received a kidney transplant, a biopsy can assess how well the transplanted kidney is functioning or identify reasons for its poor performance. It also aids in monitoring the progression of known kidney conditions or evaluating the effectiveness of ongoing treatments. In some cases, a biopsy might be used to examine an abnormal mass in the kidney to rule out kidney cancer.
Getting Ready for Your Biopsy
Thorough preparation is important for a safe kidney biopsy. Patients are advised to discuss all medications with their doctor. Blood-thinning medications like warfarin, aspirin, and NSAIDs such as ibuprofen, are often stopped several days before the biopsy to minimize bleeding risk. Blood and urine samples are typically collected beforehand to check general health, blood clotting ability, and for infection.
Fasting instructions usually require not eating or drinking for a specific period, often eight hours, before the procedure. Patients should arrange for someone to drive them home afterward, as they may receive medication that causes drowsiness. Pre-procedure consultations allow patients to ask questions and understand the benefits and risks involved.
How the Biopsy is Performed
The most common method for obtaining a kidney tissue sample is the percutaneous, or needle, biopsy. This procedure typically takes about an hour. Patients usually lie face down on an examination table, often with a pillow under their body, to allow easy access to the kidney. If the biopsy is for a transplanted kidney, usually located in the lower abdomen, the patient will lie on their back.
The skin area is cleaned with an antiseptic solution, and a local anesthetic is injected to numb the site. This injection may cause a brief stinging sensation. Imaging guidance, most commonly ultrasound or sometimes a CT scan, is then used to precisely locate the kidney and guide the biopsy needle.
A small incision may be made before the needle is inserted. The healthcare provider then inserts a thin biopsy needle through the skin and into the kidney. During this step, patients may be asked to hold their breath for a few seconds to keep the kidney still and ensure accurate needle placement. A spring-loaded instrument is often used to quickly collect small tissue samples, which might produce a clicking sound.
Several samples, typically two or three, may be taken to ensure enough tissue is available for examination. After the samples are collected, the needle is removed, and pressure is applied to the biopsy site to help stop any bleeding before a bandage is applied.
Understanding Different Biopsy Methods
While the percutaneous approach is most common, alternative kidney biopsy methods are used in specific situations. An open biopsy involves a small surgical incision to directly access the kidney and remove a tissue sample. This method is typically performed under general anesthesia and is reserved for cases where a larger tissue sample is needed or when a percutaneous biopsy cannot be performed safely, such as in patients with certain bleeding disorders.
Another method is the transjugular kidney biopsy, which involves inserting a catheter and needle into a vein in the neck, typically the jugular vein. The needle is then guided through the veins into the kidney to collect tissue. This approach is often considered for patients at high risk of bleeding from a percutaneous biopsy or those with anatomical challenges that make the percutaneous route difficult. It can also be an option when simultaneous liver and kidney biopsies are needed.
What to Expect After the Biopsy
Following a kidney biopsy, patients are typically moved to a recovery area for observation. Healthcare providers closely monitor vital signs and check the biopsy site for any signs of bleeding. It is common to experience some pain or soreness at the biopsy site, which can be managed with pain relievers. Passing urine that is pink or slightly cloudy due to a small amount of blood is also common and usually resolves within 24 to 48 hours.
Patients are usually advised to rest for 24 to 48 hours and avoid strenuous activities like heavy lifting or vigorous exercise for one to two weeks to promote healing and reduce complications. Staying still in bed for several hours immediately after the procedure helps prevent bleeding. While many patients can go home the same day, some may require an overnight hospital stay for continued monitoring.
Patients should seek medical attention if they experience severe or worsening pain, excessive bright red blood or clots in their urine, fever, or signs of infection at the biopsy site. The tissue samples are sent to a laboratory, and full results can take several days to a few weeks to become available.