A kidney biopsy, also known as a renal biopsy, is a medical procedure used to obtain a small tissue sample from the kidney for laboratory analysis. This sample is examined under a microscope by a pathologist to check for signs of damage, disease, or other abnormalities. The primary purpose of this diagnostic tool is to identify the specific cause of kidney dysfunction when it cannot be determined through blood or urine tests alone.
A biopsy can help doctors diagnose a variety of kidney problems, such as glomerulonephritis, determine how far a disease has progressed, or assess the effectiveness of current treatment plans. It is also frequently performed to monitor the health of a transplanted kidney, checking for signs of rejection or other issues. The information gathered from the tissue analysis is used to create or modify a targeted medical approach for the patient.
Preparing for the Kidney Biopsy
Preparation for a kidney biopsy begins in the days leading up to the procedure with a thorough review of the patient’s medical history and current medications. Patients are typically required to undergo blood tests, including coagulation panels, to ensure their blood clots properly and minimize the risk of post-procedure bleeding. A urine sample is also often collected to check for any underlying infection that would need to be treated beforehand.
Patients must discuss all prescription and over-the-counter medications, vitamins, and herbal supplements with their healthcare provider. Specifically, blood-thinning agents like aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, and anticoagulants must often be stopped several days to a week before the biopsy. Patients are also instructed not to eat or drink anything for a specific period before the procedure.
The Steps of the Percutaneous Biopsy
The percutaneous, or “through-the-skin,” biopsy is the most common method used to sample kidney tissue. The procedure usually takes place in a hospital or specialized procedure room with the patient lying on their stomach (prone) to allow easy access to the kidney located toward the back. A pillow is sometimes placed under the abdomen to help position the kidney correctly.
Before the tissue is collected, a local anesthetic is injected into the skin and deeper tissues to numb the area, which may cause a brief stinging sensation. Real-time imaging, typically ultrasound or sometimes a computed tomography (CT) scan, is used to precisely locate the kidney and guide the needle. The imaging helps the physician select the safest entry point and avoid surrounding organs or large blood vessels.
Once the area is numb, a small nick may be made in the skin before the biopsy needle is inserted. The physician advances the specialized biopsy needle, which is often spring-loaded or automatic, toward the kidney while continuously watching the imaging screen. The patient is asked to take a deep breath and hold it for a few seconds as the needle enters the kidney and the device is activated to quickly retrieve a tiny cylinder of tissue.
Post-Procedure Monitoring and Recovery
Immediately after the tissue sample is secured and the needle is withdrawn, a small dressing is applied to the puncture site. The patient is then moved to a recovery area where they must remain lying flat in bed, typically for six to eight hours, to apply natural pressure to the kidney and reduce the risk of bleeding. During this time, nurses closely monitor the patient’s vital signs, including blood pressure and heart rate, to detect any internal bleeding or complications.
Urine is collected and checked for the presence of blood, as a small amount of blood in the urine is common but must be monitored. Patients are usually allowed to eat and drink soon after the procedure and are encouraged to increase their fluid intake, sometimes up to two liters in the first 24 hours, to flush the urinary system. Mild soreness or a dull ache at the biopsy site is expected, and pain relief medication may be offered, though NSAIDs are usually avoided to prevent further bleeding risk.
Most patients are discharged the same day or the following morning, depending on their stability and the time of the biopsy. Upon returning home, patients are instructed to rest for the next day or two and must avoid strenuous activities, heavy lifting, and contact sports for up to two weeks.
Understanding Potential Complications
While a kidney biopsy is generally considered a safe procedure, patients should be aware of potential adverse outcomes. The most frequent complication is bleeding, which can manifest as blood in the urine (hematuria) for up to 24 hours after the procedure. In a small percentage of cases, bleeding can be severe enough to require a blood transfusion or, rarely, a follow-up procedure to stop the hemorrhage.
Other less common risks include pain at the biopsy site that persists beyond a few days, or the development of a localized infection, which would necessitate antibiotic treatment. Very rarely, the needle may cause an abnormal connection between an artery and a vein, called an arteriovenous fistula, which usually closes on its own without intervention. Puncturing other nearby organs is an extremely rare but possible risk.
Patients must receive clear instructions on when to contact their doctor immediately, as certain symptoms indicate a possible serious complication. These include passing significant bright red blood or blood clots in the urine more than 24 hours after the procedure, the onset of a fever above 100.4 degrees Fahrenheit, or experiencing worsening pain at the biopsy site. Faintness, dizziness, or an inability to pass urine should also prompt an immediate call to the healthcare provider.