A kidney biopsy is a procedure where a physician removes tissue for examination under a microscope. This tissue sample allows specialists to observe the microscopic structures of the kidney, which is often necessary when blood and urine tests alone cannot provide a definitive diagnosis. While there is an open biopsy method that involves surgery, the most common approach is the less invasive percutaneous, or needle, biopsy, performed through the skin. This technique relies on image guidance to ensure a precise and safe collection of the tissue sample.
Why Doctors Require a Biopsy
A kidney biopsy provides information about the cause and extent of kidney damage that other diagnostic tools cannot offer. Physicians request the procedure to determine the reason for unexplained kidney failure or a significant decline in function. Microscopic analysis can differentiate between various types of kidney diseases, such as the inflammatory condition known as glomerulonephritis. The biopsy also helps determine the severity of a chronic condition by assessing the amount of scarring or inflammation present. For individuals who have received a kidney transplant, a biopsy monitors the organ’s health, checks for signs of rejection, or determines if a specific treatment regimen is working.
Preparing for the Procedure
Before a kidney biopsy, patients undergo preparation to minimize the risk of complications, particularly bleeding. You will be asked to stop taking blood-thinning medications, such as aspirin, NSAIDs, or prescription anticoagulants, typically five to seven days before the appointment. Blood tests are performed shortly before the procedure to confirm that your blood is clotting normally and that your blood pressure is adequately controlled. Patients are instructed not to eat or drink anything for several hours before the biopsy, aligning with requirements for procedures involving sedation or anesthesia. You will also review and sign an informed consent document, ensuring a full understanding of the process and associated risks.
Step-by-Step Procedure Guide
The percutaneous kidney biopsy is performed in a procedure room, often by a radiologist or nephrologist, using local anesthesia. The physician cleans the skin at the biopsy site with an antiseptic solution and injects a local anesthetic to numb the area, which may cause a brief stinging sensation.
Positioning
For a biopsy of a native kidney, you will typically lie face down with a cushion beneath the abdomen to stabilize the kidney’s position. If the procedure is performed on a transplanted kidney, which is located lower in the abdomen, you will lie on your back.
Image Guidance and Needle Insertion
The physician uses real-time imaging, most commonly an ultrasound machine, to visualize the kidney and surrounding structures. This allows the provider to select the safest path for the needle, avoiding major blood vessels. Once the path is confirmed, a small nick is made in the skin, and the biopsy needle is advanced to the kidney’s outer surface under continuous guidance.
Tissue Collection
When the needle is in the correct position, you will be asked to take a deep breath and hold it for a few seconds. This pause prevents the kidney from moving during tissue collection. The physician uses a specialized, spring-loaded biopsy needle, which is rapidly deployed to collect a core of tissue, often described as feeling like a quick pressure or hearing a clicking sound. The process may be repeated two or three times to ensure enough tissue is collected for diagnosis. After the samples are secured, the needle is removed, and firm pressure is applied to the site to reduce bleeding.
Recovery and Potential Side Effects
Following the procedure, you will be moved to a recovery area and instructed to lie flat on your back for six to eight hours to place pressure on the biopsy site and prevent bleeding. During this time, the medical team frequently monitors your blood pressure, heart rate, and the biopsy site for complications. Your urine is also checked to ensure there is no significant blood loss.
The most common side effect is bleeding, which may manifest as blood in the urine, often appearing pink or slightly cloudy, and usually resolving within 24 to 48 hours. Pain at the biopsy site is common but generally mild and manageable with over-the-counter pain medication. Before being discharged, usually the next day, you will be instructed to avoid strenuous activities, heavy lifting, or intense exercise for one to two weeks. You should seek immediate medical attention if you experience severe, worsening pain, an inability to urinate, or a fever, as these may indicate a serious complication.