What is a kidney biopsy?

A kidney biopsy, also called a "renal biopsy," is a diagnostic test that involves removing small samples of tissue from a kidney in order to examine the cells under a microscope. There are two common types of kidney biopsy.

• Percutaneous ("through the skin") biopsy. In a percutaneous biopsy, a doctor removes the kidney samples by inserting a needle through the skin to the surface of the kidney. Usually doctors use ultrasound to guide the needle directly to the kidney.
• Open biopsy. In an open biopsy, a surgeon makes an incision through the skin to the kidney where the sample is taken, then uses stitches to close the incision. You are asleep under anesthesia during the surgery.

In both types of kidney biopsy, the tissue samples are sent to a laboratory to be examined and evaluated. There are several possible reasons that your doctor might want you to undergo a kidney biopsy, including the following.

• You have blood in your urine that is not going away.
• Protein is detected in your urine during a laboratory analysis.
• Your kidneys do not appear to be functioning normally.
• You have had a kidney transplant and your doctor wants to monitor how well your new kidney is functioning.
• Your kidney that has been injured.
• You have had an abnormal blood test.

A kidney biopsy can help your doctor diagnose conditions including kidney damage, kidney disease or a tumor on the kidney, and assess how well a transplanted kidney is functioning or how well a treatment for a kidney problem is working.