A biopsy is a diagnostic test that involves collecting small pieces of tissue, usually through a needle, for examination with a microscope. A kidney biopsy can help in forming a diagnosis and in choosing the best course of treatment. A kidney biopsy may be recommended for any of the following conditions:
• Hematuria, which is blood in the urine
• Proteinuria, which is excessive protein in the urine
• Impaired kidney function, which causes excessive waste products in the blood
A pathologist will look at the kidney tissue samples to check for unusual deposits, scarring, or infecting organisms that would explain a person’s condition. If a person has progressive kidney failure, the biopsy may show how quickly the disease is advancing.
A biopsy can also help explain why a transplanted kidney is not working properly.
What are the preparations for a kidney biopsy?
Patients must sign a consent form saying they understand the risks involved in this procedure. The risks are slight, but patients should discuss these risks in detail with their doctors before signing the form.
Doctors should be aware of all the medicines a patient takes and any drug allergies that a patient might have. The patient should avoid aspirin and other blood-thinning medicines for 1 to 2 weeks before the procedure.
Shortly before the biopsy, blood and urine samples are taken to make sure the patient doesn’t have a condition that would make doing a biopsy risky.
What are the procedures for a kidney biopsy?
Kidney biopsies are usually done at the hospital. The patient is fully awake with light sedation. A local anesthetic is given before the needle is inserted.
Patients lie on their stomachs to position the kidneys near the surface of their backs. Patients who have a transplanted kidney lie on their backs. The doctor marks the entry site, cleans the area, and injects a local painkiller.
For a biopsy using a needle inserted through the skin, the doctor uses a locating needle and x-ray or ultrasound equipment to find the kidney and then a collecting needle to gather the tissue. Patients are asked to hold their breath as the doctor uses a spring-loaded instrument to insert the biopsy needle and collect the tissue, usually for about 30 seconds or a little longer for each insertion.
The instrument makes a sharp clicking noise that can be startling to patients. The doctor may need to insert the needle three or four times to collect the needed samples.
The entire procedure usually takes about 30 minutes to 1 hour, including time to locate the kidney, clean the biopsy site, inject the local painkiller, and collect the tissue samples.
Patients who are prone to bleeding problems should not have a biopsy through the skin. These patients may still undergo a kidney biopsy through an open operation in which the surgeon makes an incision and can see the kidney to collect tissue samples.
What happens after a kidney biopsy?
After the test, patients lie on their backs in the hospital for 6-8 hours. During this time, the staff will monitor blood pressure and pulse and take blood samples to assess for blood loss 4-6 hours post biopsy. On rare occasions when bleeding does not stop on its own, a transfusion may be necessary to replace lost blood. Most patients leave the hospital the same day. Patients may notice some blood in their urine for 24 hours after the test.
A rare complication is infection from the biopsy.