Kidney Biopsy

A kidney biopsy is a procedure in which a small sample of kidney tissue is removed and examined under a microscope to find out what is wrong with the kidneys.

During the procedure, a thin needle is guided through the skin and into the kidney. The needle takes one or more tiny cores of tissue — each about the size of a grain of rice. In a laboratory, specialists called pathologists (doctors who study tissue and cells) look at these samples closely. They can identify inflammation (swelling and irritation inside the kidney tissue), scarring, abnormal cells, and other changes that blood or urine tests alone cannot reveal. This gives the kidney specialist, called a nephrologist, the exact information needed to plan the right treatment.

A kidney biopsy is ordered when the doctor needs information that cannot be obtained from blood tests, urine tests, or imaging scans alone. It is most often used to diagnose, monitor, or guide treatment of kidney disease.

• Unexplained blood in the urine (haematuria) that persists after other causes have been ruled out.
• Significant protein in the urine (proteinuria) — when the kidneys are leaking protein that they should be keeping in the blood.
• Nephrotic syndrome — a condition where large amounts of protein are lost in urine, causing swelling especially in the legs and around the eyes.
• Nephritic syndrome — a condition involving blood in the urine, high blood pressure, and reduced kidney function that comes on quickly.
• Unexplained fall in kidney function, known as acute kidney injury (sudden worsening) or chronic kidney disease (gradual worsening over time).
• Suspected lupus nephritis — kidney inflammation caused by the autoimmune disease lupus.
• Monitoring a transplanted kidney — to check whether the body is rejecting the new kidney or whether the original disease has returned.
• Evaluating a kidney mass or tumour when imaging results are not clear enough to guide treatment decisions.

A kidney biopsy is generally not suitable in some situations. The doctor will weigh the potential benefit against the risks carefully before proceeding.

• Uncontrolled high blood pressure that has not been brought down with medication.
• A bleeding disorder (a condition where the blood does not clot properly) that cannot be corrected beforehand.
• A single functioning kidney, unless the benefit is considered very high.
• Active kidney infection (pyelonephritis).
• Multiple cysts (fluid-filled sacs) throughout the kidney tissue.
• A patient who is unable to lie still or hold their breath briefly during the procedure.

A kidney biopsy is a well-established diagnostic procedure, but like any procedure that involves a needle entering the body, it does carry some risks that patients should understand beforehand.

• Blood in the urine (haematuria) — this is very common in the first day or two after the biopsy and usually clears on its own.
• Bleeding around the kidney — a small collection of blood, called a haematoma (a bruise inside the body), can form near the kidney. Most are minor and resolve without treatment.
• More serious bleeding — in a small number of cases, bleeding may be significant enough to require a blood transfusion or a procedure to seal the bleeding vessel.
• Pain or discomfort — aching in the back or side at and near the biopsy site is common for a day or two.
• Infection — bacteria can occasionally be introduced near the biopsy site, though this risk is reduced by using a sterile technique.
• Arteriovenous fistula (an abnormal connection between an artery and a vein inside the kidney) — this usually causes no symptoms and closes on its own, but occasionally needs treatment.
• Injury to a nearby structure — the needle can rarely affect the ureter (the tube draining urine from the kidney) or surrounding tissues.
• Allergic reaction to the local anaesthetic (numbing medicine) used at the skin — this is uncommon.

Preparing well for a kidney biopsy helps reduce the risk of bleeding and ensures the team can get a good tissue sample. The preparation covers what you do in the days before, the tests that are run, and what happens on the day itself.

In the days before the biopsy, the doctor will usually ask the patient to stop taking blood thinners (medicines that prevent clotting, such as aspirin or anticoagulants) for a period determined by the medical team. Herbal supplements and certain vitamins that can affect bleeding may also need to be paused. The patient is usually asked to avoid eating or drinking for several hours before the procedure — the exact fasting period will be specified by the hospital. Smoking and alcohol are best avoided in the days before, as both can interfere with healing.

Before the biopsy is scheduled, the doctor will order several tests to make sure it is safe to proceed.

• Blood pressure measurement — it must be within a safe range on the day.
• Blood tests to check how well the blood clots (coagulation studies), kidney function (creatinine and eGFR), and blood cell counts.
• Urine tests to look for active infection.
• Imaging — usually an ultrasound (USG) to locate the kidney precisely and check for any abnormalities that would make the biopsy unsafe.
• Blood typing, in case a transfusion is ever needed.

On the day of the procedure, the steps generally follow this order, though the exact sequence may vary by hospital and whether a native kidney or transplanted kidney is being biopsied.

• The patient changes into a hospital gown and has an intravenous (IV) line placed in a vein in the arm, so fluids or medicines can be given quickly if needed.
• The patient lies face-down on a table for a native kidney biopsy; for a transplanted kidney, the patient lies on their back, since transplanted kidneys sit lower in the abdomen.
• A pillow or cushion may be placed under the abdomen to bring the kidney closer to the surface.
• Ultrasound is used in real time to guide the needle to the right spot on the kidney.
• The skin over the target area is cleaned thoroughly with an antiseptic solution.
• Local anaesthetic is injected into the skin and deeper tissues to numb the area — the patient will feel a brief sting and then pressure, but usually not sharp pain.
• The biopsy needle is passed through the skin and into the kidney. The patient is asked to take a breath and hold it briefly while the needle takes the sample. A clicking sound from the needle device is normal.
• One to three passes are usually made to collect enough tissue. The needle is removed after each pass.
• Firm pressure is applied to the biopsy site to limit bleeding.
• A dressing is placed over the small puncture in the skin.
• The patient is moved to a recovery area for monitoring.

After a kidney biopsy, the patient is monitored closely for several hours because most bleeding, if it occurs, happens within this window. The length of the observation period and whether an overnight stay is needed will depend on the hospital's protocol and how the patient is doing.

• Monitoring: Blood pressure, heart rate, and urine colour are checked regularly in the hours after the procedure. A blood test may be repeated to detect any significant drop in the blood count.
• Rest: The patient is asked to lie flat and avoid getting up for at least a few hours. Most hospitals keep patients for observation for four to six hours or, in some cases, overnight.
• Urine checks: The patient is asked to save urine samples so the colour can be assessed — pinkish urine is expected and usually clears within a day or two. Bright red urine, clots, or difficulty urinating should be reported immediately.
• Activity restriction: Heavy lifting, strenuous exercise, and vigorous physical activity are typically avoided for about one to two weeks, or as directed by the care team.
• Driving: Because mild sedation or pain relief may have been given, driving is not recommended on the day of the procedure. The doctor will advise when it is safe to drive again.
• Blood thinners: The medical team will advise when blood thinners can safely be restarted — do not restart them without medical guidance.
• Wound care: The biopsy site has only a very small puncture. Keeping it clean and dry as instructed, and watching for signs of infection such as redness, swelling, warmth, or discharge, is important.
• Pain management: Mild achiness in the back or flank (the side of the body between the ribs and the hip) is normal. The doctor will recommend suitable pain relief.
• Follow-up: A follow-up appointment is usually scheduled within one to two weeks to discuss the biopsy results and decide on next steps for treatment.
• When to seek urgent care: Persistent or heavy bleeding, severe pain, fever, inability to urinate, or feeling faint are signs that the patient should contact the medical team or go to an emergency department immediately.