Kidney Biopsy – Procedure, Risks & Results

What is a Kidney Biopsy?

A kidney biopsy (also called a renal biopsy) is a medical procedure in which a small piece of kidney tissue is removed and examined under a microscope. This allows physicians to accurately diagnose kidney diseases, assess their severity, and determine the most appropriate course of treatment. The kidney biopsy is considered the gold standard in nephrology diagnostics.

When is a Kidney Biopsy Performed?

A kidney biopsy is recommended when other diagnostic methods cannot sufficiently explain the cause or extent of a kidney condition. Common indications include:

• Unexplained nephrotic syndrome: significant protein loss in the urine
• Nephritic syndrome: blood in the urine, high blood pressure, and reduced kidney function
• Acute kidney injury without a clear cause
• Chronic kidney disease of unknown origin
• Systemic diseases such as lupus erythematosus or vasculitis involving the kidneys
• Monitoring after a kidney transplant to detect rejection

How is a Kidney Biopsy Performed?

Preparation

Before the procedure, blood clotting parameters are checked to minimize the risk of bleeding. Blood-thinning medications are usually stopped in advance. Blood pressure is stabilized, and the patient receives detailed information about the procedure, its risks, and aftercare.

Procedure

The most common technique is a percutaneous biopsy, performed through the skin under ultrasound guidance. The patient lies face down. The skin over the kidney is disinfected and locally anesthetized. A thin biopsy needle is then inserted through the skin into the kidney tissue, and one to three small tissue cores are collected. The procedure typically takes only a few minutes.

Alternatives

In rare cases -- such as in patients with a high bleeding risk or unusual anatomy -- the biopsy may be performed transjugularly (through a vein in the neck) or as an open surgical procedure.

What Happens to the Tissue?

The collected kidney tissue is sent to a specialized laboratory for histological, immunohistochemical, and electron microscopic analysis. This allows physicians to detect and classify abnormal changes in the kidney structures, including the glomeruli (filtering units), tubules, interstitium, and blood vessels.

Possible Risks and Complications

A kidney biopsy is generally a safe procedure, but it does carry some risks:

• Bleeding: The most common complication is a blood collection around the kidney (perirenal hematoma). In rare cases, a blood transfusion or surgical intervention may be needed.
• Blood in the urine (hematuria): Often occurs briefly after the biopsy and is usually harmless.
• Infection: As with any invasive procedure, there is a small risk of infection.
• Arteriovenous fistula: A rare complication in which an abnormal connection forms between an artery and a vein.
• Injury to neighboring structures: Very rarely, adjacent organs such as the liver or spleen may be affected.

Aftercare

After the biopsy, the patient is monitored in the clinic for several hours (typically 6 to 24 hours). Blood pressure and urine are checked regularly. Physical rest is recommended for at least one week. Strenuous activities and heavy lifting should be avoided for approximately two weeks.

Results and Significance

Kidney biopsy results enable a precise diagnosis and are crucial for selecting the right therapy. Certain kidney diseases such as IgA nephropathy, Goodpasture syndrome, or various forms of glomerulonephritis can only be reliably diagnosed through a biopsy.

References

1. Kasper DL et al. - Harrison's Principles of Internal Medicine, 20th Edition. McGraw-Hill Education, 2018.
2. Kidney Disease: Improving Global Outcomes (KDIGO) - KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases. Kidney International, 2021.
3. Tondel C et al. - Indications for Renal Biopsy in Adults. BMJ Best Practice, 2022.