How to interpret renal (kidney) biopsy results?

From the Guidelines

When interpreting renal biopsy results, it is essential to schedule a follow-up appointment with your nephrologist to review the findings together, as the pathology report contains crucial information about your kidney tissue, including any inflammation, scarring, deposits, or cellular changes, and proper interpretation leads to appropriate management of your specific condition. The kidney biopsy is considered the "gold standard" for the diagnostic evaluation of glomerular diseases, as stated in the kdigo 2021 clinical practice guideline for the management of glomerular diseases 1.

Key Considerations

• The pathology report typically takes 2-7 days to complete and should be reviewed with a well-trained renal pathologist who has thorough knowledge of renal pathology and medicine to correlate tissue-derived information with clinical data 1.
• During the appointment, ask your doctor to explain the diagnosis, disease severity, and prognosis in clear terms, and discuss treatment options, which may include medications like corticosteroids or immunosuppressants, depending on your condition 1.
• It is also important to discuss potential side effects, treatment duration, and necessary lifestyle modifications, such as dietary changes or blood pressure management, and request information about follow-up testing to monitor your kidney function, typically including regular blood tests and urine tests.

Evaluation and Management

• The evaluation of the cause of chronic kidney disease (CKD) should include clinical context, personal and family history, social and environmental factors, medications, physical examination, laboratory measures, imaging, and genetic and pathologic diagnosis, as recommended in the kdoqi us commentary on the kdigo 2024 clinical practice guideline for the evaluation and management of ckd 1.
• A kidney biopsy is an acceptable and safe diagnostic test to evaluate the cause and guide treatment decisions when clinically appropriate, and its risks should be balanced against the potential benefits of diagnosing potentially treatable conditions 1.

Special Considerations

• In patients with suspected monoclonal gammopathy of renal significance (MGRS), a kidney biopsy is essential for diagnosis, but clinicians must balance the risks associated with underdiagnosis against those of complications from the biopsy procedure 1.
• The presence of MGRS-associated renal lesions, including amyloidosis, does not increase the risk of bleeding after kidney biopsy, and performing a kidney biopsy in patients with rapidly progressive loss of renal function or increasing proteinuria is reasonable, especially if their diabetes is well controlled and/or evidence of extrarenal microvascular disease is absent 1.

From the Research

Interpreting Renal Biopsy Results

To interpret renal biopsy results, it is essential to understand the different modalities used in the diagnosis, including light, immunofluorescence, and electron microscopy 2. The renal biopsy is considered the gold standard for diagnosis of kidney disease, allowing for determination of the type, extent, site, and nature of renal involvement in medical diseases.

Key Considerations

• The diagnosis of renal biopsies is complex and requires correlation of findings in multiple modalities 2.
• Appropriate division and fixation of the renal biopsy are necessary for accurate diagnosis 2.
• The kidney biopsy plays a central role in the investigational approach of the nephrologist, and its technique has significantly improved over the past two decades 3.
• Percutaneous renal biopsy has become a relatively safe procedure with life-threatening complications occurring in less than 0.1% of biopsies 2, 3.

Patient Populations

• Four groups of patients benefit from the findings of renal biopsy: those with a nephrotic syndrome, those with a renal disease in a context of systemic disorder, those with acute renal failure, and those with a renal transplant 3.
• Some patients with non-nephrotic proteinuria, hematuria, and chronic renal failure may also benefit from the procedure 3.

Complications and Risks

• Major complications from percutaneous kidney biopsies are rare, occurring in less than 0.1% of cases, but can include bleeding and the need for transfusion or invasive procedures 4, 3.
• Minor complications, such as pain, are more likely to occur in younger, healthier patients, and in those with hematuria prior to biopsy 5.
• The use of the PFA-100 may replace the bleeding time and is now considered a more valuable screening test for prebiopsy identification and management of patients with impaired haemostasis 3.

Post-Biopsy Care

• At least 24 hours of observation is recommended after the percutaneous native kidney biopsy for the development of potential complications 6.
• However, some studies suggest that centers can consider reduced observation times without compromising patient safety, as major complications are reliably identified within 4 hours of biopsy 5.