From the Guidelines
A renal biopsy is indicated after a kidney ultrasound when the ultrasound reveals abnormalities that require tissue diagnosis for definitive management, such as suspected bacterial infection-related glomerulonephritis, unexplained acute kidney injury, persistent proteinuria, hematuria with proteinuria, suspected glomerulonephritis, unexplained nephrotic syndrome, or systemic diseases with renal involvement like lupus. The decision to proceed with a renal biopsy should be based on the presence of specific clinical indications, including kidney size discrepancies, focal lesions requiring characterization, or diffuse parenchymal changes without clear cause, as identified by the kidney ultrasound 1. Before proceeding with a biopsy, coagulation studies (PT, PTT, INR, platelet count) should be normal, blood pressure controlled, and anticoagulants or antiplatelet medications should be temporarily discontinued when possible. The biopsy provides actual kidney tissue for histological, immunofluorescence, and electron microscopic examination, allowing precise diagnosis of conditions that cannot be determined by imaging alone, as emphasized by the KDIGO 2021 clinical practice guideline for the management of glomerular diseases 1. This tissue diagnosis guides specific treatment decisions, particularly for inflammatory, autoimmune, or infiltrative kidney diseases where immunosuppressive therapies might be required. In some cases, biopsy may be critical for arriving at the correct diagnosis, as comorbidities may contribute to confounding effects, highlighting the importance of careful patient selection and consideration of the potential risks and benefits of the procedure 1. The role of kidney biopsy in exploring the histopathology of acute kidney disease (AKD) is also recognized, with a limited number of studies having explored this aspect, and the historical context and finding small kidneys relative to the patient’s habitus on ultrasound may be suggestive of chronicity and point to the possibility of AKD superimposed on preexisting CKD 1. The correct diagnosis requires a well-trained renal pathologist with thorough knowledge of not only renal pathology but also renal medicine, to correlate intricate tissue-derived information with detailed and sometimes subtle clinical data, as outlined in the practice guidelines for the renal biopsy 1. Key considerations in the interpretation of renal biopsy specimens include the use of optimal methods, such as light microscopy, immunohistochemistry, and electron microscopy, to allow for a complete evaluation. Ultimately, the decision to perform a renal biopsy should be individualized, taking into account the specific clinical context, the potential risks and benefits, and the availability of resources and expertise.
From the Research
Indications for Renal Biopsy after Renal Ultrasound
- Renal biopsy is indicated in patients with suspected glomerulonephritis or vasculitis, as it is essential for accurate diagnosis and treatment 2, 3.
- A renal biopsy is necessary to confirm the diagnosis of ANCA-associated renal vasculitis and to assess the severity of renal damage 3.
- The biopsy is also important in patients with no compatible extra-renal manifestations of ANCA-associated vasculitis or any other possible renal diagnosis, such as polyvascular disease or diabetic patients 3.
- Renal biopsy is the gold standard for diagnosing glomerular kidney disease and is used to evaluate the presence, extent, and rate of progression of renal dysfunction 4, 5.
Diagnostic Yield and Safety of Renal Biopsy
- Renal biopsies are a safe procedure if contraindications are considered, and the use of semi-automatic spring-loaded biopsy devices and real-time ultrasound has declined the complication rate 5.
- A coagulation disorder needs to be excluded beforehand, and an elevated blood pressure must be reduced to the normotensive range with medications 5.
- The biopsy specimen is examined with light microscopy, immunohistochemistry, and electron microscopy, and combination with modern molecular pathology techniques will contribute to more precise insights into the development and progression of kidney disease 5.
Predictive Value of Kidney Biopsy in Renal Vasculitis
- The histopathologic classification of antineutrophil cytoplasmic antibody-associated vasculitis has been demonstrated to have prognostic value in patients with pauci-immune extracapillary glomerulonephritis 6.
- The percentage of extracapillary proliferation and glomerulosclerosis are significant predictors for renal survival, and patients with extensive extracapillary proliferation have the poorest renal survival 6.