From the Guidelines
To approach a kidney biopsy pathology slide effectively, begin with a systematic examination using light microscopy at low power to assess overall architecture and distribution of lesions, then progress to higher magnification for cellular details, as recommended by the most recent guidelines 1. When examining the slide, it is essential to follow a structured approach to ensure that all relevant features are assessed.
- First, examine the glomeruli, noting their number, size, cellularity, and any structural abnormalities.
- Next, evaluate the tubules for atrophy, casts, or cellular changes.
- Then, assess the interstitium for fibrosis, edema, or inflammatory infiltrates, and finally examine the blood vessels for hyalinosis, sclerosis, or vasculitis. Special stains are crucial for a comprehensive evaluation:
- H&E for general morphology
- PAS for basement membranes
- Silver stains for glomerular architecture
- Trichrome for fibrosis
- Congo red for amyloid. Immunofluorescence is essential to detect immune deposits, while electron microscopy helps visualize ultrastructural details like immune complex deposits and podocyte foot process effacement, as outlined in the KDIGO 2021 clinical practice guideline for the management of glomerular diseases 1. The evaluation of kidney tissue should meet standards of biopsy adequacy, with usually at least 8-10 glomeruli needed to diagnose or exclude specific histopathologic patterns with reasonable confidence, according to the KDIGO 2021 guideline 1. This comprehensive approach ensures that important diagnostic features are not missed, which could affect patient management, and is in line with the recommendations from the Mayo Clinic/Renal Pathology Society consensus report on pathologic classification, diagnosis, and reporting of glomerulonephritis 2, 3.
From the Research
Approach to Renal Biopsy Pathology Slide
To approach a renal biopsy pathology slide, several key considerations must be taken into account:
- The kidney biopsy is an essential tool for the diagnosis of many kidney diseases, and obtaining an adequate biopsy sample with appropriate allocation for various studies is crucial 4.
- The assessment of kidney biopsies is mainly confined to specialized centers, but general pathologists may also encounter kidney biopsies and should be aware of typical renal patterns of injury 5.
- Renal biopsy interpretation involves the correct assessment of different structures within the biopsy, including glomeruli, tubules, and interstitium, which can be manually visualized and interpreted by a renal pathologist or assisted by artificial intelligence tools 6, 7.
Key Lesions and Interpretation
Key lesions and their interpretation are essential elements underlying optimal approaches for interventions:
- Lesions are presented according to anatomic site as glomerular, vascular, or tubulointerstitial, and native and transplant kidney biopsy lesions are included 4.
- Correlation with immunofluorescence, electron microscopy, and clinical findings are emphasized to reach a differential diagnosis and the final diagnosis 4.
- Biopsy features associated with progression to end-stage renal disease, such as glomerulosclerosis and tubulointerstitial scarring, should be carefully evaluated 8.
Role of Artificial Intelligence
Artificial intelligence (AI) can assist in evaluating pre-implantation kidney biopsies:
- AI tools, such as Galileo, can detect the main findings evaluated in the pre-implantation setting and demonstrate high precision, sensitivity, and F1 score 7.
- AI-assisted detection of renal structures and quantitative information can be directly integrated into the final report, reducing inter-observer variability and speeding up pre-implantation kidney biopsy interpretation 7.