Background:
While light microscopy (LM) and immunofluorescence (IF) are standard in renal pathology, electron microscopy (EM) remains the gold standard for identifying ultrastructural alterations. In complex clinical scenarios, EM is often the deciding factor in differentiating overlapping pathologies.
Purpose:
This case series highlights the critical impact of EM in establishing definitive diagnoses for six patients where LM and IF findings were either inconclusive or required ultrastructural confirmation.
Methods:
A retrospective analysis was conducted on renal biopsies from six challenging cases where clinical presentations—ranging from nephrotic syndrome to deteriorating graft function—necessitated high-resolution ultrastructural examination.
Results:
The diagnostic utility of EM was demonstrated across diverse pathologies:
1. Fibrillary Glomerulonephritis: Identified via 15.4nm smudgy fibrillar deposits in a patient with cirrhosis and unexplained proteinuria.
2. Dense Deposit Disease: Confirmed by characteristic highly electron-dense intramembranous deposits despite a non-specific immunology screen.
3. Thrombotic Microangiopathy (TMA): EM confirmed TMA in a post-stem cell transplant patient, clarifying that renal decline was likely drug-induced (TKI therapy).
4. MCTD vs. Lupus Nephritis: EM identified complex deposit substructures, which, alongside clinical correlation, allowed for the differentiation of mixed connective tissue disease from systemic lupus.
5. Amyloidosis: Classical ultrastructural features established the diagnosis in a patient with Waldenström macroglobulinaemia.
6. IgA Vasculitis: In a patient with advanced diabetic nephropathy, EM identified small, sparse paramesangial deposits, confirming IgA vasculitis superimposed on diabetic changes.
Conclusion:
In all cases, EM was indispensable. It provided definitive evidence that LM and IF alone could not capture, particularly regarding deposit substructure and basement membrane morphology. These findings directly influenced clinical management, allowing for targeted treatments and the avoidance of unnecessary interventions. This series reaffirms that EM is essential for precision medicine in modern nephropathology.

BACKGROUND:
Electron microscopy (EM) remains a fundamental pillar of renal pathology, playing a pivotal role in diagnosis of glomerular diseases specially in cases where ultrastructural detail is critical. Despite its importance, laboratory processes and personnel involved in EM are often behind the scenes. This presentation, delivered from perspective of a renal pathologist, follows journey of renal biopsy from patient to final ultrastructural image. Additional scope of presentation involves emphasis on diagnostic scope and exploring strategies for cost effective utilization.

METHOD / APPROACH
1) Stages in the process are outlined, including specimen handling, fixation, processing, ultrathin sectioning, staining, and imaging. The presentation emphasizes how pre-analytical and technical factors affect diagnostic yield. It discusses common pitfalls as delayed fixation and artifact introduction, which can compromise interpretation.

2) Clinical Utility and Diagnostic Scope:
Through Interactive real time case presentations, I will demonstrate EM’s diagnostic value, particularly in scenarios where light microscopy and immunofluorescence overlap. Examples include:

 Diffuse foot process effacement -minimal change disease vs FSGS
 Distribution of immune deposits in Lupus class.
 Detecting organized deposits, as fibrillary, cyroglobins, and amyloid.
 Identifying secondary / incidental pathology and hereditary nephropathies.
 Primary tool for early ultrastructural changes that appear before overt histologic abnormalities in transplant cases, distinguishing de novo, recurrence and transplant glomerulopathy.

3) Highlights- Through series of case presentation and internal audit results and statistics the talk aim to highlight the continuing relevance of EM in renal pathology identifying as essential, contributory, and non -contributory to diagnosis.

Conclusion:
Despite its value, EM use is challenged by cost, expertise and limited availability. A design of clinical and pathological triage to utilize these services for appropriate clinical scenarios is need of the hour, as we all advocate that this domain, often invisible to many but essential to all, should be judiciously utilized.

Electron microscopy remains central to the evaluation of renal deposition diseases. By enabling precise characterisation of the location, ultrastructural morphology and size of deposits, EM provides critical discriminatory features that help distinguish entities with overlapping light microscopy and immunofluorescence findings. This presentation offers a focused overview of the key ultrastructural features and diagnostic approach to selected glomerular diseases characterised by organised deposits, including amyloidosis, fibrillary glomerulonephritis, immunotactoid glomerulopathy, collagenofibrotic glomerulopathy and cryoglobulinaemic glomerulonephritis.

The high cost and complexity of traditional transmission electron microscopy (TEM) techniques can significantly limit its use in diagnostic pathology, particularly in remote and Indigenous communities, where renal disease remains a major health challenge. Recent technical developments in scanning electron microscopy (SEM) instrumentation open the doors to new opportunities for clincal EM. The use of improved scanning TEM and back-scattered electron detectors may allow SEM to produce images suitable for use in diagnostic situations. The introduction of compact portable instruments will enable broader access in resource limited settings. In this talk I will discuss modern SEM capabilities and ask how these could be used by pathologists and scientists in future. I will show examples of SEM images produced from TEM samples and discuss the opportunities and possible impact of adopting these techniques.