The emerging role of electron microscopy in renal allograft rejection

The current criteria for renal allograft rejection are primarily based on histology, and therefore the early treatable stage of rejection is often not detected. Ultrastructural examination of renal allograft biopsy is increasingly being recognized to be essential for detecting early changes of rejection, which may not be evident on histology. These early ultrastructural lesions usually involve the glomerular and peritubular capillaries. Additionally, the routine ultrastructural examination of renal graft biopsies in patients with chronic graft dysfunction can reduce the non-specific diagnosis of interstitial fibrosis and tubular atrophy by demonstration of changes indicative of rejection-associated injury. Ultrastructural evaluation along with histology and immunofluorescence of renal graft biopsies is also vital in proteinuria to differentiate transplant glomerulopathy from recurrent or de novo glomerular pathology. The need for specific specimen collection procedures, limited graft tissue, and cost are limiting factors for routine electron microscopy in allograft biopsies. However, electron microscopy is an excellent tool for the evaluation of early changes in graft biopsies not evident on routine histology.