The Continuing Need for Electron Microscopy in Examination of Medical Renal Biopsies: Examples in Practice.

Background: For the better part of the past 6 decades, transmission electron microscopy (EM), together with routine light microscopy and immunofluorescence and/or immunohistochemistry (IHC), has been an essential component of the diagnostic workup of medical renal biopsies, particularly native renal biopsies, with increasing frequency in renal allograft biopsies as well. Studies performed prior to the year 2000 have indeed shown that a substantial fraction of renal biopsies cannot be accurately diagnosed without EM. Still, EM remains costly and labor-intensive, and with increasing pressure to reduce healthcare costs, some centers are de-emphasizing diagnostic EM. This trend has been coupled with advances in IHC and other methods in renal biopsy diagnosis over the past 2-3 decades. Summary: Nonetheless, it has been our experience that the diagnostic value of EM in the comprehensive evaluation of renal biopsies remains similar to what it was 20-30 years ago. In this review, we provide several key examples from our practice where EM was essential in making the correct renal biopsy diagnosis, ranging from relatively common glomerular lesions to rare diseases. Key Messages: EM remains an important component of the diagnostic evaluation of medical renal biopsies. Failure to perform EM in certain cases will result in an incorrect diagnosis, with possible clinical consequences. We strongly recommend that tissue for EM be taken and stored in an appropriate fixative and ultrastructural studies be performed for all native renal biopsies, as well as appropriate renal allograft biopsies as recommended by the Banff consortium.