Role of electron microscopy in transplant renal pathology.

The crucial role that electron microscopy plays in diagnostic renal pathology is undisputed. By allowing recognition of findings not identifiable by light microscopic evaluation, electron microscopy has contributed significantly to the understanding of renal diseases and has proven to be of unquestionable value in many diagnostic situations. However, the percentage of cases in which electron microscopic examination adds important information that is either key for establishing or confirming a diagnosis or provides valuable data that influence patient's management remains controversial. This figure depends on the renal biopsy service that is surveyed, but it is reported that on the average ultrastructural evaluation is of value in approximately 30 to 45% of the cases. Correct interpretation of a renal biopsy depends on the ability to correlate light, immunofluorescence, and ultrastructural findings. In contrast, the role of electron microscopy in the examination of renal transplant specimens remains controversial. Many centers do not use routine electron microscopy to examine these specimens and insist that there are only a few specific indications that require ultrastructural evaluation. There is general agreement among renal pathologists that electron microscopy is of importance in the evaluation of renal specimens from patients with proteinuria to distinguish between transplant glomerulopathy, recurrent or de novo glomerulonephritis in order to correctly manage these patients and predict survival of the graft. The other possible indications are much more controversial. This paper summarizes and critically reviews the literature available on this subject and defines recommendations based on the information available at the current time.