Plastic embedding techniques in the study of renal biopsies and bone pathology in renal disease

Abstract

The need for better correlation between light and electron microscopic studies of glomerular morphology has necessitated a search for methods beyond traditional paraffin section techniques. Although the use of plastic embedding for light microscopy appeared a logical solution, poor stain penetration and prolonged processing has hindered the introduction of such techniques into service laboratories. The development of low viscosity epoxy resins mith improved powers of penetration and short polymerization times has solved these difficulties. Methods for staining thin (0.4–1 μm) sections with haematoxylin and eosin, silver methenamine, trichromes and Congo red techniques in addition to the basic aniline dyes used by electron microscopists, have been developed. Slight changes in basement membranes and mesangial matrix and in the various cellular components of the glomerulus can be clearly defined and deposits may be recognized. Immunofluorescence and electron microscopy have been used to confirm the validity of the method. With modifications, similar techniques can be applied to undecalcified bone in the study of bone changes in renal failure. Processing does not interfere with the use of tetracycline labels as markers and the preparations are suitable for quantitative bone histology. Bone changes are invariably present in chronic renal failure. Three main components in various combinations, may be defined. Osteitis fibrosa is commonly seen, osteomalacia occurs less frequently and changes in bone mass, osteosclerosis or osteoporosis, may also be found. Although in general mild and asymptomatic, renal bone disease has become a major problem in patients treated by long-term haemodialysis as these basic patterns of bone changes tend to increase in severity during long-term dialysis.