[Calcification in nonfunctioning transplanted kidneys]. 
Failed renal allografts often are left in situ in patients who revert to chronic dialysis therapy or who undergo retransplantation.  These organs may be the site of massive calcification despite their lack of physiological function.  Calcification of an endstage renal allograft is sometimes found incidentally.  We report here two patients who developed extensive calcification of the renal graft, one was on chronic hemodialysis and the other had a second renal transplantation with normal renal function.  The precise pathogenesis of calcification and the factors which determine its tissue localization are unclear.  Factors postulated to promote the development of metastatic calcification include an elevated calcium phosphate product, severe secondary hyperparathyroidism, aluminium toxicity and duration of dialytic therapy.  In some cases local factors related with the chronic inflammatory rejection process are probably involved as well.  However, the exact relative contribution of these factors remains unresolved.  Unless specific clinical indications are present, transplant nephrectomy is not necessary for calcified end-stage renal allografts.