Differential diagnosis of Cyclosporin A nephrotoxicity versus rejection by fine needle aspiration biopsy.

Twelve transplants with signs of graft failure and five with good function on CyA, were aspiration biopsied and analysed for (a) the presence of inflammation, (b) morphological changes in the graft parenchymal cells and (c) by indirect immunofluorescence for the presence of CyA in the renal tubular cells. Four reaction patterns were recorded: (i) good transplants with a normal serum creatinine, no evidence of inflammation, no parenchymal cell changes and no deposits of CyA in the graft; (ii) patients with elevated serum creatinine, no inflammation but distinct parenchymal cell changes and massive deposits of CyA (i.e., nephrotoxicity); (iii) patients with elevated serum creatinine, distinct inflammation in situ, modest tubular cell changes and no CyA in the graft (i.e., rejection); and (iv) patients with elevated serum creatinine, distinct inflammation in situ, distinct tubular cell changes and concomitant deposits of CyA (i.e., nephrotoxicity and rejection). CyA deposits in the graft had only a marginal relationship to drug dose and concentration of the drug in serum. When the dose was reduced, the deposits rapidly disappeared and tubular cell changes resolved. We recommend the FNAB for differentiating between nephrotoxicity and rejection in renal transplants.