Significance of cyclosporin-A-associated renal surface irregularities.

The purpose of this study was to investigate unusual irregularities observed on the surface of kidneys from rats which had been treated with seven 'clinically effective doses' (25 or 50 mg/kg) of cyclosporin A (CsA). Surface corrugations were obvious on gross examination and were a universal finding in our study which involved greater than 50 rats. Examination by scanning electron microscopy (SEM) showed that the surface irregularities resulted from swollen peritubular capillaries adjacent to vacuolized and partially collapsed tubules at the cortical surface. The enlarged capillaries were associated with vascular congestion, and although peritubular capillary congestion has been recognized in CsA-treated patients, it has been difficult to determine whether this reaction is associated with drug toxicity or graft rejection. Our findings, indicating that peritubular capillary congestion in addition to vacuolization and collapse of subcapsular tubules is a drug-associated phenomenon, may help give a more accurate assessment of biopsy and autopsy material from CsA-treated patients and laboratory animals.