Electron microscopy in the diagnosis of BK-polyoma virus infection in the transplanted kidney.

BK polyomavirus has become an important etiologic agent responsible for significant morbidity in renal transplant recipients. This virus can be detected in transitional cells in the urine (decoy cells) using cytology, but correlation with allograft function status and histologic evidence of renal involvement is poor. Accurate diagnosis of BK polyomavirus infection requires a high index of suspicion and utilization of ancillary diagnostic techniques in many cases. Electron microscopy is very sensitive in depicting the presence of BK virions, but the finding of viral particles is not by itself diagnostic of BK interstitial nephritis. Management of patients with polyoma virus nephropathy is difficult since there is no specific antiviral therapy available at this time.