[Clinical feature and analysis on the clinical related factors of BK virus associated nephropathy]

To determine the incidence of BK virus associated nephropathy (BKVAN) in renal-transplantation recipients, observe its histological features.

A total of 137 renal allograft biopsy specimens collected at our hospital during December 1999 to January 2008 were analyzed by routine histologic examination, immunohistochemistry and transmission electron microscopy (TEM) to screen for BKV. The case records of involved recipients were accessed to know their clinical manifestations, diagnostic characteristic and treatment regimens at that time. And the 1-, 3-year graft survival rate were analyzed by Kaplan-Meier analysis.

A total of 16 renal biopsy specimens (11.7%) were positive for BKV. Viral particales on the size of 35 - 40 nm were seen in the tubular epithelial cells of 3 biopsy specimens and 7 urinary sediment samples. The numbers of BKVAN recipients suffering acute rejection, using ALG/ATG/OKT3 and using FK506+MMF immunosuppressive protocol were 7, 7 and 10 respectively. In 14 cases of BKVAN, there was an elevated level of serum creatine concentrations. Four cases lost their grafts after using a large dose of immunosuppressives. And renal functions improved by a reduction of immunosuppression or a replacement of FK506 with CsA in 8 cases. And graft functions deteriorated or had already failed in the remaining 4 cases whose immunosuppressive protocol were not changed. The 1-, 3-year graft survival rates were 81.3% and 54.2% in BKVAN recipients respectively.

The diagnosis of BKVAN should be considered in recipients when their graft functions are deteriorating, especially for those with the accompanied risk factors. The morphological hallmarks of BKVAN are similar to those of acute rejection. The differentiation may be made by either immunohistochemistry or TEM. A proper modification of maintenance immunosuppression is effective in slowing down the progression of BKVAN.