The clinical significance of polyomavirus BK viremia after renal transplantation is well documented, whereas the presence of BK viruria in the absence of viremia is felt to be of clinical insignificance. We performed this retrospective study to evaluate the decline in renal function at one year post-transplant in patients whose BK replication was detected on routine screening.

Methods: Charts of patients who underwent renal transplantation from July 1, 2008 to November 30, 2011 were reviewed. During this period, recipients were routinely screened for BK viruria and viremia at 1, 4, 8, and 12 months. The difference between the best estimated glomerular filtration rate (eGFR) by Modification of Diet in Renal Disease Study equation (MDRD) and eGFR at one year post-transplant were calculated to determine decline in eGFR (ΔeGFR). Patients who had nonfunction of their renal allograft or did not survive to one year were excluded.

Results: Decline in eGFR in the study population is as shown in Table 1. Upon discovery of BK viruria or viremia, immunosuppression was decreased in attempts to eradicate the virus. No patients with BK viruria or viremia experienced an acute rejection episode. There were two patients in the negative group with acute cellular rejection who did not return of their baseline renal function. Both these patients were included in the study.

Conclusion: Although the number of patients in the study was small, based on our study, patients who developed either BK viruria or viremia had greater decline of their renal function compared to those who had neither BK viruria nor viremia. Resolution of viruria resulted in lesser decline in renal function, although resolution of viremia did not. Prevention of BK viruria or viremia appears to have the better outcome; therefore, effective prophylaxis is of utmost importance.

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