BK Viremia in Kidney Transplantation

Background: BK polyomavirus can cause BK nephropathy resulting in allograft dysfunction or premature allograft loss. Reducing immunosuppression has been the cornerstone of management, effectively treating BK viremia and BK virus associated nephropathy (BKVAN), which poses a challenge for clinicians, as it involves balancing and risking rejection. The optimal post-transplant screening approach for BK has not been determined and varies among transplant centers. Methods: We examined the association of allograft function in kidney transplant recipients who had reduced immunosuppressive regimens from 3 to 2 agents due to BK viremia. We defined BK viremia as any patient with a positive result rather than a specific number of copies in the serum. This retrospective single-center analysis of 16 patients who received a kidney transplant and developed BK viremia post-transplant looked at changes in serum creatinine one month post-transplant and up to 10 years post-transplant. Results: BK viremia onset ranged from 1-35 months post-transplant with an average onset of 10 months. All 16 had dose reduction or discontinuation of the antimetabolite agent. 7 of the 16 (44%) were with sustained BK viremia at last check within 3 months. 9 (56%) tested negative for BK viremia at last check within 3 months. Serum creatinine increased by 9 - 49%. Mean sCr increase was 22%. 0 of the 16 were challenged with reintroduction of the previously discontinued antimetabolite. Post-transplant complications included Crohn’s exacerbation, bacteremia, pyelonephritis, antibody-mediated rejection, and urothelial tract carcinoma. Conclusion: Our retrospective review of 16 patients followed for 10+ years aligns with the current KDIGO BK viremia screening recommendation. Of the total 16 patients this study included, >80 % had elimination of the antimetabolite agent; however, despite this regimen 44% of patients continue to have BK viremia. Over 22% had some rise and worsening of kidney function from one month baseline. We recommend that further attention be given to the patient population with BK viremia and further reduction of immunosuppression be considered, especially of the calcineurin inhibitor (CNI) along with bimonthly evaluation of BK viremia until its resolution, and evaluation by a kidney biopsy if the viremia persists.