# Prolonged Prophylactic Ureteral Stent Placement and BK Polyomavirus Infection After Renal Transplantation—A Retrospective Case-control Study

## TL;DR

Leaving a kidney transplant stent in for more than 8 weeks increases the risk of a harmful virus reactivating, which could damage the new kidney.

## Contribution

The study identifies prolonged stent duration (beyond 8 weeks) as a novel risk factor for BK polyomavirus reactivation in kidney transplant patients.

## Key findings

- Stent placement itself does not increase BK virus risk, but leaving it in for more than 8 weeks does.
- Stent duration beyond 8 weeks is an independent predictor of BKPyV-DNAemia in kidney transplant recipients.
- Early stent removal within 8 weeks may reduce the risk of BK virus complications.

## Abstract

Prolonged ureteral stent indwelling times beyond 8 wk—not stent placement itself—is associated with an increased risk of BK polyomavirus reactivation after kidney transplantation.

BK polyomavirus (BKPyV) poses a significant challenge in kidney transplant (KTX) recipients, potentially leading to BKPyV-associated nephropathy. Prophylactic ureteral stent (UrSt) placement is the standard care following KTX. Emerging data suggest that UrSt may influence the incidence and severity of BKPyV-DNAemia. We hypothesized a dose-dependent relationship between an indwelling UrSt and the risk of BKPyV-DNAemia in KTX recipients.

We included all KTX recipients with detectable BKPyV-DNAemia at the Medical University of Vienna from 2010 to 2021; those without DNAemia served as controls. This nested, retrospective, 1:1 sex- and age-matched case-control study assessed whether UrSt placement and/or its duration was associated with BKPyV.

Of 438 KTX recipients, 51.6% of viremic patients had received UrSt, compared with 47% of nonviremic controls. While UrSt placement was not associated with the risk of BKPyV-DNAemia (odds ratio [OR] 1.20, 95% confidence interval [CI] 0.83–1.75), indwelling time of >8 wk was (OR 1.79, 95% CI 1.10–2.93, p = 0.02). In a multivariable analysis, it remained an independent predictor of BKPyV-DNAemia (adjusted OR 1.74, 95% CI 1.06–2.86, p = 0.03). Limitations include the retrospective, single-center study design.

Prophylactic UrSt placement after KTX does not increase the risk of developing BKPyV-DNAemia. However, the indwelling time of the UrSt should be limited to <8 wk to reduce the risk of BKPyV-DNAemia. Therefore, early removal of UrSt—preferably within 8 wk—should be pursued when clinically feasible. Further research is needed to define the optimal UrSt indwelling time and clarify the underlying pathophysiological mechanisms.

In this study, we examined whether the placement and duration of ureteral stents after kidney transplantation affect the risk of developing a BK polyomavirus that can harm the transplanted organ. We found that the length of time the stent remains in place—especially beyond 8 weeks—was linked to a higher risk of viral reactivation. Removal of the stent earlier may help protect patients from these complications.