# P-1806. Incidence of BK Virus Nephropathy in Kidney Transplant Recipients

## TL;DR

This study found that BK virus nephropathy occurs in about 23.5% of kidney transplant patients with BK virus reactivation, and recent organ rejection is strongly linked to developing this condition.

## Contribution

The study reports a higher-than-expected incidence of BKVAN and identifies recent rejection as the sole associated risk factor.

## Key findings

- 16 out of 68 patients (23.5%) with BK virus reactivation developed BKV-associated nephropathy (BKVAN).
- Recent organ rejection was the only factor significantly associated with BKVAN development (p < 0.0001).
- 81.3% of BKVAN patients experienced rejection, and 14.3% lost their graft.

## Abstract

BK virus (BKV) reactivation in urine and plasma occurs in 30–60% and 4.5–27% of kidney transplant (KT) recipients, respectively. Of these, 1–5% will develop BKV-associated nephropathy (BKVAN), which can lead to graft loss. BKVAN is defined as histological changes in the graft secondary to BKV reactivation.

This was a prospective cohort study. KT recipients with BKV reactivation in urine and plasma confirmed by quantitative PCR at a University Hospital (January 2020 – December 2024) were included. Chi-square tests were used for categorical variables and Student’s t-test for differences in means and medians; interquartile range (IQR) was reported for continuous variables.

During the study period, 202 KTs were performed, of which 68 (33.7%) had BKV reactivation in urine, and 27 (13.4%) also in plasma. BKV reactivation occurred more than once in 34.1% of cases. Sixteen recipients (23.5%) developed BKVAN. Of these, 81.3% were male. The median age was 53.9 years (IQR 50.5–57.2). Donor type was deceased (75%), unrelated living (5.9%), and related living (19.1%). Induction immunosuppression included corticosteroids (100%), thymoglobulin (86%), mycophenolate (82.8%), tacrolimus (10.9%), and rituximab (4.7%). 6.8% of KT receptors had concurrent CMV infection. Among BKVAN patients, 81.3% experienced rejection and 14.3% lost the graft. The median time from transplant to BKVAN diagnosis was 143 days (IQR 83–853). Recent organ rejection was the only factor associated with BKVAN (p< 0.0001). Clinical presentation included renal insufficiency (56.8%), dysuria (15.9%), hematuria (4.5%), and fever (2.3%). Treatment involved reduction of immunosuppression (77%), regimen changes (40.9%), and leflunomide administration (37%). No hospitalizations or BKVAN-related deaths were recorded.

The incidence of BKVAN was higher than that reported in the literature. Rejection was the only factor associated with BKVAN, suggesting its role in disease progression.

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