Optimal timing of double J stent removal after kidney transplantation: A multicenter KQIPS cohort study.

초록

Introduction: Double-J (DJ) ureteral stents are routinely used after kidney transplantation to protect the ureterovesical anastomosis and reduce early urologic complications. However, prolonged stent retention may increase urinary tract infection (UTI) and BK virus (BKV) viremia, while overly early removal may increase the risk of leakage or ureteral stricture. Previous studies have generally compared only a few arbitrary removal time points and have not adequately characterized the full risk profile across time. We aimed to evaluate the dose-response relationship between stent removal timing and post-transplant complications, and to identify a clinically practical timing for removal associated with the lowest overall risk. Methods: We performed a multicenter cohort study using the Korean Quality Improvement Platform in Surgery (KQIPS) registry. Among 14,487 kidney transplant recipients, 6,677 patients from 49 centers with DJ stent placement and valid removal dates were included. Patients with leakage or stricture before stent removal were excluded. The primary outcome was urinary tract infection defined as Clavien-Dindo grade I or higher. Secondary and sensitivity outcomes included UTI grade II or higher, ureteral stricture, urine leakage, and BKV viremia of at least 1,000 copies/mL. Stent removal timing was modeled as a continuous variable using restricted cubic spline Cox regression. To account for center-level practice variation, endogeneity, and possible reverse causation, nonlinear instrumental variable analysis with two-stage residual inclusion was performed using center-level leave-one-out mean removal timing as the instrument. Results: The median stent removal time was 33 days (interquartile range, 27-42). Urinary tract infection occurred in 282 patients (4.2%), and BKV viremia occurred in 723 patients (13.2%). In nonlinear instrumental variable analysis, delayed stent removal was associated with higher risks of both UTI and BKV viremia (p values <0.001 for both), whereas earlier removal showed a nonsignificant directional tendency toward more ureteral complications. The interval in which infectious risk remained low while ureteral complication risk did not appear to increase substantially was 28 to 42 days after transplantation. These patterns were consistent across sensitivity analyses, including stricter UTI definition, high-surveillance BKV centers, and alternative spline knot specifications. Conclusion: In this large multicenter cohort, DJ stent removal at 4 to 6 weeks post transplantation was associated with the most favorable balance between infectious outcomes and ureteral safety. These findings support a clinically practical removal window of 28 to 42 days after kidney transplantation. This window may help guide a more standardized approach to posttransplant stent management across centers.