Impact of DJ stenting on subacute renal recovery after flexible ureterorenoscopy

BACKGROUND: Routine ureteral stenting after flexible ureterorenoscopy (F-URS) remains controversial. While stents are used to secure drainage, their impact on subclinical renal tubular injury is not well defined. This study aimed to evaluate the effect of postoperative Double-J (DJ) stenting on acute and subacute renal injury using urinary Kidney Injury Molecule-1 (KIM-1) as a sensitive biomarker. METHODS: We conducted a retrospective analysis of a prospectively maintained database including 117 patients who underwent F-URS for renal stones. To minimize selection bias, patients with severe ureteral injury (PULS Grade ≥ 3) were excluded, and a ureteral access sheath (UAS) was utilized in all cases to standardize intrarenal pressure. Patients were stratified into two groups according to the postoperative drainage strategy: Group 1 (DJ stent) and Group 2 (no stent). Urinary KIM-1 levels normalized to creatinine (KIM-1/Cr) were measured preoperatively, at the postoperative 4th hour (acute phase), and on day 14 (subacute phase). RESULTS: Demographic characteristics and operative trauma scores (PULS) were comparable between the groups. In the acute phase (4th hour), both groups exhibited a significant and similar rise in KIM-1/Cr levels compared to baseline (p < 0.001), with no intergroup difference (p = 0.748). However, in the subacute phase (day 14), the stented group had significantly lower KIM-1/Cr levels compared to the non-stented group (0.18 vs. 0.36; p = 0.001). Additionally, the stone-free rate (SFR) was significantly higher in the stented group (89.8% vs. 65.5%; p = 0.002). Postoperative complication rates were similar (p = 0.35). CONCLUSION: DJ stent placement does not alter the acute biomarker surge associated with surgical stress but is associated with significantly lower KIM-1/Cr levels during the subacute recovery period. This finding suggests that improved drainage, together with more effective stone clearance, may contribute to better tubular recovery in stented patients. Urinary KIM-1 serves as a valuable objective tool for monitoring subclinical renal injury and may guide individualized stenting decisions.