The role of endoscopic evaluation of stone-free status at the end of retrograde intrarenal surgery. Should we trust ourselves? Prospective data over 5 years from a referral stone centre.

PURPOSE

To evaluate the reliability of the surgeon's endoscopic evaluation (EE) in assessing stone-free rate (SFR) after retrograde intrarenal surgery (RIRS), by comparing it with postoperative low-dose CT.

MATERIALS AND METHODS

From January 2019 to October 2023, patients undergoing RIRS for kidney or upper ureteral stones ≤ 2 cm and scheduled for postoperative CT were prospectively enrolled. At the end of RIRS, surgeon reported EE regarding SFR, then compared to low-dose CT about two months later. SFR was defined as ≤ 4 mm on CT. Descriptive statistics, univariate and multivariate logistic regression were used to assess clinical factors associated with inaccurate EE.

RESULTS

A total of 353 RIRS procedures were analyzed. The SFR was 82.2% based on EE and 73.7% on CT (290 vs. 260/353). EE and CT were discordant in 23.7% of cases (84/353), demonstrating poor agreement (Cohen's kappa = 0.314). EE showed a sensitivity of 38.7% and a specificity of 89.6%. Patients with discordant results had significantly larger stones (12.2 ± 4.1 mm vs. 10.8 ± 3.9 mm, p < 0.01) and a higher prevalence of stones > 10 mm (64% vs. 47.5%, p = 0.01). Univariate and multivariate logistic regression identified stone size > 10 mm (OR 2,25, 95% CI 1,18 - 4,29 - p = 0.01) and location in the upper ureter (OR 2,22, 95% CI 1,20 - 4,49 - p = 0.03) as independent predictors of EE - CT discordance.

CONCLUSION

In nearly one-quarter of cases, intraoperative EE did not accurately reflect postoperative SFR. Surgeons should not rely solely on EE but should strongly consider postoperative CT, especially in cases with stones larger than 10 mm and upper ureteral location.