Global Direct In-scope Suction Study: An EAU-endourology Multicenter Prospective Collaboration (DISS-study)

Background Direct in-scope suction (DISS) facilitates continuous stone dust evacuation during flexible ureteroscopy (FURS), but prospective evidence validating its clinical efficacy and safety remains limited. Objective To evaluate the stone-free rates (SFRs), perioperative outcomes, and limitations of DISS during successfully completed FURS for renal and ureteric stones in real-world practice, with the primary outcome being 30-d computed tomography (CT)–determined SFR. Design, setting, and participants A prospective, multicenter, investigator-led registry was conducted across 16 centers in 14 countries (NCT05297331). Adults undergoing FURS with the Pusen 7.5-Fr DISS scope for any-sized renal/ureteric stones were included. Outcome measurements and statistical analysis The primary outcome was 30-d postoperative noncontrast CT SFR, classified as grade A (zero residual fragments [ZRF]) and grade B (single ≤2-mm fragment). Multivariable logistic regression identified predictors of ZRF status. Results and limitations A total of 540 patients (median age 55 yr; 57% male) were enrolled. Anomalous kidneys were present in 12% (horseshoe 5.0% and malrotation 3.9%). Median stone volume was 590 mm 3 . Overall SFR (grades A and B) was 93% (501/540; 95% confidence interval [CI] = 90%–95%), with grade A achieved in 71% (386/540). Major complications were rare: no sepsis requiring intensive care unit admission, no transfusions, and only 2.6% ureteral access sheath (UAS)–related injuries (all Traxer grade 1). Postoperative fever >38°C occurred in 6.7% of the patients (36/540). On multivariable analysis for renal stones, stone volume (adjusted odds ratio [OR] 0.56, 95% CI = 0.39–0.79; p = 0.001) predicted lower odds of grade A status, whereas prestenting (adjusted OR 1.32, 95% CI = 0.76–2.33; p = 0.3) and UAS use (adjusted OR 0.76, 95% CI = 0.46–1.26; p = 0.3) were not statistically significantly associated with grade A status. Conclusions Flexible ureteroscopy for kidney and ureteral stones using the 7.5-Fr DISS achieves high SFR with low morbidity in real-world practice. Stone burden remains a key determinant of complete renal stone clearance using DISS.