Objectives To compare the efficacy of retrograde flexible ureterorenoscopy (FURS) in the treatment of low-density stone (LDS) and high-density stone (HDS).Patients and Methods From January 2017 to March 2019, 241 patients with 2–3 cm kidney pelvic stones were treated with retrograde flexible ureterorenoscopy. The relevant study parameter for all patients, including patients age, body mass index (BMI), gender, stone density values (Hounsfield units [HU]), stone size, stone location, operative time, hospitalization time, stone free rate (SFR), complications were evaluated. The results were assessed one month after the FURS and the follow-up time is 6 months.Results Effectively, 241 patients finish the whole process and are divided into two groups (LDS and HDS). The postoperative hemoglobin (Hb) was 13.31±1.06 vs. 13.21±1.14 g/dL (p=0.50). The mean total operating time was 83.91±13.7 vs. 130.65±19.8 min (p<0.01), respectively. The hospitalization time was 3.4±1.1 vs 3.2±1.1 days (p=0.33), respectively. The free stone rate was 91.5% vs. 93.5% (p=0.54) and the street stone rate was 12(10%) vs. 3(2.4%) (χ2=6.173 a , p=0.01) in the LDS and HDS groups.Conclusions We concluded that FURS is safe and effective for the treatment of large renal pelvic stones 2-3 cm. There is no difference in the SFR between LDS and HDS group after the FURS operation. Density (as measured by non-contrast CT) of the renal calculus can help predict the treatment outcome before FURS. For appropriate patients, FURS should be chosen as a common approach in the treatment of renal pelvic calculus.

The authors have withdrawn this preprint due to author disagreement.