Ecacy and safety of single-use exible ureteroscope(cid:0)ZebraScope TM (cid:0)for the treatment of upper urinary tract calculi ≤ 2 cm

Purpose To evaluate the clinical ecacy and safety of a Chinese single-use exible ureteroscope (ZebraScope TM ) for the treatment of upper urinary tract calculi ≤ 2 cm based on a retrospective database. Methods Overall, 84 patients with upper urinary tract calculi who underwent FURS at our hospital from July, 2020 to January, 2021 were enrolled and reviewed. Demographic characteristics and perioperative data were evaluated and analyzed. patients: 51 male and age


Conclusion
The Chinese single-use ureteral exible ureteroscope (ZebraScope TM )can be considered effective and safe for the treatment of upper urinary tract calculi ≤ 2 cm.

Background
The upper urinary tract stone was the most common diseases in urology [1] . Extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL), rigid ureteroscope (RURS) and exible ureteroscope (FURS) lithotripsy have become standard therapeutic options for urinary stones [2] . PCNL is more invasive and has higher complication rate compared to ureteroscope lithotripsy [3] , and the ESWL has low SFR and higher retreatment rate [4,5] . Comparing with FURS, the RURS has more de ciencies for renal and proximal ureteral calculi in select patients [6,7] . Nowadays, exible ureteroscopy has been the rst-line treatment for upper urinary tract calculi ≤ 2 cm [8] .
The role of exible ureteroscopy has rapidly expanded owing to improvements in endoscopes and instrumentation, technique re nement, and growing operator experience, however, the original purchasing costs, reprocessing cost, repair fees and the problem of durability of reusable ureteroscopes serve as the chief factors that hinder FURS being embraced [9][10][11] . Finally, an important concern for the use of reusable exible ureteroscopes is sterility [11,12] . Over the past years, several single-use FURS devices have been introduced [13,14] . Chinese single-use exible ureteroscope(ZebraScope TM ), each component is single-use, so, it can avoid cross infections, reprocessing costs and repair fees, which greatly improves its bene tcost ratio and safety. The purpose of this study is to evaluate the e cacy and safety of ZebraScope TM single-use exible ureteroscope for the treatment of upper urinary tract calculi ≤ 2 cm.

Study population
We collected the clinical information of patients who underwent FURS at our hospital from July, 2020 to January, 2021, overall, 84 patients were retrospectively reviewed. The demographic characters, including age, gender and BMI (body mass index, BMI), preoperative parameters, including stone size, stone location, calculi laterality, and hydronephrosis severity, routine blood examinations, urinalysis and culture, serum biochemistry, surgical parameters, postoperative complications and parameters, length of hospital stay, hospitalization costs were evaluated and analyzed. All methods were carried out in accordance with relevant guidelines and regulations.
The inclusion criteria were: patients with upper urinary tract calculi ≤ 2 cm (as diagnosed by CT, abdominal DR or ultrasound); cognitive ability was normal and the ureteral access sheathes were placed successfully at one time. The exclusion criteria were: patients with malignant tumors, uncontrolled urinary tract infection, severe urethral or ureteral stricture, severe hemorrhagic diseases and cardiopulmonary insu ciency. All methods were carried out in accordance with relevant guidelines and regulations.
ZebraScope TM ZebraScope TM single-use ureteral exible ureteroscope (Figure 1), which weighs 0.185 kg, is easy to hold, and the operating handle has an automatic locking system. The outer diameter of tip is 2.47mm, and the largest outer diameter is 2.87 mm, which can pass through the F11 / 13 expansion sheath smoothly. The operating channel is 3.6Fr, which allow the simultaneous operation of pressure perfusion and 200µm ber work at the same time. The working length of the exible ureteroscope is 670mm, and the total length of ureteroscope is 905mm. The maximum de ection in tip de ection is 275°, the lens is 1.6×10 5 pixels, and the depth of eld is 2 to 50 mm ( Figure 1).

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Statistical analysis was performed using SPSS (version 22.0, IBM, USA). Categorical variables were presented as numerical values, and continuous data were presented as mean ± standard deviation. All test results were considered signi cant at P < 0.05.

Results
Demographic characteristics and preoperative data were summarized in Table 1   The complication grade based on Clavien-Dindo: Grade I Any deviation from the normal postoperative course without the need for pharmacologic treatment or surgical, endoscopic, and radiologic interventions. Allowed therapeutic regimens are drugs as antiemetics, antipyretics, analgetics, and diuretics, and electrolytes and physiotherapy. This grade also includes wound infections opened at the bedside. Grade II Requiring pharmacologic treatment with drugs other than such allowed for grade I complications. Blood transfusions and total parenteral nutrition are also included. Grade III Requiring surgical, endoscopic, or radiologic intervention. Grade IV Life-threatening complication (including CNS complications) requiring IC/ICU management. Grade V Death as a result of complications.
The comparison of preoperative and postoperative blood test were recorded in Table 3. There were signi cant increase in leukocyte, neutrophils, and decrease in urea nitrogen, albumin and globulin after surgery (P 0.05), while no signi cant difference were observed in hemoglobin and creatinine (P 0.05) ( Table 3).  [15] . Zhu Zewu conclude the SFR between PCNL and FURS for the management of intermediate-size renal stones (2-3cm) was comparable, however, the hospitalization time and rate of intraoperative complications were higher in group PCNL [16] . Compare with FURS, ESWL showed signi cantly lower SFR for previously untreated kidney stones 5-20 mm, ESWL (71%) versus URS (84%), in study of Christian D Fankhauser [17] . The 1-month SFR for upper urinary tract calculi ≤ 2 cm was 76.19% in our study, which was similar to study of Jiaqiao Zhang (71.00%) for renal stone [18] . For some special patients, such as abnormal kidney(anatomy or location), obesity and urinary malformations, FURS performs better than ESWL and PCNL [19][20][21] .
Since the single-use FURS been introduced, they have gained widespread popularity with their e cacy becoming closer to reusable scopes [22,23] . Yongchao Li nd single-use FURS had a higher SFR in comparison with reusable FURS, and the perioperative complication rate were comparable [24] . Furthermore, there was an outbreak of urinary tract cross infection as incomplete decontamination of reusable exible ureteroscope has been reported [25] .
The most frequent complications after exible ureteroscopy were fever, sepsis, steinstrasse or ureteral injury, ureteral avulsion, ureteral strictures, kidney damage and severe bleeding [26,27] . Giusti published a retrospective analysis based on patients who underwent FURS with an overall complication rate of 29.1%, which the Clavien I and II rate was 26.9%, while the Clavien III and IV were 1.9% and 0.3% [28] . However, N F Davis reported the overall complication rate of Single-use exible ureteropyeloscopy for the treatment of renal calculi was 9.3% [29] . The overall complication rate in our study was 4.76%, the Clavien I and II rate was 3.57%, while the Clavien III was 1.19%. The most probable explanation could be our sample size was not su cient and the stone size was larger in their study.
However, the elimination of stone fragments after FURS is also affected by many factors, including anatomy of ureter and kidney, holmium laser parameter, stone factors (including size, number, location, composition), operator experience, etc. [30,31] . There were certain limitations in our study: this is a retrospective study, and the sample size is not su cient enough. More multicenter and large-sample studies are needed to verify our ndings in the future.

Conclusions
Chinese single-use ureteral exible ureteroscope (ZebraScope TM ) can be considered effective and safe for the treatment of upper urinary tract calculi ≤ 2 cm .  Figure 1 The ZebraScopeTM single-use ureteral exible ureteroscope.