A Novel Semirigid Ureterorenoscope with Vacuum Suctioning System for Management of Single Proximal Ureteral and Renal Pelvic Stones: An Initial Experience

Abstract

Introduction:

A novel semirigid ureterorenoscope, named the Sotn ureterorenoscope, was designed with a vacuum suction system. The present study aimed to evaluate the feasibility and safety of using the Sotn ureterorenoscope to manage single proximal ureteral or renal pelvic stones.

Patients and Methods:

Data were retrospectively collected from consecutive patients treated with a Sotn ureterorenoscope between February 2010 and August 2015 at Sun Yat-sen Memorial Hospital of Sun Yat-sen University and Jiangmen Wuyi Traditional Chinese Medicine Hospital in China. The primary outcome was the primary stone-free rate (SFR) in 1 month. The secondary outcomes were the final SFR and the perioperative complication rate.

Results:

A total of 386 patients were evaluated, including 240 males and 146 females. The median (interquartile range [IR]) age was 50 (40–59) years. There were 96 and 290 stones located in the renal pelvis and proximal ureter, respectively. The median (IR) operative time and console time for all patients were 40 (30–70) and 20 (12–38) minutes, respectively. The primary overall SFR was 86.5%, whereas the SFRs for stones with a diameter of ≤1, 1 to 2, and 2 to 3 cm were 95.7%, 86.9%, and 69.0%, respectively. Complications occurred in 90 patients (23.3%); these complications were classified as Clavien–Dindo grades 1 to 2 (minor) in 79 (20.5%) patients, and grades 3 to 4 (major) in 11 (2.8%).

Conclusions:

The novel semirigid Sotn ureterorenoscope featuring a vacuum suction system is effective and safe for managing proximal ureteral and renal pelvic stones.

Introduction

Urinary stone disease is a substantial worldwide problem, with increasing prevalence rates.^1,2 As a result of technological advances and development, ureteroscopy (URS) has become an essential treatment for proximal ureteral or renal calculi, along with extracorporeal shockwave lithotripsy (SWL) and percutaneous nephrolithotomy.^3,4

URS is recommended as the first option for treating proximal ureteral stones larger than 10 mm. However, for stones less than 10 mm, the EAU Urolithiasis Guidelines recommend either URS or SWL.⁵ Flexible URS is also considered the first-line treatment option for the majority of renal calculi.⁵ However, about 5% to 40% of cases treated by URS experience stone migration, which is usually managed through the placement of special antimigration instruments proximal to the stone,^6,7 incurring additional operation fees. Furthermore, the high perfusion pressure of URS often leads to increased renal pelvic pressure (RPP), which results in a high probability of complications such as systemic inflammatory response syndrome and sepsis.^8
–10

Herein, we introduce a novel semirigid endoscope named the Sotn ureterorenoscope that has irrigation and vacuum suction platform functioned by its ureteral access sheath (UAS). The present study aimed to describe the effects of this novel device on the clinical outcomes, and to evaluate the feasibility and safety of using the Sotn ureterorenoscope to manage single proximal ureteral or renal pelvic stones.

Patients and Methods

Patients

Data were retrospectively collected from a consecutive series of patients who underwent Sotn URS between February 2010 and August 2015 at Sun Yat-sen Memorial Hospital of Sun Yat-sen University and Jiangmen Wuyi Traditional Chinese Medicine Hospital in China. After obtaining the Ethics Committee's approval, we reviewed the medical records of the patients.

Inclusion criteria were patient age >18 years, either sex, the first stone treatment, and the identification of proximal ureteral and renal pelvic stones ≤3 cm in diameter on abdominal noncontrast computed tomography or intravenous urography. Exclusion criteria were multiple stones, anatomic abnormalities of the urinary tract, pregnancy, and active urinary tract infection.

Outcome evaluation

Preoperative patient demographic characteristics were assessed, including disease history, physical examination, blood tests, and urinalysis. Estimated glomerular flow rate was calculated using equation: 175 × (creatine [μmol/L]/88.42)^−1.154 × age^−0.203 × (0.742 if female).¹¹ Stone characteristics were measured preoperatively by using noncontrast computed tomography or intravenous urography. According to the maximum diameter of the stones, patients were divided into three groups: group 1 (stone diameter ≤10 mm), group 2 (stone diameter 11–20 mm), and group 3 (stone diameter 21–30 mm). Stone volumes were calculated using the equation: 0.6 × (0.25 × π × length × width)^1.27. Operative time was calculated from the insertion of first ureterorenoscope to the completion of stent placement. Console time was defined as the duration of performing stone laser fragmentation.

The primary outcome was the primary stone-free rate (SFR) in 1 month. Primary SFR was defined as the detection of residual fragments <2 mm in diameter on ultrasonography, kidney–ureter–bladder radiography or noncontrast computed tomography at 1 month postoperatively. If the primary SFR was not achieved, further treatment procedures (semirigid URS, flexible URS, or SWL) according to stone situations were selected. The secondary outcomes were the final SFR and the perioperative complication rate. Complications within 1 month postoperatively were evaluated and classified in accordance with the modified Clavien–Dindo classification system.¹²

Novel device and surgical techniques

The Sotn ureterorenoscope is described in detail on the following Supplementary Data (Supplementary Data are available online at www.liebertpub.com/end). Briefly, the Sotn ureterorenoscope comprises five main components, including a standard ureterorenoscope (patent no. ZL201110030512.9), a console ureterorenoscope (patent no. ZL201120029461.3), a UAS (patent no. ZL201430394938.7), an adapter (patent no. ZL201430394936.8 and ZL201520891360.5), and an irrigation and suctioning platform (patent no. ZL201420607795.4). The standard ureterorenoscope was 45 cm in length, with an outer diameter of 7.5 (tip)/9.8F (shaft), and a working channel diameter of 5.4F. The console ureterorenoscope was longer but smaller than that used in standard URS, with a length of 46 cm, an outer diameter of 4.0 (tip)/6.0F (shaft), and a working channel diameter of 3.9F. Both the standard and the console ureterorenoscopes were 0° semirigid ureterorenoscopes. The UAS could be connected to either the standard ureterorenoscope or the adapter by its locking part (Fig. 1A). The length of the UAS was 40 cm, with an outer diameter of 12.5F or 13.5F, and a working channel diameter of 11.5F or 12.5F. The adapter was designed to connect the UAS, console ureterorenoscope, and suctioning system (Fig. 1B), which includes a switch for adjusting negative pressure, and a container for stone dust collection. The irrigation and suctioning platform can be preset to perfusion and suctioning modes. Perfusion has continuous or pulsed modes, which can be easily switched. The perfusion flow speed ranged from 60 to 610 mL/minute. Negative pressure for suctioning ranged from −25 to −4 kpa.

FIG. 1.

Procedures of a Sotn ureterorenoscope. (A) ➀ A UAS is connected to a standard ureterorenoscope (➀, ➁); ➂ locking part of the UAS. (B) An adapter with dust container is connected to the UAS, suctioning system, and console ureterorenoscope (➀, ➁, ➂); adapter switch for real-time adjustment of negative pressure (➃). (C) The UAS reaches to proximal ureter or renal pelvis (➀) under real-time display monitoring (➁). (D) Scheme of stone dust removal by the suctioning system through interspace between the shaft of console ureterorenoscope and UAS. (E) Stone was limited by negative pressure and limited space in the pelvis or ureter. UAS = ureteral access sheath.

All procedures were performed under general or combined spinal–epidural anesthesia in the lithotomy position. The UAS was connected to the standard ureterorenoscope and inserted into the proximal ureter or renal pelvis under real-time display image monitoring (Fig. 1C). The ureterorenoscope was then disconnected and removed. The adapter with the dust container connected the UAS (Fig. 1B). Console ureterorenoscope was connected to the UAS by the assistance of adapter (Fig. 1B➂). The other side of dust container was connected to a suctioning system (Fig. 1D). Intraoperatively, a Holmium laser was inserted into the working channel of the console ureterorenoscope to disintegrate the stone at 0.4 to 1.0 J/pulse at 20 to 30 pulses/second (Lumenis, fiber diameter 200 μm). The interspace between the shaft of the console ureterorenoscope and the UAS allowed continuous outflow by vacuum suctioning (Fig. 1D). The adapter was real-time adjusted to control negative pressure and prevent stone migration (Fig. 1E). If stone migration occurred, flexible URS was performed with the UAS. When no stones >2 mm remained, the adapter was replaced by the standard ureterorenoscope. The UAS was removed from the real-time display image monitoring. At the end of the operation, a 4F Double-J ureteral stent was placed, and was removed 2 to 6 weeks postoperatively.

Statistical analyses

Statistical analyses were performed using Stata/SE 12.0 (StataCorp LP, TX). Quantitative data variables were described as the median (interquartile range [IR]). Categorical data were described as percentages. Continuous variables were compared using the Kruskal–Wallis test for nonparametric data. Differences were considered statistically significant at p < 0.05 in all tests.

Results

Overall, 386 patients were evaluated, including 240 males and 146 females. The demographic and stone characteristics by groups are shown in Table 1. The median (IR) age was 50 (40–59) years. Comorbidities were present in 112 patients. There were 96 stones located in the renal pelvis, and 290 stones located in the proximal ureter. The median (IR) overall stone size, Hounsfield units, and volume were 15 (11–20) mm, 989 (570–1200), and 228 (130–538) mm³, respectively.

Table 1.

Demographic and Stone Characteristics

Characteristic	Overall	Group 1	Group 2	Group 3
Procedure number	386	94	208	84
Age, year	50 (40–59)^a	49 (40–59)	50 (39–58)	50 (40–60)
Gender (male/female)	240/146	56/38	124/84	60/24
Patients with comorbidity, n (%)	112 (29.0)	23 (24.5)	67 (32.2)	22 (26.2)
Comorbidities, n (%)
Hypertension	76 (19.7)	18 (19.1)	41 (19.7)	17 (20.2)
Diabetes mellitus	31 (8.0)	5 (5.3)	22 (10.6)	4 (4.8)
Chronic heart disease	4 (1.0)	0	3 (1.4)	1 (1.2)
Solitary kidney	1 (0.3)	0	1 (0.5)	0
Anticoagulant medication, n (%)	6 (1.6)	0	2 (1.0)	4 (4.8)
Preoperative stenting (%)	57 (14.8)	11 (11.7)	34 (16.3)	12 (14.3)
Hydronephrosis (%)	373 (96.6)	94 (100)	199 (95.7)	80 (95.2)
Stone laterality (left/right)	221/165	60/34	119/89	42/42
Stone location, n (%)
Renal pelvis	96 (24.9)	6 (6.4)	40 (19.2)	50 (59.5)
Proximal ureter	290 (75.1)	88 (93.6)	168 (80.8)	34 (40.5)
Stone size, mm	15 (11–20)	9 (8–10)	15 (12–18)	24.5 (22–28)
Hounsfield units	989 (570–1200)	556 (369–838)	1037 (719–1243)	1125 (890–1282)
Stone volume (mm³)	228 (130–538)	80 (51–115)	227 (162–407)	757 (618–1122)
ASA grade, n (%)
1	379 (98.2)	94 (100)	202 (97.1)	81 (96.4)
2	9 (2.3)	0	6 (2.9)	3 (3.6)

Continuous variables were shown as median (interquartile range).

ASA = American Society of Anesthesiologists; group 1 = stone diameter ≤10 mm; group 2 = stone diameter 11–20 mm; group 3 = stone diameter 21–30 mm.

The intraoperative and postoperative outcomes by group are described in Table 2.

Table 2.

Intra- and Postoperative Outcomes

	Overall	Group 1	Group 2	Group 3
All patients, N	386	94	208	84
Operative time, minutes	45 (30–70)^a	35 (20–60)	45 (30–65)	65 (40–95)
Console time, minutes	20 (12–38)	10 (6–20)	20 (15–35)	40 (30–60)
Orifice dilation	30 (7.8)	6 (6.4)	21 (10.1)	3 (3.6)
eGFR
Preoperative eGFR	69 (49–86)	67.8 (49.0–82.5)	68.0 (47.1–87.1)	71.0 (57.0–84.6)
Postoperative eGFR^b	73 (53–89)	73.1 (56.2–91.6)	74.2 (53.1–87.9)	69.7 (50.8–88.6)
p	<0.001	0.14	0.003	0.37
Treated by fURS, n (%)	76 (19.7)	14 (14.9)	41 (19.7)	21 (25.0)
Primary SFR, n (%)	334 (86.5)	90 (95.7)	186 (89.4)	58 (69.0)
Secondary SFR, n (%)	357 (92.5)	—	197 (94.7)	70 (83.3)
Tertiary SFR, n (%)	364 (94.3)	—	—	77 (91.7)
Procedures per stone	1.16	1	1.11	1.48
Patients without fURS, n	310	80	167	63
Primary SFR, n (%)	270 (87.1)	78 (97.5)	150 (89.8)	42 (66.7)
Secondary SFR, n (%)	287 (92.6)	—	158 (94.6)	51 (81.0)
Tertiary SFR, n (%)	293 (94.5)	—	—	57 (90.4)
Procedures per stone	1.2	1	1.05	1.52

Significant differences were shown in bold type.

Continuous variables are shown as the median (interquartile range).

Postoperative eGFR was detected 24–48 hours after operation.

eGFR = estimated glomerular filtration rate; fURS = flexible URS; group 1 = stone diameter ≤10 mm; group 2 = stone diameter 11–20 mm; group 3 = stone diameter 21–30 mm; SFR = stone-free rate; URS = ureteroscopy.

The median (IR) operative time and console time for total patients were 40 (30–70) and 20 (12–38) minutes, respectively. The overall median estimated glomerular filtration rate significantly increased from 69 mL/minute/1.73 m² preoperatively to 73 mL/minute/1.73 m² postoperatively (p < 0.001). In total, 76 patients needed treatment of flexible URS. The overall primary SFR was 86.5%; primary SFRs for stones ≤ 10 mm, 10–20 mm, and 20–30 mm of 95.7%, 89.4% and 69% were found, respectively; secondary and tertiary SFRs were 92.5% and 94.3%, respectively. The overall mean number of procedures per stone was 1.16. When patients treated by flexible URS in this study were excluded, primary SFRs for stones ≤ 10 mm, 10–20 mm, and 20–30 mm of 97.5%, 89.8% and 66.7% were found, respectively, which were very close to all patients group.

Complications by group are summarized in Table 3. Complications were reported in 90 patients (23.3%) overall. These complications were classified as minor (Clavien–Dindo grades 1–2) in 79 (20.5%) patients, and major (Clavien–Dindo grades 3–4) in 11 (2.8%). In terms of complication type, 48 (12.4%) were ureter injuries, and 42 (10.9%) were postoperative fever (>38°C). Among the patients with ureter injuries, 37 were mild mucosal injuries caused by the laser tip, and 11 were mild ureteral perforations without any invasive operations. No patient experienced septic shock or moderate-to-severe bleeding needing further treatment.

Table 3.

Complications Classified by Clavien–Dindo Grade

	Overall (n = 386)	Group 1 (n = 94)	Group 2 (n = 208)	Group 3 (n = 84)
Total (%)	90 (23.3)	18 (19.1)	48 (23.1)	24 (28.6)
Minor, n (%)	79 (20.5)	16 (17.0)	43 (20.7)	20 (23.8)
Major, n (%)	11 (2.8)	2 (2.1)	5 (2.4)	4 (4.8)
Complication types
Ureter injury, n (%)	48 (12.4)	10 (10.6)	25 (12.0)	13 (15.5)
Fever, n (%)	42 (10.9)	8 (8.5)	23 (11.1)	11 (13.1)
Septic shock	0	0	0	0
Bleeding	0	0	0	0

Discussion

Several different approaches can be selected for the treatment of proximal ureteric and renal pelvic stones, including semirigid or flexible URS, SWL, percutaneous nephrolithotomy, laparoscopy, and open procedures.⁵ Among these treatment methods, URS is considered one of the most important methods for the primary treatment of proximal ureteral stones.⁵ For managing renal pelvic stones, flexible URS is suggested as a first-line treatment choice.^13,14 Flexible URS is still best for patients with stones <20 mm.¹⁵ However, failure of URS in the proximal ureter is often associated with stone migration into the renal pelvis and calices.¹⁶ Although flexible URS is reportedly effective for larger renal stones, the SFR of monotherapy decreases and the number of operations increases.¹⁵ In the present study, we developed a novel ureterorenoscope that can manage both ureteral and renal stones, with a high SFR and low complication rate.

SFR is one of the most important outcomes used to evaluate the feasibility of URS. Spontaneous passage of stone fragments after URS is influenced by many factors, such as stone burden, location, and previous intraureteral manipulations.¹⁷ However, the vacuum suction system in our device can clear stone dusting as much as possible intraoperatively. Furthermore, the negative pressure in the interspace between the scope and the sheath causes the stones to be sucked to the nozzle of the sheath, and the space of the renal pelvis or ureter is limited, which prevents the migration of stones. Both factors contributed to increasing the SFR. In the present study, the primary SFRs for proximal ureter and renal pelvic stones were comparable with previous studies. The final overall SFR was 94.3%, and the overall number of procedures per stone was 1.16. Although a low primary SFR was found for stones with a diameter of 2 to 3 cm, the final SFR was 91.7%. The present SFRs were higher than those reported in previous studies on semirigid URS; a previous study on patients who underwent conventional semirigid URS and laser lithotripsy for proximal ureteral stones reported 3-month SFRs for overall, stones ≤1, 1 to 2, and >2 cm of 86.6%, 87.7%, 85.4%, and 76%, respectively,^18,19 whereas another study reported an SFR of 88.4% for proximal ureteral stones treated by semirigid URS.²⁰ Furthermore, the vacuum suction system has advantages when compared with flexible URS for the treatment of renal stones. A previous study of 316 consecutive patients who underwent flexible URS and laser lithotripsy for renal stones reported primary SFRs for stones ≤1, 1 to 2, and 2 to 3 cm of 90.5%, 79.8%, and 70.5%, respectively, implying that conventional flexible URS is less satisfactory in cases with larger calculi.²¹ However, flexible URS with a suction system achieved a primary SFR of 95.6% for patients with stones sized 8 to 35 mm,²² indicating the benefits of flexible URS with our device.

The overall complication rate of URS for ureter stones is reportedly 9% to 25%, and most complications are minor and do not require intervention.⁵ In a study investigating flexible URS for renal stones, 29.1% of patients experienced complications, with the majority classified as Clavien–Dindo grade 1 (17.4%) or 2 (9.5%).²¹ This previous study reported complication rates of 20.2%, 32.2%, and 33.3% for patients with stones ≤1, 1 to 2, and 2 to 3 cm.²¹ Our study revealed low complication rates reflecting the first-month safety by using the novel device. Complications occurred in 23.3% of patients, most of which were classified as minor (20.5%). Ureter injury was defined as accidental laser tip burning of the ureteral mucosa. Although 12.4% of patients experienced ureter injuries, only 2.8% were classified as major complications. No septic shock developed, indicating the advantages of the low RPP created by the vacuum suctioning system.

The present study had some limitations. First, it was a retrospective study without randomization. Second, the procedures were performed by high-volume surgeons with extensive experience. Third, the Sotn ureterorenoscope cannot currently perform real-time monitoring of the actual RPP, which will be updated in the future.

Conclusions

The novel semirigid Sotn ureterorenoscope featuring a vacuum suction system is effective and safe for managing proximal ureteral and renal pelvic stones. Further prospective studies are needed to compare this novel device with conventional ureteroscopes.

Footnotes

Acknowledgments

K.X. received grants from the National Natural Science Foundation of China (no. 81572511, 81702525), the Natural Science Foundation of Guangdong Province (no. 2016A030313317), the Guangdong Science and Technology Department (no. 2013B021800105), and Sun Yat-Sen Clinical Research Cultivating Program from Sun Yat-sen Memorial Hospital of Sun Yat-sen University (SYS-C-201802). K.L. received grants from the National Natural Science Foundation of China for Young Scientists (no. 81702527), the Natural Science Foundation of Guangdong (no. 2015A030310091, 2016A030313185), the Medical Scientific Research Foundation of Guangdong (no. A2015027), and supported by the Chinese Scholarship Council. A grant [2013]163 was also received from the Key Laboratory of Malignant Tumor Molecular Mechanism and Translational Medicine of Guangzhou Bureau of Science and Information Technology. The funding bodies had no role in study design, data collection and analysis, decision to publish, or preparation of the article.

Author Disclosure Statement

No competing financial interests exist.

Abbreviations

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