UROLOGICAL ONCOLOGY Evaluation of Two Ureter Sealing Methods During Radical Nephroureterectomy Kun Pang1,2#, Bo Chen1#, Bo Jiang1, Zhenduo Shi1, Lin Hao1, Zhiguo Zhang1,2, Jianjun Zhang3, Longcun Cai3, Tian Xia4, ZhenningWei#5, Kun Fang6, Dianjun Yu7, Conghui Han1,2*, Xiaowen Sun8** Purpose: To investigate the safety of electrocoagulation and thulium laser (Tm-laser) sealing methods of distal ureter resection during radical nephroureterectomy (NFU) in a porcine model. Methods: 9 pigs were used in the study: 6 were used to measure the bursting pressure (BP) and 3 were used to measure the highest pressure during NFU. Twelve ureters were to measure BP after being sealed by electrocoag- ulation or Tm-laser (n = 6, each). Six experimental NFUs were performed in 3 pigs to measure the intraluminal pressure of all procedures. Results: The mean BP in the electrocoagulation group (104.3 ± 25.0 cmH2O) was similar to that of the Tm-laser group (74.8 ± 23.3 cmH2O, P > .05). The peak intraluminal pressure (35.9 ± 7.6 cmH 2 O) during NFU was signif- icantly lower than the BP (P < .05). Conclusion: The effectiveness of the sealing was confirmed using both electrocoagulation and Tm-laser during NFU. Keywords: bursting pressure; distal ureter and bladder cuff resection electrocoagulation; experimental porcine model; Pluck technique; thulium laser INTRODUCTION Upper tract urothelial carcinoma (UTUC) is a rela-tively uncommon disease that accounts for 5–7% of all renal tumors and 5–10% of all urothelial tumors, with an estimated annual incidence of 1–2 cases per 100,000(1). UTUC is encountered in approximately 25% of ureteral cancer cases and is subject to a high risk of local recurrence that ranges from 30% to 75%(2). Radical nephroureterectomy (NFU) with distal ureter and blad- der cuff (DUBC) resection is the standard treatment for UTUC (3). A large number of endourologic techniques have become promising alternatives to open DUBC re- section(4) during NFU. However, existing clinical tri- al evidence regarding their effectiveness and safety is inconclusive(5). In 1998, Keeley and Tolley(6) reported 1Department of Urology, Xuzhou Central Hospital, 199 Jie Fang Nan Road, Xuzhou, 221009, China. 2Department of Urology, The third affiliated hospital of Soochow University, No.185, Juqian Street, Changzhou City, Jiangsu Province China. 3The affiliated Suqian hospital of Xuzhou Medical University. No.138 Huanghe South Road, Sucheng District, Suqian City, Jiangsu Province. 4Xuzhou Medical University, No. 209 Tongshan Road, Xuzhou, Jiangsu, 221004, P. R. China. 5School of medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang city, Jiangsu province, China. 6 Nanjing University of Traditional Chinese Medicine, No. 138 Xianlin Avenue, Qixia District, Nanjing, Jiangsu, China. 7 Li Huili Hospital, No. 57, Xingning Road, Yinzhou District, Ningbo, Zhejiang, China. 8Department of Urology, Shanghai First People’s Hospital affiliated to Shanghai Jiaotong University. No.100 Haining Road, Hongkou District, Shanghai 200080, China. # Kun Pang, Bo Chen, Bo Jiang, Cong-hui Han, and Xiaowen Sun contributed equally to this work. *Correspondence: Department of Urology, Xuzhou Central Hospital, 199 Jie Fang Nan Road, Xuzhou, 221009, China. Tel: +8618952172133 E-mail: 479920288@qq.com. **Correspondence: Department of Urology, School of medicine, Shanghai First People’s Hospital affiliated to Shanghai Jiaotong University, No.100 Haining Road, Hongkou District, Shanghai 200080, China. E-mail: sunxiaow1973@163.com. Received December 2018 & Accepted May 2019 a cystoscopic detachment of DUBC during laparoscop- ic NFU that offered patients an additional benefit of a minimally invasive technique. However, it is related to a high potential for local relapse, which is hypothesized to be because of local tumor cell spillage(7). Oncologi- cal safety concerns arise from nonmechanically sealed ureteral openings(8). It may be that the high intraluminal pressure during the NFU after endoscopic manipulation could lead to a breakage in the seal and result in tumor cell spillage. Thus, the effectiveness of electrocoagula- tion and laser methods in sealing the ureteral orifice is controversial. As the pressure to the DUBC cannot be measured dur- ing NFU in patients, we designed a porcine NFU model to measure the peak pressure to the DUBC and com- Urology Journal/Vol 17 No. 2/ March-April 2020/ pp. 152-155. [DOI: 10.22037/uj.v0i0.4920] pared it to the bursting pressure (BP) of the ureteral openings that were sealed by either electrocoagulation (EC) or a Tm-laser. MATERIALS AND METHODS Laboratory animals The Institutional Animal Research Committee at the Sixth People’s Hospital of Shanghai Municipality ap- proved the study protocol (SCXK[SH]2007-0013). Nine Shanghai white pigs, each weighing 60 ± 5 kg, were purchased from Shanghai Nanhui Special Farm (license GB/T 8473-1987). Six pigs were used to deter- mine the BP of the sealed ureters, and 3 pigs underwent experimental NFU. Sample Size The sample size calculation followed the equation: N1=N2=2[(tα/2+tβ)S/δ] 2. We defined α = 0.05, and 1-β = 0.2. According to a Chinese article, we found that the human ureteral sealing pressure was 192.25 ± 14.27 cmH 2 O; we sealed 3 human ureters by Tm-laser in vit- ro, and the burst pressure was 165.42 ± 12.50 cmH 2 O. Therefore, the sample size was calculated to be 5.90. Study Design Six pigs were euthanized to harvest ureter specimens (n = 12). These specimens were equally and randomly di- vided into EC and Tm-laser groups. For the EC group, the distal ureteral segment was placed into a metal con- tainer full of 5% mannitol, to the bottom of which an electrode pad was attached. The ureteral orifice was sealed under direct vision using an electrosurgical hook (LISA Laser Products OHG, Katlenburg-Lindau, Ger- many) at 45 W for 8-10 s. For the Tm-laser group, the distal ureteral segment was placed into a metal container full of normal saline. A medical Tm-laser system (wavelength, 2.01 µm; maxi- mum output power, 110 W; LISA Laser Products OHG, Katlenburg-Lindau, Germany) was used for laser co- agulation in the continuous-wave mode. The ureteral orifice was sealed under direct vision using a 550-µm end-firing PercuFib fiber (LISA Laser Products OHG, Katlenburg-Lindau, Germany) at a set power of 70 W for 5-7 s. Measurement of BP The BP limit of the ureteral orifice after sealing was performed as previously described(1). For real-time monitoring of the intraluminal dynamic pressure, a 5-cm segment of the excised distal ureter was transect- ed, and the stump was connected to a tri-way adapter, which was also connected to a piezometer (Y-50, Wuxi, China) and a 20-mL syringe. The distal ureteral seg- ment was continuously perfused with saline containing methylene blue (Baxter, Suzhou, China) via the syringe at a flow rate of 0.1 mL/s. The BP was defined as the Ureter sealing methods for radical nephroureterectomy-Pang et al. Table 1. Intraluminal pressure over NFU. Stage Intraluminal pressure, cmH 2 O Incising the subcutaneous tissue 7.3 ± 4.5 Identifying the ureter 28.6 ± 8.2 Locating simulated tumor and ligating ureter 35.9 ± 7.6* After ligating the ureter 33.1 ± 7.4 On mobilizing and ligating renal pedicle 30.0 ± 7.3 On dissecting the kidney 29.6 ± 9.1 Dissecting the ureter 35.0 ± 8.8 Plucking the ureter 33.1 ± 7.0 * The peak pressure was during locating the simulated tumor Figure 1. Key stages of the experimental NFU: (A) cannulation of bilateral ureteral orifices; (B) connection to the piezometer via the tri-way adapter; (C) location of the simulated tumor and ligation of the ureter; and (D) en bloc resection of the ureter and the kidney. Vol 17 No 02 March-April 2020 153 intraluminal pressure at the time that the blue-stained saline leaked from the sealed orifice, which was the pri- mary experimental outcome. Experimental NFU The experimental NFU was performed. Under general anesthesia, the animal was placed in a supine position, and a lower median abdominal incision was made to expose the bladder. The bilateral ureteral orifices were located, and two flexible cannulas were inserted into the bilateral orifices (Figure 1A) and connected to the piezometer via the tri-way adapter (Figure 1B). The orifices were secured using silk sutures to maintain hermetic. The simulated tumor was located at the level paralleling the lower polar of the kidney, and the prox- imal ureteral segment was ligated using silk sutures 0.5 cm distally to the renal pelvis (Figure 1C). The ureter and kidney were moved to the level of the renal pedicle, and the renal vessels were securely ligated. The ureter was plucked, and the piezometer was disconnected to remove the NFU specimen en bloc (Figure 1D). The baseline pressure was defined as the intraluminal pres- sure before surgical manipulation, and the intraluminal pressure was recorded at intervals of 3s, when plucking the ureter, and at its maximum. Statistical analysis SAS v8.02 software (SAS, Cary, NC, USA) was used for statistical analyses. All continuous data are ex- pressed as the mean ± standard deviation. A normality test was performed, and the measurement data that con- formed to normal distributions were analyzed by t-tests to determine if the variances were equal, and T-test was used if the variances were unequal. The burst pressure between the two groups and the comparison between the peak pressure and the burst pressure was evaluated using t-test. P-value < 0.05 was considered statistically significant. RESULTS The BPs between the EC (104.3 ± 25.0 cmH 2 O) and Tm-laser (74.8 ± 23.3 cmH2O) groups were not sig- nificantly different (variances were equal, T=2.11, P = .0606). During NFU, the mean intraluminal pressure fluctuated significantly from 7.3 ± 4.5 cmH2O when incising the subcutaneous tissue to 35.9 ± 7.6 cmH2O when locating the simulated tumor and ligating the ure- ter (Table 1). In the Tm-laser group, the peak pressure was 35.9 ± 7.6 cmH 2 O, which was significantly lower than the BP (74.8 ± 23.3 cmH 2 O) and the difference was statistically significant (variances were unequal, T = 4.13, P = .009). DISCUSSION Radical NFU with DUBC resection is the standard treatment for UTUC(3). The DUBC are sealed by either electrocoagulation or a thulium laser (Tm-laser) before NFU to prevent the dissemination of tumor cells along the urinary tract(1,9). These two sealing methods have been shown to have comparable perioperative and on- cological outcomes(9), which were consistent with our previous research(1). DUBC resection is an effective and safe procedure in terms of disease recurrence and overall survival(10). Compared with open resection, the endoscopic management of DUBC resection signifi- cantly shortens the operative time(11), reduces intraop- erative bleeding, and expedites postoperative recovery (9). However, intraoperative tumor cell seeding is a risk factor for local recurrence(12-14). Current clinical studies do not agree on the relative risk of urine spillage and tu- mor cell seeding between the pluck technique and open resection method(15). Is the sealing pressure safe for pre- venting urine spillage and tumor cell seeding? Our porcine biomechanical study was designed to as- sess whether the intraluminal pressure would exceed the BP of the ureteral orifice when sealed by either electrocoagulation or Tm-laser. We found that the burst pressures between the EC and Tm-laser groups were not significantly different, indicating that the seal- ing effectiveness was equal between the two methods. We also found that the peak pressure was significantly lower than BP during NFU. The intraluminal pressure at each stage of the experimental NFU was well below the BP of the ureteral orifices, regardless of the sealing technique. Therefore, it is very unlikely that intraopera- tive manipulation in NFU will burst the sealed ureteral orifice and result in tumor cell spillage. This study was limited in that the BP was measured ex vivo rather than in vivo. Besides, the experimental NFU was performed on pigs, whose urinary system anatomy differs from that of humans to some extent. Finally, no actual oncological safety test was conducted, and tumor cell spillage might occur even in the absence of bursting the sealed urethral openings. CONCLUSIONS In conclusion, the efficacy of electrocoagulation and Tm-laser methods in sealing the ureteral orifice was similar, and the sealed ureteral orifice could withstand the pressure throughout the entire experimental NFU procedure. ACKNOWLEDGMENT This article is funded by National Natural Science Fund (81774089); Jiangsu Province, the medical in- novation team (CXTDA2017048); Jiangsu Province key research and development program (BE2017635); Jiangsu Province, natural science research projects (17KJB360001); Jiangsu Province, young medical tal- ents (QNRC2016386); Jiangsu Provincial Traditional Chinese Medicine Bureau of Science and Technolo- gy Project (YB2017055) and Ningbo Natural Science Foundation (2017A610194). The authors acknowledge editorial support from American Journal Experts. REFERENCES 1. Pang K, Liu SB, Wei HB, et al. Two-micron thulium laser resection of the distal ureter and bladder cuff during nephroureterectomy for upper urinary tract urothelial carcinoma. Lasers Med Sci. 2014;29:621-7. 2. Zhang XK, Yang P, Zhang ZL, Hu WM, Cao Y. Preoperative Low Lymphocyte-to-Monocyte Ratio Predicts Poor Clinical Outcomes for Patients with Urothelial Carcinoma of the Upper Urinary Tract. Urol J. 2018;15:348-54. 3. Annan AC, Stevens KA, Osunkoya AO. Urothelial carcinoma involving the ureteral orifice: a clinicopathologic analysis of 93 cases. Hum Pathol. 2017;65:101-6. 4. Fragkoulis C, Pappas A, Papadopoulos Urological Oncology 154 Ureter sealing methods for radical nephroureterectomy-Pang et al. GI, Stathouros G, Fragkoulis A, Ntoumas K. Transurethral resection versus open bladder cuff excision in patients undergoing nephroureterectomy for upper urinary tract carcinoma: Operative and oncological results. Arab J Urol. 2017;15:64-7. 5. Elawdy MM, Osman Y, Taha DE, El- Halwagy S, El-Mekresh M. Coincidental Bladder Cuff Transitional Cell Carcinoma in Nephroureterectomy Specimens: Risk Factors, Prognosis and Clinical Implementation. Urol J. 2018;15:256-60. 6. Keeley FX, Jr., Tolley DA. Laparoscopic nephroureterectomy: making management of upper-tract transitional-cell carcinoma entirely minimally invasive. J Endourol. 1998;12:139- 41. 7. Mellouli M, Charfi S, Smaoui W, et al. Prognostic Role of Lymphovascular Invasion in Patients with Urothelial Carcinoma of the Upper Urinary Tract. Urol J. 2017;14:5008- 12. 8. Upfill-Brown A, Lenis AT, Faiena I, et al. Treatment utilization and overall survival in patients receiving radical nephroureterectomy versus endoscopic management for upper tract urothelial carcinoma: evaluation of updated treatment guidelines. World J Urol. 2018. 9. Raman JD, Park R. Endoscopic management of upper-tract urothelial carcinoma. Expert Rev Anticancer Ther. 2017;17:545-54. 10. Lai WR, Lee BR. Techniques to resect the distal ureter in robotic/laparoscopic nephroureterectomy. Asian J Urol. 2016;3:120-5. 11. Giannakopoulos S, Toufas G, Dimitriadis C, et al. Laparoscopic transvesical resection of an en bloc bladder cuff and distal ureter during nephroureterectomy. ScientificWorldJournal. 2012;2012:658096. 12. Ito A, Shintaku I, Satoh M, et al. Intravesical seeding of upper urinary tract urothelial carcinoma cells during nephroureterectomy: an exploratory analysis from the THPMG trial. Jpn J Clin Oncol. 2013;43:1139-44. 13. Schwartzmann I, Pastore AL, Sacca A, et al. Upper Urinary Tract Urothelial Carcinoma Tumor Seeding along Percutaneous Nephrostomy Track: Case Report and Review of the Literature. Urol Int. 2017;98:115-9. 14. Tan P, Xie N, Yang L, Liu L, Tang Z, Wei Q. Diagnostic Ureteroscopy Prior to Radical Nephroureterectomy for Upper Tract Urothelial Carcinoma Increased the Risk of Intravesical Recurrence. Urol Int. 2018;100:92-9. 15. Pai A, Hussain M, Hindley R, Emara A, Barber N. Long-Term Outcomes of Laparoscopic Nephroureterectomy with Transurethral Circumferential Excision of the Ureteral Orifice for Urothelial Carcinoma. J Endourol. 2017;31:651-4. Ureter sealing methods for radical nephroureterectomy-Pang et al. Vol 17 No 02 March-April 2020 155