Purpose: Sequential ureteral dilatation facilitates placement of ureteral access sheath during retrograde intrarenal surgery. The authors adopted some improvisations in conventional sequential ureteral dilatation methods to achieve improved ureteral accommodation and prefer to call the sequential ureteral dilatation performed with these improvisations as “Rule of five” (ROF) ureteral dilatation. The objective of the article was to describe the “ROF” ureteral dilatation technique and share the preliminary experience with the technique. Materials and Methods: “ROF” ureteral dilatation involves repetitive dilatation of ureter for five times by 10 Fr ureteral dilator, with each dilatation lasting for 5 s. The technique was used in patients who underwent retrograde intrarenal surgery for renal calculi and in whom 12 Fr ureteral dilator passage and 9.5/11.5 Fr ureteral access sheath placement was not possible by conventional sequential ureteral dilatation methods. Preliminary efficacy and safety outcomes were reported. Results: “ROF” ureteral dilatation was performed in 14 renal units. Ureteral access sheath placement was successful in 10 renal units (71.4%) and unsuccessful in 4 renal units (28.6%). Ureteral access sheath associated low-grade ureteral wall injury was noted in 2 renal units (14.3%). None had new onset hydroureteronephrosis in follow-up ultrasonography and all patients were asymptomatic in the follow-up period. Conclusion: “ROF” ureteral dilatation is an improvisation of conventional sequential ureteral dilatation. It facilitates successful and safe ureteral access sheath placement in a proportion of patients undergoing sequential ureteral dilatation.
Keywords: Retrograde intrarenal surgery, rule of five, sequential ureteral dilatation, ureteral access sheath, ureteral wall injury
|How to cite this URL:|
Venkatachalapathy VS, Palathullil DG, Abraham GP. “Rule of five” in ureteral dilatation and its role in ureteral access sheath placement during retrograde intrarenal surgery. Urol Sci [Epub ahead of print] [cited 2023 Jun 1]. Available from: https://www.e-urol-sci.com/preprintarticle.asp?id=377440
| Introduction|| |
Retrograde intrarenal surgery (RIRS) is evolving as a surgical procedure which is safe and effective in broad clinical scenarios. A ureteral access sheath (UAS) facilitates the procedure of RIRS by making it easier, safer and cost effective. Routine use of UAS during RIRS was associated with a few safety concerns. But, recent studies have ensured the safety of the UAS use even in unstented ureters. Ureteral dilatation methods before UAS placement can be active or passive. The sequential ureteral dilatation is a method of active ureteral dilatation which facilitates placement of UAS. Despite the widespread practice, standard methodology of sequential ureteral dilatation (duration and repetition) and steps to improve its efficacy are not well defined in the literature.
Sequential ureteral dilatation had been performed by a conventional methodology at the author's institution. The authors presume the conventional sequential ureteral dilatation methodology performed at different centers around the world is not very different from the one followed at the author's institution. The authors observed that, by adding certain improvisations to the conventional sequential ureteral dilatation methods there is a chance of achieving improved ureteral accommodation. The authors prefer to call the sequential ureteral dilatation performed with these improvisations as “Rule of five” (ROF) ureteral dilatation. We describe the methodology adopted in ROF ureteral dilatation in this article. Also, the preliminary experiences on the efficacy and safety outcomes are shared in this article.
| Materials and Methods|| |
ROF ureteral dilatation during RIRS was performed in 14 renal units (of 12 patients) between July 2019 and June 2020. Written consent was obtained from all the patients to use the clinical data and clinical photographs for academic purposes. The data was collected retrospectively. The ethical guidelines of the Declaration of Helsinki and its amendments were followed in the study. The ethics committee of the hospital approved the study on April 15, 2021 and the approval number is LHRC/EC-2021-01-02. The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
All the patients in the study underwent RIRS for renal calculus/calculi. Patients with ureteral calculus, ureteral stricture or other ureteral pathologies did not undergo ROF ureteral dilatation and were not included in the study. Patients under the age of 18 years did not undergo ROF ureteral dilatation and were also not included. Pre-stented patients and patients with history of ureteroscopy and/or ureteral stenting were not considered in the evaluation. Furthermore, patients who did not undergo recommended follow-up imaging evaluation and who lost to clinical follow-up were not considered in the evaluation.
Diagnostic ureteroscopy was performed by 4.5/6.5 Fr semi-rigid ultra-thin ureterorenoscope (Richard Wolf GmBH, Knittlingen, Germany). Hybrid guidewire (0.035 inch–150 cm–Straight Tip) with nitinol core and hydrophilic floppy tip was used (Hydro Twister, Blueneem, Bangalore, India). Flexor UAS with inner diameter, outer diameter and the length of 9.5 Fr, 11.5 Fr and 35 cm respectively were used (Cook, Bloomington, IN, USA). The sequential ureteral dilatation was performed by ureteral dilators of 70 cm length and diameter of size 8 Fr, 10 Fr and 12 Fr respectively (Blueneem, Bangalore, India) in all cases [Figure 1].
|Figure 1: Tools for “Rule of five” ureteral dilatation. a: Semi-rigid ureterorenoscope, b: Ureteral access sheath, c: Sequential ureteral dilators, d: Hybrid guidewire with nitinol core and hydrophilic floppy tip|
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The polyurethane sequential ureteral dilators used in our study were not reinforced with steel coil or covered with hydrophilic coating. The cost of the ureteral dilator set (including 6 Fr, 8 Fr, 10 Fr, 12 Fr, 14 Fr, and 16 Fr) was approximately 60.40 USD. Storz Flex X2s (Karl Storz, Germany) flexible ureterorenoscope with a sheath circumference of 7.5 Fr was used for RIRS in all cases. Disposable or digital flexible ureterorenoscopes were not used in any patients.
The procedures were performed by a single endourologist. None of the patients were given alpha blockers preoperatively. Diagnostic ureteroscopy was initially performed up to pelviureteric junction. Under fluoroscopic guidance, ureteral dilatation was attempted sequentially with 8 Fr, 10 Fr and 12 Fr ureteral dilators up to L3 vertebral level. An attempt was made to pass each size ureteral dilator once and if the ureter was accommodative each dilatation lasted for a period of 10–20 s – “conventional sequential ureteral dilatation.” An attempt was made to place 9.5/11.5 Fr UAS afterwards. If the ureteral dilator could not be passed beyond the intramural and distal ureter, then it was considered as failure of passage of that ureteral dilator. If the UAS could not be passed in its entire length in males or if it could not be placed in the proximal ureter in females, then it was considered as failure of UAS placement.
If the 8 Fr or 10 Fr ureteral dilators could not be passed during conventional sequential ureteral dilatation, a ureteral stent was placed and RIRS was staged later. If the UAS could be placed after conventional sequential ureteral dilatation RIRS was proceeded with. ROF ureteral dilatation was performed in patients in whom conventional sequential ureteral dilatation was possible up to 10 Fr and in whom neither 12 Fr ureteral dilatator passage nor UAS placement was possible afterwards. In all those patients, an attempt to pass 12 Fr ureteral dilator and UAS was met with resistance or buckling of ureter.
In such cases the 10 Fr ureteral dilatation was repeated for five consecutive times, with each dilatation lasting for a duration of 5 s. The 10 Fr ureteral dilator was passed up to L3 vertebral level and was withdrawn to the level of pubic bones after 5 s. The same process was repeated for 5 times – ROF ureteral dilatation.
After ROF ureteral dilatation an attempt was made to pass 12 Fr ureteral dilator once again. If a 12 Fr ureteral dilatation was possible afterwards, UAS was placed thereafter in all cases comfortably. If 12 Fr ureteral dilatation was not possible after ROF ureteral dilatation also, one more attempt was made to place UAS and UAS was placed if the ureter was accommodative. No desperate attempt was made or excessive force was applied to pass 12 Fr ureteral dilator or UAS after ROF ureteral dilatation.
The outcome of ROF ureteral dilatation was considered successful if the UAS could be placed following ROF ureteral dilatation. The successful outcome was further subdivided as total success and partial success. If both UAS placement and 12 Fr ureteral dilatation was possible, the outcome was considered as total success [Figure 2]. If UAS placement was possible but 12Fr ureteral dilatation was not possible, the outcome was considered as partial success [Figure 3]. If neither UAS placement nor 12 Fr ureteral dilatation was possible, the outcome was considered as unsuccessful [Figure 4].
|Figure 2: Fluoroscopic illustration of outcome of total success. (a and b) Passable 8 Fr and 10 Fr ureteral dilators, (c and d) Nonpassable 12 Fr ureteral dilator and 9.5/11.5 Fr ureteral access sheath. (A) Passable 12 Fr ureteral dilator, (B and C) Passable 9.5/11.5 Fr ureteral access sheath, with and without obturator|
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|Figure 3: Fluoroscopic illustration of outcome of partial success. (a and b) Passable 8 Fr and 10 Fr ureteral dilators, (c and d) Nonpassable 12 Fr ureteral dilator and 9.5/11.5 Fr ureteral access sheath. (A) Nonpassable 12 Fr ureteral dilator, (B and C) Passable 9.5/11.5 Fr ureteral access sheath, with and without obturator (The fluoroscopic images are taken from a patient with outcome of total success and sequencing of the images is rearranged for illustration and description purposes)|
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|Figure 4: Fluoroscopic illustration of unsuccessful outcome. (a and b) Passable 8 Fr and 10 Fr ureteral dilators, (c and d) Nonpassable 12 Fr ureteral dilator and 9.5/11.5 Fr ureteral access sheath. (A) Nonpassable 12 Fr ureteral dilator, (B) Nonpassable 9.5/11.5 Fr ureteral access sheath (The fluoroscopic images are taken from a patient with outcome of total success and sequencing of the images is rearranged for illustration and description purposes)|
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If UAS placement was successful after ROF ureteral dilatation, RIRS was proceeded with eventually. During UAS removal after the procedure, it was observed if UAS was held tightly in the ureter. In unsuccessful UAS placement cases, a ureteral stent was placed and RIRS was staged. Diagnostic ureteroscopy was performed at the end to assess the ureteral wall in all patients. The observed ureteral wall injuries were graded according to the established criteria. The procedure concluded with ureteral stent placement in all cases. The principles and techniques adopted in the surgical procedure of RIRS are explained in the literature. The ureteral stent removal was performed at 2–4 weeks after the completion of RIRS procedure/procedures. The removal of ureteral stent was considered as treatment completion. All the patients underwent follow-up ultrasonography at 4–6 weeks after treatment completion. Patients were clinically followed for 6 months after treatment completion. Additional serial follow-up ultrasonography was performed at 6 months in patients in whom tightness was observed during UAS removal and/or in whom UAS associated ureteral wall injury was observed.
| Results|| |
“ROF” ureteral dilatation was performed in 14 renal units. The demographic and surgical details of the patients are shown in [Table 1]. UAS placement was successful in 10 renal units (71.4%) and unsuccessful in 4 renal units (28.6%). UAS associated ureteral wall injury was noted in 2 renal units (14.3%). The outcomes on success and associated ureteral wall injuries are shown in [Table 2].
|Table 2: Outcomes on success and ureteral access sheath associated ureteral wall injuries|
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The nonaccommodative resistance in all unsuccessful cases of UAS placement were contributed by intramural ureter. In one patient with partial success outcome there was difficulty in removing UAS as it had been tightly held in the intramural ureter. But the UAS could be eventually removed after gentle bidirectional rotatory withdrawal movements. None of the patients had UAS associated ureteral injuries of grade 2 or above. None had new onset hydroureteronephrosis in follow-up ultrasonography.
Two patients (First patient had “unsuccessful outcome” and ureteral wall injury; Second patient had “partial success outcome” with ureteral wall injury and tightly held UAS in the ureter which was appreciated during UAS withdrawal) underwent additional serial follow-up ultrasonography at 6 months. Both patients did not have new onset hydroureteronephrosis in serial follow-up ultrasonography. All patients were asymptomatic in the follow-up period.
| Discussion|| |
Our study demonstrated that “ROF” ureteral dilatation obviated the need for ureteral stenting and a staged procedure in a considerable proportion of renal units in which UAS placement was not possible after conventional sequential ureteral dilatation. It also demonstrated that “ROF” ureteral dilatation is safe which was evident from low rates of low-grade ureteral wall injuries and the absence of new onset hydroureteronephrosis in all the renal units.
The use of UAS during RIRS is recommended to improve access, reduce costs, and reduce intrarenal pressures. UAS is said to improve visibility, scope life and stone free rates. 12/14 Fr UAS is associated with ureteral wall injury in a significant proportion of patients and smaller diameter UAS are less likely to cause associated ureteral wall injuries., There has been recent trend towards miniaturization of UAS and in our study smaller diameter 9.5/11.5 Fr UAS was used in all cases. Pre-stenting can reduce the incidence of UAS associated ureteral wall injuries. But pre-stenting and staged procedures have the disadvantages of added cost and morbidity.
Ureteral dilatation can be achieved by active and passive methods. Most of the recent research focus on various methods of passive ureteral dilatation and studying their impact on successful UAS placement. Surprisingly, literature focussed on techniques for improving the efficacy of commonly practiced active ureteral dilatation methods are nonexistent. Sequential and balloon ureteral dilatation are commonly used methods of active ureteral dilatation. Sequential ureteral dilatation is a safe and effective method of active ureteral dilatation which facilitates UAS placement in a significant number of patients. It is associated with lesser costs than balloon ureteral dilatation and better familiarity among urologists. The duration and repetition of dilators passage to be performed during sequential ureteral dilatation are not defined in the literature. The authors could find the availability of literature regarding the duration of balloon dilatation in the ureter, but not on the sequential ureteral dilatation.
Unlike balloon ureteral dilatation in ureter which is performed over a period of minutes, the conventional practice of ureteral dilators passage in sequential ureteral dilatation is over a period of seconds. Possible explanation could be the need to pass multiple size dilators in sequential ureteral dilatation, unlike in balloon ureteral dilatation where there is no need to pass multiple ureteral dilators. Also, during sequential ureteral dilatation, the conventional practice is to pass each size dilator for a single repetition. The authors could not find any evidence in literature where repetitive dilatation of ureter by same size dilator was used during sequential dilatation to improve the ureteral accommodation. As the practice of repetitive ureteral dilatation itself is not described before, no literature is available comparing the efficacy of the same to other dilatation methods.
In our study, we did not include patients in whom the ureters could have been passively dilated before surgery by prior DJ stenting. Alpha blockers were not given preoperatively to achieve passive ureteral dilatation in the studied cohort. Also, none of our patients underwent balloon ureteral dilatation as primary or auxiliary procedure.
In all the cases of primary RIRS including the difficult ureters, we prefer the sequential ureteral dilatation. As diagnostic ureteroscopy is performed with 4.5/6.5 Fr semi-rigid ureterorenoscope, we initiate sequential ureteral dilatation with 8 Fr rather than 6 Fr ureteral dilator. As 12 Fr ureteral dilatation is sufficient to place 9.5/11.5 Fr UAS comfortably we do not routinely perform ureteral dilatation more than 12 Fr. We presume iatrogenic injuries/false passages while passing ureteral dilators (more common with smaller dilators) in our series are uncommon due to the following reasons. (1) Routine performance of diagnostic ureteroscopy and assessment of ureter prior to the initiation of sequential ureteral dilatation. (2) Performance of ureteral dilatation under fluoroscopic guidance. (3) Avoidance of excessive force during ureteral dilatator insertion. We do not prefer larger size single step ureteral dilatation in any cases of primary RIRS, including difficult ureters.
Initially sequential ureteral dilatation was performed by conventional methods at the authors institution in all cases and scenarios. Over a period, the authors observed that multiple and repetitive passage of same size ureteral dilator during sequential ureteral dilatation eased the passage of subsequent bigger size dilator or UAS. The idea of ROF ureteral dilatation was borne from that experience. The aforementioned ROF ureteral dilatation methodology was designed with the objective of achieving a specific clinical outcome – successful 9.5/11.5 Fr UAS placement. The authors believe the net result of improved ureteral accommodation is the summation effect of multiple admissive insertion forces and withdrawal forces. The authors also believe that the resultant enhanced ureteral accommodation made the UAS placement possible in a significant proportion of cases (71.4%), where UAS placement could have otherwise been not possible.
In a few cases, the authors had tried the technique of performing 10Fr ureteral dilatation for an extended duration of 1 min, when 12 Fr ureteral dilatation and UAS placement was not possible after conventional ureteral dilatation up to 10 Fr. But the authors observed that the ROF ureteral dilatation achieved comparatively better ureteral accommodation. Hence at the author's institution, the 'Extended duration' 10Fr ureteral dilatation technique was suspended in favor of ROF ureteral dilatation. There has also been a suggestion to improve the probability of UAS placement in tight ureters by giving antegrade pressure on the UAS with gentle retrograde traction on the guidewire for a few minutes. It had been reasoned that the ureteral muscle tone will relax after a few minutes allowing successful UAS placement. The authors tried this technique in a few cases. Even though the UAS could be successfully placed in some patients, after the completion of the procedure there was difficulty in removing the UAS as it was held tightly in the intramural ureter in a significant proportion of cases. The authors were concerned about the possibility of ureteral ischemia and stricture in that scenario and that practice was abandoned at the author's institution.
Similar problems of difficulty in removing UAS after the procedure were not encountered in patients who had undergone ROF ureteral dilatation with total success outcome. But in a patient with partial success outcome (1 out of 3) the authors could face the difficulty of removing UAS after the procedure. Also, none of the patients with total success outcome in our study who had underwent 12 Fr ureteral dilatation prior UAS placement had ureteral wall injury. The authors therefore recommend dilating the ureters to a calibre larger than the outer diameter of the UAS, before attempting UAS placement whenever possible for more assuring safety (at least 12 Fr ureteral dilatation in case of 9.5/11.5 Fr UAS placement). The main safety concern in performing any method of active ureteral dilatation in difficult ureters is the risk of ureteral stricture. But no new onset hydroureteronephrosis was noted in any renal units our study at follow-up ultrasonography and/or additional serial follow-up ultrasonography.
The objective of the article is to notify the improved ureteral accommodation observed with multiple and repetitive passage of a same size ureteral dilator during sequential ureteral dilatation. The number “five” (in both duration and repetition) in ROF ureteral dilatation is an arbitrary value. However, 5 s duration and five repetitions were used in all cases to bring consistency in the methodology. It is beyond the scope of the article to determine the ideal duration and repetition of ureteral dilator passage at which ureteral accommodation is achieved at best.
Despite ours being a high-volume center for RIRS, the sample size in our series was small. The primary reason is the strict selection criteria for the patients in the study. Also, the number of cases could not be added up on as there has been a few modifications in the methodology at our institution beyond the study period. Further, data collection was retrospective in nature. Multicentre prospective studies with more patients will clearly define the efficacy and safety of ROF ureteral dilatation. The authors also feel that the subgroup analysis of patients among various demographic and clinical profile will better identify the patients in whom ROF ureteral dilatation will be most useful. The authors also believe the future prospective studies should randomize patients in different groups to undergo conventional sequential ureteral dilatation alone and ROF ureteral dilatation alone (with 8 Fr, 10 Fr and 12 Fr ureteral dilators in both groups) and compare the efficacy and safety. Such studies could reveal the impact of ROF ureteral dilatation on UAS placement more precisely. Nevertheless, the preliminary experience with ROF ureteral dilatation and its impact on successful and safe UAS placement has been encouraging.
| Conclusion|| |
“ROF” ureteral dilatation is an improvisation of conventional sequential ureteral dilatation. It facilitates successful and safe UAS placement in a proportion of patients undergoing sequential ureteral dilatation.
The authors acknowledge the contribution of Mr. Bijoy (visual editor), for editing the photographs. The authors also thank Mr. Sarin, Ms. Jency Ali and Ms. Jisha (operating room nurses) for technical assistance during surgery.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Sanguedolce F, Bozzini G, Chew B, Kallidonis P, de la Rosette J. The evolving role of retrograde intrarenal surgery in the treatment of urolithiasis. Eur Urol Focus 2017;3:46-55.
L'esperance JO, Ekeruo WO, Scales CD Jr., Marguet CG, Springhart WP, Maloney ME, et al.
Effect of ureteral access sheath on stone-free rates in patients undergoing ureteroscopic management of renal calculi. Urology 2005;66:252-5.
Wong VK, Aminoltejari K, Almutairi K, Lange D, Chew BH. Controversies associated with ureteral access sheath placement during ureteroscopy. Investig Clin Urol 2020;61:455-63.
Shvero A, Herzberg H, Zilberman D, Mor Y, Winkler H, Kleinmann N. Is it safe to use a ureteral access sheath in an unstented ureter? BMC Urol 2019;19:80.
Hubert KC, Palmer JS. Passive dilation by ureteral stenting before ureteroscopy: Eliminating the need for active dilation. J Urol 2005;174:1079-80.
Mitchell C, Kuebker J, McCormick B, Marien T, Herrell SD, Miller NL. Lubriglide sequential ureteral Dilators®
: A safe and effective method of ureteral dilation. J Endourol 2017;31:573-6.
Traxer O, Thomas A. Prospective evaluation and classification of ureteral wall injuries resulting from insertion of a ureteral access sheath during retrograde intrarenal surgery. J Urol 2013;189:580-4.
Kaplan AG, Lipkin ME, Scales CD Jr., Preminger GM. Use of ureteral access sheaths in ureteroscopy. Nat Rev Urol 2016;13:135-40.
Venkatachalapathy VS, Palathullil DG, Sam DM, Prasad A, Abraham GP. Outcomes of retrograde intrarenal surgery in renal calculi of varying size. Indian J Urol 2022;38:128-34. [Full text]
Al-Qahtani SM, Letendre J, Thomas A, Natalin R, Saussez T, Traxer O. Which ureteral access sheath is compatible with your flexible ureteroscope? J Endourol 2014;28:286-90.
Aykanat C, Balci M, Senel C, Ozercan AY, Coser S, Aslan Y, et al.
The impact of ureteral access sheath size on perioperative parameters and postoperative ureteral stricture in retrograde intrarenal surgery. J Endourol 2022;36:1013-7.
Sener TE, Cloutier J, Villa L, Marson F, Butticè S, Doizi S, et al.
Can we provide low intrarenal pressures with good irrigation flow by decreasing the size of ureteral access sheaths? J Endourol 2016;30:49-55.
Erturhan S, Bayrak Ö, Şen H, Yılmaz AE, Seçkiner İ. Can alpha blockers facilitate the placement of ureteral access sheaths in retrograde intrarenal surgery? Turk J Urol 2019;45:108-12.
Bachar GN, Mor E, Bartal G, Atar E, Goldberg N, Belenky A. Percutaneous balloon dilatation for the treatment of early and late ureteral strictures after renal transplantation: Long-term follow-up. Cardiovasc Intervent Radiol 2004;27:335-8.
Vanlangendonck R, Landman J. Ureteral access strategies: Pro-access sheath. Urol Clin North Am 2004;31:71-81.
Delvecchio FC, Auge BK, Brizuela RM, Weizer AZ, Silverstein AD, Lallas CD, et al.
Assessment of stricture formation with the ureteral access sheath. Urology 2003;61:518-22.
Bourdoumis A, Tanabalan C, Goyal A, Kachrilas S, Buchholz N, Masood J. The difficult ureter: Stent and come back or balloon dilate and proceed with ureteroscopy? What does the evidence say? Urology 2014;83:1-3.
Vigneswara Srinivasan Sockkalingam Venkatachalapathy,
Department of Urology, VPS Lakeshore Hospital, Kochi - 682 040, Kerala
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]