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Minijfil®: a new safe and effective stent for well-tolerated repeated extracorporeal shockwave lithotripsy or ureteroscopy for medium-to-large kidney stones?

2016 September; 8(5):e40788.
Published online 2016 August 13.
MiniJFil®: A New Safe and Effective Stent for Well-Tolerated RepeatedExtracorporeal Shockwave Lithotripsy or Ureteroscopy forMedium-to-Large Kidney Stones? Benoit Vogt,1,* Francois-Noel Desfemmes,1 Arnaud Desgrippes,1 and Yves Ponsot2 1 Department of Urology, Blois Polyclinic, La Chaussee Saint-Victor, France2 Department of Urology, University of Sherbrooke, Sherbrooke, Canada * Corresponding author: Benoit Vogt, Department of Urology, Blois Polyclinic, La Chaussee Saint-Victor, France. Tel: +33-663220844, Fax: +33-254906566, E-mail:[email protected] Received 2016 July 13; Accepted 2016 August 02.
Background: Percutaneous nephrolithotomy (PCNL) is recommended for treating staghorn stones or stones measuring > 20 mm.
Extracorporeal shockwave lithotripsy (ESWL) or flexible ureteroscopy (URS) may be used as a complement. However, PCNL can cause
trauma to the kidney parenchyma, and patients may find a noninvasive procedure, such as ESWL, to be more attractive.
Objectives: The aim of this study was to evaluate the clinical efficiency of MiniJFil® stenting associated with ESWL or second-line
URS for the treatment of medium-to-large kidney stones. The MiniJFil® is a stent reduced to a suture of 0.3F attached to a renal
pigtail. The entire ureter is occupied only by the suture of the stent.
Methods: We retrospectively analyzed the data of 28 patients. Twenty-four patients had kidney stones measuring > 15 mm (group
1) and four patients had staghorn stones (group 2). All of the patients were fitted with MiniJFil® 2 - 3 weeks before any treatment.
ESWL was always our first-line therapy. Stone-free (SF) status was defined as no evidence of stones.
Results: In group 1, the mean largest and cumulative stone diameters, respectively, were 18.7 ± 5.7 mm and 45.0 ± 12.0 mm. In group
2, the mean volume was 6,288.4 ± 2,733.0 mm3. The overall SF was 96.4% (100% for group 1 and 75% for group 2). The mean number
of sessions of ESWL and URS, respectively, was 1.4 ± 0.7 and 0.8 ± 0.9 in group 1 and 4.0 ± 2.0 and 1.5 ± 1.3 in group 2. The mean
times to achieve these rates were 3.2 ± 1.7 months and 5.6 ± 2.3 months for groups 1 and 2, respectively. One patient in group 2 was
treated with only three sessions of ESWL. Renal colic was observed in only five patients (17.9%).
Conclusions: MiniJFil® stenting is safe and may be an alternative for the treatment of kidney stones during minimally invasive
procedures.
Keywords: Staghorn Stone, Stent, Thread, Dilation, Lithotripsy, Ureteroscopy JFil® stents as a means of decreasing urinary symptoms In these innovative stents, the lower part of the double- Percutaneous nephrolithotomy (PCNL) is recom- pigtail stent is replaced by a 0.3F suture thread, signifi- mended as a first step to treat staghorn stones or cantly decreasing urinary symptom and pain scores and stones measuring > 20 mm. Extracorporeal shockwave constituting a medical advance in the domain of ureteral lithotripsy (ESWL) or flexible ureteroscopy (URS) may stent tolerance. Fortuitously, we discovered that the su- be used as a complement However, PCNL can cause tures had surprising properties. First, we observed a clear trauma to the kidney parenchyma and blood transfusion dilation of the ureter containing the sutures. Secondly, af- may be required Moreover, patients find noninvasive ter ESWL, the stone fragments gradually slid down the su- procedures, such as ESWL, more attractive tures, without renal colic in most cases After ESWL, the incidence of steinstrasse increases with the stone burden and can reach 40% for stones measuring These surprising properties led us to create the MiniJ- > 31 mm. Stenting with a double-pigtail stent reduces ste- Fil®, which is reduced to a thread attached to a simple loop instrasse However, the double-pigtail stent is poorly of a 4.8F pigtail stent. With the suture thread, the entire tolerated and reduces the patient's quality of life ureter can be dilated, and the luminal vacuity of the ureter It has been suggested that changes in the size and form is preserved. Thus, we believe that the use of the MiniJFil® of stents could decrease discomfort, and we developed may accelerate removal of stone fragments.
Copyright 2016, Nephrology and Urology Research Center. This is an open-access article distributed under the terms of the Creative CommonsAttribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just innoncommercial usages, provided the original work is properly cited.
Vogt B et al. for the patients with MiniJFil®. The treatment was per-formed beside the MiniJFil®. Stones were fragmented us- In this study, we evaluated the clinical efficiency and ing a pneumatic lithotripter (Swiss LithoClast® Master, safety of MiniJFil® stenting associated with minimally in- EMS, Switzerland) during rigid URS. Flexible URS was per- vasive procedures for the treatment of kidney stones mea- formed after insertion of a ureteral sheath (10-12 Fr, ACXL10, suring >15 mm and staghorn stones.
Porges-Coloplast, France). The stones were fragmented us-ing a StoneLightTM laser (Boston Scientific, USA), then re-moved with a stone basket.
3. Methods
At the end of the operation, the threads of the Mini- JFil® should cross the junction between the ureter and From April 2013 to October 2015 in a single institution, the bladder, and float in the bladder or the urethra. Af- we retrospectively reviewed the records of 28 patients with ter URS, the patients were fitted with an external ureteral non-obstructive kidney stones who had undergone exclu- stent (5 Fr, Open-End Flexi-Tip®, G14521, Cook, USA) beside sive MiniJFil® stenting before and during minimally inva- the threads, overnight following the operation. Two hours sive procedures.
before external stent removal, 8 mg of betamethasone was Among the 28 patients, 24 had kidney stones measur- ing > 15 mm (group 1) and four had staghorn stones (group ESWL was always our first-line therapy. After the pro- 2). No staghorn stones were included in group 1. To evalu- cedure, appropriate medical therapy was offered if renal ate stone status in group 1, we used the largest stone diam- colic occurred. Abundant fluid intake (3 liters/day) and eter (LSD), cumulative stone diameter (CSD), and volume body gymnastics with head down and feet up were recom- (VOL). The stone volume was calculated using the sphere mended for all patients.
formula (4/3*π*r3). Computed tomographic (CT) 3D re- The patients were assessed with X-ray immediately af- construction allowed volume measurements of staghorn ter the procedure and 2 - 4 weeks after an ESWL session. The stones (Image Analyser AVA, Philips Brilliance, 16 detec- required number of subsequent sessions of ESWL or URS tor arrays). The CSD is a well-established parameter used was determined based on residual stones. The determina- most frequently in clinical practice to evaluate stone sta- tion of stone-free status was achieved by direct visualiza- tus; however, for stones measuring > 20 mm, the use of tion of the kidney with URS or by sonography, non-contrast volume is recommended CT, and X-ray. Stone-free (SF) status was defined as no ev- All of the patients were fitted with the MiniJFil® 2 - 3 idence of stones, and patients who did not meet the crite- weeks before any treatment. The minimally invasive pro- ria required further treatment with ESWL or URS. The MiniJ- cedures consisted of ESWL and URS, which were performed Fil® was withdrawn under local anesthesia when the treat- by the same surgeons (B.V., F.N.D., and A.D.). ESWL was al- ment was considered complete. The data are presented as ways our first-line therapy. The patients were informed about the different techniques, and preferred to undergothe minimally invasive procedures. All patients under- 3.1. Technique: Construction, Implantation, and Ablation of the stood that the number of sessions and the duration of treatment would be important.
The MiniJFil® stent (WO2014096264 A1) was previ- ESWL was performed with a mobile lithotripter (Com- ously used in another study [7].
In this procedure, a pact Sigma, Dornier MedTech, Germany). ESWL was admin- polyurethane double-pigtail stent (double-loop ureteral istered on an outpatient basis. All patients were treated stents, 4.8F, 26 cm, Coloplast) is sectioned perpendicularly with intravenous analgesia, and no anesthesia was re- to the main axis, just outside of the renal loop. The sec- quired. Stones were radiographically located in two planes tioned part is then cut parallel to the main axis to form a and were sometimes located with the inline ultrasound beveled tail that is 2 cm long. The tail is then thinned out head. The shockwave intensity was 4, and 2,500 shocks toward the lower end, where its diameter should not ex- were delivered to each patient. The mean time for one ceed 0.5 mm. The length of the tail and the thinning out ESWL session was 30 minutes. In our center, only one ses- of the lower end are important in order to limit the catch- sion of ESWL per month can be offered to each patient.
ing of the stent on the junction and the ureter during stent The URS was performed with direct videoscopic guid- removal. A polypropylene suture (Ethicon monofilament ance under general anesthesia, with a rigid ureteroscope polypropylene suture; gauge size U.S.P.1; 0.1 to 0.15 mm; 5 (12 Fr, 27002 L, Karl Storz, Germany) or a flexible uretero- - 0) perforates the loop and the end of the tail, and a knot scope (8.5 Fr, 11278 A, Richard Wolf, Germany), or both.
is tied at the loop. The distal end of the MiniJFil® consists No active dilatation of the ureteral orifice was necessary of two 0.3F sutures, each suture approximately 36 cm long.
2016; 8(5):e40788.
Vogt B et al. This stent has a total length of 38 cm. shows the dif- Table 1. Patients, Kidney Stone Details, and Outcomes
ferent sizes between native 4.8F pigtail stents and the 0.3Fsutures.
Group 1 (n = 24)
Group 2 (n = 4)
Stones >15 mm
Figure 1. MiniJFil® Used in the Present Study
Side (R/L)
Mean stone volume, mm3 1.907.8 ± 1.876.2a 6.288.4 ± 2.733.0b This innovative stent is reduced to a thread attached to a simple loop of a 4.8F pigtailstent.
Stone-free status Processing time, mo 3.2. Ethics Statement The study design was approved by the French ethical committee, Comite de Protection des Personnes (CPP), Ile de France 2 (IRB registration 00001072). The local ethics committee also provided approval. Methods were carriedout in accordance with the approved guidelines. Written information was provided to all patients, and all patients Abbreviations: CSD, cumulative stone diameter; CT, computed tomography;ESWL, extracorporeal shockwave lithotripsy; LSD: largest stone diameter.
gave their informed consent.
a Mean stone volume calculated using the sphere formula (4/3*π*r3).
b Mean stone volume calculated using 3D CT reconstruction.
4. Results
The age, sex, side of stone, stone specifications, local- mean number of ESWL sessions was 1.4 ± 0.7 for group 1 ization, number of procedures, and outcomes for the pa- and 4.0 ± 2.0 for group 2. The mean number of URS ses- tients are summarized in In group 1, five patients sions was 0.8 ± 0.9 for group 1 and 1.5 ± 1.3 for group 2. The had multiple stones, with an average of 2.2 stones per kid- mean time to achieve these rates was 3.2 ± 1.7 months for ney, and preoperative measurements of stone burden were group 1 and 5.6 ± 2.3 months for group 2.
assessed in 16 non-contrast CTs and 12 X-rays. Mean LSD, Ten patients from group 1 were treated only by ESWL. In CSD, and VOL, respectively, were 18.7 ± 5.7 mm, 45.0 ± 12.0 this subgroup, mean LSD, CSD, and VOL, respectively, were mm, and 1,907.8 ± 1,876.2 mm3. In group 2, mean VOL was 18.8 ± 6.5 mm, 46.6 ± 10.8 mm, and 1,975.0 ± 1,264.5 mm3.
6,288.4 ± 2,733.0 mm3.
The mean number of ESWL sessions was 1.7 ± 0.9 and the The overall SF rate was 96.4% (100% for group 1 and 75% mean time for SF status was 2.4 ± 1.0 months. In three pa- for group 2). One patient from group 2 had tients, renal colic occurred and was treated only by medical an asymptomatic stone on sonography (LSD: 7 mm). The therapy. One patient from group 2 was treated 2016; 8(5):e40788.
Vogt B et al. with only three ESWL sessions (VOL: 4,225 mm3).
The SF rate is defined as no evidence of stones and In five patients (17.9%), renal colic was observed. Three the clinical success (CS) rate is defined as the presence of patients were treated with medical therapy and two with stone fragments measuring < 4 mm In most of URS. In the case of one patient from group 1, MiniJFil® the referenced studies, patients were assessed after three was replaced with a double-pigtail stent after URS because of a finding of ureteropelvic junction stenosis. Calcifica- The probability of renal stone clearance after ESWL de- tions were encountered around the bladder thread in two creased with increasing stone size in all locations patients. No major complications, such as perforation or Tan et al. reported a SF rate of 53% and a CS rate of 81% at gross hematuria, were encountered three-month follow-up for the ESWL treatment of 1,666 re-nal stones. For renal stones measuring > 20 mm, the SFand CS rates depended on their location in the kidney, and were 31% - 52% and 44% - 63%, respectively. For lower-polecalyceal stones, the SF rate was only 31% However, the The introduction of ESWL in the early 1980s revolution- best results were obtained by the urologist who treated the ized the treatment of renal stones However, PCNL is greatest number of patients recommended as a first step to treat staghorn stones or Interestingly, Fall et al. reported a similar CS rate of stones measuring > 20 mm Technical developments in 52.7% for renal stones measuring > 20 mm and treated by endoscopic techniques for the treatment of kidney stones URS Better results were reported by Cohen et al. for re- have led to considerable changes in treatment modalities.
nal stones measuring 19 - 37 mm, with CS of 81% - 94% Moreover, changes in the mechanical design of ESWL could The incidence of steinstrasse increases with the stone reduce the success rate Recent years have seen a shift burden, and staghorn stones are unsuitable for ESWL from ESWL to endoscopic techniques or PCNL. PCNL may be monotherapy In the treatment of staghorn effective for the treatment of medium-sized kidney stones stones, Yan et al. reported a SF rate of 53.2% with one and URS may be effective for the treatment of large session of PCNL, and of 82.9% after multiple procedures and complex kidney stones ESWL remains the stan- (PCNL, ESWL, URS) Good results were reported by Netto dard for stones measuring < 20 mm, and may be used as a with multiple procedures (ESWL and URS), for a CS rate of complement to other procedures for large stones Thus, ESWL is not recommended for large stones due to an in- In the present study, we achieved SF rates of 100% and creased incidence of steinstrasse, and double-pigtail stent- 75% in groups 1 and 2, respectively. While our results are ing does not prevent steinstrasse Moreover, the double- better than those of other reported series, our study was pigtail stent is poorly tolerated and reduces the patient's limited by a low number of patients. Moreover, the out- comes were assessed after more than three months. In In previous studies, we discovered fortuitously that su- the case of staghorn stones, ESWL was always our first-line tures had surprising, unknown properties in the ureter. In therapy, and we cannot now compare our results to those all cases, we observed clear dilation of ureters containing of other series. However, ESWL and URS during MiniJFil® sutures, with a ureteral diameter two to three times larger stenting seem to be a possible treatment for large stones.
than the contralateral ureter on CT. No inflammation was One patient from group 2 with a staghorn stone was suc- visible in the ureteral or bladder mucosa. After ESWL, the cessfully treated with ESWL alone.
stone fragments gradually slid down the sutures, without Several factors could explain the SF rates in the present renal colic in most cases These unexpected proper- ties naturally led us to expand the list of indications for - Our mobile ESWL device is available only monthly.
ESWL and to include staghorn stones.
Several studies showed that elimination of stones may in- Complications from ESWL are rarely encountered, with crease with postoperative time In our study, the rates of 2.9% to 7.1% Significant complications are better tolerance of MiniJFil® led us to wait for the elimi- associated with PCNL, with rates of 16% to 28.5% nation of all fragments and these especially include the risk of blood loss requir- - In comparison with the double-pigtail stent, the lumi- ing transfusion. In our practice, minimally invasive proce- nal burden of the ureter was reduced to the threads of the dures, such as ESWL, are always our first-line therapy. More- MiniJFil®. Moreover, the MiniJFil® allowed dilation of the over, patient preferences must be considered. Kuo et al.
ureter without any inflammation Sfoungaristos et al.
and, recently, Raja et al. have pointed out that patients showed that ureteral stents, even if they were removed just preferentially chose ESWL rather than invasive procedures, before ESWL, decreased the SF rate. Edema formation with decreasing functional ureteral lumen diameter and low 2016; 8(5):e40788.
Vogt B et al. Figure 2. Appearance of Staghorn Stones and MiniJFil® on X-Ray
Figure 3. Appearance of a 24-mm Renal Stone on X-ray During Treatment With Extracorporeal Shockwave Lithotripsy (ESWL) and MiniJFil®
A, MiniJFil® and stone before ESWL; B, stone fragmentation and steinstrasse on day 4 after ESWL; C, spontaneous evacuation of steinstrasse on day 10 after ESWL; D, completeevacuation of the rest of the stone on day 28 after ESWL.
ureteral peristalsis may minimize the likelihood of stone ited, they concerned the immediate complications of pro- passage The absence of edema around the suture cedures Few studies have so far attempted to de- may facilitate stone elimination. Thus, luminal freedom scribe the patient's quality of life over long-term follow-up with ureteral dilatation may allow elimination of the stone Sahin et al. evaluated the possible effects of residual - In a previous study, in addition to ureteral dilatation, fragments on quality of life in 71 patients after ESWL. In the pelvic and calyceal dilation was observed in 50% of cases af- first month following ESWL, 40.5% of patients with stones ter MiniJFil® stenting Brewer et al. showed that lumi- measuring <4 mm and 69.0% of patients with stones of nal flow in the stent increased with the internal diameter > 4 mm had renal colic. Additional procedures were re- of the lumen A better ureteral flow, thanks to abun- quired for 40.8% of the patients Streem et al. deter- dant fluid intake, may facilitate mobilization and elimina- mined the natural history and the clinical implications of tion of stone fragments.
160 patients with stones of < 4 mm after ESWL for a mean - Finally, we always recommended postural gymnas- period of 23 months. Renal colic was observed in 43.1% of tics. It has been shown that gymnastics associated with hy- the patients, and additional procedures were required in drotherapy was effective for the elimination of stone frag- 27.5% Even after URS, additional procedures were re- ments after ESWL quired for 8.2% - 46.2% of patients for residual fragments The SF rate, which was the main objective of these over a period of five years Hubner et al. suggested that studies, did not take into account the patient's quality of 39% of asymptomatic renal calyceal stones were increased life. Although the complication rates of ESWL were lim- in size, and 83% of patients required surgical procedures 2016; 8(5):e40788.
Vogt B et al. within five years of diagnosis Meanwhile, Kelley et al.
plantation of a MiniJFil® could be used to prepare the observed that prophylactic ESWL for asymptomatic renal ureter for the insertion of a sheath for flexible URS, without calyceal stones measuring < 15 mm reduced the risk of in- excessive discomfort for the patient Ureteral dilation vasive procedures in cases of renal colic over a mean follow- could facilitate the introduction of a large endoscope (11F) up of two years Several studies have shown that elimi- for ureteroscopic treatment of large stones nation of stones may increase with postoperative time In our study, the better tolerance of MiniJFil® led us to 5.1. Conclusions wait for the elimination of all fragments, without excessivediscomfort for the patient MiniJFil® stenting is safe and seems to be an alterna- In the present study, only five out of 28 patients (17.9%) tive for the treatment of medium-to-large kidney stones had renal colic during the observation period, and two during minimally invasive procedures. ESWL is not rec- patients (7.1%) required an additional procedure (URS). In ommended for large stones, but the potential of Mini- group 2, it was remarkable that only one case of renal colic JFil® led us to reassess the list of indications. In this occurred during the 5.6 months of treatment. MiniJFil® study, we present a new method for the treatment of renal stenting seems to limit renal colic, as we have previously stones. MiniJFil® stenting could change current endourol- observed, even when steinstrasse occurs ogy techniques by providing greater patient comfort and MiniJFil® stenting with ESWL is not intended to re- improvements in the daily practice of urologists.
place other techniques, but provides a minimally inva-sive alternative treatment. ESWL is not recommended for staghorn stones, but the potential of MiniJFil® led us to re-assess the list of indications.
We thank Dr. Loïc Besnier, radiologist, Polyclinique de There were several limitations to this study due to its Blois, for his calculations of stone burden on CT images, retrospective character and low number of patients. An- and Professor Janine Dove-Rumé, English Department at other limitation was that the study included only a single the University of Tours, for re-reading our text.
medical center. Further studies from multiple centers in arandomized, controlled trial should confirm the improve-ments in treatment reported here. The evaluation of SF sta- tus in the present study can also be criticized because thevisualization of small stones may be difficult. In this study, Authors' Contribution: Benoit Vogt and Francois-Noel
four patients were assessed with plain abdominal X-rays, Desfemmes developed the original idea.
and SF status may have been overestimated.
developed the protocol, analyzed data, and wrote the Based on our experience with 580 JFil® and MiniJFil® manuscript. All authors approved the manuscript's con- stentings, we can declare other limitations to the use of tent before submission.
MiniJFil®. First, the ureter must always be healthy inits entirety. In the presence of inflammatory or fibrousstenosis or post-radiation stenosis, MiniJFil® will be inef- fective for dilation and for the descent of the stone frag-ments. In group 1 in this study, one patient had moder- 1. Turk C, Petrik A, Sarica K, Seitz C, Skolarikos A, Straub M, et al.
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2016; 8(5):e40788.

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