- Email: [email protected]
Use of holmium laser for urethral strictures in pediatrics: A prospective study
+
MODEL
Journal of Pediatric Urology (2015) xx, 1.e1e1.e6
Use of holmium laser for urethral strictures in pediatrics: A prospective study
a
Pediatric Urology Department, Abu El Rish Children Hospital, Cairo University, KasrAlAiny Street, Cairo, Egypt
b
Urology Department, Kasr Alainy Hospital, Cairo University, KasrAlainy Street, Cairo, Egypt Correspondence to: A. I. Shoukry, Pediatric Urology Department, Abu El Rish Children Hospital, Cairo University, KasrAlAiny Street, Cairo, Egypt, Tel.: þ201065332220
A.I. Shoukry a, W.N. Abouela a, M.S. ElSheemy a, A.M. Shouman a, K. Daw a, A.A. Hussein a, H. Morsi a, M.A. Mohsen b, H. Badawy a, M. Eissa a Summary Introduction The management of urethral strictures is very challenging and requires the wide expertise of different treatment modalities ranging from endoscopic procedures to open surgical interventions. Objective To assess the effectiveness and complications of retrograde endoscopic holmium: yttrium-aluminumgarnet laser (Ho: YAG) urethrotomy (HLU) for the treatment of pediatric urethral strictures.
ahmedshoukry@kasralainy. edu.eg (A.I. Shoukry) waseem_aboul_ela@yahoo. com (W.N. Abouela) mohammedshemy@ yahoo.com (M.S. ElSheemy) [email protected] (A.M. Shouman) [email protected] (K. Daw) ahmedalyhussein@ kasralainy.edu.eg (A.A. Hussein) [email protected] (H. Morsi) [email protected] (M.A. Mohsen) [email protected] (H. Badawy) [email protected] (M. Eissa)
Patients and Methods From January 2010 to January 2013, 29 male pediatric patients with a mean age of 5.9 years and primary urethral strictures 0.5e2 cm long were treated using HLU. The stricture length was <1 cm in 16 (55%) patients and >1 cm in 13 (45%). Fifteen (51.7%) patients had an anterior urethral stricture, while 14 (48.3%) had a posterior urethral stricture. No positive history was found in 14 (48.3%) patients for the stricture disease, while six (20.7%) had straddle trauma and nine (31%) had an iatrogenic stricture. All of the patients were pre-operatively investigated and at 3 and 6 months postoperation by uroflowmetry and voiding cystourethrography (VCUG). If there were suspicious voiding symptoms, selective uroflowmetry and VCUG were performed at 12 months postoperation.
Keywords Urethral stricture; Holmium laser; Visual internal urethrotomy; Children; Cystoscopy
Results The mean operation time was 31.7 min (20e45 min). Twenty-three (79.3%) and 18 (62.1%) patients showed normal urethra on VCUG with improvement of symptoms at 3 and 6 months, respectively. Thus, recurrence was 37.9% after 6 months of follow-up. The mean pre-operative peak urinary flow rate
Received 4 February 2015 Accepted 3 June 2015 Available online xxx
(Qmax) was 6.47 ml/s. The mean postoperative Qmax at 3 and 6 months was 17.17 ml/s and 15.35 ml/s, respectively. The success rate and flowmetry results did not show any statistical significance in relation to site, length and cause of the strictures. The other 11 patients who failed to improve underwent repeated HLU sessions: 4/11 (36.3%) achieved successful outcomes. Among the seven patients with failed HLU for the second time, a third session was conducted. However, only one patient (14.2%) was cured, while open repair was needed for the remaining six. Discussion One study has previously been published on the management of pediatric urethral strictures using HLU. The present results are similar to short-term studies after a single session of visual internal urethrotomy using cold knife (VIU). In the present study, the length, location and cause of strictures did not significantly affect the results. However, the outcomes with strictures <1 cm were better than strictures >1 cm, although patients with strictures >2 cm were excluded. In the present study, the success rates among patients with second and third sessions of HLU were 36.3% and 14.2%, respectively. This was similar to other studies, which reported low success rate with the second session of VIU. The present study was limited by the relatively short period of follow-up and the small number of patients. However, it was the first prospective study evaluating HLU for pediatric strictures. The use of flowmetry and VCUG for evaluation of all patients added to the strength of the study. Conclusion HLU can be safely used with good success rates for the treatment of primary urethral strictures (<2 cm) in children. Repeat HLU (more than twice) adds little to success.
http://dx.doi.org/10.1016/j.jpurol.2015.06.016 1477-5131/ª 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e2
A.I. Shoukry et al.
Introduction The management of urethral strictures is very challenging and requires the wide expertise of different treatment modalities ranging from endoscopic procedures to open surgical interventions. If not treated properly, pediatric urethral strictures can have a massive impact on the future life of children with them. The ultimate goal of the surgeon and patient, as well as the family, is searching for a minimally invasive procedure with a high cure rate. Several studies have been performed to assess the effectiveness of different laser modalities [1e3], including holmium: yttrium-aluminum-garnet laser (Ho: YAG) in adult urethral strictures [4]. However, for pediatric urethral strictures, only one study has previously been conducted to assess the efficacy of Ho: YAG [5]. It is believed that the present study is the first prospective study that assess the effectiveness and complications of retrograde endoscopic Ho: YAG laser urethrotomy (HLU) for treating pediatric urethral strictures.
antibiotic was pre-operatively given to all patients as a prophylaxis. An 11-Fr pediatric cystoscope (Karl Storz, Germany) was initially inserted to reach the stricture, and then a 0.035 inch guide wire or 3-Fr ureteric catheter was introduced through the stricture to the urinary bladder. Scar tissue was incised at the 12-o’clock position under the guidance of a guide wire or ureteric catheter until fresh mucosa appeared. This was performed using a 0.73 mm laser fiber (SphinX 30W, holmium-YAG laser, LISA Laser ProductseOHG, Germany) (2.75 J, 11.0 Hz). Finally, a 10-14-Fr silicone catheter was indwelled, according to age of the patient, which remained for 7 days and was then removed. None of the patients received any medical or intralesional steroid injections. Two patients were <3 years old. In all patients, the urethra accommodated the 11-Fr cystoscope. The procedure was considered successful if the patient did not report any postoperative voiding difficulty, with a postoperative maximum flow rate (Qmax) > 15 ml/s and normal VCUG. Lastly, the effects of different clinical parameters on the outcome e including length, location and cause of strictures e were analyzed.
Materials and methods Twenty-nine boys with a urethral stricture 2 cm were included in the present study from January 2010 to January 2013 using HLU. Exclusion criteria were patients who had undergone previous open urethroplasty, urethral dilatation, visual internal urethrotomy, or those presenting with diverticulum, multiple level urethral strictures or following a fractured pelvis with urethral disruption. All patients were pre-operatively investigated with history, examination, uroflowmetry and VCUG (Fig. 1 and Fig. 2). They were followed up with urine analysis and culture, uroflowmetry and VCUG at 3 and 6 month postoperation. If there were suspicious voiding symptoms, selective uroflowmetry and VCUG were performed at 12 months postoperation. All patients were toilet trained and could void upon request to perform the uroflowmetry. Stricture location was categorized as posterior (membranous) or anterior (penile (six patients) or bulbar (nine patients)) urethral stricture.
Surgical technique Under general anesthesia, all patients were placed in the lithotomy position. A third-generation cephalosporin
Figure 1
Statistical method Statistical analysis was performed using the statistical package SPSS version 15 (IBM, USA). Statistical differences between groups were tested using the Chi-squared test, Nonparametric ManneWhitney test, Wilcoxon signed-rank test, KruskaleWallis test and Friedman test. A P-value <0.05 was considered to be statistically significant.
Results The pre-operative data and different causes of urethral strictures are presented in Table 1. The mean age was 5.9 years (median 5.0, range 2e13 years). All patients presented with obstructive symptoms. The period from the onset of urethral stricture to time of treatment was difficult to precisely identify as most patients were without clear cause (48.3%). However, this period ranged from 3 to 6 months in the remaining patients (iatrogenic and traumatic patients). The mean operative time was 31.7 6.2 min (range 25e45, median 30 min). The operative time was longer in
Uroflowmetry of one of the patients.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
Holmium laser for urethral strictures in pediatrics
1.e3 Table 1
Pre-operative data. Patients, n (%)
Figure 2 Pre-operative ascending cystourethrogram of one of the patients.
the initial patients then gradually decreased with the improving learning curve. Four patients (13.8%) had intraoperative complications: two were bleeding per urethra, which was stopped by mild perineal compression, fixing a urethral catheter and tying a gauze around it and pushing it proximally so it compresses the penis mildly for around 15 min; two had urethral extravasation, which was complicated by penile edema at the end of the procedure e this subsided a couple of days afterwards while giving antiinflammatory drugs. All patients were followed up for at least 12 months. Success was achieved in 23 (79.3%) and 18 (62.1%) patients at 3 and 6 months postoperation, respectively. Thus, recurrence rate was 37.9% after 6 months of follow-up. The peak urinary flow rate (Qmax) showed significant improvement at 3 and 6 months postoperation (Table 2). The effect of different factors on the success (flowmetry and VCUG) was analyzed at 3 and 6 months postoperation (Table 3) (Fig. 3). The outcomes with strictures <1 cm and posterior urethral strictures were better than strictures >1 cm and anterior urethral strictures, respectively. However, the difference was not statistically significant (Table 3). There was also no significant difference in the postoperative Qmax and success rate according to cause of stricture. There was also no correlation between ages of the patients or the stricture cause with the percent change of Qmax. The 11 patients with failure (six primary failure at 3 months and five recurrent failure at 6 months) had repeated HLU sessions. Among these patients, four (36.3%) achieved successful outcomes. Among the seven patients with failed HLU for the second time, a third session was conducted. However, only one patient (14.2%) improved, while open repair was required for the remaining six. Thus, the success rate after the second session increased to 75.8% (22 patients), while it increased to (79.3%) after the third
Length of stricture 0.5e0.9 cm 1e2 cm Site of stricture Anterior urethraa Posterior (membranous) urethra Etiology: Unknown cause Straddle traumab Iatrogenic PUV fulguration Catheter fixation Urethral diverticulectomy Hypospadias repairc Stone bladder Failed trial of catheterization Qmax, mean (range) Site of stricture: Anterior urethra Posterior urethra Length of stricture 0.5e0.9 cm 1e2 cm Etiology: Unknown cause Straddle traumab Iatrogenic
16/29 (55.2%) 13/29 (44.8%) 15/29 (51.7%) 14/29 (48.3%) 14/29 (48.3%) 6/29 (20.7%) 9/29 (31%) 2 (6.3%) 2 (12.4%) 1 (3.1%) 2 (6.3%) 1 (3.1%) 1 (3.1%)
5.58 (3e9) ml/s 7.35 (4e10) ml/s 7.14 (5e10) ml/s 5.7 (3e8) ml/s 6.22 ml/s 6.83 ml/s 6.64 ml/s
a Anterior urethral strictures included three penile and 12 bulbous strictures. b Straddle trauma is a urethral stricture resulting from straddle trauma (blunt perineal trauma). c One patient had proximal penile hypospadius (treated by tubularised incised plate), while the second patient had penoscrotal hypospadias (treated in two stages).
session (23 patients). The follow-up ranged from 12 to 15 months starting from the first session. However, the followup after the second and third session was limited (3e9 months). At 12 months postoperation, the success rate remained (subjectively evaluated by clinical symptoms) at 62.1%. Open repair was in the form of: staged buccal grafts for two penile strictures; resection with end-to-end anastomosis for one bulbar stricture <1 cm; ventral buccal graft for one bulbar stricture >1 cm; and resection with end-toend anastomosis for two posterior strictures.
Discussion Urethral stricture is one of the most challenging urological problems. Traditional treatment options include metal dilatation, visual internal urethrotomy using cold knife (VIU) and open surgical urethroplasties. The VIU has shown a wide range of success rates from 21 to 87% [6e9]. Although open urethroplasties have shown very high success rates (85e93%) [10,11], minimally invasive procedures
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e4 Table 2
A.I. Shoukry et al. Pre-operative and postoperative flowmetry.
Qmax (ml/s)
Pre-operativea
3 months postoperationb
6 months Postoperationb
P-value
Mean (range) Median
6.47 (3e10) 6.1
17.17 (5e25) 19.0
15.35 (5e25) 19.5
<0.001*
*Significant (Friedman test). a There was significant difference between pre-operative Qmax and both 3 (P < 0.001) and 6 months (P < 0.001) postoperation (Wilcoxon signed ranks test). b There was no significant difference between the 3- and 6-month postoperative Qmax (P Z 0.272) (Wilcoxon signed ranks test).
are still preferred, and widely practiced, by many surgeons and patients, as they offer shorter convalescence and hospitalization time, thus allowing patients to return to full occupational activity in a shorter time [12]. In the hope of reducing the high re-stricture rate of the conventional VIU by both cutting and vaporizing the scar tissue, many studies have used different types of laser for urethrotomy [1e3]. The fibrosis and re-stricture after urethrotomy is affected by the thermal effect and absorption of the energy by tissues. The Ho: YAG laser displays the shallowest absorption (0.5 mm) with the least scar formation when compared with other medical lasers including the Nd:YAG (neodymium-doped yttrium aluminium garnet), potassium-titanyl-phosphate (KTP), argon and diode laser, in which the depth of absorption by tissues may reach 5 mm [13e16]. However, Hampson et al. reported that there is no clear consensus as to which laser is best to use. Overall, data seem to show equivalence in terms of both complication and success rates for these different lasers and urethrotomy techniques [16]. One study, by Sun et al., has been published on the management of pediatric urethral strictures using HLU in 28 patients [5]. The average age was 5.1 years (range 2e14), which is similar to the present study. Hypospadias repair was the cause of stricture in 19 patients, while pelvic and perineal traumas were the causes of nine strictures, as reported by Sun et al. [5]. This is different from the present study, as most patients were without a clear cause (14 patients), while hypospadias was the cause in two patients. In the Sun study, the length of strictures ranged from 0.1 to
Table 3
2.5 cm, with an average of 0.6 cm. Seventeen patients had the lesions <0.5 cm; five had lesions from 0.5 to 2.0 cm; and four had lesions >2.0 cm [5]. This is similar to the present study, but in the present study there were no strictures >2 cm or <0.5 cm. In the Sun study, the strictures were located in the posterior urethra in nine patients and in the anterior urethra in 17 [5]; the distribution of strictures in the present study between the anterior and posterior urethra was similar. Sun et al. excised the scar tissue at the positions of 4, 8, and 12-o’clock [5], but the 12-o’clock position was preferable in the present study. The average operative time was 44 min (range 15e120 min) as reported by Sun et al., which was longer than the present study, although they had more patients with short strictures (<0.5 cm). There were no intraoperative complications in the study by Sun et al., but in the present study there were four complications, which were conservatively treated. Of the 28 patients in the Sun study after initial incision, 25 (89.3%) achieved satisfactory results without complications [5]. This is better than the present study (62%), which may be due to the presence of 17 patients in the Sun study with strictures <0.5 cm [5]. The present results are similar to short-term studies (50e53%) after a single session of VIU for treatment of pediatric urethral strictures [17,18]. However, Hafez et al. noted a long-term success rate of 36% after initial VIU in 31 children, which increased to 58% after repeat incision. They recommended one trial only followed by open repair, if initially unsuccessful [6]. In a recent study, Launonen et al. reported a final success rate of 71%
Effect of different factors on success and flowmetry.
Follow-up
Length of stricture: 0.5e0.9 cm 1e2 cm P-value Site of stricture: Anterior urethra Posterior urethra P-value Cause of stricture: Negative history Straddle trauma Iatrogenic P-value
Success at 3 months postoperation, n (%)
Success at 6 months postoperation, n (%)
Qmax 3 months postoperation, mean (range) (ml/s)
Qmax 6 months postoperation, mean (range) (ml/s)
14 (87.5%) 9 (69.2%) (P Z 0.364)
12 (75%) 6 (46.2%) (P Z 0.143)
18.73 (6e25) 15.38 (5e24) (P Z 0.079)
17.47 (6e25) 12.92 (5e23) (P Z 0.105)
11 (73.3%) 12 (85.7%) (P Z 0.651)
9 (60%) 9 (64.3%) (P Z 0.812)
16.07 (5e25) 18.28 (5e25) (P Z 0.356)
14.8 (5e24) 15.8 (5e25) (P Z 0.781)
11 (78.6%) 5 (83.3%) 7 (77.8%) (P Z 0.96)
8 (57.1%) 3 (50.0%) 7 (77.8%) (P Z 0.48)
16.71 (5e25) 19.00 (6e25) 16.63 (6e23) (P Z 0.501)
14.50 (5e25) 14.83 (6e24) 17.25 (6e23) (P Z 0.538)
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
Holmium laser for urethral strictures in pediatrics
Figure 3 Postoperative ascending cystourethrogram of one of the patients.
after repeated VIU in 34 pediatric patients; the stricture length was >2 cm in five patients (15%). In the KaplaneMeier analysis, the stricture recurrence rates at a 2- and 5-year follow-up were 53e78% and 67e78%, respectively, after each VIU or dilatation under general anesthesia [9]. Among the three recurrent patients (10.7%) reported by Sun et al., two were successfully treated by another HLU session and open end-to-end anastomosis, while the last patient failed to follow-up. The length of lesion was the major factor of re-stenosis, as the recurrence rate was 75% in the four children with lesions >2 cm [5]. In another study using HLU in 32 male patients, Kamp et al. reported that long segment (>1.5 cm) strictures were a risk factor for recurrence. However, the location of the stricture had no impact on the success of treatment [14]. In the present study, the length, location and cause of strictures did not significantly affect the results. However, the outcomes with strictures <1 cm were better than strictures >1 cm, although patients with strictures >2 cm were excluded. Similarly, Launonen et al. found no significant difference in the outcome of VIU according to cause or location of strictures in children, but they reported poor results when the length of stricture >2 cm [9]. In the present study, the success rates among patients with second and third sessions of HLU were 36.3% and 14.2%, respectively. This was similar to other studies, which have reported low success rate (17%) of the second session of VIU in pediatric strictures [19]. Although some surgeons might not attribute repeated sessions of VIU for causing difficulties in subsequent open surgeries, several studies have attempted it. In a recent study, Launonen et al. reported that single VIU was successful in 25% of the patients. In strictures <2 cm, up to three VIUs can be attempted, but longer strictures need open correction if the patient does not wish to follow the home dilatation program [9]. Kamp et al. evaluated HLU in 32 male patients, the strictures ranged in length from 0.5 to 4 cm, with a mean of 1.5 cm. It was recurrent in 62.5% of patients, but most (68.7%) did not need any intervention. The success rate increased to 75%
1.e5 after repeat HLU. Most of the recurrences appeared within the first 12 months [14]. Dutkiewicz et al. compared HLU with VIU in the treatment of primary or refractory urethral strictures <3 cm in 50 men aged 17e78 years. Neither complication rate nor degree of efficacy revealed a significant difference between HLU and cold knife [20]. The present study was limited by the relatively short period of follow-up and the lack of a control group. Additionally, the small number of patients, together with different causes and locations of strictures, affected the statistical significance and prevented multivariate analysis due to small subgroups. However, the present study was the first prospective study evaluating HLU for pediatric strictures. The use of flowmetry and VCUG for pre-operative evaluation of all patients, and at the third and sixth months postoperation adds to the strength of the study. To help the choice of the proper modality for treatment for pediatric urethral strictures, further randomized studies with a larger number of patients are needed to compare VIU with HLU after a longer period of follow-up in selective sites and sizes of strictures.
Conclusion HLU can be safely used, with good success rates, for the treatment of primary urethral strictures (<2 cm) in children. It is a minimally invasive, simple and reproducible technique with results comparable to those of the adult population and the conventional cold knife urethrotomy. Repeat HLU (more than twice) adds little to success. However, randomized studies against VIU are necessary.
Conflict of interest None.
Funding None.
References [1] Smith JA, Dixon JA. Neodymium: YAG laser treatment of benign urethral strictures. J Urol 1984;131:1080e1. [2] Rothauge CF. Urethroscopic recanalization of urethral stenosis using argon laser. Urology 1980;16:158e61. [3] Turek PJ, Malloy TR, Cendron M, Carpiniello VL, Wein AJ. KTP532 laser ablation of urethral strictures. Urology 1992;40: 330e4. [4] Hussain M, Lal M, Askari SH, Hashmi A, Rizvi SAH. Holmium laser urethrotomy for treatment of traumatic stricture urethra: a review of 78 patients. J Pak Med Assoc 2010;60:829e32. [5] Sun F, Zhang W, Zhuang Y, Dong Q, Li A. Application of endoscopic Ho:YAG laser incision technique treating urethral strictures and urethral atresias in pediatric patients. Pediatr Surg Int 2006;22:514e8. [6] Hafez AT, El-Assmy A, Dawaba MS, Sarhan O, Bazeed M. Longterm outcome of visual internal urethrotomy for the management of pediatric urethral strictures. J Urol 2005;173:595e7. [7] Noe HN. Long-term follow-up of endoscopic management of urethral strictures in children. J Urol 1987;137:951e3.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e6 [8] Duel BP, Barthold JS, Gonzalez R. Management of urethral strictures after hypospadias repair. J Urol 1998;160:170e1. [9] Launonen E, Sairanen J, Ruutu M, Taskinen S. Role of visual internal urethrotomy in pediatric urethral strictures. J Pediatr Urol 2014;10(3):545e9. [10] Micheli E, Ranieri A, Peracchia G, Lembo A. End-to-end urethroplasty: long-term results. BJU Int 2002;90:68e71. [11] Barbagli G, Palminteri E, Lazzeri M, Guazzoni G, Turini D. Long-term outcome of urethroplasty after failed urethrotomy versus primary repair. J Urol 2001;165:1918e9. [12] Bullock TL, Brandes SB. Adult anterior urethral strictures: a national practice patterns survey of board certified urologists in the United States. J Urol 2007;177:685e90. [13] Matsouka K, Inoue M, Iida S, Tomiyasu K, Noda S. Endoscopic antegrade laser incision in the treatment of urethral stricture. Urology 2002;60:968e72. [14] Kamp S, Knoll T, Osman MM, Kohrmann KU, Michel MS, Alken P. Low-power holmium:YAG laser urethrotomy for treatment of urethral strictures: functional outcome and quality of life. J Endourol 2006;20(1):38e41.
A.I. Shoukry et al. [15] Smith Jr JA, Stein BS, Benson RC. Lasers in Urologic Surgery. 3rd ed. St Louis: CV Mosby; 1994. p. 10e1. [16] Hampson LA, McAninch JW, Breyer BN. Male urethral strictures and their management. Nat Rev Urol 2014;11(1): 43e50. [17] Diamond DA, Xuewu J, Bauer SB, Cilento Jr BG, Borer JG, Nguyen H, et al. What is the optimal surgical strategy for bulbous urethral stricture in boys? J Urol 2009;182:1755e8. [18] Hsiao KC, Baez-Trinidad L, Lendvay T, Smith EA, Broecker B, Scherz H, et al. Direct vision internal urethrotomy for the treatment of pediatric urethral strictures: analysis of 50 patients. J Urol 2003;170:952e5. [19] Gargollo PC, Cai AW, Borer JG, Retik AB. Management of recurrent urethral strictures after hypospadias repair: is there a role for repeat dilation or endoscopic incision? J Pediatr Urol 2011;7:34e8. [20] Dutkiewicz SA, Wroblewski M. Comparison of treatment results between holmium laser endourethrotomy and optical internal urethrotomy for urethral stricture. Int Urol Nephrol 2012;44:717e24.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
MODEL
Journal of Pediatric Urology (2015) xx, 1.e1e1.e6
Use of holmium laser for urethral strictures in pediatrics: A prospective study
a
Pediatric Urology Department, Abu El Rish Children Hospital, Cairo University, KasrAlAiny Street, Cairo, Egypt
b
Urology Department, Kasr Alainy Hospital, Cairo University, KasrAlainy Street, Cairo, Egypt Correspondence to: A. I. Shoukry, Pediatric Urology Department, Abu El Rish Children Hospital, Cairo University, KasrAlAiny Street, Cairo, Egypt, Tel.: þ201065332220
A.I. Shoukry a, W.N. Abouela a, M.S. ElSheemy a, A.M. Shouman a, K. Daw a, A.A. Hussein a, H. Morsi a, M.A. Mohsen b, H. Badawy a, M. Eissa a Summary Introduction The management of urethral strictures is very challenging and requires the wide expertise of different treatment modalities ranging from endoscopic procedures to open surgical interventions. Objective To assess the effectiveness and complications of retrograde endoscopic holmium: yttrium-aluminumgarnet laser (Ho: YAG) urethrotomy (HLU) for the treatment of pediatric urethral strictures.
ahmedshoukry@kasralainy. edu.eg (A.I. Shoukry) waseem_aboul_ela@yahoo. com (W.N. Abouela) mohammedshemy@ yahoo.com (M.S. ElSheemy) [email protected] (A.M. Shouman) [email protected] (K. Daw) ahmedalyhussein@ kasralainy.edu.eg (A.A. Hussein) [email protected] (H. Morsi) [email protected] (M.A. Mohsen) [email protected] (H. Badawy) [email protected] (M. Eissa)
Patients and Methods From January 2010 to January 2013, 29 male pediatric patients with a mean age of 5.9 years and primary urethral strictures 0.5e2 cm long were treated using HLU. The stricture length was <1 cm in 16 (55%) patients and >1 cm in 13 (45%). Fifteen (51.7%) patients had an anterior urethral stricture, while 14 (48.3%) had a posterior urethral stricture. No positive history was found in 14 (48.3%) patients for the stricture disease, while six (20.7%) had straddle trauma and nine (31%) had an iatrogenic stricture. All of the patients were pre-operatively investigated and at 3 and 6 months postoperation by uroflowmetry and voiding cystourethrography (VCUG). If there were suspicious voiding symptoms, selective uroflowmetry and VCUG were performed at 12 months postoperation.
Keywords Urethral stricture; Holmium laser; Visual internal urethrotomy; Children; Cystoscopy
Results The mean operation time was 31.7 min (20e45 min). Twenty-three (79.3%) and 18 (62.1%) patients showed normal urethra on VCUG with improvement of symptoms at 3 and 6 months, respectively. Thus, recurrence was 37.9% after 6 months of follow-up. The mean pre-operative peak urinary flow rate
Received 4 February 2015 Accepted 3 June 2015 Available online xxx
(Qmax) was 6.47 ml/s. The mean postoperative Qmax at 3 and 6 months was 17.17 ml/s and 15.35 ml/s, respectively. The success rate and flowmetry results did not show any statistical significance in relation to site, length and cause of the strictures. The other 11 patients who failed to improve underwent repeated HLU sessions: 4/11 (36.3%) achieved successful outcomes. Among the seven patients with failed HLU for the second time, a third session was conducted. However, only one patient (14.2%) was cured, while open repair was needed for the remaining six. Discussion One study has previously been published on the management of pediatric urethral strictures using HLU. The present results are similar to short-term studies after a single session of visual internal urethrotomy using cold knife (VIU). In the present study, the length, location and cause of strictures did not significantly affect the results. However, the outcomes with strictures <1 cm were better than strictures >1 cm, although patients with strictures >2 cm were excluded. In the present study, the success rates among patients with second and third sessions of HLU were 36.3% and 14.2%, respectively. This was similar to other studies, which reported low success rate with the second session of VIU. The present study was limited by the relatively short period of follow-up and the small number of patients. However, it was the first prospective study evaluating HLU for pediatric strictures. The use of flowmetry and VCUG for evaluation of all patients added to the strength of the study. Conclusion HLU can be safely used with good success rates for the treatment of primary urethral strictures (<2 cm) in children. Repeat HLU (more than twice) adds little to success.
http://dx.doi.org/10.1016/j.jpurol.2015.06.016 1477-5131/ª 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e2
A.I. Shoukry et al.
Introduction The management of urethral strictures is very challenging and requires the wide expertise of different treatment modalities ranging from endoscopic procedures to open surgical interventions. If not treated properly, pediatric urethral strictures can have a massive impact on the future life of children with them. The ultimate goal of the surgeon and patient, as well as the family, is searching for a minimally invasive procedure with a high cure rate. Several studies have been performed to assess the effectiveness of different laser modalities [1e3], including holmium: yttrium-aluminum-garnet laser (Ho: YAG) in adult urethral strictures [4]. However, for pediatric urethral strictures, only one study has previously been conducted to assess the efficacy of Ho: YAG [5]. It is believed that the present study is the first prospective study that assess the effectiveness and complications of retrograde endoscopic Ho: YAG laser urethrotomy (HLU) for treating pediatric urethral strictures.
antibiotic was pre-operatively given to all patients as a prophylaxis. An 11-Fr pediatric cystoscope (Karl Storz, Germany) was initially inserted to reach the stricture, and then a 0.035 inch guide wire or 3-Fr ureteric catheter was introduced through the stricture to the urinary bladder. Scar tissue was incised at the 12-o’clock position under the guidance of a guide wire or ureteric catheter until fresh mucosa appeared. This was performed using a 0.73 mm laser fiber (SphinX 30W, holmium-YAG laser, LISA Laser ProductseOHG, Germany) (2.75 J, 11.0 Hz). Finally, a 10-14-Fr silicone catheter was indwelled, according to age of the patient, which remained for 7 days and was then removed. None of the patients received any medical or intralesional steroid injections. Two patients were <3 years old. In all patients, the urethra accommodated the 11-Fr cystoscope. The procedure was considered successful if the patient did not report any postoperative voiding difficulty, with a postoperative maximum flow rate (Qmax) > 15 ml/s and normal VCUG. Lastly, the effects of different clinical parameters on the outcome e including length, location and cause of strictures e were analyzed.
Materials and methods Twenty-nine boys with a urethral stricture 2 cm were included in the present study from January 2010 to January 2013 using HLU. Exclusion criteria were patients who had undergone previous open urethroplasty, urethral dilatation, visual internal urethrotomy, or those presenting with diverticulum, multiple level urethral strictures or following a fractured pelvis with urethral disruption. All patients were pre-operatively investigated with history, examination, uroflowmetry and VCUG (Fig. 1 and Fig. 2). They were followed up with urine analysis and culture, uroflowmetry and VCUG at 3 and 6 month postoperation. If there were suspicious voiding symptoms, selective uroflowmetry and VCUG were performed at 12 months postoperation. All patients were toilet trained and could void upon request to perform the uroflowmetry. Stricture location was categorized as posterior (membranous) or anterior (penile (six patients) or bulbar (nine patients)) urethral stricture.
Surgical technique Under general anesthesia, all patients were placed in the lithotomy position. A third-generation cephalosporin
Figure 1
Statistical method Statistical analysis was performed using the statistical package SPSS version 15 (IBM, USA). Statistical differences between groups were tested using the Chi-squared test, Nonparametric ManneWhitney test, Wilcoxon signed-rank test, KruskaleWallis test and Friedman test. A P-value <0.05 was considered to be statistically significant.
Results The pre-operative data and different causes of urethral strictures are presented in Table 1. The mean age was 5.9 years (median 5.0, range 2e13 years). All patients presented with obstructive symptoms. The period from the onset of urethral stricture to time of treatment was difficult to precisely identify as most patients were without clear cause (48.3%). However, this period ranged from 3 to 6 months in the remaining patients (iatrogenic and traumatic patients). The mean operative time was 31.7 6.2 min (range 25e45, median 30 min). The operative time was longer in
Uroflowmetry of one of the patients.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
Holmium laser for urethral strictures in pediatrics
1.e3 Table 1
Pre-operative data. Patients, n (%)
Figure 2 Pre-operative ascending cystourethrogram of one of the patients.
the initial patients then gradually decreased with the improving learning curve. Four patients (13.8%) had intraoperative complications: two were bleeding per urethra, which was stopped by mild perineal compression, fixing a urethral catheter and tying a gauze around it and pushing it proximally so it compresses the penis mildly for around 15 min; two had urethral extravasation, which was complicated by penile edema at the end of the procedure e this subsided a couple of days afterwards while giving antiinflammatory drugs. All patients were followed up for at least 12 months. Success was achieved in 23 (79.3%) and 18 (62.1%) patients at 3 and 6 months postoperation, respectively. Thus, recurrence rate was 37.9% after 6 months of follow-up. The peak urinary flow rate (Qmax) showed significant improvement at 3 and 6 months postoperation (Table 2). The effect of different factors on the success (flowmetry and VCUG) was analyzed at 3 and 6 months postoperation (Table 3) (Fig. 3). The outcomes with strictures <1 cm and posterior urethral strictures were better than strictures >1 cm and anterior urethral strictures, respectively. However, the difference was not statistically significant (Table 3). There was also no significant difference in the postoperative Qmax and success rate according to cause of stricture. There was also no correlation between ages of the patients or the stricture cause with the percent change of Qmax. The 11 patients with failure (six primary failure at 3 months and five recurrent failure at 6 months) had repeated HLU sessions. Among these patients, four (36.3%) achieved successful outcomes. Among the seven patients with failed HLU for the second time, a third session was conducted. However, only one patient (14.2%) improved, while open repair was required for the remaining six. Thus, the success rate after the second session increased to 75.8% (22 patients), while it increased to (79.3%) after the third
Length of stricture 0.5e0.9 cm 1e2 cm Site of stricture Anterior urethraa Posterior (membranous) urethra Etiology: Unknown cause Straddle traumab Iatrogenic PUV fulguration Catheter fixation Urethral diverticulectomy Hypospadias repairc Stone bladder Failed trial of catheterization Qmax, mean (range) Site of stricture: Anterior urethra Posterior urethra Length of stricture 0.5e0.9 cm 1e2 cm Etiology: Unknown cause Straddle traumab Iatrogenic
16/29 (55.2%) 13/29 (44.8%) 15/29 (51.7%) 14/29 (48.3%) 14/29 (48.3%) 6/29 (20.7%) 9/29 (31%) 2 (6.3%) 2 (12.4%) 1 (3.1%) 2 (6.3%) 1 (3.1%) 1 (3.1%)
5.58 (3e9) ml/s 7.35 (4e10) ml/s 7.14 (5e10) ml/s 5.7 (3e8) ml/s 6.22 ml/s 6.83 ml/s 6.64 ml/s
a Anterior urethral strictures included three penile and 12 bulbous strictures. b Straddle trauma is a urethral stricture resulting from straddle trauma (blunt perineal trauma). c One patient had proximal penile hypospadius (treated by tubularised incised plate), while the second patient had penoscrotal hypospadias (treated in two stages).
session (23 patients). The follow-up ranged from 12 to 15 months starting from the first session. However, the followup after the second and third session was limited (3e9 months). At 12 months postoperation, the success rate remained (subjectively evaluated by clinical symptoms) at 62.1%. Open repair was in the form of: staged buccal grafts for two penile strictures; resection with end-to-end anastomosis for one bulbar stricture <1 cm; ventral buccal graft for one bulbar stricture >1 cm; and resection with end-toend anastomosis for two posterior strictures.
Discussion Urethral stricture is one of the most challenging urological problems. Traditional treatment options include metal dilatation, visual internal urethrotomy using cold knife (VIU) and open surgical urethroplasties. The VIU has shown a wide range of success rates from 21 to 87% [6e9]. Although open urethroplasties have shown very high success rates (85e93%) [10,11], minimally invasive procedures
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e4 Table 2
A.I. Shoukry et al. Pre-operative and postoperative flowmetry.
Qmax (ml/s)
Pre-operativea
3 months postoperationb
6 months Postoperationb
P-value
Mean (range) Median
6.47 (3e10) 6.1
17.17 (5e25) 19.0
15.35 (5e25) 19.5
<0.001*
*Significant (Friedman test). a There was significant difference between pre-operative Qmax and both 3 (P < 0.001) and 6 months (P < 0.001) postoperation (Wilcoxon signed ranks test). b There was no significant difference between the 3- and 6-month postoperative Qmax (P Z 0.272) (Wilcoxon signed ranks test).
are still preferred, and widely practiced, by many surgeons and patients, as they offer shorter convalescence and hospitalization time, thus allowing patients to return to full occupational activity in a shorter time [12]. In the hope of reducing the high re-stricture rate of the conventional VIU by both cutting and vaporizing the scar tissue, many studies have used different types of laser for urethrotomy [1e3]. The fibrosis and re-stricture after urethrotomy is affected by the thermal effect and absorption of the energy by tissues. The Ho: YAG laser displays the shallowest absorption (0.5 mm) with the least scar formation when compared with other medical lasers including the Nd:YAG (neodymium-doped yttrium aluminium garnet), potassium-titanyl-phosphate (KTP), argon and diode laser, in which the depth of absorption by tissues may reach 5 mm [13e16]. However, Hampson et al. reported that there is no clear consensus as to which laser is best to use. Overall, data seem to show equivalence in terms of both complication and success rates for these different lasers and urethrotomy techniques [16]. One study, by Sun et al., has been published on the management of pediatric urethral strictures using HLU in 28 patients [5]. The average age was 5.1 years (range 2e14), which is similar to the present study. Hypospadias repair was the cause of stricture in 19 patients, while pelvic and perineal traumas were the causes of nine strictures, as reported by Sun et al. [5]. This is different from the present study, as most patients were without a clear cause (14 patients), while hypospadias was the cause in two patients. In the Sun study, the length of strictures ranged from 0.1 to
Table 3
2.5 cm, with an average of 0.6 cm. Seventeen patients had the lesions <0.5 cm; five had lesions from 0.5 to 2.0 cm; and four had lesions >2.0 cm [5]. This is similar to the present study, but in the present study there were no strictures >2 cm or <0.5 cm. In the Sun study, the strictures were located in the posterior urethra in nine patients and in the anterior urethra in 17 [5]; the distribution of strictures in the present study between the anterior and posterior urethra was similar. Sun et al. excised the scar tissue at the positions of 4, 8, and 12-o’clock [5], but the 12-o’clock position was preferable in the present study. The average operative time was 44 min (range 15e120 min) as reported by Sun et al., which was longer than the present study, although they had more patients with short strictures (<0.5 cm). There were no intraoperative complications in the study by Sun et al., but in the present study there were four complications, which were conservatively treated. Of the 28 patients in the Sun study after initial incision, 25 (89.3%) achieved satisfactory results without complications [5]. This is better than the present study (62%), which may be due to the presence of 17 patients in the Sun study with strictures <0.5 cm [5]. The present results are similar to short-term studies (50e53%) after a single session of VIU for treatment of pediatric urethral strictures [17,18]. However, Hafez et al. noted a long-term success rate of 36% after initial VIU in 31 children, which increased to 58% after repeat incision. They recommended one trial only followed by open repair, if initially unsuccessful [6]. In a recent study, Launonen et al. reported a final success rate of 71%
Effect of different factors on success and flowmetry.
Follow-up
Length of stricture: 0.5e0.9 cm 1e2 cm P-value Site of stricture: Anterior urethra Posterior urethra P-value Cause of stricture: Negative history Straddle trauma Iatrogenic P-value
Success at 3 months postoperation, n (%)
Success at 6 months postoperation, n (%)
Qmax 3 months postoperation, mean (range) (ml/s)
Qmax 6 months postoperation, mean (range) (ml/s)
14 (87.5%) 9 (69.2%) (P Z 0.364)
12 (75%) 6 (46.2%) (P Z 0.143)
18.73 (6e25) 15.38 (5e24) (P Z 0.079)
17.47 (6e25) 12.92 (5e23) (P Z 0.105)
11 (73.3%) 12 (85.7%) (P Z 0.651)
9 (60%) 9 (64.3%) (P Z 0.812)
16.07 (5e25) 18.28 (5e25) (P Z 0.356)
14.8 (5e24) 15.8 (5e25) (P Z 0.781)
11 (78.6%) 5 (83.3%) 7 (77.8%) (P Z 0.96)
8 (57.1%) 3 (50.0%) 7 (77.8%) (P Z 0.48)
16.71 (5e25) 19.00 (6e25) 16.63 (6e23) (P Z 0.501)
14.50 (5e25) 14.83 (6e24) 17.25 (6e23) (P Z 0.538)
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
Holmium laser for urethral strictures in pediatrics
Figure 3 Postoperative ascending cystourethrogram of one of the patients.
after repeated VIU in 34 pediatric patients; the stricture length was >2 cm in five patients (15%). In the KaplaneMeier analysis, the stricture recurrence rates at a 2- and 5-year follow-up were 53e78% and 67e78%, respectively, after each VIU or dilatation under general anesthesia [9]. Among the three recurrent patients (10.7%) reported by Sun et al., two were successfully treated by another HLU session and open end-to-end anastomosis, while the last patient failed to follow-up. The length of lesion was the major factor of re-stenosis, as the recurrence rate was 75% in the four children with lesions >2 cm [5]. In another study using HLU in 32 male patients, Kamp et al. reported that long segment (>1.5 cm) strictures were a risk factor for recurrence. However, the location of the stricture had no impact on the success of treatment [14]. In the present study, the length, location and cause of strictures did not significantly affect the results. However, the outcomes with strictures <1 cm were better than strictures >1 cm, although patients with strictures >2 cm were excluded. Similarly, Launonen et al. found no significant difference in the outcome of VIU according to cause or location of strictures in children, but they reported poor results when the length of stricture >2 cm [9]. In the present study, the success rates among patients with second and third sessions of HLU were 36.3% and 14.2%, respectively. This was similar to other studies, which have reported low success rate (17%) of the second session of VIU in pediatric strictures [19]. Although some surgeons might not attribute repeated sessions of VIU for causing difficulties in subsequent open surgeries, several studies have attempted it. In a recent study, Launonen et al. reported that single VIU was successful in 25% of the patients. In strictures <2 cm, up to three VIUs can be attempted, but longer strictures need open correction if the patient does not wish to follow the home dilatation program [9]. Kamp et al. evaluated HLU in 32 male patients, the strictures ranged in length from 0.5 to 4 cm, with a mean of 1.5 cm. It was recurrent in 62.5% of patients, but most (68.7%) did not need any intervention. The success rate increased to 75%
1.e5 after repeat HLU. Most of the recurrences appeared within the first 12 months [14]. Dutkiewicz et al. compared HLU with VIU in the treatment of primary or refractory urethral strictures <3 cm in 50 men aged 17e78 years. Neither complication rate nor degree of efficacy revealed a significant difference between HLU and cold knife [20]. The present study was limited by the relatively short period of follow-up and the lack of a control group. Additionally, the small number of patients, together with different causes and locations of strictures, affected the statistical significance and prevented multivariate analysis due to small subgroups. However, the present study was the first prospective study evaluating HLU for pediatric strictures. The use of flowmetry and VCUG for pre-operative evaluation of all patients, and at the third and sixth months postoperation adds to the strength of the study. To help the choice of the proper modality for treatment for pediatric urethral strictures, further randomized studies with a larger number of patients are needed to compare VIU with HLU after a longer period of follow-up in selective sites and sizes of strictures.
Conclusion HLU can be safely used, with good success rates, for the treatment of primary urethral strictures (<2 cm) in children. It is a minimally invasive, simple and reproducible technique with results comparable to those of the adult population and the conventional cold knife urethrotomy. Repeat HLU (more than twice) adds little to success. However, randomized studies against VIU are necessary.
Conflict of interest None.
Funding None.
References [1] Smith JA, Dixon JA. Neodymium: YAG laser treatment of benign urethral strictures. J Urol 1984;131:1080e1. [2] Rothauge CF. Urethroscopic recanalization of urethral stenosis using argon laser. Urology 1980;16:158e61. [3] Turek PJ, Malloy TR, Cendron M, Carpiniello VL, Wein AJ. KTP532 laser ablation of urethral strictures. Urology 1992;40: 330e4. [4] Hussain M, Lal M, Askari SH, Hashmi A, Rizvi SAH. Holmium laser urethrotomy for treatment of traumatic stricture urethra: a review of 78 patients. J Pak Med Assoc 2010;60:829e32. [5] Sun F, Zhang W, Zhuang Y, Dong Q, Li A. Application of endoscopic Ho:YAG laser incision technique treating urethral strictures and urethral atresias in pediatric patients. Pediatr Surg Int 2006;22:514e8. [6] Hafez AT, El-Assmy A, Dawaba MS, Sarhan O, Bazeed M. Longterm outcome of visual internal urethrotomy for the management of pediatric urethral strictures. J Urol 2005;173:595e7. [7] Noe HN. Long-term follow-up of endoscopic management of urethral strictures in children. J Urol 1987;137:951e3.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016
+
MODEL
1.e6 [8] Duel BP, Barthold JS, Gonzalez R. Management of urethral strictures after hypospadias repair. J Urol 1998;160:170e1. [9] Launonen E, Sairanen J, Ruutu M, Taskinen S. Role of visual internal urethrotomy in pediatric urethral strictures. J Pediatr Urol 2014;10(3):545e9. [10] Micheli E, Ranieri A, Peracchia G, Lembo A. End-to-end urethroplasty: long-term results. BJU Int 2002;90:68e71. [11] Barbagli G, Palminteri E, Lazzeri M, Guazzoni G, Turini D. Long-term outcome of urethroplasty after failed urethrotomy versus primary repair. J Urol 2001;165:1918e9. [12] Bullock TL, Brandes SB. Adult anterior urethral strictures: a national practice patterns survey of board certified urologists in the United States. J Urol 2007;177:685e90. [13] Matsouka K, Inoue M, Iida S, Tomiyasu K, Noda S. Endoscopic antegrade laser incision in the treatment of urethral stricture. Urology 2002;60:968e72. [14] Kamp S, Knoll T, Osman MM, Kohrmann KU, Michel MS, Alken P. Low-power holmium:YAG laser urethrotomy for treatment of urethral strictures: functional outcome and quality of life. J Endourol 2006;20(1):38e41.
A.I. Shoukry et al. [15] Smith Jr JA, Stein BS, Benson RC. Lasers in Urologic Surgery. 3rd ed. St Louis: CV Mosby; 1994. p. 10e1. [16] Hampson LA, McAninch JW, Breyer BN. Male urethral strictures and their management. Nat Rev Urol 2014;11(1): 43e50. [17] Diamond DA, Xuewu J, Bauer SB, Cilento Jr BG, Borer JG, Nguyen H, et al. What is the optimal surgical strategy for bulbous urethral stricture in boys? J Urol 2009;182:1755e8. [18] Hsiao KC, Baez-Trinidad L, Lendvay T, Smith EA, Broecker B, Scherz H, et al. Direct vision internal urethrotomy for the treatment of pediatric urethral strictures: analysis of 50 patients. J Urol 2003;170:952e5. [19] Gargollo PC, Cai AW, Borer JG, Retik AB. Management of recurrent urethral strictures after hypospadias repair: is there a role for repeat dilation or endoscopic incision? J Pediatr Urol 2011;7:34e8. [20] Dutkiewicz SA, Wroblewski M. Comparison of treatment results between holmium laser endourethrotomy and optical internal urethrotomy for urethral stricture. Int Urol Nephrol 2012;44:717e24.
Please cite this article in press as: Shoukry AI, et al., Use of holmium laser for urethral strictures in pediatrics: A prospective study, Journal of Pediatric Urology (2015), http://dx.doi.org/10.1016/j.jpurol.2015.06.016