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Abstract
Objective: The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser is the
standard lithotrite for ureteroscopy. This paper is to evaluate a Ho:YAG laser with a novel
effect function in vitro, which allows a real-time variation of pulse duration and pulse
peak power.
Methods: Two types of phantom calculi with four degrees of hardness were made for fragmentation
and retropulsion experiments. Fragmentation was analysed at 5 (0.5 J/10 Hz), 10 (1 J/
10 Hz), and 20 (2 J/10 Hz) W in non-floating phantom calculi, retropulsion in an ureteral model
at 10 (1 J/10 Hz) and 20 (2 J/10 Hz) W using floating phantom calculi. The effect function was
set to 25%, 50%, 75%, and 100% of the maximum possible effect function at each power setting.
Primary outcomes: fragmentation (mm3), the distance of retropulsion (cm); 5 measurements
for each trial.
Results: An increase of the effect feature (25% vs. 100%), i.e., an increase of pulse peak power
and decrease of pulse duration, improved Ho:YAG laser fragmentation. This effect was remarkable
in soft stone composition, while there was a trend for improved fragmentation with an
increase of the effect feature in hard stone composition. Retropulsion increased with
increasing effect function, independently of stone composition. The major limitations of the
study are the use of artificial stones and the in vitro setup.
Conclusion: Changes in pulse duration and pulse peak power may lead to improved stone fragmentation,
most prominently in soft stones, but also lead to increased retropulsion. This new　effect function may enhance Ho:YAG laser fragmentation when maximum power output is
limited or retropulsion is excluded.

Abstract
Background: We aimed to assess the effectiveness of semi-rigid ureteroscopy and holmium laser lithotripsy in the treatment
of impacted ureteral stones in children.
Material/Methods: We evaluated a total of 32 children under the age of 18 years treated with ureteroscopic holmium laser lithotripsy　for impacted ureteral stones between January 2005 and July 2013. Their stone-free state was defined as
the absence of any residual stone on radiologic evaluation performed 4 weeks postoperatively. Complications
were evaluated according to the modified Clavien classification.
Result: The mean patient age was 9.5±5.1 years (range 1–18 years). Seven (21.8%) of the stones were located in the
proximal ureter, 9 (28.2%) were in the mid-ureter, and 16 (50%) were in the distal ureter. The mean stone size
was calculated as being 10.46±3.8 mm2 (range 5–20). The stone-free rate was 93.75% (30/32 patients) following
primary URS. Additional treatment was required for only 2 (6.25%) of the patients. After the procedure, a
D-J stent was placed in all the patients. The total complication rate was 15.6% (5 patients). The 10 total complications
in these 5 patients were 5 (15.6%) Grade I, 1 (3.1%) Grade II, 2 (6.25%) Grade IIIa, and 2 (6.25%)
Grade IIIb. The mean follow-up period was 16.5 months (range 3–55).
Conclusions: For the treatment of impacted ureteral stones in children, holmium laser lithotripsy with semi-rigid ureteroscopy,
with its low retreatment requirement and acceptable complication rates, is an effective and reliable method
in experienced and skilled hands as a first-choice treatment approach.

Abstract
Objective: To compare the success rates and complications of Lithoclast® and holmium laser-assisted ureterorenoscopy (URS) in managing upper-ureteral stones.

Material and Methods: We retrospectively analyzed the records of 394 patients with upper-ureteral stone who underwent ureteroscopic lithotripsy at our institution from January 2000 to December 2005. In 193 patients (mean stone size 12.3 mm), pneumatic lithotripsy was used; in 201 patients (mean stone size 11.5 mm), laser lithotripsy was performed. Patients were monitored as outpatients at 2 weeks, at 3 months, and then annually with a kidneys, ureters, and bladder radiograph and ultrasonography. Patients with migrated stones or incomplete clearance underwent an auxiliary procedure such as shockwave lithotripsy (SWL) or repeated URS. Follow-up ranged from 6 to 24 months.

Results: Fragmentation of stones to fine pieces that pass eventually was assessed at 2 weeks. This did not include proximal migration of a stone or fragments that required auxiliary treatment. This occurred in 166/193 (86.01%) patients in the Lithoclast group and in 195/201 (97.01%) in the laser group. Ureteral perforations were nine in the Lithoclast group and six in the laser group. Auxiliary procedures included SWL (27/193 [13.98%] patients in the Lithoclast group and 4/201 [1.99%] patients in the laser group) or repeated URS (two in the Lithoclast group). Urosepsis after URS occurred in 11/193 patients in the Lithoclast group and 5/201 patients in the laser group.

Conclusion: In our study, the fragmentation rates of holmium laser-assisted ureteroscopy were significantly better in the upper ureter. The complications and the need for auxiliary procedures were significantly less for holmium laser-assisted ureteroscopy when compared with pneumatic lithotripsy.

Abstract
Objectives:
To evaluate the impact of age, stone size, location, radiolucency, extraction of stone fragments, size of ureteroscope and presence and degree of hydronephrosis on the efficacy and safety of holmium:YAG (Ho:YAG) laser lithotripsy in the ureteroscopic treatment of ureteral stones in children.

Methods:
Between October 2011 and May 2013, a total of 104 patients were managed using semirigid Ho:YAG ureterolithotripsy. Patient age, stone size and site, radiolucency, use of extraction devices, degree of hydronephrosis and size of ureteroscope were compared for operative time, success and complications.

Results
In all, 128 URS were done with a mean age of 4.7 years. The mean stones size was 11 mm. Success rate was 81.25 %. Causes of failure were 12.5 % access failure, 1.5 % extravasation and 4.7 % stone migration. Overall complications were 23.4 %. Failure of dilatation and extravasation were detected only in children <2 years old. Extravasation was significantly higher in smaller ureters and cases with stone size >15 mm. Stone migration was significantly higher in upper ureteric stones.

Conclusions:
Failure and complications rates in Ho:YAG ureterolithotripsy were significantly affected by younger age (<2 years), upper ureteric stones and smaller ureters but were not related to stone radiolucency or degree of hydronephrosis. Larger stones (>15 mm) were associated with increased complications. After multivariate analysis, the age of the patients remained significant predictor for failure of dilatation and stone migration, while size of the ureter was the only significant predicting factor for failure.

Keywords:
Holmium laser Intracorporeal lithotripsy Stones Endourology Children

Abstract
Objective:
To study the effectiveness of two laser techniques clinically used to fragment renal stones: fragmenting technique (FT) and popcorn technique (PT).

Methods:
Phantom stones were placed in a test tube filled with water, mimicking a renal calyx model. A Holmium:YAG laser was used for fragmentation using both techniques. Four series of experiments were performed with two parameters: the technique (FT or PT) and the number of stones in the test tube (one or four). The mass decrease of the phantom stones was measured before, during, and after the experiment to quantify the effect of both techniques.

Results:
Visualization of PT showed that the main effect of PT takes place, when the stone moves in front of the laser fiber and is subject to direct radiant exposure. Both FT and PT resulted in a decrease in stone weight; the mass decrease of the stones subjected to FT exceeded that of the stones subjected to PT, even with less laser energy applied. This difference in mass decrease was evident in both the experiments with one and four stones.

Conclusions:
PT was less effective in decreasing stone weight compared with FT. The FT is more effective regarding the applied energy than PT, even in a shorter time period and regardless of the number of stones. This study suggests that FT is to be preferred over PT, when stones are accessible by the laser fiber. Lasers Surg. Med. 49:698–704, 2017. © 2017 Wiley Periodicals, Inc.

Abstract
Background and Purpose: Holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy is the standard lithotrite in ureteroscopy. We investigated the influence of pulse frequency, energy and length on the fragmentation efficiency of Ho:YAG laser lithotripsy in non-floating artificial stones in vitro.

Materials and Methods: Stone fragmentation efficiency of three different Ho:YAG laser devices were evaluated in vitro at different pulse energy (1.0 and 2.0 J) and frequency settings (5 and 10 Hz), resulting in a standardized output power of 10W, respectively. Where possible, pulse length was modified (350 vs 700 μsec). Each setting was performed with a 273 μm and a 365 μm fiber. Lithotripsy was conducted using non-repulsive stones consisting of soft stone (plaster of Paris) and hard stone composition (Fujirock type 4).

Results: Our results showed an increased stone disintegration efficiency at higher pulse energy (2.0 J/5 Hz vs 1.0 J/10 Hz) independently of two fiber diameters and stone types applied in this study (P < 0.05 in 18 of 20 groups). Similarly, reduction of the pulse length from 700 to 350 μsec resulted in a higher stone disintegration (P < 0.05 in 13 of 16 groups). This effect was most prominent when applied to soft stones. Higher fiber diameter was not constantly associated with an increase in stone disintegration.

Conclusion: We demonstrate that an increase of pulse energy and a reduction of pulse length at a standardized output power of 10W can improve Ho:YAG laser fragmentation efficiency in vitro in nonfloating stones. These results may potentially affect clinical practice of Ho:YAG laser lithotripsy in impacted or large stones, when retropulsion is excluded.

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-aluminum-garnet laser (Ho: YAG) urethrotomy (HLU) for the treatment of pediatric urethral strictures.

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 0.5–2 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.

Results:
The mean operation time was 31.7 min (20–45 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 (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.

Abstract
Objective:
Treatment options for urolithiasis in children include URSL and RIRS. Various types of energy are used in the disintegration of deposits in these procedures. We decided to evaluate the usefulness of URSL and RIRS techniques and compare the effectiveness of pneumatic lithotripters and holmium lasers in the child population based on our experience.
Materials and Methods:
One hundred eight (108) children who underwent URSL and RIRS procedures were enrolled in the study and divided into two (2) groups according to the type of energy used: pneumatic lithotripter versus holmium laser. We evaluated the procedures’ duration and effectiveness according to the stone-free rate (SFR) directly after the procedure and after fourteen (14) days and the rate of complications. Results. The mean operative time was shorter in the holmium laser group. A higher SFR was observed in the holmium laser but it was not statistically significant in the URSL and RIRS procedures. The rate of complications was similar in both groups.
Conclusions:
The URSL and RIRS procedures are highly efficient and safe methods. The use of a holmium laser reduces the duration of the procedure and increases its effectiveness in comparison with the use of a pneumatic lithotripter.

Objective:　We conducted a study to detect, quantify and compare irrigation fluid absorption in transurethral resection of the prostate (TURP) and Holmium laser enucleation of the prostate (HoLEP), using BEC.

Materials and Methods:　The study included 50 patients of lower urinary tract symptoms, secondary to benign enlargement of prostate. The patients were nonrandomly allocated to undergo TURP and HoLEP. Twenty-six patients underwent TURP and the remaining 24 underwent HoLEP. Sterile water tagged with 1% ethanol w/v was used for irrigation. Absorption was detected and quantified every 10min by BEC levels. Data was analyzed using standard nomograms.

Results:　In HoLEP, 14/24 had no fluid absorption. The remaining 10/24 showed fluid absorption ranging from 95 ml to 300 ml. In TURP, all had fluid absorption ranging from 250-980 ml. Three TURP patients developed overt symptoms, while none did in the HoLEP group.

Conclusions:　Fluid absorption observed in our study in the HoLEP group was lower than in the TURP group.

Introduction & Objectives: Holmium Laser enucleation of the prostate (HoLEP) is still waiting for its break-through as an alternative to conventional transurethral resection (TUR). Although the steep learning curve is a major drawback, potentional technical problems are generally not mentioned.
Material & Methods: Starting in July 2003, 105 patients underwent HoLEP at our institution.
Initially we used an 80 W laser (Lisa Laser) with a prototype (Wolf) morcellator. In March 2006 we purchased a 100 W Versapulse (Lumenis) laser and a Versacut morcellator. Surgery was performed with an 26 Fr continuous flow resectoscope (Storz) with a specially adapted nephroscope insert. Maximum power was 80 W or 100 W. Irrigation fluid was 0,9 % saline.
In many cases tissue fragmentation was performed by traditional electrocautery loop resection
(TUR) of the free flotating devascularized lobes; in addition smaller fragments could be extracted directly with a cold (Gilling) loop.
Results: Mean operative time was 92 min. (18 - 254) for a mean prostate volume of 67 cc (15- 350 cc). Bleeding problems occured in 8 patients (7,6%) with a transfusion rate of 2.8% (3pts.). Those patients had an incomplete HoLEP and had their surgery completed by TUR. In 4
patients capsular perforation or undermining of the trigone occurred during surgery. This was uneventful in 2 cases, but 2 patients had conversion to open surgery or had postponed TUR. A
common intraoperative problem was malfunction of the (sphinx) laser system due to overheating or dysfunction of the tissue morcellator. This occured in 22% of the 27 patients (group A) with smaller (< 40 cc) glands and in 50% of the 76 patients (group B) with larger (> 40cc) glands; in those cases TUR was required to complete the surgery or for tissue fragmentation. Mean operative time varied accordingly: 63 min (group A) and 102 min (group B). Reinterventions for persisting dysuria were necessary in 29,6% of the patients in group A and in 26,3 % of the
patients in group B, mostly because of residual tissue at the apex or dorsal bladder neck. Free flotating remaining tissue was another cause in 4 patients with the larger glands. Late problems were caused by urethral stricture formation in 4 patients, adding up to an overall reintervention rate of 26,7%.
Conclusions: HoLEP has many benefits over conventional TUR in glands > 40 cc. Enucleation of smaller glands is difficult because of the lack of tissue planes; remaining tissue at the apex
or dorsal bladder neck is a frequent cause for persisting voiding problems. On the other hand enucleation of larger glands may be a real challenge due to malfunction of the laser system
(overheating) or problems with the morcellator. This means one has to create optimal conditions by using a heavy duty 100 W laser system and a functioning morcellator. A specially adapted
endoscopic equipment is equally important. Keeping this in mind will shorten the learning curve
dramatically.

Background and Objectives: The holmium laser has a　short absorption depth in tissue and possesses excellent　properties both in ablation and hemostasis. We have
performed endoscopic incision for ureteral stricture
using the holmium laser through a small-caliber ureteroscope.
Methods: This method was used on five patients andseven ureters. The etiology of the stricture was stone　scar in two patients, ureteroenteroanastomosis of Indiana　urinary pouch in two, and primary in one. We used an　8F semi-rigid or 6.9F flexible ureteroscope. No prior procedures,
such as balloon dilation, were necessary in any　of the cases. The stricture was incised with the holmium　laser using a 365-μm fiber through the working channel　of the ureteroscope. The holmium laser operated at a　wavelength of 2100 nm, with an output of 1.0J/pulse at
a rate of 10 Hz. After completion of the incision, a 12F　Double-J catheter was left in for six weeks.
Results: The mean operative time was 89 minutes. Thestricture resolved completely in all cases at an average　follow-up of 8.6 months.
Conclusions: The holmium laser incision for ureteral　stricture using a small-caliber　ureteroscope is an easy-toperform,　safe and effective procedure.

Abstract
Controversy remains on how to treat lower pole calculi between 1 and 2 cm of size. Treatment options like shock wave lithotripsy (SWL) or percutaneous stone treatment (PCNL) are associated with poor stone-free rates or high morbidity.

Due to the ongoing development in endourologic technology, especially in flexible renoscopy, laser technique and grasping devices (tipless Nitinol baskets) retrograde intrarenal surgery (RIRS) has become an option in treating these patients.

Based on personal experience and an overview of the published literature we discuss RIRS as a valuable alternative to PCNL in treating patients with larger calculi of the lower pole.

The technical developments in laser technology as well as significant improvement in flexible renoscopes have made RIRS for larger lower pole stones possible. The low complication rate gives RIRS for lower pole stones superiority over the invasive percutaneous approach, which is associated with significant morbidity, even in experienced hands.

Keywords: Lower pole calculi, percutaneous nephrolithotomy, ureterorenoscopy, urolithiasis

静脈奇形の治療法として、硬化療法、レーザ療法、外科手術等、多くの方法が適用されてきました。今日では、内視鏡レーザ手術が普及し、ほとんどの咽喉静脈奇形の治療に使用されています。さまざまな種類のレーザが適用されてきましたが、ホルミウムヤグレーザ（Hoレーザ）に関しては、まだ報告がありません。Hoレーザは、ホルミウム、クロミウム、ツリウムと混合したイットリウムアルミニウムガーネットで作られている、iraserの種類によって生成されています。本研究の目的は、成人の咽喉静脈奇形における、ホルミウムレーザ組織内治療の有効性と安全性を評価することです。過去12年間に内視鏡Hoレーザ組織内治療を受けた、咽喉静脈奇形患者42人の臨床データを、遡及的に調査・分析しました。Hoレーザ波長2.1µm、光ファイバー径550µm、パルスエネルギー0.5J、持続時間600µm、最高出力は100Wです。結果は、治癒（完全解消）、相当低減（＞60-80%低減）、明白な変化なし（＜50%低減）の3グループに格付け分類しました。病変は重篤な合併症もなく、適切に処置が行われました。病変の完全解消は95.1%、隆起部の相当低減は4.9%、合併症は4.9%の患者に見られました。呼吸トラブル、その他重篤な合併症は発生しませんでした。内視鏡Hoレーザ組織内治療は、成人の咽喉静脈奇形における、効果的かつ安全な治療法です。