Stesura Seveso


Archivio Italiano di Urologia e Andrologia 2020; 92, 2149

ORIGINAL PAPER

Comparison of the efficiency, safety and pain scores 
of holmium laser devices working with 20 watt 
and 30 watt using in retrograde intrarenal surgery:
One center prospective study
Sercan Sari 1, Mehmet Çağlar Çakici 2, İbrahim Güven Kartal 2, Volkan Selmï 1, Harun Özdemïr 3, 
Hakkı Ugur Ozok 4, Ahmet Nihat Karakoyunlu 2, Serkan Yildiz 5, Emre Hepşen 6, Serra Ozbal 7,
Hamit Ersoy 2

1 Bozok University, Department of Urology,Yozgat, Turkey;
2 University of Health Sciences, Dışkapı Yıldırım Beyazıt Training and Research Hospital, Department of Urology, Ankara, Turkey;
3 University of Health Sciences, Haseki Training and Research Hospital, Istanbul, Turkey;
4 Karabuk Unıversity, Department of Urology, Karabuk, Turkey;
5 Siirt State Hospital, Department of Urology, Siirt, Turkey;
6 Çubuk State Hospital,Department of Urology, Ankara,Turkey;
7 University of Health Sciences, Dışkapı Yıldırım Beyazıt Training and Research Hospital, Department of Radiology, Ankara, Turkey.

Objectives: Holmium:Yttrium Aluminum
Garnet laser lithotripsy is used in Retrograde

Intrarenal Surgery. Fragmentation is made with a certain value
of pulse energy (Joule) and frequency (Hertz) in Holmium laser
lithotripsy and the multiplication of these values gives us total
power (Watt). Devices with maximum power of 20 Watt and 30
Watt are used in clinical practice. We want to compare the effi-
ciency, safety and pain scores of the lithotripsy made below 20
Watt and over 30 Watt with 30 Watt laser device. 
Materials and methods: 60 patients who had 2-3 cm sized kidney
stones and operation planned were prospectively divided into
three groups. Groups were random identified. In the first group,
fragmentation was performed below 20 Watt power with 20
Watt laser device. In the second group, fragmentation was per-
formed below 20 Watt power with 30 Watt laser device. In the
third group, fragmentation was performed over 20 Watt power
with 30 Watt laser device. Demographic, stone, intraoperative
and postoperative data were recorded. We compared these
groups regarding efficiency, safety and pain score.
Results: For demographic and stone data, there was a statistical-
ly significant difference only for stone number. For intraopera-
tive and postoperative data, there was a statistically significant
difference only for ureteral access sheath usage between the
groups. Success was lower than the other groups in Group 1. 
Conclusions: Success was higher in groups using 30 Watt laser
device. There was not statistically significantly difference
between complications and pain. 30 Watt laser device is safe and
efficient in Retrograde Intrarenal Surgery.

KEY WORDS: Comparison; Efficiency; Kidney stone; Pain; 
Safety; Watt.

Submitted 16 December 2019; Accepted 23 Decembe 2019 

Summary

No conflict of interest declared.

DOI: 10.4081/aiua.2020.2.149

INTRODUCTION
The increasing incidence of kidney stone disease caused
the increasing number of lithotripsy in urology clinics
(1). Retrograde intrarenal surgery (RIRS) is a new
method. Its usage recently widened with advances of
technology (2). Holmium:Yttrium Aluminum Garnet

(Ho:YAG) laser lithotripsy is a lithotripsy method used
in RIRS. Ho:YAG laser lithotripsy fragments stone with
the photothermal mechanism (3). In Ho:YAG laser
lithotripsy fragmentation is made with a certain value of
pulse energy (Joule/J) and frequency (Hertz/Hz.). 
The multiplication of these values gives us total power
(Watt/W). In clinical practice, the device with the maxi-
mum power of 20 W was at first available. Recently the
device with maximum power of 30 W has been used. In
our study, we used these two devices. We want to com-
pare efficiency, safety and pain scores of the lithotripsy
made below 20 W and over 30 W with 30 W laser device. 

MATERIALS AND METHODS
After receiving local ethical board approval, a randomized
prospective study was planned. Study was recorded into
National Clinical Trials (NCT) and NCT code was taken
(NCT 02443909). Sixty patients who had 2-3 cm sized
kidney stones and for whom RIRS was planned were
divided into three groups. Groups were random identified.
Informed consent was obtained from all individual partic-
ipants included in the study. All procedures performed in
studies involving human participants were in accordance
with the ethical standards of the institutional and/or
national research committee and with the 1964 Helsinki
declaration and its later amendments or comparable ethi-
cal standards. Blood count, biochemical tests, coagulation
tests, urine analysis, urine culture, kidney ureter bladder X-
graphy (KUBG), urinary system ultrasonography (US),
 computerized tomography (CT) were preoperatively per-
formed. Patients age, gender, body mass index (BMI), his-
tory of shock wave lithotripsy (SWL), American Society of
Anesthesiologists (ASA) score, previous stone surgery histo-
ry, preoperative double J stent (JJ) history, anticoagulant
usage, kidney anomaly, stone laterality, stone number,
stone size and stone localization were recorded. 



150Archivio Italiano di Urologia e Andrologia 2020; 92, 2

Comparison of 20 Watt 30 Watt laser devices

Preoperative urine culture was sterile
Patients were taken Dexketoprofen Trometamol twice a
day as the analgesic and anti-inflammatory treatment
after the operation. Visual analogue scale (VAS) was filled
at postoperative eighth hours by patients. Patients
marked the value equal to his/her pain in the VAS. The
marked value was recorded. Intraoperative operation
time, scopy time, postoperative JJ stent rate, ureteral
access sheath (UAS) usage, hospitalization time and com-
plications were recorded. Complications were evaluated
according to modified Clavien and Dindo classification. 
The patients who had kidney anomalies, were < 18 years
old, had urinary system infections in the preoperative
evaluations were excluded from the study. The patients
were divided into three groups. In the first group, frag-
mentation was performed below 20 W power with 20 W
laser device. In the second group, fragmentation was
performed below 20 W power with 30 W laser device. In
the third group, fragmentation was performed over 20 W
power with 30 W laser device. We used dusting and
fragmentation methods in our study. 
Preoperative antibiotic was administered to all patients.
RIRS was performed under general anesthesia with 7.5
French (Fr) flexible renoscope (Flex-X2; Karl Storz,
Tutlingen, Germany). After general anesthesia in modified
supine position, the patient was taken to modified dor-
sal lithotomy position. Semi-rigid ureterorenoscope was
applied into the ureter under fluoroscopic control and
0.035/0.038 inch hydrophilic safety wire was placed into
the ureter under fluoroscopic control. Semi-rigid
ureterorenoscopy was performed. In case of semirigid
ureterorenoscopy failure due to ureteral stricture, JJ stent
was placed and the operation ended. After semirigid
ureterorenoscopy, 9.5-11.5 Fr or 11-13 Fr access sheath
(Elit Flex, Ankara, Turkey) was placed into the ureter up
to the ureteropelvic junction under fluoroscopic control.
Then flexible renoscope was placed through the UAS to
provide access to the kidney. When access sheath was
not placed, flexible renoscope was moved via safety wire
to access the kidney. Fragmentation
was performed via 200 mm: Yttrium
Aluminum Garnet laser probe (Dornier
Medilas H20 and HSolvo; Medtech,
Munich, Germany) after the stone had
been reached. In Group 1 and 2, 8-10
Hz. frequency and 1.2-1.8 J pulse ener-
gy were used. In Group 3, 10-12 Hz.
frequency and 2-3 J pulse energy were
used. We used dusting and fragmenta-
tion methods. All calices were explored
with flexible renoscope at the end of
operation under fluoroscopic control.
JJ stent was placed into the ureter due
to intraoperative conditions. JJ stent
was taken three weeks later with an
outpatient procedure. 
KUBG and US were performed on post-
operative first day. CT was performed
at postoperative third month. Patients
who were stone free or had clinically
insignificant residual fragment (< 2
mm) after intraoperative and postoper-

ative controls, were evaluated as successful. We com-
pared groups regarding efficiency, safety and pain score.

Statistical analysis
Analysis was made with SPSS for Windows 16.0 package
program. Normality of numerical measurement values
distributions was at first researched. One-Sample
Kolmogorov-Smirnov test was used to determine the dis-
tributions of parameters except for age, BMI and opera-
tion time. The distributions were not normal (p < 0.05).
Kruskal Wallis test was used to determine whether there
was difference between two groups for gender, ASA
score, stone laterality, stone localization, stone number,
stone size, UAS usage, postoperative JJ stent usage, resid-
ual stone, scopy time, previous stone surgery history,
SWL history, intraoperative and postoperative complica-
tions, anticoagulant usage and VAS score. In the patients
with statistically significant differences in Kruskal Wallis
test, to determine from which group the difference orig-
inated in the analyze, Mann-Whitney U test was used to
perform dual comparisons. One-Way Anova test was
performed to determine whether there was a statistical
difference between the groups for age, BMI and opera-
tion time. P < 0.05 value was accepted as statistically sig-
nificant for results. 

RESULTS
When we look at demographic and stone data, there was
no statistically significant difference for the parameters
age, gender, BMI, ASA, SWL history, previous stone sur-
gery history, anticoagulant usage, preoperative JJ stent,
stone laterality, stone size and stone localization between
the groups. There was a statistically significant difference
for stone number (p = 0.036) (Table 1). 
When we evaluate intraoperative and postoperative data,
there was no statistically significant difference for opera-
tion time, scopy time, postoperative JJ stent usage and
hospitalization time. There was a statistically significant

Table 1. 
Demographic and stone characteristics.

Group 1 (n = 20) Group 2 (n = 20) Group 3 (n = 20) p
Age (years) ( ±  SD) 51.15 ± 12.58 47.75 ± 14.26 54.45 ± 14.45 0.315
Gender (M/F) (n) 8/12 14/6 12/8 0.154
BMI (kg/m2) ( ± SD) 28.57 ± 4.43 28.12 ± 4.60 26.42 ± 3.97 0.265
ASA mean (n) 1.551 1.3525 1.671 0.409
SWL history (n, %) 5 (25) 2 (10) 3 (15) 0.438
Previous surgery history (n, %) 9 (45) 5 (25) 5 (25) 0.298
Anticoagulant usage (n, %) 1 (5) 0 0 0.368
Preoperative JJ stent (n, %) 8 (40) 2 (10) 5 (25) 0.094
Stone laterality (R/L) (n) 9/11 7/13 7/13 0.758
Stone number (n) ( ±  SD) 1.85 ± 0.48 2.20 ± 0.89 1.75 ± 1.41 0.036
Stone size (mm) (± SD) 22.30 ± 3.21 22.60 ± 3.33 23.90 ± 4.09 0.56
Stone localization (n, %) 0.55
Upper calyx (n, %) 1 (5) 1 (5) 1 (5)
Lower  calyx (n, %) 6 (30) 6 (30) 5 (25)
Mid calyx (n, %) 0 0 2 (10)
Pelvis (n, %) 2 (10) 3 (15) 8 (40)
Multicaliceal (n, %) 11 (55) 10 (50) 4 (20)
M/F: Male/female; BMI: Body Mass Index; ASA: American Society of Anesthesiologists; JJ: Double J; SWL: Shock Wave Lithotripsy. 



Archivio Italiano di Urologia e Andrologia 2020; 92, 2

S. Sari, M. Çağlar Çakici, İ. Güven Kartal, V. Selmï, H. Özdemïr, H. Ugur Ozok, A. Nihat Karakoyunlu, S. Yildiz, E. Hepşen, S. Ozbal, H. Ersoy

151

difference for UAS usage between the groups. There was
no statistically insignificant difference between the
groups for VAS score (Table 2).
When we look at success, in Group 1 seven patients, in
Group 2 sixteen patients, and in Group 3 fifteen patients
were stone free. The difference was statistically significant
(p = 0.006). In Group 1 the operation was unsuccessful in
one patient due to malfunctioning of the device, in four
patients due to ureteral stricture and in eight patients due
to inability to reach the stone. In Group 2, the operation
was unsuccessful in one patient due to the malfunctioning
of the device, in three patients due to inability to reach the
stone. In Group 3, the operation was unsuccessful due to
ureteral stricture in one patient, in two patients due to
inability to reach the stone and in two patients due to
stone burden. There was not clinically insignificant resid-
ual fragment in any group (Table 2). 
Complications were seen in five patients for Group 1,
eight patients for Group 2 and four patients for Group 3
(p = 0.35). Intraoperative complications were seen in
three patients for Group 1, five patients for Group 2 and
one patient for Group 3 (p = 0.214). Postoperative com-
plications were seen in two patients for Group 1, six
patients for Group 2 and three patients for Group 3.
Bleeding was the intraoperative and postoperative asso-
ciated complication in Group 2 (Table 2).

DISCUSSION
RIRS is a method of increasing use in kidney stone treat-
ment (4). Ho:YAG laser is used in RIRS. A certain value of
frequency (Hz.) and pulse energy (J) are used in Ho:YAG
laser lithotripsy. The multiplication of these values give us
power (W). There are studies to determine optimum
power settings in Ho:YAG laser lithotripsy in the literature

(5-7). These are in vitro studies. Human
stones or stone-like material were used
in these studies. In the same power set-
tings, low frequency/high pulse energy
and high frequency/low pulse energy
were compared in these studies. In the
same power settings, the low-frequency
high pulse energy is more effective.
There are studies that report pulse ener-
gy is the major variable affecting frag-
mentation efficiency (6). Total fragmen-
tation increases as pulse energy increase
(6). The increase of pulse energy pro-
vides fast fragmentation but produces
larger fragments (6). Retropulsion
increases due to the increase of pulse
energy (7-10). As retropulsion increases,
the distance between fiber tip and stone
decreases (7) and the energy applied to
the stone decreases (11), so retropulsion
decreases fragmentation efficiency (9).
Also, the high pulse energy is associated
with fiber tip malfunctioning and this
causes low efficiency (6, 12).
When we look at literature, fragmenta-
tion speed increases as total power
increases. There are studies about low

power settings (13). In a study, shorter lithotripsy time
was reported by high power settings (2.8 J and 15 Hz.),
but there was not a comparison (14). In our study, we
aimed to compare the efficiency, safety and pain score of
the lithotripsy under 20 W and over 20 W power with two
different laser devices in the same sized stones. 
When we look at demographic and stone characteristics,
there was no statistically significant difference between
the groups except the stone number. When we look at
the operation data, there was statistically significant dif-
ference between the groups for UAS usage rate and suc-
cess. In group 1, UAS usage rate was lower than the
other groups, that may explaun the higher number of
ureteral stricture observed in Group 1. 
When success was evaluated, it was lower than the other
groups in Group 1. The inability to reach the stone was
seen in 8 patients for group 1, three patients for group 2
and two patients for group 3. The lower caliceal stone
rates were similar between the groups. Multicaliceal stones
rate was higher in group 1 and 2 than group 3. Failure due
to ureter stricture was higher in group 1 than the other
groups. This result can explain the lower success rate in
group 1. Success was higher in the group in which 30 W
laser device was used. The success rate was similar with
literature except for group 1. In group 1, due to ureter
stricture and multicaliceal stones, success was lower. 
In our study, first operation success was evaluated.
Success reached 90-95% after repeating operations in all
groups. 
There was no statistically significant difference between
the groups for complications. The increasing pulse energy
produces larger fragments (6), so larger residual fragments
were seen in group 3. Also, steinstrasse was seen in one
patient of group 3. Operation time was lower in group 3
than group 2 due to increasing pulse energy. Operation

Table 1. 
!ntraoperative and Postoperative Data.

Group 1 (n = 20) Group 2 (n = 20) Group 3 (n = 20) p
Average Operation Time (min.) ( ± SD) 52.40 ± 21.29 61.45 ± 21.60 52 ± 18.23 0.263
Average Scopy Time (Sc.) (± SD) 57.05 ± 74.40 35.85 ± 24.13 32.50 ± 21.13 0.57
Postoperative JJ stent, n (%) 19 (95) 20 (100) 19 (95) 0.368
Uretheral Access Sheath Usage, n (%) 14 (70) 20 (100) 19 (95) 0.007
Average Hospitalisation Time (± SD) (day) 1 1 1 1
Success, (n) (%) 7 (35) 16 (80) 15 (75) 0.006

Stone-free 7 (35) 16 (80) 15 (75)
Residual fragment (< 3 mm) 0 0 0

Residual fragment (≥ 3 mm) 13 (65) 4 (20) 5 (25)
VAS Score (point) (± SD) 3.30 ± 2.15 2.20 ± 1.61 2.60 ± 1.23 0.409
Complication rate, n (%) 5 (25) 8 (40) 4 (20) 0.35
Intraoperative complication 3 (15) 5 (25) 1 (5) 0.214
Mucosal Injury, n (%) 1 (5) 1(5) 0
Bleeding, n (%) 1 (5) 3 (15) 0
Malfunctioning or breakage of instruments, n(%) 1 (5) 1(5) 0
Perforation, n (%) 0 0 1 (5)
Postoperative complication 2 (10) 6 (30) 3 (15)
Fever (Clavien I), n (%) 1 (5) 2 (10) 2 (10)
Bleeding (Clavien I), n (%) 0 3 (15) 0
Urinary Tract Infection (Clavien II), n (%) 1 (5) 1(5) 0
Steinstrasse (Clavien IIIb), n (%) 0 0 1 (5)
Min: Minutes; Sec: Seconds; JJ: Double J ; VAS: Visuel Analog  Scale.



152Archivio Italiano di Urologia e Andrologia 2020; 92, 2

Comparison of 20 Watt 30 Watt laser devices

time was similar between group 1 and 3. Due to the high
number of unsuccessful patients in group 1, operation
time was lower in group 1. The complication rate is high-
er in our study when we compared it with literature data.
The fewer patient number may explain this result, there-
fore studies with larger patient number are needed. 
There was not a statistically significant difference between
the groups for VAS score. There are few studies evaluating
pain in the literature. Shoshtari et al. reported the main
cause of admission to the hospital was pain (15). Singh et
al. reported that patients undergoing RIRS had more pain
than patients undergoing SWL at postoperative first and
second day (16). Oguz et al. reported that female gender,
stone size and UAS duration time in ureter were statisti-
cally significant factors affecting pain (17). In a review
researching the effect of female gender on pain scores,
Tighe et al. observed that postoperative pain scores at first
day were higher in females (18). Although there are stud-
ies that report postoperative JJ stent decreases postopera-
tive pain significantly, other studies report that JJ stent
increases postoperative pain (19). In our study, postoper-
ative JJ stent rate was similar between the groups. 
A limitation of our study was the absence of stone analy-
sis. In a study, comparing Ho:YAG laser settings, differ-
ent types stones or stone-like materials were used in vitro
(5-7). Another limiting factor was the type of laser fiber
used. A study reported that fragmentation changed due
to use of different laser fiber types (6). The same laser
fiber was used in three groups. Patient number is anoth-
er limiting factor because larger patient number studies
are needed.

CONCLUSIONS
For Ho:YAG laser lithotripsy in RIRS, success was higher
in groups using 30 W laser device. There was not statisti-
cally significantly difference between complication and
pain rates. 30 W laser device is safe and efficient in RIRS.

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Correspondence
Sercan Sari, MD - sercansari92@hotmail.com
Volkan Selmi, MD - volkanselmi@hotmail.com
Bozok University, Department of Urology, Yozgat (Turkey)

Mehmet Caglar Cakici, MD - mcaglarcakici@hotmail.com
!brahim Güven Kartal, MD - igk84@hotmail.com
Ahmet Nihat Karakoyunlu, MD - nkarakoyunlu@gmail.com
Hamit Ersoy, MD - hamitersoy@gmail.com
University of Health Sciences, Dışkapı Yıldırım Beyazıt Training and 
Research Hospital, Department of Urology, Ankara (Turkey)

Harun Özdemir, MD - dr.harun-17@hotmail.com
University of Health Sciences, Haseki Training and Research Hospital, 
Istanbul (Turkey)

Hakkı Ugur Ozok, MD - drozok@gmail.com
Karabuk Unıversity, Department of Urology, Karabuk (Turkey)

Serkan Yildiz, MD - s_yildiz55@yahoo.com
Siirt State Hospital, Department of Urology, Siirt (Turkey)

Emre Hepsen, MD - emreepsen@hotmail.com 
Çubuk State Hospital,Department of Urology, Ankara (Turkey)

Serra Ozbal, MD - sozbal@gmail.com
University of Health Sciences, Dışkapı Yıldırım Beyazıt Training and Research 
Hospital, Department of Radiology, Ankara (Turkey)