Review Article
Investig Clin Urol 2021;62:121-135.
https://doi.org/10.4111/icu.20200526
pISSN 2466-0493 • eISSN 2466-054X

Retrograde intrarenal surgery: Past, present, andfutureTakaaki Inoue1,2 , Shinsuke Okada3, Shuzo Hamamoto4, Masato Fujisawa2
1

Department of Urology and Stone Center, Hara Genitourinary Hospital, Kobe, Hyogo, 2Department of Urology, Kobe University, Kobe, Hyogo, 3Department of Urology,
Gyotoku General Hospital, Ichikawa, Chiba, 4Department of Urology, Medical School, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi, Japan

With the recent technological advancements in endourology, retrograde intrarenal surgery has become a more popular procedure
for treatment of urolithiasis. Furthermore, since the introduction of new laser systems and advanced flexible ureteroscopy withminiaturized ureteroscopes, the treatment indications for retrograde intrarenal surgery have expanded to include not only larger
renal stones of >2 cm but also upper urinary tract urothelial carcinoma, ureteral stricture, and idiopathic renal hematuria. Cliniciansmust keep up with these trends and make good use of these technologies in the rapidly changing field of endourology. Simultaneously, we must consider the risk of various complications including thermal injury due to laser use, ureteral injury caused by theureteral access sheath, and radiation exposure during retrograde intrarenal surgery with fluoroscopic guidance. This review focuseson the past, present, and future of retrograde intrarenal surgery and provides many topics and clinical options for urologists toconsider.
Keywords: Flexible ureteroscopy; Kidney stone; Laser; Retrograde intrarenal surgery
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted
non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

INTRODUCTION
Current advancements in endoscopic technology forthe upper urinary tract have allowed for the diagnosis andmanagement of kidney stones, upper urinary tract urothelial carcinoma (UTUC), ureteral stricture, renal bleeding,and other disorders. In particular, these technological developments have expanded the treatment options for upper
urinary tract stones. Retrograde intrarenal surgery (RIRS),
defined as the use of flexible ureteroscopes (fURSs) and effective lithotripters such as holmium:yttrium aluminium
garnet (holmium:YAG) lasers for intrarenal pelvic diseases,
is a useful, versatile, and minimally invasive procedure forkidney stone management. The current guideline for man-agement of kidney stones includes RIRS as the first or second recommended procedure in all categories, even for largestones of >2 cm [1,2]. In addition, new instruments such as
high-power holmium:YAG lasers, thulium fiber lasers, andsingle-use ureteroscopes have been introduced for greater
safety, efficiency, and comfort for both patients and surgeons. However, various concerns have emerged in clinicalpractice, including complications, cost-effectiveness, and how
to use these new devices simultaneously [3]. As technologicaladvancements have progressed, the quality of medical carehas changed. This review provides an overview of endourological procedures, RIRS for the upper urinary tract, key
points of surgical techniques including required instruments,and future trends in this field.

Received: 12 November, 2020 • Revised: 9 December, 2020 • Accepted: 10 December, 2020 • Published online: 22 February, 2021
Corresponding Author: Takaaki Inoue https://orcid.org/0000-0002-6050-5452
Department of Urology and Stone Center, Hara Genitourinary Hospital, 5-7-17 Kitanagasadori, Chuo-ku, Kobe, Hyogo 650-0012, Japan
TEL: +81-72-804-0101, FAX: +81-72-804-0131, E-mail: inouetak@harahospital.jpⓒ The Korean Urological Associationwww.icurology.org
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Inoue et al
Table 1. The specification of current available fURSs
Company
LumenisOlympus Gyrus ACMI

Olympus

Storz
Wolf

StrykerfURS
Polyscope
DUR-8 Elite
DUR-8 Ultra
DUR-D
URF P5
URF P6
URF P7
URF V2
FLEX-X2s
FLEX-Xc
Cobra-M
Viper
Boa-vision
Cobra-vision
Flex Vision U-500

Imagingsystem
Optical
Optical
OpticalDigital
Optical
Optical
OpticalDigital
OpticalDigital
Optical
OpticalDigitalDigital
OpticalField of view Active deflection
Working
Length (mm)(°)(up/down; °)channel (Fr)
180/0
3.6
80
270/270640
3.6
80
270/270650
3.6
80250/250
650
3.6
3.6
670
275/18090
3.6
670
275/27590
3.6
670
275/27590
3.6
670
275/27580110
270/270675
3.6
90
270/270700
3.6
3.3 (dual)
680
270/27085
3.6
680
270/27086
3.6
270/270
3.6/2.4
270/27090
275/275640
3.6

Diamter(tip/shaft; Fr)
8.0/8.0
8.7/9.4
8.6/9.36
8.7/9.3
5.3/8.4
4.9/7.95
4.9/7.95
8.5/9.9
7.5/8.4
8.5/8.5
6.0/9.9
6.0/8.8
8.7/9.9/6.9/7.1

fURS, flexible ureteroscope; -, no information.

RETROGRADE INTRARENAL SURGERY
1. Past state of retrograde intrarenal surgery
1) History of the flexible ureteroscope

The first fURS, designed by Marshall [4] in 1964, wascomposed of glass fiber that was used to observe a ureteralstone through a 26-Fr cystoscope. In the early 1970s, Takagi
et al. [5] and Takayasu et al. [6] first reported the clinicalapplication of a fiberoptic pyeloureteroscope. A few years
later, Bagley et al. [7] published their first clinical outcomesof the use of an fURS for diagnosis and treatment of upper urinary tract disorders. This fURS had a 13-Fr gauge
with no working channel or integrated deflecting function.
Therefore, the developments of the fURS during that time
were mainly related to decreasing the diameter of the device
and increasing the deflection angle. In 1991, however, Grasso
et al. reported an advanced fURS with a 7.5-Fr tip and an
up 120º/down 170º deflection system. In 1998, they publisheda clinical study of 492 patients using an fURS with a larger
3.6-Fr working channel [8]. Later, in 2001, an fURS with a
two-way deflection system (270º/270º) and stronger durability was introduced to the market, improving access to thepelvicalyceal system [9]. With continued progress in technological developments thereafter, the first digital fURS was
manufactured in 2006. This digital fURS provided better
image quality and was much lighter in weight because of
the integrated light cable and camera head within the ureteroscope, which improved the surgeon’s ergonomics. In 2010,
Yinghao et al. [10] described a newly designed ureteroscopetermed “Sun’s ureteroscope” that had a rigid shaft with aflexible tip. Advancements in endourological technology

122

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have progressed to realize ureteroscopes of much smaller
diameter, stronger durability, and improved image quality.
Many fURSs from several companies can now be utilized inclinical practice (Table 1).

2) Past indications for retrograde intrarenal
surgery

Several decades ago, fURSs were used only for the observation and diagnosis of diseases in the pelvicalyceal systembecause of the lack of a useful working channel. Therefore, the indications for use of fURSs were limited. In 1986,
Streem et al. [11] first described the use of ureteropyeloscopy
for evaluation of upper tract filling defects. In 1990, Bagley
and Rivas [12] subsequently reported the diagnosis andmanagement of upper urinary tract filling defects using an
fURS. In 1994, Abdel-Razzak et al. [13] first described the performance of biopsy of upper urinary tract tissues througha small working channel in an fURS. Furthermore, Bagley
and Erhard [14] reported the first use of a holmium:YAG laser for ureteral stones through the working channel in clinical practice in 1995. Finally in 1998, Bagley [15] published thefirst ureteroscopic laser treatment of upper urinary tract tumors, which was accomplished using a holmium:YAG laser
and neodymium-doped YAG laser.
It has become possible to perform certain procedures
through the working channel, such as stone removal, since
Grasso and Bagley [8] reported an fURS with a more useful 3.6-Fr working channel. In addition, successful use of theholmium:YAG laser as a flexible lithotripter expedited thetreatment of upper urinary tract stones in the late 1990s. In
1998, Grasso et al. [16] reported the clinical outcomes of 51 pahttps://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
tients with medical comorbidities who underwent RIRS for>2-cm upper urinary tract stones. They used small-diameter
fiberoptic ureteroscopes and a holmium laser lithotripter
with a 200-micron laser fiber. The stone-free rate (SFR) was
encouraging at 76% in the first procedure and the postoperative complication rate was 6.2% [16]. Thereafter, many
endourologists increasingly utilized the fURS for treatment of upper urinary stones. Sofer et al. [17] reported theirexperience with 598 patients who underwent ureteroscopy
and holmium laser lithotripsy from 1993 to 1999. The average stone size was 11.3 mm, and 56 patients with intrarenalstones were treated using an fURS. The SFR among patientswith kidney stones was 84% with a low complication rate of
4% [17].
Until the 1990s, the definite indications for use of an
fURS were unclear with the exception of evaluating anddiagnosing certain upper urinary tract diseases. The main
clinical indications for RIRS seemed to be upper urinary
tract stones, especially kidney stones of various sizes. The advancements of fURSs and the introduction of holmium:YAG
lasers to the clinical setting have promoted progression ofurolithiasis treatment [18].

2. Present state of retrograde intrarenal surgery
1) Current flexible ureteroscope: single-use
flexible ureteroscope

The fURS has become a mainstay of treatment of nephrolithiasis with increasing indications for surgical modalities. Most fURSs were manufactured as reusable endoscopes.
However, reusable fURSs have high costs associated withproduction, maintenance, processing, sterilization, repairs,
and personnel [19]. Therefore, the cost-effectiveness decreases
if an fURS breaks during short procedures. Hennessey etal. [3] conducted an economic analysis of a single-use fURS
(LithoVue; Boston Scientific, Marlborough, MA, USA) anda reusable fURS (URF-V; Olympus, Tokyo, Japan). They
found that the cumulative cost (costs of purchase, maintenance, and repair) of 28 procedures performed with thereusable fURS was approximately $50,000 (average of $1,786
per case). The cumulative cost was lower with the singleuse fURS (approximately $35,000; average of $1,200 per case).
However, if the price of the single-use fURS were $2,500,
the 28 procedures would cost approximately $70,000. In sucha case, the reusable fURS would be more favorable from afinancial standpoint [3,20]. Although the cost-effectiveness ofa single-use fURS depends on the price of the instrument,
the cost-effectiveness of a reusable fURS is also affected by
the number of procedures in which the instrument is used.
Martin et al. [21] performed a cost assessment between asingle-use fURS (LithoVue) and reusable fURS (Flex-XC;
Karl Storz, Tuttlingen, Germany). They found that after 99
ureteroscopic procedures, the cost–benefit analysis favoredthe reusable fURS over the single-use fURS and concluded
that a single-use fURS may be cost-beneficial at centers witha lower annual case volume. However, institutions with ahigh case volume may find reusable fURSs to be more costbeneficial [21].
A single-use fURS can be very beneficial in patientswith large stones, complicated lower pole stones, anterior
lower pole stones, and an anomalous renal anatomy as wellas in training of novices, during which an fURS can be easily damaged [22,23]. Several single-use fURSs are now available for treatment of upper urinary tract diseases (Table 2).
However, although these single-use fURSs have almost thesame specifications, they have a much thicker tip and shaft
than reusable fURSs. Therefore, it is often difficult to accessthe upper urinary tract in patients with a narrow ureter
and when using a ureteral access sheath (UAS) smaller than
10 to 12 Fr. In the current era of endourology, the decision
to use a single-use or reusable fURS for treatment of upper
urinary tract disease is based on the preoperative evaluationand intraoperative findings in each case.

2) Current indications for retrograde intrarenal
surgery

The treatment indications for RIRS have been markedly

Table 2. The specification of single-use fURSs
Company

Single-use fURS

Boston Scientific
PUSEN
Neoscope Inc
YouCare TechOTU medical
Karl-Storz

LithoVue
Uscope UE3022
Neo Flex
YC-FR-A
WiscopeVideo uretero-renoscopes

Imagingsystem
CMOS
CMOS
CMOS
CMOS
CMOS

Active deflection(up/down; °)270/270
270/270
280/280
270/unilateral275/275
270/270

Workingchannel (Fr)
3.6
3.6
3.6
4.2
3.6
3.6

Length
(mm)
680
630
905
700

Diamter(tip/shaft; Fr)
7.7/9.5
9.5/9.5-/9.0-/8.0
7.4/8.6-/8.5

fURS, flexible ureteroscope; -, no information.
Investig Clin Urol 2021;62:121-135.

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Inoue et al
extended with the advancements in endoscopic technology
and lithotripters, such as laser systems. The European Association of Urology (EAU) guidelines on urolithiasis statethat RIRS can generally be applied in patients without specific contraindications, such as an untreated urinary tract
infection (UTI). The guidelines also suggest that the indications for RIRS include renal stones of <20 mm that are unsuitable for shock wave lithotripsy (SWL); an unfavorable
anatomy for SWL, such as a steep infundibular-pelvic angle,
long lower pole calyx, and narrow infundibulum; lower
pole stones of >15 mm not feasible for SWL; the patient’s
preference for kidney stone treatment; and the patient’ssocial situation (e.g., professions involving travel, such as apilot) (Fig. 1) [24,25]. The other possible indications for RIRS
in patients with kidney stones include radiolucent stones,
multiple renal stones unfeasible for SWL, treatment with
anticoagulants, coexistence of renal and ureteral stones, andbleeding disorders [25]. In general, the first recommended
treatment option for >20-mm kidney stones is percutaneous nephrolithotomy (PCNL). However, the current surgical
techniques of RIRS and laser lithotripsy make it possible toperform minimally invasive treatment for >20-mm kidneystones. In a recent systematic review and meta-analysis, theSFR of 20- to 35-mm kidney stones treated by RIRS was 71%
to 95% [26,27]. However, although it is possible for highly
skilled surgeons to successfully perform single proceduresAfor larger kidney stones, several staged procedures are usually required to achieve a stone-free status. In addition, multisession RIRS might be needed to avoid severe complicationsuch sepsis, septic shock, and longer operation time in highrisk patients with many comorbidity, infected stone as wellas larger stone >20-mm. Therefore, decisions regarding RIRS
for larger kidney stones should be made with comprehensive
consideration of various risk factors including the surgeon’s
experience, the patient’s comorbidities and preferences, andthe equipment available at the institution [28,29].

3) Favorable indications for single-use flexible
ureteroscope in retrograde intrarenal surgery

A single-use fURS has specific indications in RIRS, including large, hard kidney stones; lower pole stones with anacute infundibular-pelvic angle; anterior lower pole stones;
drug-resistant bacteria in urine culture; an anomalous renal
anatomy; and use by novice trainees. These situations easily
induce damage to the fURS during procedures. Therefore,a single-use fURS would be optimal if the surgical findings
during RIRS allow its use [30].

4) Potential indications for retrograde intrarenal
surgery

With the continued technological developments in endourology, the indications for RIRS have mainly focused onaKidney stone(middle, upper pole stone, and a part of lower pole)>20 mm

10-20 mm

<10 mm

1. PCNL
2. RIRS or SWLb
3. Laparo or open or robotic surgery(if anatomic abnomalities, requringconcomitant reconstruction, andunsuccessful endourological approach)

SWL or RIRS or PCNL

1. Active surveillance (if asymptomatic)
2. RIRS or SWL (if symptomatic)
3. PCNL

Ba

Kidney stone(lower pole stone)

10-20 mm

Unfavorable factors for SWL
1. Shock wave resistant stones
2. Steep infundibular pelvic angle
3. Long lower pole calyx
4. Narrow infundibulum
5. Long skin to stone distanceYes
1. RIRS or PCNL
2. SWL124

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No
SWL or URS or PCNL

Fig. 1. Flow chart of kidney stone management. (A) Middle, upper pole stone,
and part of lower pole. (B) Lower polestone. PCNL, percutaneous nephrolithotomy; RIRS, retrograde intrarenal surgery; SWL, shock wave lithotripsy; URS,
ureteroscopy. a:If uncorrected bleeding
diatheses or continuous anticoagulation/antiplatelet therapy, URS should
be use. b:If negligible kidney function,
nephrectomy is one of treatment.
https://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
diseases such as UTUC, ureteral stricture, and ureteropelvic
junction stenosis. One recent topic of interest is ureteroscopic
treatment of UTUC by laser ablation using a holmium:YAG
laser or thulium:YAG laser. The EAU guidelines suggest
nephron-sparing management as the primary treatment
option not only in patients with low-risk tumors (unifocal,<2 cm in size, low-grade cytology, low-grade fURS-obtained
biopsy, and no invasive aspect on computed tomographyurography) but also in patients with kidney deficiency andsevere comorbidities [31,32]. The role of RIRS in the management of UTUC will be increasingly extended in the field of
endourologic oncology.

5) Surgical steps of retrograde intrarenal surgery

Acquiring the adequate manipulation in RIRS is noteasy way. Therefore, flexible ureteroscopic experience duringresidency is important for the maintenance and development of skills, even though they appear to plateau after 1
year. Botoca et al. [33] evaluated how accumulating experience led to a satisfactory level of skills. The acceptable levelof skills was defined as the moment when the rates of success and complications showed a tendency to plateau at alevel similar to the results mentioned in the EAU guidelines[33]. The tendency to plateau appeared after approximately
50–60 procedures in the study [34]. The ureterosocopy learning curve is relatively long although we should not forgetthat individual skills may differ and each urologist may
have their own learning curve pattern. Therefore, endourological basic and advanced training such as using benchmodel or virtual reality simulator is important to promote
and keep fURS technical skill [35]. Furthermore, if making a
false step of fURS handling, they are easily damaged during
RIRS procedure, post-operative sterilization, and processing
due to quite fragile characteristics. Therefore, we should
figure out the handling methods and accomplish gentle manipulation.

(1) Role of semi-rigid ureteroscope

Semi-rigid ureteroscopes are mainly utilized for the active management of ureteral stones, direct axial dilation of
the distal ureter and ureteral strictures, and the diagnosis
of ureteral tumors. However, semi-rigid ureteroscopes arealso used in RIRS to examine the ureteral stone, check for
ureteral relaxation, and assess the extent of the lumen. Selection of an appropriately sized UAS is very important fornegotiation of the renal collecting system [36].
Karabulut et al. [37] investigated the efficacy of placing
the UAS without the obturator over a semi-rigid ureteroscope under direct vision as the technique of inserting theInvestig Clin Urol 2021;62:121-135.

UAS into the ureter in RIRS [36]. This method protects thesurgeon and patients from radiation exposure by shortening
the fluoroscopy and operating times [37].

(2) Safety guide wire

In the first published manual on endourology in 1983,
Clayman et al. [38] described the proper retrograde use of a
0.035- to 0.038-inch wire as a safety guide wire (GW). In 1987,
Ekman et al. [39] reported the first use of a safety GW ina patient undergoing ureteroscopic stone removal. During
the past three decades, the safety GW has become an indispensable device in ureteroscopic surgery for ensuring directaccess to the collecting system or ureter, decreasing loss ofdisorientation in the ureter, avoiding intraoperative complications such as ureteral injury and perforation, and facilitating insertion of a ureteral stent in cases of failed retrograde
ureteroscopic procedures. However, the use of a safety GW
increases the resistance to passage of the ureteroscope. In
particular, the presence of a safety GW interferes with manipulation of the fURS. Because of current advancements inminiaturized instruments (e.g., ureteroscope and UAS) andthe development of endourological techniques, routine intraoperative placement of a safety GW might not be needed.
Patel et al. [40] reported a 2.6% complication rate in a seriesof 268 ureteroscopic procedures without a safety GW, withno perforations or avulsions. Dickstein et al. [41] publisheda series of 305 ureteroscopic procedures, 270 (89%) of whichwere uncomplicated even without placement of a safety
GW. However, the remaining 11% of cases required a safety
GW because of obstructing ureteral stones, crushed ureteralstones, and difficult access due to an abnormal anatomy [41].
Similarly, a safety GW is not required in our institution
when performing RIRS with a UAS because the placementof a UAS in the upper ureteral portion to access the renal
pelvis substitutes for a safety GW. Therefore, insertion of a
UAS in RIRS increases ureter safety intraoperatively. However, the EAU guideline generally recommends placement ofa safety GW in accordance with best clinical practice in ureteroscopy [42]. In particular, a safety GW should be placed
for increased ureteral safety in difficult cases, such as an
impacted ureteral stone, stricture, aberrant anatomy, or tortuous ureter, as well as during training of novices.

(3) Ureteral access sheath

The f irst UAS was described as a “guide tube” by
Takayasu and Aso [43] in 1974. They utilized a UAS to accessthe proximal ureter with a rigid ureteroscope. The UAS has
become an increasingly popular instrument for treatmentof kidney stones and other diseases in the collecting system
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Inoue et al
Table 3. Available UAS
Company
COOK Medical
COOK Medical
Coloplast
Boston Scientific
Boston Scientific
Olympus
BARD
BARD
Rocamed
Takai

UAS
FlexorFlexor parallel
Retrace
Navigator HD
Navigator NEO
UroPass
ProxisAQUAGUIDE
Bi-FlexJ Flexisheath

Length (cm)20, 28, 35, 45, 55
20, 28, 35, 45, 55
35, 4528, 36, 46
28, 36, 46
24, 38, 54
25, 35, 45
35, 4535, 4528, 35, 45, 55

Diameter (inner/outer; Fr)
9.5/11.5, 10.7/12.7, 12/14, 14/16
9.5/11.5, 10.7/12.7, 12/14, 14/16
10/12, 12/14
11/13, 12/14, 13/15
11/13, 12/14, 13/15
10/12, 12/14
10/12, 12/14
10 (12)/14, 11 (13)/15
10/12, 12/14
11/13, 12/14

Lumen
1
1
1
1
1
1
1
2
1
1

UAS, ureteral access sheath.

during RIRS. A UAS has many advantages, including easyreentry of the fURS into the collecting system, prevention ofincreased intrarenal pressure, maintenance of visualizationin the surgical field to facilitate saline irrigation, and use as
a possible substitute for a safety GW [25,44]. Various UAS
sizes ranging from 9.5/11.5 to 14/16 Fr in diameter and from
20 to 55 cm in length are now available for clinical use (Table3). However, selection of the UAS size mostly depends on thesurgeons performing the procedure. Ureteral injury may
easily occur if using a UAS larger that the actual ureterallumen diameter. Traxer and Thomas [45] reported that UASrelated ureteral wall injuries occurred in 46.5% of RIRS procedures when using a 12- to 14-Fr UAS. They suggested thatthe ureteral injury severity determines the grade of injury
in terms of the depth of ureteral damage, with a low-grade
injury classified as grade 0 or 1 and a high-grade as grade 2,
3, or 4/5. Grade 2 injuries involve the ureteral smooth muscle
layer (10.1%) and grade 3 injuries involve full-thickness
ureteral perforation (3.3%) [45]. Generally, the incidence of
ureteral injury using a UAS depends on the relationshipbetween the ureteral diameter and UAS size. Although thestandard UAS size in the United States and Europe seems
to be 12 to 14 Fr, the Asian standard might be 11 to 13 Fr oreven smaller because of differences in body size.
Interestingly, one of the current topics in use of a UAS
is intrarenal pressure. As mentioned above, the UAS facilitates the irrigation inflow and outflow of saline. High intrarenal pressure during procedures may cause urosepsis ora subcapsular renal hematoma. According to some research,pyelosinus, pyelovenous, and pyelolymphatic backflow of irrigating solution might occur at intrarenal pressures above
40 cmH2O [46]. Therefore, keeping the intrarenal pressure
below the limit for intrarenal and pyelosinus backflow
might prevent complications during RIRS. Auge et al. [47]reported that a UAS can protect the kidney by reducing the126

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intrarenal pressure by 57% to 75% during RIRS. Additionally, using a thicker UAS intraoperatively can decrease theintrarenal pressure [48]. However, the irrigation inflow andoutflow of saline through a 9.5- to 11.5-Fr UAS is poor. A
UAS of this size may result in excessive intrarenal pressureduring RIRS. Therefore, the minimum standard UAS size of
10 to 12 Fr is needed to acquire acceptable irrigation inflow
and outflow of saline and thus maintain good surgical visualization. In addition, different intrarenal pressures and saline outflow are produced among the various kinds of available 10- to 12-Fr UASs. Among UASs of this size, the Bi-Flex(Rocamed, Monaco) and UroPass (Olympus) induce lower
intrarenal pressure than the ReTrace (Coloplast, Humlebæk,Denmark) and Proxis (C.R. Bard, Murray Hill, NJ, USA) because of their different inner diameters [49].

(4) Irrigation methods: maintenance of surgicalfield

In endourological surgery, saline irrigation is mandatory
to open and maintain the surgical field. Visualization of
the surgical field is maintained through optimal irrigationof saline. The irrigation methods used during RIRS have
evolved during the past few decades. Lyon et al. [50] first reported the use of an fURS with irrigation connected to theureteroscopic working channel and used gravity to maintainthe irrigation flow by placing a saline bag 30 cm above thelevel of the kidney. A handheld activated syringe-based system was historically used as the standard method of gravityinduced saline irrigation during RIRS. A foot-activated syringe-based system is currently available (Peditrol; Wismed,
Durban, South Africa) [51]. In addition, pressurized irrigant
bags and an automatic irrigation pump (AIP) have been
introduced for irrigation during endourological procedures.
The view of the surgical field during RIRS has changed
because of increased efficiency of the irrigation flow, whichhttps://doi.org/10.4111/icu.20200526

Investig Clin Urol 2021;62:121-135.

(-)
(-)
(-)
(-)
(-)
(-)

www.icurology.org

YAG, yttrium aluminium garnet; Ho, holmium-YAG laser; Ho/Nd, holmium-YAG/Neodymium; -, no information.

(-)(-)
VirtualBasketVapor
tunnel
(-)
(-)
Moses
technology
(-)
(-)

(-)

(+)
-/(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)
(+)

(+)

≤4.0/≤4.2
20/25
≤7.0
60
≤3.0
0.5–4.530≤3.520≤4.0/≤5.0
25/60
≤5.0
100
≤4.0
25
0.2–2.850≥0.2
80
5.0/3.5
25

Ho
120
Ho
100
Ho
30/50

Laser type
Max power
output (W)Laser energy (J)Max pulse rate
(Hz)
Stone dusting
effectSpecial mode

0.2–3.5
50

Ho
30
Ho
30
Ho
30/50
Ho
30
Ho
30
Ho
45/60/80/100
Ho
20
Ho
30/70
Ho
60/100Ho30
Ho/Nd
80/100Odyssey 30
Omni Pulse
MAX
ThemisSPHINX

Versa
Pulse
Power
Suite
Ho
100
Pulse 120H
Pulse
30H/50H
Laser
specifications

Pulse
100H

LumenisCharacteristic

Table 4. Recent available various Holmium:YAG laser system

In RIRS, the holmium:YAG laser system has been thegold standard lithotripsy instrument for stone management
since Denstedt et al. [54] first described its use in endourology in their preliminary report in 1995. Various laser systems
with high efficacy and excellent safety profiles are currently available for stone lithotripsy (Table 4). Traditionally,laser lithotripsy only allowed for adjustment of the pulse
energy and frequency. However, the pulse duration (width)
can now be utilized for stone disintegration. Therefore, stone
endourologists can manipulate these three parameters to
perform fragmentation using a lower frequency (5–15 Hz)
and higher energy setting (0.6–1.2 J) with a short or longpulse duration or perform dusting using a high frequency(50–80 Hz) and low energy setting (0.2–0.5 J) with a shortor long pulse duration depending on the particular clinicalsituation and stone hardness [55]. The clinical advantages ofa long pulse mode over a short pulse mode are less stone retropulsion, less fiber degradation, and greater stone dust [56].
Stone fragmentation involves the creation of fragments thatcan be extracted through the UAS with a basket, whereasstone dusting involves the creation of tiny stone particles of

Versa Pulse
PowerSuite(5) Laser instruments and various settings

Laser
litho

QuantaRichard
EMS
Wolf
Cyber Ho Mega pulse Swiss Laser clast

LISA

DiREX

TrimedyneStarmedtec30W Auriga

Convergent

Olympusis influenced by the location and size of the UAS, size ofthe fURS, and irrigation method. Irrigation inflow andoutflow through the UAS during RIRS is required to open
and maintain optimal renal pelvic distention, good visualization, and low intrarenal pressure. A handheld activatedsyringe-based system is commonly used to achieve adequate
renal pelvic distention and a good surgical view. However, a
handheld activated syringe-based pump and a foot-activatedsyringe-based system may increase the risk of perioperative pyelonephritis and sepsis secondary to high intrarenalpressure. Therefore, it is crucial to maintain a constant irrigation flow regardless of the type of instruments in theworking channel and ensure an adequate surgical field toprevent the drastic increases in the intrarenal pressure thatmight occur with a handheld activated syringe-based system[52]. An AIP may help to maintain an optimal surgical field
for easy manipulation of the fURS during RIRS. Lama et al.
[53] reported the use of an AIP for irrigation that maintains
the same irrigation flow over time in contrast to gravity irrigation. In addition, Inoue et al. [52] recently reported thatthe irrigation flow from the tip of the fURS remains almost
unchanged by adjusting the pressure control in the AIP system even when instruments are placed through the working
channel of the fURS. Therefore, the use of an AIP system
during RIRS might help to maintain the surgical field andthus manipulate the fURS with comfort.

HLS 30W

Retrograde intrarenal surgery in the past, present, and future127

Inoue et al<2 mm that can be spontaneously passed with no basketing[57]. However, one currently advocated definition of stone
dust (particles of <250 µm) defines dust as particles smallenough to meet the following criteria: spontaneous floating
under 40 cmH2O irrigation pressure, mean sedimentation
time of <2 seconds through 10 cm of saline solution, and fullsuitability for aspiration through a 3.6-Fr working channel [58]. According to data from the Endourological Society
worldwide survey in 2014, 26.7% of 414 endourologists from44 countries actively removed all stone fragments with abasket, whereas 37.4% retrieved only larger fragments but
not small fragments. The stone dusting technique has been
increasingly applied in Western countries because of the difficulty of stone basketing for fragments [59]. However, Humphreys et al. [60] examined whether the SFR is better withdusting or basketing during RIRS. They concluded that the
short-term SFR was higher with active basket retrieval offragments (74.3% vs. 58.2%). El-Nahas et al. [61] also reported
that the dusting technique had a shorter operation time,
whereas the fragmenting technique led to a significantly
higher SFR (78.6% vs. 58.6%). The combination of fragmenting and dusting may be a more feasible method to breakstones. Endourologists choose one of these methods depending on the situation encountered during surgery (including
the stone size, stone composition, stone location, impaction ofstone, stone retropulsion, and surgeon preference) to improvethe effectiveness and outcome of surgery.
High-power holmium:YAG laser therapy with Moses
Technology by Lumenis (Clarion Medical Technologies, Cambridge, ON, Canada) has recently become available in clinical practice. Furthermore, Virtual Basket mode in Cyber-Ho(Quanta System SpA, Samarate, Italy), which is similar toMoses Technology, has also been introduced. Moses Technology has improved the stone fragmentation capacity byincreasing the energy transmission in water and reducing
stone retropulsion compared with the long pulse mode [62].
Therefore, Moses Technology is capable of much less stone
retropulsion. In addition, Moses Technology produces more
pronounced disruption of morphological characteristics because it may deliver a superior laser beam through a vapor
channel compared with the conventional holmium:YAG
laser. Higher local temperatures occur during the use of
Moses Technology (direct photothermal effect) [63]. Therefore, Moses Technology can create a large amount of tinystone dust fragments; this is termed the “snow globe effect.”In their in vitro study, Elhilali et al. [62] reported that theMoses mode resulted in a significantly higher stone ablation
volume (160% higher) and less stone movement (50 times
less retropulsion) than the regular mode. Ibrahim et al. [64]128

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recently published a randomized clinical trial showing that
the Moses mode was associated with a significantly shorter
pulverization time and procedural time than the regularmode. In addition, there were no significant differences inthe success rate at the end of 3 months (83.3% vs. 88.4%) or
intraoperative complications between the Moses mode groupand regular mode group. However, one patient required endoureterotomy for ureteral stricture in the Moses group [64].
Thus, close attention should be paid to the risk of thermal
injury and resultant ureteral stricture when using highpower holmium:YAG laser therapy [65].
As a cutting-edge instrument in the field of stone lithotripsy, the thulium fiber laser was launched to disintegrate
urinary tract stones. Comparison of the differences between
a holmium laser and thulium fiber laser translate into
multiple potential advantages in favor of the thulium fiber
laser, such as a four-fold higher absorption coefficient in water, smaller operating laser fibers (50- to 150-µm core diameter), lower energy per pulse (as low as 0.025 J), and higher
maximal pulse repetition rate (up to 2,000 Hz). Comparativein vitro studies have shown a 1.5- to 4.0-times faster stoneablation rate and much lower stone retropulsion with thethulium fiber laser than holmium laser [66,67]. This innovative laser technology is particularly advantageous for RIRS
and may become the next important therapeutic milestone.

(6) Role of preoperative and postoperative
ureteral stenting

Preoperative stenting for kidney stone treatment has
advantages including a higher SFR, lower incidence of intraoperative complications (especially ureteral injuries), andgreater facilitation of UAS placement. Preoperative stenting for patients without perioperative infection, severe selfsymptom, anatomical abnormalities, and/or tortuous ureters
is not mandatory in most clinical settings for access to theupper urinary tract because it induces hematuria, pain, urgency, and a risk of febrile UTI. However, most endourologists have experienced failed access to the upper urinary
tract because of a tight or difficult ureter (8.4%–16.0%) [68,69].
Once failed access has occurred, staged procedures are required to achieve passive ureteral dilation 1 to 2 weeks after
placing the ureteral stent in the first ureteroscope.
Postoperative stenting is a quite standard procedure
after ureteroscopic surgery not only to prevent ureteralobstruction due to mucosa edema and ureteral healing but
also to avoid ureteral injury, perforation, residual fragments, bleeding, and UTI. However, the optimal duration of
postoperative ureteral stenting is unknown. The indwelling
time preferred by most urologists appears to be 1 to 2 weeks
https://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
after ureteroscopy. However, routine postoperative stenting
is not required if no ureteral injury is observed under direct
ureteroscopic vision at the end of the ureteroscopic surgery,even in patients who undergo uncomplicated ureteroscopy
for impacted ureteral stones [70,71]. Postoperative stenting
might be associated with higher postoperative morbidity
and costs [31]. Byrne et al. [72] reported that flank discomfort
on postoperative day 1 was significantly less common in patients who did not undergo stenting; however, there was no
significant difference in patient-reported postoperative hematuria between those who did and did not undergo stenting. With the recent advancements of smaller instruments
for ureteroscopic treatment, the number of patients who do
not need postoperative stenting has increased. However, how
to determine which patients do not require postoperative
stenting after ureteroscopic surgery remains unclear.

6) Surgeon’s safety from radiation exposure

Extended low-dose radiation exposure can greatly affecthuman health in the long term, resulting in an increased
incidence of malignancies including thyroid cancer, breast
cancer, and leukemia [73]. In the current urological field, radiation exposure among medical personnel and patients has
increased. Therefore, urologists must be aware of the riskof harmful effects caused by radiation exposure. A major
source of radiation exposure for surgeons and medical staff
members is scattered radiation produced by interaction of
the primary radiation beam with the patient’s body and theoperating table. Although the dose limit of medical exposurefor patients has not been established, the occupational radiation exposure dose limit has been defined as 50 mSV peryear by the National Council on Radiation Protection andMeasurements [74]. The International Commission on Radiological Protection has recommended limiting radiation exposure to levels “as low as reasonably achievable (ALARA)” [75].
Medical radiation protection principles should be applied
for both the patients and medical staff members involved
in imaging, the latter of which include surgeons, nurses, andmedical engineers. The following are general methods to optimize radiation protection.
① Time: the radiation exposure time should be minimized in terms of both the fluoroscopy time and thequantity of X-ray photographs acquired.
② Distance: medical staff members should position
themselves as far as possible from the X-ray source.
③ Shielding: medical staff members should use adequate
shielding materials, such as lead aprons, lead glasses,
and lead radiation-shielding glass.
Shielding for such personnel is usually performed by
Investig Clin Urol 2021;62:121-135.

wearing personal protective clothing. The standard lead protection protocol requires the use of a 0.35-mm lead apron andthyroid shield by the operating surgeon and 0.25-mm leadaprons for other personnel [76]. However, protection fromscattered radiation by protective clothing is incomplete, especially that to the arms, eyes, and brain.
In the endourological field, PCNL using radiologic guidance was initially described by Fernström and Johansson [77],who performed this procedure in three patients in 1976. In
PCNL, the mean radiation exposure dose for the surgeon is12.7 mSV per procedure. This value is higher than the doseof 11.6 mSV per exposure in flexible ureteroscopy becauseof the longer fluoroscopic time and close distance between
the radiation source and the surgeon [78]. The mean fluoroscopy screening time during PCNL reportedly ranges from
4.5 to 6.04 minutes (range, 1–12.16 min) [79]. Furthermore,
one study showed that the mean radiation exposure to thesurgeon’s finger and ocular region was 0.28 and 0.125 mSV,
respectively, because of the non-uniform radiation exposure
caused by scattered radiation [80]. Therefore, the operator’s
hands and eyes should also be protected from scattered radiation exposure using gloves and glasses with lead-threading.
Most endourologists generally perform needle puncture forrenal access under fluoroscopy. Therefore, an ultrasoundguided approach is beneficial because it offers better protection to surgeons from radiation exposure during PCNL thandoes the fluoroscopic approach. The surgeon’s radiation doseis lower in ureteroscopy than in PCNL in almost all cases
because ureteroscopy is characterized by a shorter fluoroscopic time and longer distance between the radiation sourceand surgeon. Pulsed fluoroscopy was introduced to reduce
the radiation dose by limiting the X-ray exposure time andnumber of exposures per second. The duration of exposure
during ureteroscopy has been decreased from the original 4.7
minutes to 0.62 minutes, and the mean fluoroscopy screening time during ureteroscopy is reportedly 44.1 seconds(range, 36.5–51.6 s) [81]. Kokorowski et al. [82] described theefficacy of a preoperative checklist related to radiation protection. The checklist was useful for decreasing radiation
exposure during procedures. Furthermore, Inoue et al. [83]reported that using protective lead curtains on both sidesof the patient table, the operating table end, and the image
intensifier was useful for reducing the surgeon’s radiation
exposure during ureteroscopy. The presence of protective
lead curtains caused a 75% to 80% reduction of the scatteredradiation dose compared with the absence of lead curtains.
Novel shielding curtains containing bismuth and antimony,
which are also suitable for radiation protection because of
their high density and potential weight savings compared
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129

Inoue et alwith lead, have also been designed. In modern radiation protection practice, active personal dosimeters are essential tosatisfy the ALARA principle. Most urologists have an insufficient perception of their own personal radiation protection.
A previous study showed that although 84.4% of urologists
who were chronically exposed to ionizing radiation wore leadaprons, only 53.9% wore a thyroid shield and only 27.9% wore
eyeglasses with lead linings. Moreover, only 23.6% of urologists wore a personal dosimeter [84]. Awareness of occupational radiation exposure among physicians in the urologicalfield remains low. Although the risks of harmful effects ofoccupational radiation exposure may be relatively low, theyshould not be ignored. On our best knowledge, there describe
the various preventive methods from radiation exposure
during operation (Table 5).

3. Future state of retrograde intrarenal surgery
1) Possible indications for retrograde intrarenal
surgery

Various laser systems can be used in RIRS, including ahigh-power holmium:YAG laser (120 W) with Moses Technology, thulium fiber laser, thulium:YAG laser, and neodymium-doped YAG laser. All of these are promising treatment
options for several diseases in patients undergoing RIRS. In
addition, a single-use fURS can provide safe and easy accessto the kidney anatomy.
The indications for treatment of kidney stones are expected to expand to include larger stones of >2 cm in future
guidelines; less basketing is being performed because of theability to create large amounts of stone dust (snow globe
Table 5. Reduction technique from radiation exposure for patients andoperators during surgery
Instrument/
operator
Image intensifier

C-arm
Operator

Others130

Preventive technique① Maximizing the distance between the X-ray
tube and the patient② Minimizing the distance between patientsand the image Intensifier① Collimating of image monitor② Using pulsed fluoroscopic mode
① Minimizing fluoroscopy time
② Protective shielding for operator; wearing eyeglass, lead apron, thyroid shield③ Protective shielding of patient table① Using ultrasound instead of fluoroscopy② Direct retrograde endoscopic vision combinedwith ultrasound in PCNL
③ Last image hold④ Laser guided C-arm⑤ Dedicated educational training (including preoperative checklist)

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effect), and surgical access has improved in patients with adifficult renal pelvic anatomy, even when the lower pole hasan anatomically acute angle. In addition, for patients withmultifocal <3-cm UTUC with low-grade pathological findings
and no invasive aspect on computed tomography urography,
retrograde endourological procedures might become a morecommon treatment. Furthermore, novel laser systems might
help to manage postoperative ureteral stricture, symptomatic renal cysts, and recurrent ureteropelvic junction stenosis[85,86].

2) New trends in retrograde intrarenal surgery(1) New flexible ureteroscope with joystick

Usually, fURS manipulation involves torque movementof the hand, back-and-forth movement of the fURS shaft,and up-and-down movement of the fURS lever. Surgeonsmust perform optimal manipulation in a coordinated manner by combinations of these complicated maneuvers, which
may be difficult in some cases. A new fURS with an omnidirectional bending tip using a joystick unit integrated intoa handgun-type control unit was recently introduced. Inoueet al. [87] first reported that this novel fURS provided agreater range of reach along all directions in the lower-polecalyx compared with some usual fURSs in their ex vivo
study. Tambo et al. [88] subsequently investigated whether
a conventional fURS or novel joystick fURS is easier to manipulate in their initial constructive validation study. They
found that the novel joystick fURS allowed for much better
manipulation by novice trainees and provided better ergonomics for surgeons. This joystick fURS might have benefits
in terms of ureteroscopic performance [88].

(2) Thulium versus high-power holmium laser
therapy

High-power holmium:YAG lasers have long been available for management of upper urinary tract stones. Like
Moses Technology, the Virtual Basket mode is a special
technology that is quite beneficial in terms of producing
tiny particles of stone dust by two forms of ablation: thephotothermal effect and photomechanical effect. In addition, the novel thulium fiber, which is capable of more
quickly producing large amounts of tiny stone dust than theholmium:YAG laser in vivo, has been introduced to clinicaluse. Therefore, the stone management strategy during RIRS
has changed from more stone basketing to less stone basketing or no stone basketing. The differences in the clinical outcomes between the two laser systems are unclear. However,further refinement of how to use these laser systems will bea key point in the management of stones, UTUC, and otherhttps://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
disorders during RIRS in the coming years.

(3) New stone removal devices

Although stone dusting is beneficial, its SFR is still
lower than that produced by stone basketing after RIRS.
Therefore, new instruments might be needed to remove thetiny stone dust particles, such as stone vacuum devices or anovel type of basket. One stone vacuum device is currently
available in clinical practice. Zhu et al. [89] compared theefficacy between a suctioning UAS and traditional UAS.
The suctioning UAS had a significantly higher SFR on
postoperative day 1 (82.4% vs. 71.5%), lower incidence of infectious complications (5.5% vs. 13.9%), and shorter operation
time (49.7±16.3 min vs. 57.0±14.0 min) [89]. In addition, a newsteerable multi-lumen irrigation/aspiration device (K-VAC;
Kalera Medical, San Diego, CA, USA) was introduced in
2019. This device can be used to access all calyces and navigate under fluoroscopy to each calyx. The preliminary report
showed that it was quite efficient to remove tiny stone dust
fragments and achieve a stone-free status [90].

3) Expected trend in retrograde intrarenal
surgery: robotic flexible ureteroscopy

In RIRS, scope manipulation can be technically challenging with a conventional hand-operated fURS. Therefore, theeducation to acquire the technical skills of fURS manipulation, such as hands-on training using a bench model simulator or virtual reality simulator, has recently been expanded[91]. However, such education is provided in limited regions
and countries. In addition, there are some another concerns
regarding the surgeon’s ergonomics, including radiation
exposure, the wearing of a heavy lead-protector, and thesurgeon’s position when operating the fURS. Robotic-assisted
fURS technologies have recently been developed to overcome
some of these disadvantages [92]. The first robotic fURS
(Sensei-Magellan system; Hansen Medical, Mountain View,
CA, USA) was reported in 2011. Desai et al. [93] initiallyattained a 94% technical success rate for stone disintegration and a complete stone clearance rate of 89% among 18
patients with 5- to 15-mm renal calculi using the Sensei-Magellan system. However, this robotic fURS was abandoned
because difficulties were encountered in development of thescope design. A few years later, in 2014, Saglam et al. [92]introduced a new robotic fURS system (Roboflex Avicenna;
ELMED, Ankara, Turkey). The Roboflex consisted of a console for operation by the surgeon and a robotic arm for the
fURS. The authors preliminarily reported the clinical efficiency and safety of the Roboflex in 81 consecutive patients;
the clinical outcomes included a short robot docking time
Investig Clin Urol 2021;62:121-135.

of 59.6 s, feasible operation time of 74 min, and comparable
SFR of 96%, all of which were quite acceptable comparedwith the conventional hand-operated fURS [92]. In addition,
the Roboflex provided significant advantages in terms of thesurgeon’s ergonomics [93,94]. Therefore, the system gained
CE (Communauté Européenne) approval for use in Europe
in 2013, but Food and Drug Administration approval is still
pending. Although the Roboflex might be optimal in termsof clinical use, it has some limitations included difficulty ofstone removal, hand-operated insertion of the UAS, and difficult adjustment of kidney movement. However, the newly
available high-power holmium:YAG laser and thulium fiber
laser are able to produce large amounts of tiny stone dust
particles and may become the next revolutionary technology
in robotic-assisted RIRS [26,95].

CONCLUSIONSThe endourological technology in RIRS has continued
to advance. The single-use fURS, high-power holmium:YAG
laser, and thulium fiber laser may be the next key players
in RIRS. Furthermore, robotic-assisted fURS systems havehelped to standardize surgical technical skills and produce
more sustainable surgical outcomes, more comfortable surgeon ergonomics, much less radiation exposure, and muchless surgeon fatigue. Although there are still issues to resolve in RIRS, endourological procedures are expected to expand the range of treatment indications and become muchless invasive surgical treatment options for patients andsurgeons.

CONFLICTS OF INTEREST
The authors have nothing to disclose.

ACKNOWLEDGMENTS
We thank Angela Morben, DVM, ELS, from Edanz
Group (https://en-author-services.edanzgroup.com/ac), for editing a draft of this manuscript.

AUTHORS’ CONTRIBUTIONS
Reserch conception and design: Takaaki Inoue. Draftingof manuscript: Takaaki Inoue. Revision of manuscript: Shinsuke Okada, Shuzo Hamamoto, and Masato Fujisawa.

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Inoue et al

REFERENCES
1. Assimos D, Krambeck A, Miller NL, Monga M, Murad MH,

17. Sofer M, Watterson JD, Wollin TA, Nott L, Razvi H, Denstedt
JD. Holmium:YAG laser lithotripsy for upper urinary tract calculi in 598 patients. J Urol 2002;167:31-4.

Nelson CP, et al. Surgical management of stones: American

18. Van Cleynenbreugel B, Kılıç Ö, Akand M. Retrograde intrare-

Urological Association/Endourological Society Guideline, partnal surgery for renal stones - part 1. Turk J Urol 2017;43:112-

I. J Urol 2016;196:1153-60.

21.

2. Türk C, Knoll T, Petrik A, Sarica K, Skolarikos A, Straub M, et

19. Tom WR, Wollin DA, Jiang R, Radvak D, Simmons WN, Pr-

al. EAU guidelines on urolithiasis: specific stone management

eminger GM, et al. Next-generation single-use ureteroscopes:of ureteral stones [Internet]. Arnhem: European Association of

an in vitro comparison. J Endourol 2017;31:1301-6.

Urology; 2016 Mar [cited 2017 Nov 8]. Available from: https://

20. Scotland KB, Chan JYH, Chew BH. Single-use flexible uretero-uroweb.org/wp-content/uploads/EAU-Guidelines-Urolithia-

scopes: how do they compare with reusable ureteroscopes? J

sis-2016-1.pdf.

Endourol 2019;33:71-8.

3. Hennessey DB, Fojecki GL, Papa NP, Lawrentschuk N, Bolton

21. Martin CJ, McAdams SB, Abdul-Muhsin H, Lim VM, Nunez-

D. Single-use disposable digital flexible ureteroscopes: an ex

Nateras R, Tyson MD, et al. The economic implications of avivo assessment and cost analysis. BJU Int 2018;121 Suppl

reusable flexible digital ureteroscope: a cost-benefit analysis. J

3:55-61.

Urol 2017;197(3 Pt 1):730-5.

4. Marshall VF. Fiber optics in urology. J Urol 1964;91:110-4.
5. Takagi T, Go T, Takayasu H, Aso Y. Fiberoptic pyeloureteroscope. Surgery 1971;70:661-3 passim.
6. Takayasu H, Aso Y, Takagi T, Go T. Clinical application offiber-optic pyeloureteroscope. Urol Int 1971;26:97-104.

22. Leveillee RJ, Kelly EF. Impressive performance: new disposable digital ureteroscope allows for extreme lower pole accessand use of 365 μm holmium laser fiber. J Endourol Case Rep
2016;2:114-6.
23. Salvadó JA, Cabello JM, Moreno S, Cabello R, Olivares R,

7. Bagley DH, Huffman JL, Lyon ES. Flexible ureteropyeloscopy:

Velasco A. Endoscopic treatment of lower pole stones: is a dis-diagnosis and treatment in the upper urinary tract. J Urolposable ureteroscope preferable? Results of a prospective case-

1987;138:280-5.

control study. Cent European J Urol 2019;72:280-4.

8. Grasso M, Bagley D. Small diameter, actively deflectable, flex-

24. Türk C, Petřík A, Sarica K, Seitz C, Skolarikos A, Straub M, etible ureteropyeloscopy. J Urol 1998;160:1648-53; discussion

al. EAU guidelines on interventional treatment for urolithiasis.

1653-4.

Eur Urol 2016;69:475-82.

9. Ankem MK, Lowry PS, Slovick RW, Munoz del Rio A, Na-

25. Inoue T, Okada S, Hamamoto S, Yoshida T, Matsuda T. Cur-kada SY. Clinical utility of dual active deflection flexible

rent trends and pitfalls in endoscopic treatment of urolithiasis.

ureteroscope during upper tract ureteropyeloscopy. Urology

Int J Urol 2018;25:121-33.

2004;64:430-4.

26. Kang SK, Cho KS, Kang DH, Jung HD, Kwon JK, Lee JY. Sys-

10. Yinghao S, Yang B, Gao X. The management of renal caliceal

tematic review and meta-analysis to compare success rates ofcalculi with a newly designed ureteroscope: a rigid uretero-

retrograde intrarenal surgery versus percutaneous nephroli-scope with a deflectable tip. J Endourol 2010;24:23-6.

thotomy for renal stones >2 cm: an update. Medicine (Balti-

11. Streem SB, Pontes JE, Novick AC, Montie JE. Ureteropyeloscopy in the evaluation of upper tract filling defects. J Urol
1986;136:383-5.
12. Bagley DH, Rivas D. Upper urinary tract filling defects: flexible
ureteroscopic diagnosis. J Urol 1990;143:1196-200.
13. Abdel-Razzak OM, Ehya H, Cubler-Goodman A, Bagley DH.
Ureteroscopic biopsy in the upper urinary tract. Urology
1994;44:451-7.
14. Bagley D, Erhard M. Use of the holmium laser in the upper
urinary tract. Tech Urol 1995;1:25-30.
15. Bagley DH. Ureteroscopic laser treatment of upper urinary
tract tumors. J Clin Laser Med Surg 1998;16:55-9.

more) 2017;96:e9119.
27. Wilhelm K, Hein S, Adams F, Schlager D, Miernik A, Schoenthaler M. Ultra-mini PCNL versus flexible ureteroscopy: amatched analysis of analgesic consumption and treatmentrelated patient satisfaction in patients with renal stones 10-35
mm. World J Urol 2015;33:2131-6.
28. Ricchiuti DJ, Smaldone MC, Jacobs BL, Smaldone AM, Jackman SV, Averch TD. Staged retrograde endoscopic lithotripsy
as alternative to PCNL in select patients with large renal calculi. J Endourol 2007;21:1421-4.
29. Inoue T, Murota T, Okada S, Hamamoto S, Muguruma K,
Kinoshita H, et al.; SMART Study Group. Influence of pelvi-

16. Grasso M, Conlin M, Bagley D. Retrograde ureteropyeloscopic

caliceal anatomy on stone clearance after flexible ureteroscopy

treatment of 2 cm. or greater upper urinary tract and minor

and holmium laser lithotripsy for large renal stones. J Endou-

Staghorn calculi. J Urol 1998;160:346-51.

rol 2015;29:998-1005.

132

www.icurology.org

https://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
30. Ozimek T, Cordes J, Wiessmeyer JR, Schneider MH, Hupe

1974;112:176-8.

MC, Gilbert N, et al. Steep infundibulopelvic angle as a new

44. Yong C, Knudsen BE. Ureteroscopy: accessory devices. In:

risk factor for flexible ureteroscope damage and complicated

Humphreys MR. Ureteroscopy for stone disease. Torino: Mi-

postoperative course. J Endourol 2018;32:597-602.

nerva Medica; 2016;55-70.

31. Rouprêt M, Babjuk M, Burger M, Compérat E, Cowan NC,

45. Traxer O, Thomas A. Prospective evaluation and classification

Gontero P, et al. EAU guidelines on upper urinary tract uro-of ureteral wall injuries resulting from insertion of a ureteralthelial carcinoma. Disease management [Internet]. Arnhem:

access sheath during retrograde intrarenal surgery. J Urol

European Association of Urology; 2019 Mar [cited 2020 Nov 1].

2013;189:580-4.

Available from: https://uroweb.org/wp-content/uploads/EAU-

46. Rehman J, Monga M, Landman J, Lee DI, Felfela T, Conradie

Guidelines-on-Upper-urinary-Tract-Tumours-2019.pdf.

MC, et al. Characterization of intrapelvic pressure during

32. Kalaitzis C, Zisimopoulos A, Giannakopoulos S, Touloupidis S.

ureteropyeloscopy with ureteral access sheaths. Urology

Ureteroscopic laser treatment of upper urinary tract urothelial
cell carcinomas: can a tumour free status be achieved? Adv
Urol 2013;2013:429585.
33. Botoca M, Bucuras V, Boiborean P, Herman I, Cumpanas A,
Miclea F. The learning curve in ureteroscopy for the treatmentof ureteric stones. How many procedures are needed to achievesatisfactory skills? Eur Urol Suppl 2004;3:138.
34. Skolarikos A, Gravas S, Laguna MP, Traxer O, Preminger GM,
de la Rosette J. Training in ureteroscopy: a critical appraisal of
the literature. BJU Int 2011;108:798-805; discussion 805.

2003;61:713-8.
47. Auge BK, Pietrow PK, Lallas CD, Raj GV, Santa-Cruz RW,
Preminger GM. Ureteral access sheath provides protection
against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol 2004;18:33-6.
48. Sener TE, Cloutier J, Villa L, Marson F, Butticè S, Doizi S, et al.
Can we provide low intrarenal pressures with good irrigation
flow by decreasing the size of ureteral access sheaths? J Endourol 2016;30:49-55.
49. Yoshida T, Inoue T, Abe T, Matsuda T. Evaluation of intrapel-

35. Brunckhorst O, Aydin A, Abboudi H, Sahai A, Khan MS, Das-vic pressure when using small-sized ureteral access sheaths

gupta P, et al. Simulation-based ureteroscopy training: a sys-of ≤10/12F in an ex vivo porcine kidney model. J Endourol

tematic review. J Surg Educ 2015;72:135-43.

2018;32:1142-7.

36. Aghamir SMK, Salavati A. Endovisually guided zero radiation
ureteral access sheath placement during ureterorenoscopy.
Minim Invasive Ther Allied Technol 2018;27:143-7.
37. Karabulut I, Keskin E, Bedir F, Yilmazel FK, Ziypak T, Doluoglu OG, et al. Rigid ureteroscope aided insertion of ureteral access sheath in retrograde intrarenal surgery. Urology
2016;91:222-5.

50. Lyon ES, Huffman JL, Bagley DH. Ureteroscopy and ureteropyeloscopy. Urology 1984;23(5 Spec No):29-36.
51. Blew BD, Dagnone AJ, Pace KT, Honey RJ. Comparison of
Peditrol irrigation device and common methods of irrigation. J
Endourol 2005;19:562-5.
52. Inoue T, Yamamichi F, Okada S, Hamamoto S, Fujisawa M;
SMART Study Group. Change in irrigation flow through a

38. Clayman RV, Castaneda-Zuniga WR, Hunter DW, Miller RP,

flexible ureteroscope with various devices in the working chan-

Lange PH, Amplatz K. Rapid balloon dilatation of the nephros-nel: comparison between an automatic irrigation pump andtomy track for nephrostolithotomy. Radiology 1983;147:884-5.

gravity-based irrigation. Int J Urol 2020;27:333-8.

39. Ekman P, Husain I, Sharma ND, Al-Faqih SR. Transurethral

53. Lama DJ, Owyong M, Parkhomenko E, Patel RM, Landman

ureteroscopy. Safety guide wire as an aid to a more aggressive

J, Clayman RV. Fluid dynamic analysis of hand-pump infuser

approach. Br J Urol 1987;60:23-7.

and UROMAT Endoscopic Automatic System for Irrigation

40. Patel SR, McLaren ID, Nakada SY. The ureteroscope as a safety

through a flexible ureteroscope. J Endourol 2018;32:431-6.

wire for ureteronephroscopy. J Endourol 2012;26:351-4.

54. Denstedt JD, Razvi HA, Sales JL, Eberwein PM. Preliminary

41. Dickstein RJ, Kreshover JE, Babayan RK, Wang DS. Is a safety
wire necessary during routine flexible ureteroscopy? J Endourol 2010;24:1589-92.
42. Türk C, Neisius A, Petrik A, Seitz C, Skolarikos A, Thomas
K, et al. EAU guidelines on urolithiasis: disease management,

experience with holmium: YAG laser lithotripsy. J Endourol
1995;9:255-8.
55. Sourial MW, Knudsen BE. Ho:YAG laser lithotripsy. In:
Schwartz BF, Denstedt JD. Ureteroscopy: a comprehensive
contemporary guide. Cham: Springer; 2020;101-12.

ureteroscopy [Internet]. Arnhem: European Association of

56. Wollin DA, Ackerman A, Yang C, Chen T, Simmons WN,

Urology; 2020 Mar [cited 2020 Nov 1]. Available from: https://Preminger GM, et al. Variable pulse duration from a newuroweb.org/guideline/urolithiasis/#3-4.

holmium:YAG laser: the effect on stone comminution, fiber

43. Takayasu H, Aso Y. Recent development for pyeloureteroscopy:
guide tube method for its introduction into the ureter. J Urol
Investig Clin Urol 2021;62:121-135.

tip degradation, and retropulsion in a dusting model. Urology
2017;103:47-51.
www.icurology.org

133

Inoue et al
57. Kronenberg P, Somani B. Advances in lasers for the treatmentof stones-a systematic review. Curr Urol Rep 2018;19:45.
58. Keller EX, De Coninck V, Doizi S, Daudon M, Traxer O. What

71. Cevik I, Dillioglugil O, Akdas A, Siegel Y. Is stent placement
necessary after uncomplicated ureteroscopy for removal of impacted ureteral stones? J Endourol 2010;24:1263-7.

is the exact definition of stone dust? An in vitro evaluation.

72. Byrne RR, Auge BK, Kourambas J, Munver R, Delvecchio F,

World J Urol 2020 Apr 8 [Epub]. https://doi.org/10.1007/

Preminger GM. Routine ureteral stenting is not necessary afters00345-020-03178-z.

ureteroscopy and ureteropyeloscopy: a randomized trial. J En-

59. Dauw CA, Simeon L, Alruwaily AF, Sanguedolce F, Holling-

dourol 2002;16:9-13.

sworth JM, Roberts WW, et al. Contemporary practice patterns

73. Pukkala E, Kesminiene A, Poliakov S, Ryzhov A, Drozdovitch V,of flexible ureteroscopy for treating renal stones: results of a

Kovgan L, et al. Breast cancer in Belarus and Ukraine after theworldwide survey. J Endourol 2015;29:1221-30.

Chernobyl accident. Int J Cancer 2006;119:651-8.

60. Humphreys MR, Shah OD, Monga M, Chang YH, Krambeck

74. United States Nuclear Regulatory Commission. Section

AE, Sur RL, et al. Dusting versus basketing during ureteros-

20.1201-occupational dose limits for adults, subpart C-occu-

copy-which technique is more efficacious? A prospective

pational dose limits, part 20-Standards for Protection Against

multicenter trial from the EDGE research consortium. J Urol

Radiation, Chapter I-Nuclear Regulatory Commission, NRC

2018;199:1272-6.

Regulations Title 10 of the Code of Federal Regulations [Inter-

61. El-Nahas AR, Almousawi S, Alqattan Y, Alqadri IM, Al-Shaijinet]. Rockville (MD): United States Nuclear Regulatory Com-

TF, Al-Terki A. Dusting versus fragmentation for renal stones

mission; 1991 [cited 2020 Nov 1]. Available from: https://www.

during flexible ureteroscopy. Arab J Urol 2019;17:138-42.

nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1201.

62. Elhilali MM, Badaan S, Ibrahim A, Andonian S. Use of theMoses technology to improve holmium laser lithotripsy out-

html.
75. Durán A, Hian SK, Miller DL, Le Heron J, Padovani R, Vano

comes: a preclinical study. J Endourol 2017;31:598-604.

E. Recommendations for occupational radiation protection

63. Keller EX, de Coninck V, Audouin M, Doizi S, Bazin D,

in interventional cardiology. Catheter Cardiovasc Interv

Daudon M, et al. Fragments and dust after Holmium laser
lithotripsy with or without “Moses technology”: how are theydifferent? J Biophotonics 2019;12:e201800227.
64. Ibrahim A, Elhilali MM, Fahmy N, Carrier S, Andonian S.

2013;82:29-42.
76. Institute of Physics and Engineering in Medicine. Medical anddental guidance notes: a good practice guide on all aspects ofionising radiation protection in the clinical environment. York:

Double-blinded prospective randomized clinical trial compar-

Institute of Physics and Engineering in Medicine; 2002.

ing regular and Moses modes of holmium laser lithotripsy. J

77. Fernström I, Johansson B. Percutaneous pyelolithotomy. A new

Endourol 2020;34:624-8.

extraction technique. Scand J Urol Nephrol 1976;10:257-9.

65. Liang H, Liang L, Yu Y, Huang B, Chen J, Wang C, et al. Ther-

78. Hellawell GO, Mutch SJ, Thevendran G, Wells E, Morgan RJ.

mal effect of holmium laser during ureteroscopic lithotripsy.

Radiation exposure and the urologist: what are the risks? J UrolBMC Urol 2020;20:69.

2005;174:948-52; discussion 952.

66. Traxer O, Keller EX. Thulium fiber laser: the new player for

79. Kumari G, Kumar P, Wadhwa P, Aron M, Gupta NP, Dogra PN.

kidney stone treatment? A comparison with Holmium:YAG

Radiation exposure to the patient and operating room person-

laser. World J Urol 2020;38:1883-94.

nel during percutaneous nephrolithotomy. Int Urol Nephrol

67. Andreeva V, Vinarov A, Yaroslavsky I, Kovalenko A, Vybornov A, Rapoport L, et al. Preclinical comparison of superpulse
thulium fiber laser and a holmium:YAG laser for lithotripsy.
World J Urol 2020;38:497-503.
68. Cetti RJ, Biers S, Keoghane SR. The difficult ureter: what is theincidence of pre-stenting? Ann R Coll Surg Engl 2011;93:31-3.

2006;38:207-10.
80. Majidpour HS. Risk of radiation exposure during PCNL. Urol
J 2010;7:87-9.
81. Elkoushy MA, Shahrour W, Andonian S. Pulsed fluoroscopy
in ureteroscopy and percutaneous nephrolithotomy. Urology
2012;79:1230-5.

69. Viers BR, Viers LD, Hull NC, Hanson TJ, Mehta RA, Bergs-

82. Kokorowski PJ, Chow JS, Strauss KJ, Pennison M, Tan W, Ci-

tralh EJ, et al. The difficult ureter: clinical and radiographic

lento B, et al. Prospective systematic intervention to reducecharacteristics associated with upper urinary tract access at thepatient exposure to radiation during pediatric ureteroscopy. Jtime of ureteroscopic stone treatment. Urology 2015;86:87884.

Urol 2013;190(4 Suppl):1474-8.
83. Inoue T, Komemushi A, Murota T, Yoshida T, Taguchi M,

70. Haleblian G, Kijvikai K, de la Rosette J, Preminger G. Ureteral

Kinoshita H, et al. Effect of protective lead curtains on scat-stenting and urinary stone management: a systematic review. J

tered radiation exposure to the operator during ureteroscopy

Urol 2008;179:424-30.

for stone disease: a controlled trial. Urology 2017;109:60-6.

134

www.icurology.org

https://doi.org/10.4111/icu.20200526

Retrograde intrarenal surgery in the past, present, and future
84. Borges CF, Reggio E, Vicentini FC, Reis LO, Carnelli GR,
Fregonesi A. How are we protecting ourselves from radiation
exposure? A nationwide survey. Int Urol Nephrol 2015;47:2714.
85. Zewu Z, Hequn C, Yu C, Yang L, Zhongqing Y, Zhiyong C, etal. Long-term outcome after flexible ureteroscopy with holmium laser for simultaneous treatment of a single renal cyst andipsilateral renal stones. J Int Med Res 2019;47:3601-12.
86. Geavlete P, Georgescu D, Mirciulescu V, Niţă G. Ureteroscopic
laser approach in recurrent ureteropelvic junction stenosis. Eur
Urol 2007;51:1542-8.
87. Inoue T, Okada S, Hamamoto S, Miura H, Matsuzaki J, Tambo
M, et al. Evaluation of flexible ureteroscope with an omni-

ible ureteroscopy in the treatment of renal stones. World J Urol
2019;37:921-9.
90. Proietti S. New technology in retrograde intrarenal surgery:unnecessary luxury vs. measurable benefit [abstract]. 35th Annual European Association of Urology Congress; 2020 Jul 1719. Arnhem: European Association Urology; 2020.
91. Inoue T, Okada S, Hamamoto S, Matsuda T. New advanced
bench model for flexible ureteroscopic training: the Smart
Simulator. J Endourol 2018;32:22-7.
92. Saglam R, Muslumanoglu AY, Tokatlı Z, Caşkurlu T, Sarica K,Taşçi Aİ, et al. A new robot for flexible ureteroscopy: development and early clinical results (IDEAL stage 1-2b). Eur Urol
2014;66:1092-100.

directional bending tip, using a JOYSTICK unit (URF-Y0016):

93. Desai MM, Grover R, Aron M, Ganpule A, Joshi SS, Desaian ex-vivo study. World J Urol 2020 Mar 14 [Epub]. https://doi.

MR, et al. Robotic flexible ureteroscopy for renal calculi: initialorg/10.1007/s00345-020-03151-w.

clinical experience. J Urol 2011;186:563-8.

88. Tambo M, Inoue T, Miura H, Matsuzaki J, Nutahara K, Hama-

94. Geavlete P, Saglam R, Georgescu D, Mulţescu R, Iordache V,

moto S, et al. A novel flexible ureteroscope with omnidirec-

Kabakci AS, et al. Robotic flexible ureteroscopy versus classic

tional bending tip using joystick-type control unit (URF-

flexible ureteroscopy in renal stones: the initial Romanian ex-

Y0016): initial validation study in bench models. J Endourol

perience. Chirurgia (Bucur) 2016;111:326-9.

2020;34:676-81.
89. Zhu Z, Cui Y, Zeng F, Li Y, Chen Z, Hequn C. Comparison of

95. Brodie A, Vasdev N. The future of robotic surgery. Ann R Coll
Surg Engl 2018;100(Suppl 7):4-13.

suctioning and traditional ureteral access sheath during flex-

Investig Clin Urol 2021;62:121-135.

www.icurology.org

135