EURURO-7240; No. of Pages 16

Platinum Priority – Stone DiseaseEditorial by XXX on pp. x–y of this issue

Tract Sizes in Miniaturized Percutaneous Nephrolithotomy:

A Systematic Review from the European Association of Urology

Urolithiasis Guidelines Panel

Yasir Ruhayel a, Abdulkadir Tepeler b, Saeed Dabestani a, Steven MacLennan c, Ales Petrık d,e,Kemal Sarica f, Christian Seitz g, Andreas Skolarikos h, Michael Straub i, Christian Turk j,Yuhong Yuan k, Thomas Knoll l,*

a Department of Urology, Skane University Hospital, Malmo, Sweden; b Department of Urology, Sen Jorj Austria Hospital, Istanbul, Turkey; c Academic Urology

Unit, University of Aberdeen, Aberdeen, UK; d Department of Urology, Region Hospital, Ceske Budejovice, Czech Republic; e Department of Urology, First

Faculty of Medicine, Charles University in Prague, Prague, Czech Republic; f Department of Urology, Dr. Lutfi Kirdar Kartal Research and Training Hospital,

Istanbul, Turkey; g Department of Urology, Medical University Vienna, Vienna, Austria; h Second Department of Urology, Sismanoglio Hospital, Athens

Medical School, Athens, Greece; i Department of Urology, Technical University Munich, Munich, Germany; j Department of Urology, Hospital of the Sisters of

Charity, Vienna, Austria; k Department of Medicine, McMaster University, Hamilton, Canada; l Department of Urology, Sindelfingen-Boeblingen Medical

Center, University of Tubingen, Sindelfingen, Germany

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X

ava i lable at www.sc iencedirect .com

journa l homepage: www.europea nurology.com

Article info

Article history:

Accepted January 30, 2017

Associate Editor:

Giacomo Novara

Keywords:

Mini-perc

Percutaneous nephrolithotomy

Residual fragments

Stone surgery

Stenting

Systematic review

Urinary calculi

Abstract

Context: Miniaturized instruments for percutaneous nephrolithotomy (PNL), utilizingtracts sized �22 Fr, have been developed in an effort to reduce the morbidity andincrease the efficiency of stone removal compared with standard PNL (>22 Fr).Objective: We systematically reviewed all available evidence on the efficacy and safetyof miniaturized PNL for removing renal calculi.Evidence acquisition: The review was performed according to the Preferred ReportingItems for Systematic Reviews and Meta-analyses statement. Since it was not possible toperform a meta-analysis, the data were summarized in a narrative synthesis.Evidence synthesis: After screening 2945 abstracts, 18 studies were included (tworandomized controlled trials [RCTs], six nonrandomized comparative studies, and 10 caseseries). Thirteen studies were full-text articles and five were only available as congressabstracts. The size of tracts used in miniaturized procedures ranged from 22 Fr to 4.8 Fr.The largest mean stone size treated using small instruments was 980 mm2. Stone-freerates were comparable in miniaturized and standard PNL procedures. Procedures per-formed with small instruments tended to be associated with significantly lower bloodloss, while the procedure duration tended to be significantly longer. Other complicationswere not notably different between PNL types. Study designs and populations wereheterogeneous. Study limitations included selection and outcome reporting bias, as wellas a lack of information on relevant confounding factors.Conclusions: The studies suggest that miniaturized PNL is at least as efficacious andsafe as standard PNL for the removal of renal calculi. However, the quality of theevidence was poor, drawn mainly from small studies, the majority of which were

* Corresponding author. Department of Urology, Klinikum Sindelfingen-Boblingen, University ofTubingen, Arthur-Gruber-Strasse 70, 71065 Sindelfingen, Germany. Tel. +49 7031 9812501;Fax: +49 703 9812354.E-mail address: t.knoll@klinikverbund-suedwest.de (T. Knoll).

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

http://dx.doi.org/10.1016/j.eururo.2017.01.0460302-2838/# 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.

EURURO-7240; No. of Pages 16

single-arm case series, and only two of which were RCTs. Furthermore, the tract sizes usedand types of stones treated were heterogeneous. Hence, the risks of bias and confoundingwere high, highlighting the need for more reliable data from RCTs.Patient summary: Removing kidney stones via percutaneous nephrolithotomy (PNL) usingsmaller sized instruments (mini-PNL) appears to be as effective and safe as using larger(traditional) instruments, but more clinical research is needed.

# 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X2

1. Introduction

Kidney stone disease is considered to be an important

health issue; its incidence has increased over the years to

almost 9% [1]. Despite efforts in prevention and advances in

management methods, urolithiasis is still an important

cause of morbidity in all age groups and carries a significant

economic burden because of associated direct and indirect

costs [2,3].

Percutaneous nephrolithotomy (PNL) has gained accep-

tance as the gold standard for the treatment of large renal

calculi [4,5]. During the past 20 yr, the instruments used

have been miniaturized in an effort to decrease morbidity

associated with standard PNL and increase the efficiency of

stone removal. Jackman et al [6] and Helal et al [7] initially

used smaller instruments in 1997 for pediatric cases with

the proposed advantage of lower morbidity. Today, the term

mini-perc, or mini-PNL (mPNL), usually describes tract sizes

between 14 Fr and 22 Fr, although a clear definition does not

exist [4]. Recently, even smaller systems—ultramini-PNL

(umPNL) using tracts sized 11–13 Fr and microperc (mPNL)

using tracts sized 4.8–10 Fr—have been introduced as

alternative modalities to reduce procedure-related morbid-

ity [8,9].

The primary goal of PNL is to achieve stone-free status

while minimizing morbidity and complications. It has been

reported that tract size is one of the main parameters

affecting the complication rate [10]. However, reducing the

tract size may adversely affect some procedure-related

factors such as operation time [11]. We performed a

systematic review to assess the relative benefits and harms

of different PNL tract sizes for the treatment of renal stones.

2. Evidence acquisition

2.1. Search strategy

This systematic review was performed according to the

Preferred Reporting Items for Systematic Reviews and

Meta-analyses (PRISMA) statement [12] and the Cochrane

Handbook for Systematic Reviews of Interventions

[13]. Studies on PNL (from January 1, 2000 to October 30,

2014) were identified by highly sensitive searches of

electronic databases (Embase, Medline, the Cochrane

Central Register of Controlled Trials, and the Health

Technology Assessment Database). Studies in languages

other than English were excluded. The protocol for the

review is available on PROSPERO (CRD42015023766; www.

crd.york.ac.uk/PROSPERO).

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

The articles identified were independently screened by

two reviewers (Y.R. and A.T.). Full-text articles of potentially

relevant studies were subsequently independently scruti-

nized for eligibility. Disagreements were resolved by a third

party (T.K.).

2.2. Selection of studies

We included randomized controlled trials (RCTs), nonran-

domized comparative studies (NRCSs), and single-arm

studies with at least one study arm reporting efficacy or

safety data on PNL procedures using tracts sized �22 Fr

(mPNL, umPNL, or mPNL) for treatment of renal stones in

adults (age �18 yr). Studies published as full-text articles or

as congress abstracts were included. The exclusion criteria

were: case series (single arm) of <20 patients; pediatric

studies (age <18 yr); patients with pre-existing nephros-

tomy before PNL; anatomic abnormalities (eg, horse-shoe

kidney, transplanted kidney, malrotated kidney); use of

electrohydraulic lithotripsy for stone fragmentation; and

multitract punctures (ie, more than one tract used during

procedure). However, studies fulfilling any exclusion

criterion were included if groups of patients of interest to

this review were reported separately, or if the fraction of

procedures or patients with criteria meriting exclusion

constituted <10% of the total study population.

The primary benefit outcomes were the immediate

stone-free rate (ISFR) and the stone-free rate (SFR) at a later

date (after auxiliary procedures for a period of up to 3 mo).

For this review, ‘‘stone-free’’ was defined as there being no

detectable stone fragments on radiology; if an alternative

definition was used by the trialist (eg, residual fragments

sized <4 mm), the data were reclassified accordingly. The

imaging modality used to assess stone-free status was not

considered.

The primary harm outcomes were intraoperative and

postoperative complications. These were recorded as the

incidence of grouped complications according to severity,

such as Clavien grade, or as the incidence of ad hoc

individual complications such as blood loss (as defined by

the trialist; eg, ml of blood or change in hemoglobin

concentration), the need for blood transfusions, visceral

injury, urosepsis, pneumothorax, or death.

The secondary benefits and harms outcomes were:

duration of the procedure; quality of life (QOL; as defined by

the trialist); pain (as defined by the trialist; eg, analgesic

requirement, pain scores quantified on a visual analog scale

[VAS], etc); need for a secondary procedure (procedure to

clear the stone beyond the primary procedure, including

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 3

EURURO-7240; No. of Pages 16

retreatment using the same modality [ie, more than one

PNL session] or other modality such as shockwave

lithotripsy [SWL] or transurethral endoscopic lithotripsy);

need for adjunctive procedure (a procedure to deal with a

complication [eg, nephrostomy or double-J stent insertion

for obstruction] and procedures incidental to the stone

removal process such as stent insertion and/or removal);

duration of hospital stay; hospital readmission; and

emergency department visit.

2.3. Data extraction

A data extraction form was developed a priori to collect

information on study design, characteristics of participants

and interventions, and primary and secondary outcome

measures (benefits and harms).

2.4. Risk-of-bias assessment

Two reviewers (Y.R. and A.T.) independently assessed the

risk of bias (RoB) for individual studies. Any disagreements

were resolved by discussion or by consulting a third author

(T.K.). The RoB in RCTs was assessed using the recom-

mended tool in the Cochrane Handbook for Systematic

Reviews of Interventions [13]. This included assessment of

random sequence generation, allocation concealment,

blinding of participants and personnel, blinding of outcome

assessment, incomplete outcome data, selective reporting,

and other sources of bias.

RoB in NRCSs was assessed using all seven domains

above and an extra item to assess the risk of findings being

explained by confounding. This is a pragmatic approach

informed by methodological literature pertaining to asses-

sing RoB in NRCSs [14,15]. A list of the most important

potential confounders for harm and benefit outcomes was

developed a priori with clinical content experts (European

Association of Urology Urolithiasis Guidelines Panel). The

potential confounding factors were stone size, stone

location, obesity, previous open surgery on a kidney (eg,

open nephrolithotomy), subcostal versus intercostal punc-

ture, and calyceal access (upper vs middle vs lower calyx).

For each study, an algorithmic approach was used to

assess the risk of confounding bias. The following were

considered in sequence. (1) Was the prognostic confounder

considered? If ‘‘no’’, the study was deemed to be at ‘‘high’’

RoB for this confounder. If ‘‘yes’’, go to the next question. (2)

Was the confounder balanced between the intervention(s)

and control group (s)? If ‘‘yes’’, the study was at ‘‘low’’ RoB. If

‘‘no’’, go to the next questions. (3) Was the confounder

controlled for in the analysis, for example via statistical

adjustment such as univariate or multivariate analysis or

propensity score matching? If ‘‘yes’’, the study was at ‘‘low’’

RoB. If ‘‘no’’, the study was at ‘‘high’’ RoB.

The approach described above cannot be used to assess

RoB in NRCSs. To address the external validity (ie,

applicability of the results to different people, places, or

time) of the NRCSs, we assessed whether study participants

were selected consecutively or representative of a wider

patient population, and whether the specified confounding

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

factors were comparable across studies reporting on the

same intervention. This too was a pragmatic approach

informed by the methodological literature [16,17]. Further

details on the approach outlined above are available on

PROSPERO (CRD42015023766; www.crd.york.ac.uk/

PROSPERO).

The key RoB and confounder assessments from the tools

described above were summarized and presented graphi-

cally (Fig. 2).

2.5. Data analysis

For the purposes of this review, we refer to all procedures

using smaller tract sizes (�22 Fr) as mPNL when compared

with procedures using larger instruments (unless otherwise

specified). A meta-analysis for the two RCTs was not feasible

because of heterogeneity in study design. Forest plots were

created for the RCTs and NRCSs reporting SFRs to show the

direction and magnitude of effects.

3. Evidence synthesis

3.1. Search results

The search returned 2945 abstracts (Fig. 1), of which

240 were scrutinized for eligibility. Four articles in

languages other than English were excluded, as were an

additional 218 studies that did not meet the remaining

inclusion criteria. A total of 18 studies were eligible for final

inclusion, of which 13 were full-text articles [8,11,18–28]

and five were conference abstracts [29–33].

3.2. Study and patient characteristics

Of the 18 studies included, two were RCTs [19,28], six were

NRCSs [11,21,22,24,26,27], and ten were single-arm case

series on mPNL only [8,18,20,23,25,29–33]. There was one

study on PNL using tract size 22 Fr [21] and one on tract

sizes <20 Fr [29]. Three studies evaluated tract size 18 Fr

[18,22,23], two studies 16 Fr [19,26], and two 14 Fr

[11,25]. One study reported on tracts sized 14–18 Fr [24],

and another on tracts �18 Fr [27]. There were three studies

on tract sizes 11–13 Fr [8,20,30] and one on 4.8 Fr [28]. Three

studies presented as conference abstracts did not explicitly

state the tract size, but the procedures were termed mPNL

[31–33]. No studies reported QOL outcomes. The baseline

characteristics of the participants in the studies included

are outlined in Table 1 and the findings are summarized in

Table 2.

3.3. RCTs

Two RCTs were identified, both of which were full-text

articles. Only one study investigated the benefits and harms

of mPNL using ‘‘regular’’ (16 Fr) compared to standard PNL

(24 Fr) [19]. Both blood loss and the need for blood

transfusion were significantly lower in the mPNL group

(both p < 0.05), although the types of stone were not fully

comparable. The SFR was only significantly different for

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

Records identified through database searching(n = 2945 )

Abstr acts screened (n = 2945 )

Excluded

(n = 222)(n = 99)(n = 123)

Abstracts assessed for eligibilit y

Tota l (n = 240)Full-text articles (n = 112)

Conference abstracts (n = 128)

Full-text articles included (n = 13)

Scr

een

ing

Incl

ud

edE

ligib

ility

Iden

tifi

cati

on

Conference abstracts included (n = 5)

Records exclude dn = 2705

Reasons for exclusio n

• Language other than Englis h• Interventio n no t relevant• Popula tio n unclea r• Ba sic scien ce studie s• Participant s in cas e serie s with n <2 0• Case s <1 8 yr of ag e >10%• Cases wi th ana tomica l anomalie s >10 %• Case s treate d bilaterall y >10%• Multipl e tract s use d in >10 % of cases• Dat a not in useabl e format• Imagin g studies• Duplicat e studie s or duplicat e data

Studies included in systema tic reviewTota l (n = 18)• 2 RC Ts• 6 NRCS s• 10 case serie s

Fig. 1 – Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) flow diagram showing the screening process for inclusion ofstudies. RCT = randomized controlled trial; NRCS = non-randomized comparative study.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X4

EURURO-7240; No. of Pages 16

multiple calyceal stones (85% for mPNL vs 70% for standard

PNL, p < 0.05). The duration of the procedure was longer in

the mPNL group for all stone types (all p < 0.05; Table 1).

The other RCT was a comparison of mPNL (4.8 Fr) and

standard PNL (30 Fr) [28]. No benefit was found with respect

to ISFR (p = 1), although blood loss and procedure duration

were lower (p = 0.004 and 0.034, respectively) and hospital

stay was shorter (p = 0.001). Intrarenal pelvic pressure was

higher in the mPNL group (p < 0.0001; Table 1).

3.4. NRCSs

Six NRCSs were included, all of which were full-text articles.

One study compared five groups with successively increas-

ing PNL tract size (22, 24, 26, 28, and 30 Fr) [21]. Blood loss

increased with the tract size (p < 0.05) but the procedure

duration did not significantly differ between the groups

(Table 2). Another study using the PNL Global Study database

of The Clinical Research Office of the Endourological Society

(CROES) reported data for four groups (�18, 24–26, 27–30,

and �32 Fr) [27]. The only relevant outcomes were blood

loss and blood transfusion rates, which significantly

increased with the tract size (p = 0.00016 and <0.0001).

Four comparative studies comprised two main comparator

groups (mPNL vs standard PNL). In one of the studies [11],

the control arm (30 Fr) was further divided into two groups:

patients who received a nephrostomy tube and patients who

did not (tubeless). SFR was lower in the mPNL group (14 Fr)

than in either of the standard PNL groups (tube p = 0.016 and

tubeless p = 0.009). Blood loss was lower than in the tube

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

standard PNL group (p = 0.021) but not the tubeless standard

PNL group (p = 0.041). Tubeless standard PNL was also

superior in terms of analgesic requirement, pain (VAS), and

duration of procedure and hospital stay (Table 2). Xu et al

[26] compared 16 Fr mPNL with 24 Fr PNL, and observed

lower blood loss in the mPNL group (p = 0.015), although the

stones treated were also smaller. ISFR, complication rates,

procedure duration, and hospital stay did not differ (Table 2).

Mishra et al [24] compared mPNL (14–18 Fr) with standard

PNL (24–28 Fr), but interpretation of the results is obscured

by the use of different energy sources for stone fragmenta-

tion: laser in the mPNL group and pneumatic in the standard

PNL group [24]. The study reported similar SFR (p = 0.49) and

analgesic requirement (p = 0.28), but lower blood loss

(p = 0.0098) and procedure duration (p = 0.0008), and

shorter hospital stay (p <0.00001) in the mPNL group. A

greater proportion of procedures were tubeless in the mPNL

(78%) than in the standard PNL group (14%; p < 0.001). Knoll

et al [22] compared mPNL (18 Fr) and standard PNL (26 Fr)

and found similar ISFR in both groups (p = 1.00). However,

stones were significantly larger in the standard PNL group

(p = 0.042). The study also revealed similar blood loss,

complication rates, procedure duration, and analgesic

requirements for both groups (all p > 0.05). However pain

scores (VAS) were lower (p = 0.048) and hospital stay was

shorter (p = 0.021) among mPNL patients. All mPNL proce-

dures were tubeless if uncomplicated and the patient was

rendered stone-free, otherwise a nephrostomy tube was

placed. All patients undergoing standard PNL received a

nephrostomy tube.

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

Karaköse2014 [21]

Xu 2014 [26]

Knoll 2010 [22]

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Fig. 2 – Risk of bias and confounding assessment summary. (A) Risk of bias assessment for randomized controlled trials. (B) Risk of bias andconfounding assessment for non-randomized comparative studies. (C) Risk of bias assessment for case series. Green circle = low risk of bias orconfounding; red circle = high risk of bias or confounding; yellow circle = unclear risk of bias or confounding.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 5

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

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01

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20

12

[21

]

mP

NL

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50

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12

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[26

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1]

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37

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PN

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26

46

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12

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37

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14

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5]

mm

18

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PN

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8Fr

18

41

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16

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[22

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9]8

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36

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11

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[25

–5

0]

mm

9/9

PN

L3

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32

45

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13

.80

[24

–7

2]2

1/1

13

7.5

3�

12

.23

[30

–5

5]

mm

15

/17

Xu

20

14

,co

mp

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tiv

est

ud

y,

Ch

ina

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01

1–

20

13

[26

]

mP

NL

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50

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14

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42

2.7�

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Re

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20

mm

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18

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33

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10

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mN

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5B

en

efi

ts:

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Ha

rms:

CG

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L

Se

con

da

ryo

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om

es:

DP

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HS

Oth

er

ou

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me

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olu

me

of

flu

id

ab

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ed

PN

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4Fr

34

45

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13

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3/2

12

2.8�

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41

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10

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6

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ma

gu

chi

20

11

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mp

ara

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e

stu

dy

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lob

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20

07

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00

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7]�

18

Fr2

71

NR

NR

NR

NR

NR

Inco

mp

lete

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n

(n=

26

6)

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NR

NR

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rms:

BL,

BT

24

–2

6Fr

10

39

27

–3

0Fr

35

33

�3

2Fr

37

1

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20

11

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mp

ara

tiv

e

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dy

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dia

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00

9–

20

10

[24

]

mP

NL

14

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8Fr

26

NR

42

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19

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23

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Re

na

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on

es

10

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m

Pe

dia

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pa

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UT

I

Mo

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esi

ty

Un

corr

ect

ed

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gu

lop

ath

ies

14

7�

30

mm

22

(8%

)U

C

1(4

%)

MC

15

(58

%)

LC

9(3

5%

)P

8/1

9B

en

efi

ts:

ISFR

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DH

S,

DP

,

an

alg

esi

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ire

me

nt

PN

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28

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16

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8/8

22

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2.7

14

9�

60

mm

23

(12

%)

UC

2(8

%)

MC

10

(38

%)

LC

13

(50

%)

P

10

/18

Kn

oll

20

10

,co

mp

ara

tiv

est

ud

y,

Ge

rma

ny

,2

00

7–

20

09

[22

]

mP

NL

18

Fr2

5N

R5

2�

11

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7–

77

]2

.1:1

(17

/8

)27�

3.5

[19

–3

6]

Pa

tie

nts

wit

hso

lita

ryre

na

l

sto

ne

loca

ted

inlo

we

rp

ole

or

ren

al

pe

lvis

NR

18�

3.3

[10

–2

1]

mm

NR

NR

Be

ne

fits

:IS

FR

Ha

rms:

BL,

fev

er,

VI

Se

con

da

ryo

utc

om

es:

DP

,P

ain

:

VA

S,

AR

,D

HS

PN

L2

6Fr

25

48�

15

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3–

73

]1

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(16

/9

)29�

5.6

[19

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2]

22�

4.2

5[1

4–

29

]m

m

Giu

sti

20

07

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mp

ara

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est

ud

y,

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ly,

19

99

–2

00

4[1

1]

mP

NL

14

Fr4

00

an

d1

48

.0[2

9–

70

]2

0/

20

26

.0K

idn

ey

sto

ne<

20

mm

.

Incl

usi

on

crit

eri

afo

rT

LP

NL:

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gle

tra

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ab

sen

ceo

f

coll

ect

ing

syst

em

pe

rfo

rati

on

an

db

lee

din

g,

com

ple

test

on

e

cle

ara

nce

NR

28

0m

m2

20

(50

%)

LC

20

(50

%)

P

21

/1

9B

en

efi

ts:

SFR

Ha

rms:

BL,

BT

Se

con

da

ryo

utc

om

es:

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ain

:

VA

S,

AR

,D

HS

Oth

er

ou

tco

me

s:T

RN

A

PN

L3

0Fr

67

51

.3[1

9–

78

]3

6/

31

24

.63

10

mm

2N

R3

0/

37

TL

PN

L3

0Fr

27

48

.5[2

2–

77

]1

4/

13

23

.83

20

mm

2N

R1

2/

15

Mil

ler

20

14

,ca

sese

rie

s,U

K,

20

09

–2

01

3,

ab

stra

ct[3

2]

mP

NL

16

.5Fr

11

60

63

.2

(re

po

rte

da

s

‘‘av

era

ge

ag

e’’)

60

/5

6N

RN

RN

RN

RN

RN

RB

en

efi

ts:

ISFR

,IC

IRFR

,

Ha

rms:

CG

,B

T,

US

,S

P

Se

con

da

ryo

utc

om

es:

DP

,D

HS

Bh

att

u2

01

4,

case

seri

es,

Ind

ia,

20

09

–2

01

3,

ab

stra

ct[2

9]

mP

NL

(�2

0Fr

)3

01

NR

42

NR

NR

NR

Act

ive

ble

ed

ing

dis

ord

er,

UT

I,

pre

gn

an

cy

14

.7�

4.3

mm

NR

NR

Be

ne

fits

:S

FR

Ha

rms:

CG

,B

L,S

P

Se

con

da

ryo

utc

om

es:

DP

,D

HS

Ka

rata

g2

01

4,

case

seri

es,

Tu

rke

y,

20

13

,a

bst

ract

[31

]

mP

NL

68

NR

41

.4N

R2

6.3

NR

NR

12

2m

m2

NR

NR

Be

ne

fits

:S

FR

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DP

,D

HS

Oth

er

ou

tco

me

s:D

F

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X6

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

Desai 2013, case series, India,

recruitment period NR,

abstract [30]

umPNL 12 Fr 74 1 NR

4 (5%) pediatric cases

NR NR umPNL NR 16.6 mm NR NR Benefits: SFR

Harms: CG, BL,

Secondary outcomes:

DHS

Other outcomes: conversion to

mPNL due to bleeding

Desai 2013, case series, India,

recruitment period NR [8]

umPNL 13 Fr 62 1 NR

4 (7%) pediatric cases

NR NR

2 (3%) obese

Renal stones

umPNL

NR 16.8 mm NR NR Benefits: SFR

Harms: CG, BL,

Secondary outcomes:

DHS

Other outcomes: conversion to

mPNL due to bleeding

Desai 2013, case series,

China, 2012 [20]

umPNL 11–13 Fr 36 1 48.2 � 15.7 [2–79]

No. pediatric cases NR

23 / 13 24.63

[18.1–33.2]

Renal stone

<20 mm

NR 14.9 � 4.1 [6–20] mm

Area:

160.6 � 82.7 [30–380] mm2

7 (19%) UC

8 (22%) MC

10 (28%) LC

3 (7%) Multiple C

5 (14%) P

3 (8%) UUr

21 / 15 Benefits: ISFR, SFR,

Harms: CG, BL, US

Secondary outcomes: DP, SP,

DHS

Other outcomes:

Puncture locations

Abdelhafez 2013, case series,

Germany, 2007–2011 [18]

mPNL 18 Fr

Stone size <20 mm

Stone size �20 mm 98

93

1

1

49.6 � 15.9

48.8 � 17.6

NR

NR

25.8 � 5.2

26.5 � 5.9

Consecutive patients with

stones >15 mm or lower calyx

stones >8 mm, or any

previously failed SWL and URS

NR

13.6 � 3.4 mm

37.5 � 22.9 mm

NR NR Benefits: ISFR, SFR,

Harms: CG, BL, BT

Secondary outcomes: DP, SP,

DHS

Zimmermans 2012, case series,

recruitment period NR,

Germany, abstract [33]

mPNL, 18 Fr

All patients, all stone sizes

Stones �500 mm2 652

183

NR 54.1 � 15.7 NR NR mPNL Access not possible

410 mm2

950 mm2

NR NR Benefits: ISFR

Harms: CG, BL, BT, VI

Secondary outcomes: DP, SP

Lu 2012, case series, China,

2009–2010 [23]

Tubeless mPNL

Standard mPNL

(with 16 Fr nephrostomy tube)

16

16

0.5 43.81 � 18.89

46 � 22.37

6/10

7/9

NR Pelvic stone <40 mm Urinary tract obstruction

(BPH, UPJ stenosis), UTI,

Coagulopathies

32.9 � 6.2 mm

31.1 � 6.2 mm

NR

NR

NR Benefits: ISFR

Harms: CG, BL,

Secondary outcomes: DHS, DP,

pain

Sung 2006, case series, Korea,

1999–2002 [25]

mPNL 14 Fr 72 7.2 � 8.3

[0.5–37]

49.5 � 14.7 [1.4–73] 45/27 NR Failed SWL and/or URS

(n = 19), large stone burden

(>600 mm2) (n = 25), P and/or

LC stones, (n = 62), UC stones

(n = 2), calyceal diverticulum

stone (n = 1)

1 pediatric case

31/72 patients had >2

indications

NR 34.2 � 19.9 [6–102] mm 62 (86%) P and/or LC

2 (2%) UC

1 (1%) calyceal

diverticulum

31/41 Benefits: ISFR, SFR

Harms: fever, BL

Secondary outcomes: SP, DHS

AP = adjunctive procedure; BL = blood loss; BT = blood transfusion; C = calyx; CG = Clavien grade; CIRFR = clinically insignificant residual fragment rate; DB = database; DHS = duration of hospital stay; DP = duration of

procedure; EDV = emergency department visit; FU = follow-up (here meaning time point for delayed assessment of stone status, if applicable); HR = hospital readmission; ISFR = immediate SFR; ICIRFR = immediate CIRFR;

LC = lower calyceal; MC = middle calyceal; mPNL = mini-PNL; NR = not reported; P = pelvis; PNL = percutaneous nephrolithectomy; QOL = quality of life; RCT = randomized controlled trial; SFR = stone-free rate;

SP = secondary procedure; UC = upper calycal; umPNL = ultra-mini-PNL; UPJ = ureteropelvic junction; URS = ureteroscopy; US = urosepsis; UUr = upper ureteral; VI = visceral injury.

E U

R O

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ay

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et

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izes

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NL

30

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en

efi

ts:

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rms:

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L

Se

con

da

ry

ou

tco

me

s:D

P,

DH

S

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er:

intr

are

na

l

pe

lvic

pre

ssu

re

10

10

ISFR

:8

(80

%)

CG

1:

1(1

0%

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1.8

%�

0.8

%(0

.9–

3.2

%)

DP

:3

6.5�

14

.2(2

0–

60

)m

in

DH

S:1

.1�

0.3

(1–

2)

d

IPP

:3

0.3�

3.9

mm

Hg

ISFR

:9

(90

%)

CG

3a

:1

(10

%)

BL:

3.5

%�

1.5

%(1

.2–

6.1

%)

DP

:4

9�

9.8

(32

–6

5)

min

DH

S:2�

0.5

(1–

3)

d

IPP

:2

0.1�

3.1

mm

Hg

1 0.0

04

0.0

34

0.0

01

<0

.00

01

BL

rep

ort

ed

as

pe

rce

nt

dro

pin

he

ma

tocr

it

mP

NL

vs

PN

Lsh

ow

ed

no

ISFR

be

ne

fit,

alt

ho

ug

hB

La

nd

DP

we

relo

we

r.IP

Pw

as

hig

he

rin

the

mP

NL

gro

up

Ch

en

g2

01

0,

RC

T,

Ch

ina

,2

00

4–

20

07

[19

]

To

tal

Sta

gh

orn

sto

ne

s(S

S)

Sim

ple

ren

al

pe

lvic

sto

ne

s(S

RP

S)

Mu

ltip

leca

lyce

al

sto

ne

s(M

CS

)

mP

NL

16

FrP

NL

24

FrB

en

efi

ts:

ISFR

Ha

rms:

CG

,B

L

Se

con

da

ry

ou

tco

me

s:D

HS

,

DP

,a

na

lge

sic

req

uir

em

en

t

72

18

27

27

11

5

29

46

40

BL:

0.5

3�

0.7

9g

/dL

BT

:1

(1.4

%)

Pn

eum

oth

ora

x:

1(1

.4%

)

Uri

ne

leak

age:

0(0

%)

DH

S:7

.3(6

–1

2)

d

AR

(pet

hid

ine)

:8

8.7�

40

.6m

g

VA

S(1

–2

d)

SFR

for:

SS:

13

/18

(72

.2%

)

SRP

S:2

5/2

7(9

2.6

%)

MC

S:2

3/2

7(8

5.2

%)

DP

for:

SS:

13

4.4�

19

.7m

in

SRP

S:8

9.4�

21

.5m

in

MC

S:1

13

.9�

20

.3m

in

BL:

0.9

7�

1.4

2g

/dL

BT

:1

2(1

0.4

%)

Pn

eum

oth

ora

x:

0

Uri

ne

leak

age:

2(1

.7%

)

DH

S:7

.5(6

–1

5)

d

AR

(pet

hid

ine)

:9

4.3�

37

.2m

g

VA

S(1

–2

d)

SFR

for:

SS:

22

/29

(75

.9%

)

SRP

S:4

0/4

6(9

1.3

%)

MC

S:2

8/4

0(7

0.0

%)

DP

for:

SS:

11

8.9�

21

.5m

in

SRP

S:7

7�

17

.6m

in

MC

S:1

01

.2�

19

.1m

in

<0

.05

<0

.05

>0

.05

>0

.05

>0

.05

>0

.05

>0

.05

>0

.05

>0

.05

<0

.05

<0

.05

<0

.05

<0

.05

BL

an

dn

ee

dfo

rB

Tw

ere

low

er

inm

PN

Lg

rou

p,

ho

we

ve

rst

on

es

we

ren

ot

full

y

com

pa

rab

le.

mP

NL

resu

lts

mo

stfa

vo

rab

lefo

rm

ult

iple

caly

cea

lst

on

es.

DP

wa

slo

ng

er

inm

PN

Lg

rou

p.

Ka

rak

ose

20

14

,

com

pa

rati

ve

stu

dy

,

Tu

rke

y,

20

11

–2

01

2[2

1]

NA

mP

NL

22

FrU

ncl

ea

r–

chi–

squ

are

test

use

d

Ha

rms:

CG

,B

L,B

T,

AP

,S

P

Se

con

da

ry

ou

tco

me

s:D

P

Oth

er

ou

tco

me

s:

pre

op

vs

po

sto

p

cre

ati

nin

e

15

NA

CG

1:

1,

CG

2:

0

Pre

op

Hb

:1

4.3�

1.5

[11

.6–

17

]g

/dl

Po

sto

pH

b:

13

.7�

1.7

[10

.2–

16

.1]

g/d

l

BT

(n):

0

AP

(n):

4

SP(n

):0

DP

:1

02

.8�

30

.0[5

5–

12

6]

min

Re

fere

nce

gro

up

for

sta

tist

ica

l

an

aly

sis

no

tst

ate

d

PN

L2

4Fr

19

CG

1:

2,

CG

2:

0

Pre

op

Hb

:1

3.9�

1.8

[9.1

0–

17

]g

/dl

Po

sto

pH

b:

12

.9�

1.7

[9.6

–1

5.3

]g

/dl

BT

(n):

0

AP

(n):

2

SP(n

):0

DP

:1

05

.5�

39

.5[7

5–

21

0]

min

PN

L2

6Fr

26

CG

1:

1,

CG

2:

2

Pre

op

Hb

:1

4.7�

1.4

[11

.7–

17

]g

/dl

Po

sto

pH

b:

12

.3�

2.1

[7.9

–1

4.7

]g

/dl

BT

(n):

2

AP

(n):

0

SP(n

):0

DP

:1

03

.7�

40

.5[4

0–

11

5]

min

PN

L2

8Fr

18

CG

1:

0,

CG

2:

4

Pre

op

Hb

:1

4.4�

1.4

[11

.6–

16

.9]

g/d

l

Po

sto

pH

b:

11

.7�

1.8

[8.5

–1

4.1

]g

/dl

BT

(n):

4

AP

(n):

0

SP(n

):0

DP

:1

10

.6�

45

.3[7

0–

24

0]

min

PN

L3

0Fr

32

CG

1:

3,

CG

2:

7

Pre

op

Hb

:1

4.2�

1.6

[9.1

0–

17

]g

/dl

Po

sto

pH

b:

10

.4�

1.8

[8.3

–1

2.3

]g

/dl

BT

(n):

7

AP

(n):

2

SP(n

):0

DP

:1

08

.1�

48

.6[6

5–

22

0]

min

>0

.05

<0

.05

>0

.05

Xu

20

14

,co

mp

ara

tiv

e

stu

dy

,C

hin

a,

20

11

–2

01

3[2

6]

NA

mP

NL

16

FrP

NL

24

FrB

en

efi

ts:

ISFR

Ha

rms:

CG

,B

L

Se

con

da

ry

ou

tco

me

s:D

P,

DH

S

Oth

er

ou

tco

me

s:

vo

lum

eo

ffl

uid

ab

sorb

ed

37

34

ISFR

:2

9/3

7(7

8%

)

CG

2:

5(1

3.3

%)

BL:

7.4�

3.5

g/l

DP

:1

15

.4�

13

.5m

in

DH

S:9

.8�

3.4

d

ISFR

:2

7/3

4(7

9%

)

CG

:5

(14

.7%

)

BL:

9.6�

4.0

g/l

DP

:1

10

.6�

17

.0m

in

DH

S:9

.3�

3.0

d

0.9

15

1.0

00

0.0

15

0.1

88

0.5

73

No

tra

nd

om

ize

d:

sele

ctio

no

f

tech

niq

ue

ba

sed

on

join

t

de

cisi

on

by

surg

eo

ns

an

d

pa

tie

nts

.S

ton

es

inP

NL

gro

up

sig

nifi

can

tly

larg

er

BL

wa

ssi

gn

ifica

ntl

ylo

we

rin

mP

NL

gro

up

,h

ow

ev

er

sto

ne

s

tre

ate

dw

ere

sma

lle

r.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X8

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

Ya

ma

gu

chi

20

11

,

com

pa

rati

ve

stu

dy

,

Glo

ba

l,2

00

7–

20

09

[27

]

NA

�1

8Fr

NA

Ha

rms:

BL,

BT

27

1N

AB

L:1

1(4

.1%

)

BT

:3

(1.1

%)

NA

NR

CR

OE

Sd

ata

ba

se

BT

rate

sd

iffe

rsl

igh

tly

be

twe

en

Ta

ble

s5

an

d8

(aft

er

sum

min

g

dil

ata

tio

nm

eth

od

s).

Da

tafo

rB

L

calc

ula

ted

fro

mT

ab

le8

(to

tal

of

bo

thd

ila

tati

on

me

tho

ds)

.D

ata

for

BT

are

as

sta

ted

inT

ab

le5

.

Fact

ors

pre

dic

tiv

eo

fb

lee

din

g

com

pli

cati

on

sin

clu

de

she

ath

size

24

–2

6Fr

10

39

BL:

53

(5.1

%)

BT

:5

0(4

.8%

)

27

–3

0Fr

35

33

BL:

30

6(8

.7%

)

BT

:2

08

(5.9

%)

�3

2Fr

37

1B

L:3

3(8

.9%

)

BT

:4

5(1

2.1

%)

Mis

hra

20

11

,

com

pa

rati

ve

stu

dy

,

Ind

ia,

20

09

–2

01

0[2

4]

NA

mP

NL

14

–1

8Fr

PN

L2

4–

28

FrB

en

efi

ts:

SFR

(at

1m

o)

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DH

S,

DP

,a

na

lge

sic

req

uir

em

en

t

27

28

SFR

:2

6/2

7(9

6)%

BL:

0.8�

0.9

%

Pel

vic

per

fora

tio

n:

1

Ble

edin

g0

Fev

er:

2

DP

:4

5.2�

12

.6m

in

DH

S:3

.2�

0.8

d

AR

(tra

mad

ol)

:5

5.4�

50

mg

TL:

21

(78

%)

SFR

:2

8/2

8(1

00

%)

BL:

1.3�

0.4

%

Pel

vic

per

fora

tio

n:

2

Ble

edin

g4

Fev

er4

DP

:3

1�

16

.6m

in

DH

S:4

.8�

0.6

d

AR

(tra

mad

ol)

:7

0.2�

52

mg

TL:

4(1

4%

)

0.4

9

0.0

09

8

1 0.1

1

0.6

6

0.0

00

8

<0

.00

00

1

0.2

8

<0

.00

1

BL

rep

ort

ed

as

pe

rce

nt

dro

pin

he

ma

tocr

it.

En

erg

yso

urc

efo

rst

on

e

fra

gm

en

tati

on

:

Lase

rfo

rm

PN

L(1

9/1

)

Pn

eu

ma

tic

for

sta

nd

ard

(22

/0)

mP

NL

ha

dsi

mil

ar

SFR

for

1–

2-c

mk

idn

ey

sto

ne

s.

De

spit

elo

ng

er

op

era

tio

n

tim

e,

mP

NL

ha

dsh

ort

er

DH

S

an

dh

igh

er

tub

ele

ssra

te

rela

ted

tole

ssb

lee

din

g

Kn

oll

20

10

,co

mp

ara

tiv

e

stu

dy

,G

erm

an

y,

20

07

–2

00

9[2

2]

NA

mP

NL

18

FrP

NL

26

FrB

en

efi

ts:

ISFR

Ha

rms:

BL,

fev

er,

VI

Se

con

da

ryo

utc

om

es:

DP

,

Pa

in:

VA

S,

AR

,D

HS

25

25

ISFR

:2

4/2

5(9

6%

)

BL:

1/2

5(4

%)

Fev

er:

3/2

5(1

2%

)

VI

(pe

rfo

rati

on

):0

(0%

)

DP

:5

9�

29

.1[3

4–

82

]m

in

Pai

n,

VA

S:3�

3[0

–5

]

AR

(pir

itra

mid

e):

25�

12

mg

DH

S:3

.8�

2.1

d

ISFR

:2

3/2

5(9

2%

)

BL:

2/2

5(8

%)

Fev

er:

5/2

5(2

0%

)

VI

(pe

rfo

rati

on

):1

(4%

)

DP

:4

9�

21

.7[2

6–

73

]m

in

Pai

n,

VA

S:4�

3[1

–7

]

AR

(pir

itra

mid

e):

37�

10

mg

DH

S:6

.9�

2.9

d

NR

NS

0.0

48

NS

0.0

21

Sto

ne

ssi

gn

ifica

ntl

yla

rge

r

(p=

0.0

42

)in

PN

Lg

rou

p.

mP

NL

wa

sT

Lw

ith

thro

mb

in-

ma

trix

tra

ctcl

osu

reif

un

com

pli

cate

da

nd

sto

ne

-fre

e.

Oth

erw

ise

16

Frtu

be

wa

s

pla

ced

.

All

PN

Lh

ad

22

Frtu

be

.B

L

rep

ort

ed

as

‘‘pro

lon

ge

d

po

sto

pe

rati

ve

ble

ed

ing

’’,

alt

ho

ug

hn

op

ati

en

tsre

qu

ire

d

BT

Sh

ort

er

ho

spit

al

sta

ya

nd

less

po

sto

pe

rati

ve

pa

inm

ay

sup

po

rtu

seo

fm

PN

Lfo

r

sma

lle

ra

nd

inte

rme

dia

te

sto

ne

s.Lo

we

rst

on

eb

urd

en

an

dT

Lfa

shio

no

fm

PN

L,m

ay

ha

ve

infl

ue

nce

dre

sult

s

Giu

sti

20

07

,

com

pa

rati

ve

stu

dy

,

Ita

ly,

19

99

–2

00

4[1

1]

NA

mP

NL

14

FrP

NL

30

FrB

en

efi

ts:

SFR

Ha

rms:

BL,

BT

Se

con

da

ryo

utc

om

es:

DP

,

pa

in:

VA

S,

AR

,D

HS

Oth

er

ou

tco

me

s:T

RN

A

40

67

mP

NL

14

Fr

SFR

:3

1/4

0(7

7.5

%)

BL:

4.4

9�

3.1

%

BT

:0

/40

(0%

)

DP

:1

55

.5�

32

.9m

in

Pai

nV

AS:

5.5

3�

1.1

4

AR

(su

bst

ance

NR

):7

3.8�

50

mg

DH

S:3

.05�

1.6

9d

TR

NA

:1

2.3

1�

4.6

5d

PN

L3

0Fr

SFR

:6

3/6

7(9

4%

)

BL:

6.3

1�

4.2

9%

BT

:2

/67

(2.9

%)

DP

:1

06

.6�

24

.4m

in

Pai

nV

AS:

6.3

6�

1.6

7

AR

:8

8.1�

78

.5m

g

DH

S:5

.07�

2.1

5d

TR

NA

:1

7.6

7�

4.7

d

NR

NR

BL

rep

ort

ed

as

pe

rce

nt

dro

pin

he

ma

tocr

it.

An

alg

esi

csu

bst

an

ce

NR

.SD

for

ag

es

NR

.La

cko

f

sta

tist

ica

lca

lcu

lati

on

sfo

re

ve

n

imp

ort

an

to

utc

om

es

such

as

SFR

,d

esp

ite

con

clu

sio

ns

be

ing

dra

wn

for

this

ou

tco

me

mP

NL

SFR

an

dB

Lw

ere

low

er

tha

nfo

rsP

NL.

TL

sPN

Lw

as

sup

eri

or

inte

rms

of

red

uce

d

pa

in,

sho

rte

rh

osp

ita

lst

ay

,

an

dh

igh

er

SFR

,w

hil

e

sho

win

gsi

mil

ar

com

pli

cati

on

rate

s

Tu

be

less

PN

L3

0Fr

27

TL

PN

L3

0FR

SFR

:2

7/2

7(1

00

%)

BL:

5.1

8�

3.6

3

BT

:1

/27

(3.7

%)

DP

:9

5.9�

45

.5m

in

Pai

nV

AS:

3.4

5�

0.6

5

AR

:4

1.1�

30

.2m

g

DH

S:2

.18�

2.1

3d

TR

NA

:1

0.9

3�

4.8

7d

Mil

ler

20

14

,ca

sese

rie

s,

UK

,2

00

9–

20

13

,

ab

stra

ct[3

2]

NA

mP

NL

16

.5Fr

NA

Be

ne

fits

:IS

FR,

ICIR

FR,

Ha

rms:

CG

,B

T,

US

,S

P

Se

con

da

ryo

utc

om

es:

DP

,D

HS

11

6N

AIS

FR:

54

(46

.5%

)

ICIR

FR:

79

.4%

CG

:2

[BT

]3

(2.6

%)

+2

[IN

F]1

8(1

6%

)

BT

:3

(2.6

%)

US

:1

5(1

2.9

%)

DP

:1

74

min

SP

:2

4(2

0.7

%):

SW

L1

0(8

.6%

),U

RS

9

(7.8

%),

PN

L5

(4.3

%)

DH

S:

3.9

d

NA

NR

Co

mp

ari

son

of

retr

osp

ect

ive

ly

rev

iew

ed

case

so

fm

PN

La

nd

PN

L

fro

mC

RO

ES

da

tab

ase

,b

ut

no

com

pa

riso

nd

ata

or

pv

alu

es

incl

ud

ed

inth

ea

bst

ract

Bh

att

u2

01

4,

case

seri

es,

Ind

ia,

20

09

–2

01

3,

ab

stra

ct[2

9]

NA

mP

NL�

20

FrN

AB

en

efi

ts:

SFR

Ha

rms:

BL,

CG

Se

con

da

ryo

utc

om

es:

DP

,D

HS

,A

R

30

1N

AS

FR:

29

7(9

9%

)

BL:

1.0

1g

/dl

CG

1:

2%

,C

G2

:5

%

DP

:5

9m

in

DH

S:

2.9

d

AR

(tra

ma

do

l):

54

mg

NA

NR

Ure

teri

cca

the

ter:

98

Ure

teri

cca

the

ter

+

ne

ph

rost

om

y:

26

DJ

ste

nt:

11

0

DJ

ste

nt

+n

ep

hro

sto

my

:2

8

Ne

ph

rost

om

y:

39

mP

NL

isa

lte

rna

tiv

eto

sta

nd

ard

PN

Lfo

rm

ed

ium

ren

al

sto

ne

s,w

ith

be

tte

r

mo

rbid

ity

pro

file

.H

ow

ev

er

the

reis

no

com

pa

riso

ng

rou

p.

Tu

be

less

mP

NL

ass

oci

ate

d

wit

hb

ett

er

mo

rbid

ity

pro

file

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 9

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

Ta

ble

2(C

on

tin

ued

)

Stu

dy

ID,

de

sig

n,

cou

ntr

y,

recr

uit

me

nt

pe

rio

d

Su

bg

rou

ps

(of

mP

NL

gro

up

)

Inte

rve

nti

on

Co

mp

ara

tor

Ou

tco

me

s

me

asu

red

na

tb

ase

lin

eO

utc

om

es

Re

po

rte

d

pv

alu

es

No

tes

Su

mm

ary

Int

Co

mIn

tC

om

Ka

rata

g2

01

4,

case

seri

es,

Tu

rke

y,

20

13

,a

bst

ract

[31

]

NA

mP

NL

4.8

FrN

AB

en

efi

ts:

SFR

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DP

,D

HS

Oth

er

ou

tco

me

s:D

F

68

NA

SFR

:9

8.5

%

BL:

0.9

5g

/dl

CG

1:

1.4

%+

3a

:4

.2%

DP

:4

0m

in

DH

S:

27

.5h

DF:

10

8s

NA

NR

NA

mP

NL

reco

mm

en

de

da

s

alt

ern

ati

ve

for

me

diu

mre

na

l

sto

ne

sre

sist

an

tto

SW

L

De

sai

20

13

,ca

sese

rie

s,

Ind

ia,

recr

uit

me

nt

pe

rio

dN

R,

ab

stra

ct[3

0]

NA

um

PN

L1

2Fr

NA

Be

ne

fits

:S

FR

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DH

S

Oth

er

ou

tco

me

s:

con

ve

rsio

nto

mP

NL

du

eto

ble

ed

ing

74

NA

SFR

:9

2.4

%

CG

1:

1(1

.4%

)

BL:

1.6�

1.0

g/d

l

DH

S:1

.2�

0.8

d

Co

nv

ersi

on

tom

PN

L:2

(2.7

%)

NA

NR

FU:

1m

ou

mP

NL

ve

rysa

fea

nd

effi

caci

ou

sfo

rre

mo

va

lo

f

ren

al

calc

uli

up

to1

8m

m.U

se

of

dis

po

sab

les

ism

inim

al

an

d

pa

tie

nt

reco

ve

ryfa

st

De

sai

20

13

,ca

sese

rie

s,

Ind

ia,

recr

uit

me

nt

pe

rio

dN

R[8

]

NA

um

PN

L1

3Fr

NA

Be

ne

fits

:S

FR

Ha

rms:

CG

,B

L,

Se

con

da

ryo

utc

om

es:

DH

S

Oth

er

ou

tco

me

s:

con

ve

rsio

nto

mP

NL

du

eto

ble

ed

ing

62

NA

SFR

:8

6.6

6%

CG

1(1

.6%

)

BL:

1.4�

1.0

g/d

l

DH

S:1

.2�

0.8

d

Co

nv

ersi

on

tom

PN

L:2

(3.2

%)

NA

NR

FU:

1m

ou

mP

NL

issa

fea

nd

ea

syto

lea

rnb

ut

sho

uld

be

rest

rict

ed

tom

ed

ium

sto

ne

s(<

2.0

cm)

De

sai

20

13

,ca

sese

rie

s,

Ch

ina

,2

01

2[2

0]

NA

um

PN

L1

1–

13

FrN

AB

en

efi

ts:

ISFR

,S

FR,

Ha

rms:

CG

,B

L,U

S

Se

con

da

ryo

utc

om

es:

DP

,S

P,

DH

S

Oth

er

ou

tco

me

s:

Pu

nct

ure

loca

tio

ns

36

NA

ISFR

:8

8.9

0%

SFR

:9

7.2

0%

CG

1:

3(8

.3%

),C

G2

:2

(5.6

%)

BL:

5.4�

7.8

[0–

21

]g

/dl

US:

2(5

.6%

)

DP

:5

9.8�

15

.9[3

0–

90

]m

in

SP:

1(2

.8%

)

DH

S:3

.0�

0.9

[2–

5]

d

NA

NR

FU:

1m

o

Pu

nct

ure

loca

tio

ns:

Up

pe

rca

lyx

:7

(19

.4%

)

Mid

dle

caly

x:

15

(41

.7%

)

Low

er

caly

x:

14

(38

.9%

)

um

PN

Lsa

fea

nd

effi

caci

ou

s

alt

ern

ati

ve

for

sma

ll-v

olu

me

dis

ea

sew

ith

ad

va

nta

ge

of

hig

hIS

FRa

nd

fin

al

SFR

an

d

low

er

com

pli

cati

on

rate

s.

Ind

ica

tio

ns

for

um

PN

La

re

mo

de

rate

-siz

ed

sto

ne

sa

s

alt

ern

ati

ve

toE

SW

Lo

rR

IRS

,

low

po

lest

on

es

no

ta

me

na

ble

toR

IRS

,d

ive

rtic

ula

rre

na

l

sto

ne

s,a

nd

sto

ne

sre

fra

cto

ry

toE

SW

L

Ab

de

lha

fez

20

13

,

case

seri

es,

Ge

rma

ny

,

20

07

–2

01

1[1

8]

Sto

ne

size

<2

cmm

PN

L1

8Fr

NA

Be

ne

fits

:IS

FR,

SFR

,

Ha

rms:

CG

,B

L,B

T

Se

con

da

ryo

utc

om

es:

DP

,S

P,

DH

S

98

NA

Sto

ne

size

<2

0m

m

ISFR

:9

0.8

%

SFR

:9

8.9

%

CG

1:

9(9

.2%

),C

G2

(2.0

%):

5(5

.1%

),C

G

3:

5(5

.1%

)

BL:

1.3�

0.9

g/d

l

BT

:0

(0%

)

DP

:6

9.2�

34

.8m

in

SP:

8(8

.16

%)

DH

S:3

.7�

1.2

d

Sto

ne

size�

20

mm

ISFR

:7

6.7

%

SFR

:9

4.6

%

CG

1:

14

(15

%),

CG

2:

6(6

.5%

),C

G3

:5

(5.4

%)

BL:

1.7�

1.2

g/d

l

BT

:1

(1.1

%)

DP

:9

7.4�

48

.7m

in

SP:

17

(18

.3%

)

DH

S:4

.3�

1.5

d

0.0

07

0.1

0.2

0.0

15

NR

<0

.00

1

0.0

02

FU:

1m

oT

ota

lS

FRg

rea

ter

for

sma

ll

sto

ne

s.M

ost

pa

tie

nts

cou

ldb

e

ren

de

red

sto

ne

-fre

ew

ith

1a

ux

ilia

ryp

roce

du

re.

Th

e

hig

hsu

cce

ssra

tea

nd

low

rate

of

hig

he

rg

rad

eco

mp

lica

tio

ns

just

ify

mP

NL

for

larg

est

on

es

Sto

ne

size�

2cm

93

Zim

me

rma

ns

20

12

,

case

seri

es,

Ge

rma

ny

,

recr

uit

me

nt

pe

rio

dN

R,

ab

stra

ct[3

3]

All

pa

tie

nts

,a

llst

on

esi

zes

mP

NL

18

FrN

AB

en

efi

ts:

ISFR

Ha

rms:

CG

,B

L,B

T,

VI

Se

con

da

ryo

utc

om

es:

DP

,S

P

65

2N

AA

llst

on

esi

zes

ISFR

:9

3.6

%

CG

2[P

N]:

49

(7.5

%),

CG

3

[BL]

:2

(0.3

%)

CG

4[C

I]:

1(0

.15

%)

BL:

1(0

.15

%)

AV

F,2

(0.3

%)

recu

rre

nt

ble

ed

ing

s

BT

:9

(1.4

%)

VI:

1(0

.15

%)

cere

bra

lis

che

mia

DP

:6

5�

31

min

SP:

17

2(2

6.4

%)

Su

bg

rou

p:

sto

ne

s�

50

0m

m2

ISFR

:9

1.8

%

CG

2[P

N]:

16

(8.7

%)

BL:

NR

BT

:2

(1.1

%)

VI:

NR

DP

:7

7�

34

min

SP:

65

(35

.5%

)

NR

2/3

pa

tie

nts

wit

hre

curr

en

t

ble

ed

ing

or

AV

Fre

qu

ire

d

rad

iolo

gic

al

inte

rve

nti

on

mP

NL

isre

lia

ble

an

de

ffe

ctiv

e

tech

niq

ue

for

pe

rcu

tan

eo

us

surg

ery

.mP

NL

ise

ffe

ctiv

ea

nd

eq

ua

lly

safe

for

larg

er

sto

ne

bu

rde

ns

Su

bg

rou

po

fst

on

es�

5cm

21

83

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X10

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes in Miniaturized Percutaneous Nephrolithotomy: A SystematicReview from the European Association of Urology Urolithiasis Guidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/j.eururo.2017.01.046

Lu2

01

2,

case

seri

es,

Ch

ina

,2

00

9–

20

10

[23

]

NA

mP

NL

18

Fr

(wit

h1

6Fr

ne

ph

rost

om

ytu

be

)

NA

Be

ne

fits

:IS

FR

Ha

rms:

CG

,B

L

Se

con

da

ryo

utc

om

es:

DH

S,

DP

,p

ain

16

NA

Tu

be

dm

PN

L

ISFR

:1

3(8

1.3

%)

CG

:1

:2

(12

.5%

)

BL:

2.1

4�

0.5

1

TL

mP

NL

ISFR

:1

4(8

7.5

%)

CG

:1

:3

(18

.8%

)

BL:

1.9

1�

0.6

2

1 1 0.2

6

0.4

3

0.0

03

0.0

32

TL

mP

NL

ha

sth

ea

dv

an

tag

es

of

sho

rte

rh

osp

ita

lst

ay

an

d

less

ba

ckp

ain

com

pa

red

to

tub

ed

mP

NL

Tu

be

less

mP

NL

18

Fr1

6D

P:

65

.19�

21

.5

Pai

n:

14

(87

.5%

)

DH

S:4

(3–

12

)d

Oth

er:

uri

nar

yex

trav

asat

ion

:0

DP

:5

9.6

9�

17

.95

Pai

n:

5(3

1.3

%)

DH

S:3

(2–

7)

d

Oth

er:

uri

nar

yex

trav

asat

ion

:1

Su

ng

20

06

,ca

sese

rie

s,

Ko

rea

,1

99

9–

20

02

[25

]

NA

mP

NL

14

FrN

AB

en

efi

ts:

ISFR

,S

FR

Ha

rms:

fev

er,

BL

Se

con

da

ryo

utc

om

es:

SP

,D

HS

72

NA

ISFR

:5

8/7

2(8

0.6

%)

SFR

:6

3/7

2(8

7.5

%)

CG

1[f

ev

er]

:7

(9.7

%),

CG

3[e

mb

oli

zed

he

mo

rrh

ag

e]:

1(1

.4%

)

BL:

1/7

2(1

.4%

)

SP

:1

1/7

2(1

5.3

%)

DH

S:

7.6

8�

3.2

1[4

–2

2]

d

NA

NR

FU:

7m

oH

igh

ISFR

infl

ue

nce

db

yst

on

e

dia

me

ter

an

db

urd

en

.Lo

w

com

pli

cati

on

rate

an

dsh

ort

ho

spit

al

sta

y

AP

=a

dju

nct

ive

pro

ced

ure

;A

R=

an

alg

esi

cre

qu

ire

me

nt;

BL

=b

loo

dlo

ss;

BT

=b

loo

dtr

an

sfu

sio

n;

CG

=C

lav

ien

gra

de

;C

IRFR

=cl

inic

all

yin

sig

nifi

can

tre

sid

ua

lfr

ag

me

nt

rate

;C

RO

ES

=C

lin

ica

lR

ese

arc

hO

ffice

of

the

En

do

uro

log

ica

lS

oci

ety

;D

B=

da

tab

ase

;D

HS

=d

ura

tio

no

fh

osp

ita

lst

ay

;D

P=

du

rati

on

of

pro

ced

ure

;E

DV

=e

me

rge

ncy

de

pa

rtm

en

tv

isit

;FU

=fo

llo

w-u

p(h

ere

me

an

ing

tim

ep

oin

tfo

rd

ela

ye

da

sse

ssm

en

to

fst

on

est

atu

s,if

ap

pli

cab

le);

HR

=h

osp

ita

lre

ad

mis

sio

n;

IPP

=in

tra

ren

al

pe

lvic

pre

ssu

re;

ISFR

=im

me

dia

teS

FR;

ICIR

FR=

imm

ed

iate

CIR

FR;

LC=

low

er

caly

ces;

MC

=m

idd

leca

lyce

s;m

PN

L=

min

i-P

NL;

NR

=n

ot

rep

ort

ed

;P

=p

elv

is;

PN

L=

pe

rcu

tan

eo

us

ne

ph

roli

the

cto

my

;Q

OL

=q

ua

lity

of

life

;R

CT

=ra

nd

om

ize

dco

ntr

oll

ed

tria

l;S

FR=

sto

ne

-fre

era

te;

SP

=se

con

da

ryp

roce

du

re;

sPN

L=

sta

nd

ard

PN

L;T

L=

tub

ele

ss;

TR

NA

=ti

me

tore

turn

ton

orm

al

act

ivit

ies;

UC

=u

pp

er

caly

ces;

um

PN

L=

ult

ra-m

ini-

PN

L;U

PJ

=u

rete

rop

elv

icju

nct

ion

;U

S=

uro

sep

sis;

VI

=v

isce

ral

inju

ry.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 11

EURURO-7240; No. of Pages 16

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

3.5. Case series

Ten case series were included, five of which were full-text

articles [8,18,20,23,25] and five congress abstracts [29–

33]. The smallest tract size studied was 4.8 Fr (mPNL) in a

case series of 68 patients (70 renal units) [31]. SFR was high

(98.5%), while blood loss, complication rates, procedure

duration, and hospital stay were low (Table 2). Three

studies [8,20,30] involved case series in which patients

(n = 74, 62, and 26, respectively) were treated using tract

sizes of 11–13 Fr. SFRs were high (92.4%, 86.7%, and 97.2%,

respectively), while blood loss, complication rates, proce-

dure duration, and hospital stay were low (Table 2).

Conversion to mPNL occurred in approximately 3% of the

procedures. One study of 72 patients treated with 14 Fr

mPNL [25] had SFR of 87.5% and an extended hospital stay

of 7.7 � 3.2 d (range 4–22). Two studies reported on a tract

size of 18 Fr. Lu et al [23] compared procedures with and

without placement of a final nephrostomy tube (both n = 16)

[23], and Abdelhafez et al [18] compared stones measuring in

<20 mm (n = 98) to stones measuring �20 mm (n = 93) in

maximal diameter. Lu et al [23] found that ISFRs were

comparable, but that tubeless procedures were associated

with fewer patients reporting back pain (p = 0.003) and

shorter hospital stay (3 vs 4 d; p = 0.032; Table 2). Abdelhafez

et al [18] found that the ISFR was higher for patients with

smaller stones (90.8% vs 76.7%; p = 0.007), while the SFRs at

1 mo after auxiliary procedures were comparable (98.9% vs

94.6%; p = 0.1). Complication rates were comparable (p = 0.2),

while blood loss was lower (p = 0.015) and the procedure

duration (p < 0.001) and hospital stay were shorter

(p = 0.002) in patients with smaller stones. One abstract

reported on 301 procedures utilizing tracts sized �20 Fr (the

smallest tract size used was not stated) [29]. The SFR was high

at 99%, while blood loss, analgesic requirements, and

complication rates were low, and procedure duration and

hospital stay short. Two abstracts reporting on mPNL did not

explicitly state the size of the sheaths used [32,33], so this

information was obtained via e-mail correspondence with

the authors: Miller et al [32] used 16.5 Fr and Zimmermanns

et al [33] used 18 Fr. Using data from the CROES PNL Global

Study, Miller et al [32] reported a comparatively low ISFR

(46.5%) with a fair rate for immediate clinically insignificant

residual fragments (79.4%). Complication rates were com-

paratively high (eg, urosepsis in 12.9% of patients) and the

procedure duration was 174 min (Table 2). Zimmermanns

et al [33] presented results for two groups: the complete

cohort of 652 patients (all stone sizes) and a subgroup of

183 patients with stones measuring �500 mm2 in area. No p

values were reported, although the ISFR was comparable in

both groups (93.6% vs 91.8%).

3.6. RoB and confounding assessment

Figure 2 summarizes the key RoB and confounding

assessments. Only two studies were RCTs; the remaining

16 were either NRCSs or case series resulting in high RoB

associated with no randomization, incomplete outcome

data (attrition bias), and selective outcome data reporting.

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

Fig. 3 – Forest plot showing the stone-free rates reported in the randomized controlled trial (RCTs) and nonrandomized comparative studies (NRCSs).Reference numbers for studies are given in Table 1. PCNL = percutaneous nephrolithotomy; M-H = Mantel-Haenszel; CI = confidence interval.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X12

EURURO-7240; No. of Pages 16

Most studies reported stone sizes but did not report

stone location. Fewer than half of the studies contained

information on obesity (or body mass index). The risk of

confounding was moderate to high for previous open

surgery, access site, and access location, since only one or

two studies reported on these factors (Fig. 2). The tract size

used and the stone types and locations (when reported)

were heterogeneous.

3.7. Discussion

3.7.1. Principal findings

SFRs were comparable in patients with renal stones treated

with mPNL and standard PNL (Fig. 3). Smaller tracts tended

to be associated with significantly lower blood loss (Fig. 4)

or need for blood transfusion [11,19,21,24,26–28] at the

cost of a significantly longer procedure [11,19,24,28]

Fig. 4 – Forest plot showing the postoperative hemoglobin decrease in (A) g/dlnonrandomized comparative studies (NRCSs). Reference numbers for studies adeviation; CI = confidence interval; IV = inverse variance.

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

(Fig. 5). Hospital stay length was mostly shorter for mPNL

[11,22,24,34] (Fig. 6). The studies were heterogeneous with

respect to tract and stone sizes, and the RoB and

confounding risk were generally high.

The terms used to describe tract sizes, such as ‘‘mini-

PNL’’, ‘‘ultra-mini-PNL’’, and ‘‘micro-PNL’’, have not been

well defined and partly overlap. In general, tracts sized �18

Fr are used for miniaturized techniques [28,35]. Urologists

need to be aware that such terms describe not only the size

of the access sheath but also of specific instruments,

dilators, and operative concepts [36–40]. This systematic

review indicates that mPNL is a safe and effective evolution

of the PNL technique, and thus warrants further investiga-

tion. RCTs are necessary to better assess the benefits and

harms in relation to both disease-related parameters (stone

size, quantity and location) and interventional parameters

(tract size, puncture locations, and intrapelvic pressure).

and (B) percent reported in randomized controlled trials (RCTs) andre given in Table 1. PCNL = percutaneous nephrolithotomy; SD = standard

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

Fig. 6 – Forest plot showing the length of hospital stay (d) reported in randomized controlled trials (RCTs) and nonrandomized comparative studies(NRCS). Reference numbers for studies are given in Table 1. PCNL = percutaneous nephrolithotomy; SD = standard deviation; CI = confidence interval;IV = inverse variance.

Fig. 5 – Forest plot showing the duration of the procedure (min) reported in randomized controlled trials (RCTs) and nonrandomized comparativestudies (NRCS). Reference numbers for studies are given in Table 1. PCNL = percutaneous nephrolithotomy; SD = standard deviation; CI = confidenceinterval; IV = inverse variance.

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 13

EURURO-7240; No. of Pages 16

3.7.2. Implications for practice

Our systematic review demonstrates that the use of

miniaturized PNL systems is effective. This was demon-

strated in most studies, including the first series published

by Jackman et al [6]. The authors reported SFR of 85% in

children and 85% in adults for stones sized 12–15 mm. One

of the few studies showing inferiority for smaller instru-

ments was the series described by Giusti et al [11]. However,

this study demonstrates the confusion caused by non-

standardized terminology, as the instruments used were

not dedicated for PNL but rigid ureteroscopes of small

diameters. The major disadvantage of small instruments is

that it is necessary to fragment stones into smaller pieces

that fit through the narrower sheaths, leading to longer

operating times compared to standard PNL, which allows

removal of large stone fragments with forceps and baskets.

Conversely, extraction of stone fragments seems to be

facilitated by modified Amplatz sheaths, as fragments can

be removed via vacuum suction, an effect that works best

for tracts sized 13–18 Fr [41–43].

The idea behind downsizing PNL is based on the

assumption of lower morbidity than for conventional

PNL. However, there is still controversy regarding whether

miniaturization leads to such a benefit. Li et al [44]

investigated systemic responses to both standard and

mPNL by measuring acute-phase proteins, and found no

significant differences between the groups. In another

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

experimental approach, Traxer et al [45] measured the

extent of damage to the renal parenchyma in pigs

undergoing placement of 11 Fr or 30 Fr nephrostomy tubes.

There were no detectable differences in fibrotic scar

volumes. The hypothesis of lower blood loss with minia-

turized tracts has only been confirmed in a few studies.

Mishra et al [24] reported a slight but clinically significant

advantage for 18 Fr compared to 26 Fr access. However,

others could not confirm such a benefit [22]. The observa-

tion in many series that the rate of tubeless procedures is

much higher than in conventional PNL series may support

the idea of lower intraoperative bleeding, if it is assumed

that a tubeless procedure is performed after uncomplicated

access and stone removal [22,24]. In addition, a meta-

analysis of tubeless versus standard PNL procedures [46]

indicated that tubeless procedures led to shorter hospital

stay, less postoperative pain, and possible quicker recovery,

and may therefore contribute to lower morbidity in

miniaturized PNL. However, most patients with so-called

tubeless procedures received a double-J stent instead of a

nephrostomy tube. As stent-related discomfort is common,

this has to be taken into account and evaluated in future

studies. Sealants are used in tubeless procedures, but their

potential benefit remains controversial [47,48]. Complica-

tion rates for mPNL according to the Clavien-Dindo

classification range from 11.9% to 37.7% [49,50]. Most

complications in published series were of low grade, with

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EURURO-7240; No. of Pages 16

higher rates of blood transfusion and arterial embolization

in complex stone situations [51].

Identifying the right indications remains key in estab-

lishing the optimal use of miniaturized systems, but

published outcomes are heterogeneous in terms of SFR

and complication rates reported. Miniaturized PNL seems to

be more effective for smaller rather than larger renal stones

>20 mm [18,52]. The question arises whether miniaturized

PNL may compete more with SWL and ureteroscopy (URS)

than with conventional PNL. While most published series so

far reported an advantage for percutaneous techniques over

URS [53,54], De et al recently published a meta-analysis

comparing percutaneous stone removal with URS [51]. Al-

though the overall SFR was in favor of PNL, subgroup

analysis indicated that URS provided a significantly higher

SFR rate than miniaturized systems. However, the same

limitations as for the present analysis apply to their

systematic review, with one of the major weaknesses being

the inclusion of different tract sizes. De et al concluded that

URS should be recommended over minimally invasive PNL

for stones sized <20 mm because of the generally lower

morbidity of retrograde access. When compared to SWL,

miniaturized PNL demonstrates higher SFR and a lower rate

of auxiliary measures, although most data come from

pediatric series that were not included in this systematic

review [55–58]. On the basis of the current literature and

experiences, downsized instruments may be used for stones

in all locations accessible for standard PNL. The best

indications seem to be medium stones of up to 20 mm,

although there are no data to support an upper limit. In

general, instruments should be adapted to the anatomy.

Patients with tiny collecting systems may especially benefit

from the use of smaller systems. Another potential

indication might be stones located within calyceal divertic-

ula. Future research should evaluate such issues.

Hemodynamic, electrolyte, and metabolic changes have

been prospectively evaluated when comparing miniaturized

with standard PNL [26]. Interestingly, a trend towards

metabolic acidosis was observed in the mPNL group, possibly

associated with prolonged operating time and higher

intrarenal irrigation pressure. Tepeler et al [28] measured

intrarenal pelvic pressure during PNL procedures using 4.8 Fr

nephroscopes in comparison to conventional PNL. Intrarenal

pressure was significantly lower in the conventional group

during all steps of the procedure. Even though there was no

difference in outcome in their series, surgeons should be

aware of higher pressure for downsized systems [36]. Place-

ment of a ureteral catheter may be helpful for irrigation

outflow to allow intermittent flushing [59].

It is sobering that even the simplest parameter, SFR, is

generally difficult to compare because of different defini-

tions of SFR with regard to the time until stone-free status is

achieved and whether or not residual fragments are

accepted, as well as the maximum fragment size allowable

to justify classification as ‘‘clinically insignificant’’. Further-

more, the imaging modality used to assess stone-free status

varies, with most series using ultrasound or kidney/ureter/

bladder X-ray (KUB), although CT is more sensitive for small

residual fragments [60,61].

Please cite this article in press as: Ruhayel Y, et al. Tract Sizes inReview from the European Association of Urology Urolithiasis Gj.eururo.2017.01.046

3.7.3. Implications for research

The concept of reducing the morbidity of PNL by downsizing

the access tract seems convincing. The findings that success

rates are high with miniaturized instruments demonstrate

that the concept does not negatively impact the outcome.

However, well-designed studies are missing and no conclu-

sion can be drawn in terms of potentially lower morbidity.

3.7.4. Limitations

This review has several limitations. Many of the studies

included may be affected by selection bias, outcome-

reporting bias, and the use of different tract sizes. More

than half of the studies were single-arm case series. For five of

the studies, only abstracts were published, severely limiting

the information available and its quality. Furthermore, the

studies were heterogeneous in design, with differences in the

size of tracts used in both the interventional and control arms

(when available) and in the size and location of stones

treated.

Many of the studies included also suffered from other

important methodological limitations. Importantly, most of

the studies on mPNL used single-step dilatation, whereas

conventional PNL procedures were performed with step or

balloon dilatation, entailing different complication rates for

bleeding, for example [62]. Moreover, most mPNL proce-

dures were performed with low intrapelvic pressure, while

standard PNL operations were much more frequently

performed at high pressure, with implications for postop-

erative fever and sepsis, for example [63,64]. In addition,

assessment of the postoperative SFR was obfuscated by the

use of both less sensitive standard radiology (KUB) and

significantly more sensitive CT [65]. Finally, many studies

did not report statistical calculations of differences between

interventional groups for the main outcome measures.

4. Conclusions

The available evidence indicates that mPNL is at least as

efficacious and safe as standard PNL for the removal of renal

calculi, with a limited risk of significant (Clavien grade �2)

complications. However, the quality of the evidence was

poor and drawn mainly from small studies, the majority of

which were single-arm case series and NRCSs, and only two

of which were RCTs. Hence, the risks of bias and

confounding were high. Furthermore, the tract sizes used

and the types of stones treated were heterogeneous. Thus,

more reliable data from well-designed and adequately

sampled and powered RCTs are warranted.

Author contributions: Thomas Knoll had full access to all the data in the

study and takes responsibility for the integrity of the data and the

accuracy of the data analysis.

Study concept and design: Knoll, Turk, Ruhayel, Tepeler.

Acquisition of data: Knoll, Ruhayel, Tepeler, Yuan.

Analysis and interpretation of data: Knoll, Turk, Ruhayel, Tepeler.

Drafting of the manuscript: Knoll, Ruhayel, Tepeler, MacLennan, Yuan.

Critical revision of the manuscript for important intellectual content: Knoll,

Turk, Ruhayel, Tepeler, Dabestani, MacLennan, Petrık, Skolarikos, Seitz,

Straub, Yuan.

Miniaturized Percutaneous Nephrolithotomy: A Systematicuidelines Panel. Eur Urol (2017), http://dx.doi.org/10.1016/

E U R O P E A N U R O L O G Y X X X ( 2 0 1 7 ) X X X – X X X 15

EURURO-7240; No. of Pages 16

Statistical analysis: None.

Obtaining funding: None.

Administrative, technical, or material support: None.

Supervision: Knoll, Turk, Ruhayel, Dabestani.

Other: None.

Financial disclosures: Thomas Knoll certifies that all conflicts of interest,

including specific financial interests and relationships and affiliations

relevant to the subject matter or materials discussed in the manuscript

(eg, employment/affiliation, grants or funding, consultancies, honoraria,

stock ownership or options, expert testimony, royalties, or patents filed,

received, or pending), are the following: Ales Petrık has received speaker

honoraria from GSK and fellowship and travel grants from Astellas and

Olympus. Christian Seitz has received consultant fees from Astellas and

speaker honoraria from Rowa Wagner. Michael Straub has received

consultant fees from Richard Wolf Endoskope and Sanochemia

Pharmazeutika. Thomas Knoll has received consultant fees from

Schoelly, Boston Scientific, Olympus, and Storz Medical, and speaker

honoraria from Karl Storz, Richard Wolf, Olympus, Boston Scientific, and

Ibsen; and has participated in trials by Cook and Coloplast. The

remaining authors have nothing to disclose.

Funding/Support and role of the sponsor: None.

Acknowledgments: We are grateful for the valuable help of Karin Plass,

European Association of Urology Guidelines Office, Arnhem, The

Netherlands, for providing administrative support. We also thank

Richard Sylvester and Thomas Lam, of the EAU Guidelines Office, for

providing methodological supervision and support.

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