ORIGINAL ARTICLE

Acta Med Indones - Indones J Intern Med • Vol 50 • Number 1 • January 2018

Meta-analysis of Optimal Management of Lower Pole
Stone of 10 - 20 mm: Flexible Ureteroscopy (FURS) versus
Extracorporeal Shock Wave Lithotripsy (ESWL) versus
Percutaneus Nephrolithotomy (PCNL)

Prahara Yuri1, Rinto Hariwibowo2, Indrawarman Soeroharjo1, Raden Danarto1,
Ahmad Z. Hendri1, Sakti R. Brodjonegoro1, Nur Rasyid2, Ponco Birowo2,
Indah S. Widyahening3

1 Division of Urology, Department of Surgery, Faculty of Medicine Universitas Gadjah Mada - Sardjito Hospital,
Yogyakarta, Indonesia.
2 Department of Surgery, Faculty of Medicine Universitas Indonesia – Cipto Mangunkusumo Hospital, Jakarta,
Indonesia.
3 Department of Community Medicine, Faculty of Medicine Universitas Indonesia, Jakarta, Indonesia.

Corresponding Author:
Prahara Yuri, MD. Division of Urology, Department of Surgery, Faculty of Medicine Universitas Gadjah Mada-
Sardjito Hospital. Jl. Kesehatan no. 1, Sekip Yogyakarta 55284, Indonesia. email: prahara.yuri@gmail.com.

ABSTRAK
Latar belakang: pengelolaan optimal batu kaliks inferior masih kontroversial, karena tidak ada suatu metode

tunggal yang sesuai untuk menghilangkan semua batu kaliks inferior. Prosedur invasif (fURS) minimal seperti
extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL) dan flexible ureteroscopy
adalah pilihan terapi untuk batu kaliks inferior. Tujuan penelitian ini adalah untuk mengetahui manajemen
optimal batu kaliks inferior ukuran 10 - 20 mm. Metode: studi meta-analisis dari penelitian kohort sebelum
Juli 2016 dengan menggunakan database Medline dan Cochrane dilakukan. Batu kaliks inferior ukuran 10-20
mm ditatalaksana dengan fURS, ESWL dan PCNL dengan follow up 1-3 bulan setelah tindakan merupakan
kriteria inklusi, sedangkan batu saluran kemih di lokasi lain dan dengan ukuran yang berbeda di eksklusi. Data
dianalisis dengan fixed-effects model menggunakan metode Mantzel-Haenzel untuk menghitung pooled Risk
Ratio (RR) dan 95% Confidence Interval (CI). Heterogenitas dinilai dengan menghitung statistik I2. Semua
analisis dilakukan dengan Review manager 5.3. Hasil: kami menganalisis 8 penelitian kohort. Angka bebas
batu dari 958 pasien (271 PCNL, 174 fURS dan 513 ESWL), 3 bulan pasca operasi, adalah 90,8% (246/271)
setelah PCNL, 75,3% (131/174) setelah fURS dan 64,7 % (332/513) setelah ESWL. Berdasarkan angka bebas
batu, PCNL lebih baik dari fURS (overall RR 4,12 (95% CI 2,09 – 8,09); p<0,001 dan I2=0%) dan ESWL
(overall RR 0,23 (95% CI 0,16 – 0,35); p = <0,001 dan I2 = 32,8%). Namun, bila dibandingkan antara fURS
dan ESWL, fURS lebih baik dari pada ESWL dengan overall RR 0,66 (95% CI0,47 - 0,92; p = 0.015 dan I2 =
45,5%). Kesimpulan: PCNL memberikan angka bebas batu yang lebih tinggi dibandingkan dengan fURS dan
ESWL. Studi meta-analisis ini diharapkan dapat membantu ahli urologi sebelum melakukan tindakan intervensi
pada batu kaliks inferior ukuran 10-20 mm.

Kata kunci: batu kaliks inferior, flexible ureteroscopy, extracorporeal shock wave lithotripsy, percutaneus
nephrolithotomy.

Vol 50 • Number 1 • January 2018 Meta-analysis of optimal management of 10-20 mm lower pole stone

ABSTRACT
Background: the optimal management of lower calyceal stones is still controversial, because no single method

is suitable for the removal of all lower calyceal stones. Minimally invasive procedures such as extracorporeal
shock wave lithotripsy (ESWL), percutaneous nephrolithotomy (PCNL) and flexible ureteroscopy (fURS) are the
therapeutic methods for lower calyceal stones. The aim of this study was to identify the optimal management of
10-20 mm lower pole stones. Methods: a meta-analysis of cohort studies published before July 2016 was performed
from Medline and Cochrane databases. Management of 10-20 mm lower pole stone treated by fURS, ESWL and
PCNL with follow-up of residual stones in 1-3 months after procedure were include and urinary stone in other
location and size were excluded. A fixed-effects model with Mantzel-Haenzel method was used to calculate the
pooled Risk Ratio (RRs) and 95% Confidence Interval (CIs). We assessed the heterogeneity by calculating the I2
statistic. All analyses were performed with Review manager 5.3. Results: we analized 8 cohort studies. The stone
free rate from 958 patients (271 PCNL, 174 fURS and 513 ESWL), 3 months after operation, was 90.8% (246/271)
after PCNL; 75.3% (131/174) after fURS; and 64.7% (332/513) after ESWL. Base on stone free rate in 10-20 mm
lower pole stone following management, PCNL is better than fURS (overall RR was 1.32 (95% CI 1.13 – 1.55);
p<0.001 and I2=57%) and ESWL (overall risk ratio 1.42 (95% CI 1.30 – 1.55); p=<0.001 and I2 = 85%). But, if
we compare between fURS and ESWL, fURS is better than ESWL base on stone free rate in 10-20 mm lower pole
stone management with overall RR 1.16 (95% CI 1.04 – 1.30; p=0.01 and I2=40%). Conclusion: percutaneus
nephrolithotomy provided a higher stone free rate than fURS and ESWL. This meta-analysis may help urologist
in making decision of intervention in 10-20 mm lower pole stone management.

Keywords: lower pole stone, flexible ureteroscopy, extracorporeal shock wave lithotripsy, percutaneus
nephrolithotomy.

INTRODUCTION
The optimal management of lower calyceal

stones is still in debate controversial and a
dilemmatic for urologist.1–5 No single method is
suitable for the removal of all lower calyceal stones.
The goal of lower calyceal stone management is
to achieve maximal stone clearance with minimal
morbidity. Newly developed minimally invasive
procedures have displaced open stone surgery.1,6
Extracorporeal shock wave lithotripsy (ESWL),
percutaneous nephrolithotomy (PCNL), and
flexible ureteroscopy are the currently used
therapeutic methods.5,7

To date, guidelines have confirmed ESWL as
the method of first choice for small and mid-sized
urinary calculi. However, currently urologists
and patients are more critical about ESWL when
considering the best treatment for a stone. The
limited results of ESWL, even after repeated
treatment sessions for stones, in the lower pole,
or for difficult stone compositions (e.g. calcium
oxalate monohydrate, brushite or cystine), might
explain stone development.8,9

Advances in distal-tip deflection and scope
durability have expanded the role of fURS from

a diagnostic to a therapeutic procedure. This
improvement in technology has built on existing
experience to expand the potential indications
of flexible ureteroscopy including intrarenal
stones, ESWL failure, infundibular stenosis,
morbid obesity, musculoskeletal deformities, and
bleeding diathesis. Endourological techniques
and skills, especially for fURS have been
improved significantly, making fURS both very
efficient and safe.8

Fernstrom and Johansen in 1976 first described
the technique of removing a kidney stone
percutaneously. Since then advances in technology,
technical skill, and understanding of physiological
principles have allowed percutaneous stone
retrieval with increasing efficiency.10 It has a
confirmed efficacy for managing lower-pole renal
calculi, with a constantly high stone free rate
(SFR) independent of stone size. The Lower Pole
I Study showed SFRs of 100%, 93% and 86% for
stones of <10 mm, 10–20 mm and larger stones,
respectively. Other studies have confirmed these
excellent results.8

Patients prefer a noninvasive procedure and
accept that long-term follow-up will be managed

Prahara Yuri Acta Med Indones-Indones J Intern Med

by shockwave lithotripsy (ESWL) if other factors
allow. The impact of stone size on the results of
ESWL is more pronounced in lower pole (LP)
stones than others. The recent advances in renal
endoscopies and the development of percutaneous
nephrolithotomy (PCNL) have provided the
urologist with a safe and effective method for
the treatment of 10 - 20 mm stones in the lower
calyx.1 Therefore, we did a systematic review to
compare the outcome of ESWL, fURS and PCNL
as different modalities of management of midsize
(10–20 mm) lower calyceal stones.

METHODS
We searched the Medline and Cochrane

databases for publications before July 2016.
(lower pole) AND urinary calculi) AND flexible
ureteroscopy) AND extracorporeal shock wave
lithotripsy) AND percutaneus nephrolithotomy)
OR lower pole) OR urinary calculi) OR flexible
ureteroscopy) OR extracorporeal shock wave
lithotripsy) OR percutaneus nephrolithotomy
were used as search strategy. Finally, we checked
references from relevant publications and review

articles.

Eligibility Criteria
Prospective study were included if treatment

was done in adult patient (>18 years old), patient
with lower pole stone (10-20 mm) who is
treated by flexible ureteroscopy (FURS) and/or
extracorporeal shock wave lithotripsy (ESWL)
and/or percutaneus nephrolithotomy (PCNL) with
follow-up of the stone free rate for 1-3 months
after procedure. Patients with urinary stone in
other locations, non-English articles, case reports
or case series were excluded.

Methodological Quality
Quality of study was assessed by reviewing

paper titles and abstracts. In the first screening,
authors assessed all of the abstracts retrieved
from the search and then obtained the full-text
version of the articles that met the inclusion
criteria. These authors evaluated the studies’
eligibility and quality, and they subsequently
extracted the data. The process of identifying
eligible studies is summarized in Figure 1.

412 publications from

database

41 publications were assessed

in detail

8 publications are analyzed

371 publication are

excluded base on title

33 publications are excluded :

- 5 publications treated by FURS only

- 8 publications treated by ESWL only

- 10 publications treated by PCNL only

- 19 publications the urinary stone in

other location

MEDLINE

235 publications

COCHRANE

177 publications

Figure 1. Literature search

Vol 50 • Number 1 • January 2018 Meta-analysis of optimal management of 10-20 mm lower pole stone

Statistical Analysis
A fixed-effects model with Mantzel-Haenzel

method was used to calculate the pooled Risk
Ratio (RRs) and 95% Confidence Interval
(CIs) by comparing fURS, ESWL and PCNL
in management of 10-20 mm lower pole stone.
We assessed the heterogeneity by calculating the
I2 statistic. The heterogeneity was classified as
low (I2 25%-50%), moderate (I2 50%-75%) and
high (I2>75%). All analyses were performed with
Review manager 5.3.

RESULTS
As presented in Figure 1, 412 publications

were identified from the database, out of which
371 publications were excluded based on the
screening of the title and abstract. Forty one
potentially eligible publications were assessed
in detail, and 8 publications met the eligibility
criteria and analyzed (2 studies compare of all
managements, 3 studies compare ESWL and
fURS, 3 studies compare ESWL and PCNL
and a study compare fURS and PCNL. (Table
1) summarize the characteristics of the eligible
studies.

Flexible Ureteroscopy versus Extracorporeal
Shock Wave Lithotripsy

We obtained data from 705 patients from 5
literatures, comprises of 174 patients in fURS
and 531 patients in ESWL group. We found 43
patient with residual stone from 174 patients
treated with fURS (follow-up 3 month, 75.3%)
and 187 patients from 531 patients treated with
ESWL (follow-up 3 month, stone free rate
64.8%).

Figure 2 shows that FURS is better than
ESWL based on the stone free rate in following
<20 mm lower pole stone management with
overall RR 1.16 (95% CI 1.04 – 1.30); p = 0.01
and I2 = 40%.

Flexible Ureteroscopy versus Percutaneous
Nephrolithotomy

We obtained data from 463 patients from 5
literatures, comprises of 174 patients in fURS
and 289 patients in PCNL group. We found 43
patient with residual stone from 174 patients
treated with fURS (follow-up 3 month, 75.3%)
and 25 patients from 289 patients treated with
PCNL (follow-up 3 month, stone free rate
91.3%). (Table 1)

Table 1. Summary of findings table: stone free rate in management of lower pole stone

Outcome
Comparative Risks

(95% CI) Risk Ratio
(95% CI)

Comparative Risks
(95% CI) Risk Ratio

(95% CI)

Comparative Risks
(95% CI) Risk Ratio

(95% CI)

Quality of
Evidence
(GRADE)ESWL FURS ESWL PCNL FURS PCNL

Stone
Free rate

286/406,
stone
free rate
70.4%.

122/155,
stone
free rate
78.7%

1.16
(1.04–1.30)

229/352,
stone
free rate
65.1%.

228/251,
stone
free rate
90.8%

1.42
(1.30-1.55)

48/70,
stone
free rate
68.5%

171/183,
stone
free rate
93.4%

1.32
(1.13-1.55)

moderate

(5 studies
with 561
participants)

(4 studies
with 603
participants)

(3 studies
with 253
participants)

Figure 2. Forest plot comparison between FURS and ESWL stone free rate in lower pole stone ≤20 mm management.

Prahara Yuri Acta Med Indones-Indones J Intern Med

Figure 3 shows PCNL is better than fURS
based on the stone free rate in ≤ 20 mm lower
pole stone management with overall RR 1.32
(95% CI 1.13 – 1.55); p<0.001 and I2=57%.

Percutaneous Nephrolithotomy versus
Extracorporeal Shock Wave Lithotripsy

We obtained data from 820 patients from 4
literatures, comprised of 289 patients in PCNL
and 531 patients in ESWL group. We found 25
patient with residual stone from 289 patients
treated with PCNL (follow-up 3 month, 91.3%)
and 187 patients from 531 patients treated with
ESWL (follow-up 3 month, stone free rate
64.8%).

Figure 4 shows PCNL is better than ESWL
based on the stone free rate in ≤ 20 mm lower
pole stone following management with overall
RR 1.42 (95% CI 1.30 – 1.55); p = <0.001 and
I2 = 85%.

DISCUSSION
Lower pole (LP) renal stones provide

a unique challenge when considering their
management.11 The issues are mostly around the
presence of one or more lower pole anatomical
variations, an increased infundibular (IF) length
and a decreased IF width and angle.12 LP stones

that are symptomatic, locally obstructing,
infection related, or increasing in size require
intervention.13,14 Methods for treatment of
LPSs 10 – 20 mm in length represent a major
controversy in the urological literature.1,15,16
Smaller, asymptomatic stones can be managed
expectantly, though with periodic follow-up a
significant number will exhibit increasing size
or become symptomatic.17,18

For most stones smaller than 10 mm, SWL
is the treatment of choice, while for stones
greater than 20 mm, percutaneous management
is generally indicated.19,20 Stones in the range
of 10 - 20 mm represent an area of ongoing
controversy regarding respective roles of SWL,
PCNL and ureteroscopy.1,13–15,17 In such cases,
consideration should also be given to intrarenal
anatomy and stone fragility in determining
appropriate therapeutic intervention.17,21

Based on this meta-analysis, it shows
that PCNL is better than fURS and ESWL
(p=<0.001). Then, fURS is better than ESWL
base on stone free rate in ≤20 mm lower pole
stone management (p=0.01). With the minimal
morbidity and widespread availability of ESWL,
PCNL had assumed a diminished role in stone
management over the past two decades. Several

Figure 3. Forest plot comparison between FURS and PCNL stone free rate in lower pole stone ≤ 20 mm management.

Figure 4. Forest plot comparison between PCNL and ESWL stone free rate in lower pole stone ≤ 20 mm management.

Vol 50 • Number 1 • January 2018 Meta-analysis of optimal management of 10-20 mm lower pole stone

indications remain well accepted, however,
including stones failing SWL, stones associated
with distal obstruction, and the occasional patient
in whom SWL is contraindicated for factors
such as body habitus or proximate calcified
aneurysm. Additionally virtually all studies to
date comparing SWL and PCNL demonstrate
an inverse relationship between stone burden
and stone free rates after SWL, particularly in
the lower pole calyx. In contrast, the success of
PCNL is almost independent of stone size. Stone
burden, therefore, is a well recognized factor in
the decision for SWL or PCNL.17,21

A multicentre lower pole study group,
conducted the first prospective randomized trial
with the aim of determining the optimal treatment
of lower pole calculi. The group compared
stone-free rates in 52 patients undergoing SWL
and 55 randomized to PCNL. Overall stone
free rates for PCNL were far superior to that
of SWL (95% v. 37%), retreatments were more
common in the SWL group (16% v. 9%) and
auxillary procedures were more frequent with
SWL patients (16% v. 2%). Stratification by
stone size was also consistent with prior studies,
demonstrating SWL stone-free rates of 68% for
stones smaller than 10 mm in diameter, 55% for
10–20 mm stones and 29% for stones larger than
20 mm. The corresponding stone-free rates for
PCNL were 100%, 93% and 86%, demonstrating
that, for PCNL, stone-free rates are largely
independent of stone size.4 The comparison
of stone clearance rate between ESWL and
more invasive treatments such as PCNL or
ureteroscopy was also done by many authors,
however, overall complication rates in the Lower
Pole Study were not significantly different.4,20

In the treatment of lower calices stone of
less than 20 mm, El-Nahas et al.2 reported the
matched groups which included 37 patients who
underwent fURS and 62 patients who underwent
ESWL. Retreatment rate was significantly higher
for ESWL (60% vs 8%, p<0.001). Preminger
found that stone-free rates for calculi between
11 and 20 mm were 21% and 92% for SWL
and PNL, respectively.15 Similarly, Haroon et
al3 reported the proportion of patients who were
stone-free after 4 weeks was significantly higher
in the PCNL group than in the SWL group (83%

vs. 51%, p<0.001). The cause of the higher
retreatment and stone free rate in ESWL may be
the use of a second generation electromagnetic
lithotripsy machine with a small focal area and
lower shock energy in comparison with the
original HM3. Thus a stone larger than 10 mm is
expected to require multiple sessions of ESWL.
On the other hand, the causes of retreatment
in the fURS group had unexpected incidents
such as malfunction of the ureteroscope or laser
machine and development of complications (e.g.
perforation of the ureter).2,22

Of the patients with nephrolithiasis in
the United States who received commercial
healthcare in 2000, the overall distribution of
procedures was approximately 54% for ESWL,
40% for URS, 5% for PCNL, and 1% for
open surgery. Although it is accepted that the
selection criteria for PCNL (e.g. large and/or
complex stone disease) will lead to lower usage
rates, the factors affecting the disparity between
the rates of ESWL and URS are not as clear.
Understanding the trends in treatment choice
requires accounting for numerous considerations
through the perspective of hospitals, physicians,
and patients.17,19,21

Flexible ureteroscopy (fURS) offers
advantages in certain patient populations such
as those with bleeding diathesis, those taking
anticoagulants, those with renal anomalies
such as a calyceal diverticulum, morbidly
obese patients and those with orthopedic or
other abnormalities with body habitus that may
make ESWL or PCNL challenging to perform.4
Ozturk et al14 reported that success rates were
76, 94, and 73% respectively in ESWL, PCNL,
and fURS. The highest stone-free rate was
in the PNL group (p<0.05). For treatment of
lower pole stones 10 – 20 mm in length, fURS
provide a significantly higher stone free rate and
lower retreatment compared with ESWL. The
incidence of complications after fURS was not
significantly higher than after ESWL and the
severity of complications was comparable. These
results support the increasing role of fURS in the
treatment of 10–20 mm lower pole stones.1,23,24

Renal stones of less than 10 mm are
usually treated successfully with ESWL; larger
stones, especially within the lower pole, are

Prahara Yuri Acta Med Indones-Indones J Intern Med

more efficiently treated by PCNL. FURS is
recommended as a second-line treatment for
smaller lower-pole stones and an as alternative
for stones of moderate size if there are negative
predictors for the success of ESWL.16,25,26 In
10 – 20 mm renal stone, PCNL seem to be the
most successful but most invasive method.
Despite this recommendation, fURS is already
used as the method of choice for such stones by
many urologists, although individual factors and
preferences must be considered.8,14

In this study, we are not considering
individual factors and types of lithotriptors
that may influence stone free rate. The rate of
symptomatic episodes and stone growth can be
low depending on disease factors and the patient
population, and systematic re-treatment in the
short term is not justified. Further study is needed
to improve our understanding of the risk of stone
recurrence or progression after surgery using
consistent definitions of small residual fragments
and uniform treatment protocols.

CONCLUSION
Percutaneus Nephrolithotomy (PCNL)

provides a higher stone free rate than fURS and
ESWL and may help urologist making decision
of an intervention in 10-20 mm lower pole stone
management.

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