Single Percutaneous Tract Combined with Flexible Nephroscopy in the Management of Kidney Stones
2-4 cm: Better Options of Treatment Protocols
Xiaobo Zhang1,2,3, Jie Gu1,2, Xiong Chen1,2, Yuanqing Dai2, Mingquan Chen1, Sheng Hu1, Zhenyu Liu1,
Dongjie Li1,2*
Purpose: To investigate the safety and efficacy of single percutaneous tract combined with flexible nephroscopy
in the Management of 2-4 cm renal calculi.
Materials and Methods: We retrospectively analysed the treatment data of patients with 2-4 cm renal calculi
from June 2010 to June 2017. The data included 217 cases of percutaneous nephrolithotomy (PNL), 441 cases of
retrograde intrarenal surgery (RIRS) and 217 cases of single-access percutaneous nephrolithotomy combined with
flexible nephroscopy (PNCFN). The collected data were analyzed.
Results: A total of 875 cases were studied, with an average age of 42.35 ± 10.29 years. Group PNCFN showed the
highest stone-free rates (SFRs)(73.7 vs 66.7 vs 80.2, P = .00), best patient satisfaction (89.84 vs 87.23 vs 92.29,
P = .00). The length of stay was shorter in the RIRS group relative to the other two groups (5.22 vs 5.65 vs 3.72,
P = .00). Haemoglobin decrease (> 10 g/L) was higher in group PNL than that in group RIRS and group PNCFN
(P = .012). Hospitalization fees (RMB) were Increased in group PNCFN compared with that in group PNL and
group RIRS (34563.45 vs 21334.69 vs 33343.16, P = .000). Treatment protocols of PNL decreased from 17.51%
to 9.22%, those for RIRS from 5.22% to 17.69%, peaking at 2012, PNCFN from 8.29% to 15.67% showed a rapid
growth trend.
Conclusion: The percutaneous nephrolithotomy combined with flexible nephroscopy treatment on renal calculi of
2-4 cm was associated with higher stone-free rates and better patient satisfaction than RIRS and PNL.
Keywords: flexible nephroscopy; percutaneous nephrolithotomy; retrograde intrarenal surgery; stone free rate;
patient satisfaction
INTRODUCTION
Renal calculi larger than two cm are known for their complexity of clearance, high risk in operation, and
high rate of residuals and relapse. Percutaneous Neph-
rolithotomy (PNL) had been recommended as the first-
choice treatment for renal calculi larger than 2 cm(1).
The advantages of PNL included higher efficiency and
lower rates of residual stones(2). However, single-access
PNL cannot effectively deal with parallel calices calcu-
li; multiple-tract PNL in one session is effective while it
caused more surgical trauma(3-5). Many researchers have
explored RIRS to remove kidney stones 2 cm, reduc-
ing operation trauma and shortening length of stay. As
RIRS has a lower efficiency than PNL, it takes 1.2 to
1.7 more times of operation and leading to higher ex-
penses to the patients(6), the one stage SFR was reported
in 72.2% and even lower. Residual stones are related to
future stone events and concomitant surgery. Flexible
nephroscopy is able to reach more calyces and inspect
them for residual fragments, it may reduce the use of
the fluoroscopy and detection of the residual stones to
1Xiangya International Medical Center, Department of Geriatrics, Xiangya Hospital, Central South University,
Changsha, P. R. China, 410008.
2National Clinical Research Center for Geriatric Disorders, Central South University Changsha, P. R. China,
410008.
3Urolithiasis Institute of Central South University, Changsha, P. R. China, 410008.
*Correspondence: Department of Geriatrics, Xiangya International Medical Center, Xiangya Hospital, Central
South University, Changsha, P. R. China, 410008.
Tel: +86 0731 89753054, E-mail: jerry1375@126.com.
Received June 2019 & Accepted December 2019
improve the efficacy and reduce the morbidity of the
procedure(7,8).
In current research, with the emergence of new instru-
ment flexible nephroscopy, single-access PNCFN was
used to deal with the 2-4 cm renal calculi. This method
was expected to have higher calculi removal efficiency,
lower risks in operation and a lower rate of residuals.
So far, the study of the comparison among PCNL, RIRS
and PNCFN in the management of kidney stones 2-4
cm at the same time is lacking. Hence, we compared our
clinical experiences and previous clinical cases, where
RIRS and PNL were adopted for 2-4 cm renal calculi
removal for better reference when selecting treatment
protocols.
MATERIALS AND METHODS
Clinical Data
Our study was based on the clinical cases of 2-4 cm re-
nal calculus treatment in our hospital from June 2010 to
June 2017. The calculi sizes were measured through CT
examination (single calculus 2-4 cm or multiple stones
Urology Journal/Vol 18 No. 1/ January-February 2021/ pp. 28-33. [DOI: 10.22037/uj.v0i0.5427]
ENDOUROLOGY AND STONE DISEASE
Vol 18 No 1 January-February 2021 20
2-4 cm combined). The participants were divided into 3
groups according to treatment methodology, including
217 cases of PNL, 441 cases of RIRS and 217 cases of
single-channel PNCFN.
All patients were informed about the procedures, and
the surgical choice was made by the patient with coun-
selling from the surgeon. All patients received appro-
priate preoperative antibiotic. The operation time was
recorded from insertion of the endoscope to the com-
pletion of stent placement. All protocols in the present
investigation were reviewed and approved by the ethi-
cal review committee of the Xiangya Hospital, Central
South University of China. An independent third-party
survey center participated in the accurate reporting of
patient satisfaction after surgery. All surgeries were
completed by the same doctor. We recorded and ana-
lyzed patients' general information such as age, gender,
the size of the calculi and BMI. The operation time,
variation of haemoglobin, the SFRs, complications and
length of stay were collected. The length of stay was
recorded from admission to discharge.
The inclusion criteria were applicable to all three surgi-
cal procedures: 1. age 20-80 years; 2. renal calculi 2~4
cm; 3. serious heart and lung diseases were excluded;
4. systemic haemorrhagic disease was excluded; 5. the
ipsilateral GFR was more than 10 ml/min; 6. if both
sides met the requirements, bilateral treatment was not
included in the study; If staging treatment was per-
formed, the first side of the clinical data was included
in the study.
Operation protocol
For the group PNL, operations were performed on pa-
tients under general anaesthesia in lithotomy position.
A 4 Fr retrograde ureteral catheter was inserted into the
surgical side of the ureter with a ureteroscope. Then
the position was changed to prone. With the guidance
of colour Doppler ultrasound, the puncture point was
located at the 11th-12th intercostal between the poste-
rior axillary line and scapular line. The puncture was
made through the fornix of calices, and then the tract
was dilated to 20 Fr with a balloon or coaxial dilators.
A nephrostomy sheath was advanced over the balloon
The Management of Kidney Stones 2-4 cm -Zhang et al.
Table 1. The detailed general patient information.
PCNL RIRS PNCFN P Value
Cases, n 217 441 217 N/A
Age, years 42.35 ± 11.20 42.62 ± 9.63 41.44 ± 10.36 0.379
BMI (kg/m2) 24.60 ± 3.40 24.99 ± 3.54 24.35 ± 3.37 0.069
Gender (M/F) 100/117 220/221 107/110 0.647
Stone burden (mm) 34.21 ± 4.81 34.57 ± 3.32 34.53 ± 2.86 0.470
Stone location, n(%) 0.000
Upper pole 20(9.22) 34(7.71) 18(8.29)
Middle pole 37(17.05) 113(25.62) 33(15.21)
Lower pole 74(34.10) 108(24.49) 84(38.71)
Renal pelvis 53(24.42) 131(29.70) 41(18.89)
Multiple stones 33(15.20) 55(12.47) 41(18.89)
Hydronephrosis, n(%) 0.327
No 58(26.73) 103(23.36) 49(22.58)
Mild 77(35.48) 140(31.75) 87(40.10)
Moderate 61(28.11) 152(34.47) 62(28.57)
Severe 21(9.68) 46(10.43) 19(8.76)
Urine leukocyte positive, n (%) 51 (23.50) 93 (21.09) 47 (21.66) 0.778
Urine erythrocyte positive, n (%) 24 (11.06) 42 (9.52) 28 (12.9) 0.414
Abnormal serum creatinine, n (%) 18 (8.29) 42 (9.52) 24 (11.06) 0.618
Measurement data between groups were expressed as the mean ± SD (¯x ± s) One-way Analysis of Variance was used to compare the
variables in different groups. Counting data were shown as the number and/or percentage (%), using the chi-square test (χ2). P < 0.05
illustrates statistical significance.
Figure 1. Changes in treatment protocols
Vol 18 No 1 January-February 2021 29
and the nephroscope or ureteroscope was placed along
the sheath; when the calculi were detected, they were
removed with a holmium laser (2.0-2.5 J, 20-25 Hz, 550
μm). A routine postoperative indwelling ureteral stent
was placed on the operative side.
For the group RIRS, the operations were performed on
patients under general anaesthesia and in the lithotomy
position. A 8.0-9.5 Fr ureteroscopy was used to check
the surgical side of the ureter up to the pelvis, and a
smooth guidewire (0.89 mm, 150 cm, Cook® Medical,
America) was placed. Along the guidewire, a ureteral
access sheath (12 Fr Cook® Medical) was installed,
then an Olympus flexible ureteroscope was used. Every
calyx was examined via the flexible ureteroscope, and
the calculi were removed with a holmium laser (0.8-
1.0 J, 20 Hz, 200 μm). Larger stone fragments were re-
moved using a 1.7 Fr N GageTM nitinol basket (Cook®
Medical, Bloomington America). Upon finishing the
operation, each calyx was examined again. When the
flexible ureteroscope was removed, the whole ureter
was checked at the same time, while a routine postop-
erative indwelling ureteral stent was placed on the op-
erative side.
For the group PNCFN a 20 Fr tunnel was established in
the same way as for group PNL. Calculi were removed
with a holmium laser (2.0-2.5 J, 20-25 Hz, 550 μm) af-
ter the insertion of a nephroscope or ureteroscope. Note
that the angle change was avoided in the access to re-
duce the risk of laceration of calices’ necks. When cal-
culi were difficult to reach, flexible nephroscopy with a
holmium laser (0.8-1.0 J, 20 Hz, 200 μm) was used to
enter the calices through the 20 Fr tunnel and remove
the calculi. Upon finishing the operation, each calyx,
the pelvis and ureteropelvic junction was examined.
and a routine postoperative indwelling ureteral stent
was placed on the operative side.
Collected data consisted of patient age, gender, the size
of the calculi and BMI. Information about the operation
time, variation of haemoglobin, SFRS, complications
and length of stay were collected. After 4 weeks, if
the non-contrast CT examination indicated no residual
calculi or if the residual calculi were less than 4 mm
and the patients showed no related symptoms, calculi
removal was effectively performed. The ureteral stent
was maintained for 4 weeks.
An independent third party (Hualun Consulting Co.,
Ltd. Hunan) was responsible for the satisfaction survey,
which was conducted by telephone one month after
discharge. Patient satisfaction is a subjective quanti-
tative score of the medical service. This questionnaire
includes six main parts and 15 detailed indicators
(Figure 2).
Statistical Analysis
The statistical analysis was conducted using SPSS soft-
ware, version 19.0. Measurement data between groups
were expressed as the mean ± SD ( ¯X ± s), one-way
Analysis of Variance was used to compare the variables
in different groups. Counting data were shown as the
number and/or percentage (%), using the chi-square test
(χ2) to compare the variables in different groups. P <
0.05 illustrates statistical significance.
RESULTS
A total of 875 cases was studied, with an average age
of 42.25 ± 10.35 years. The general information of the
patients in each group is shown in Table 1. Among
different groups, features such as age, BMI, maximum
Table 2. Comparison of the perioperative related data.
PCNL RIRS PNCFN P Value
stone-free n (%) 160(73.7) 294(66.7) 174(80.2) 0.000
Operation time (min) 104.35 ± 40.65 129.17 ± 41.91 131.88 ± 45.63 0.000
Bleeding (mL) 60.65 ± 40.42 23.86 ± 18.09 54.17 ± 31.81 0.000
Conversion to open surgery n (%) 4(1.8) 2(0.5) 3(1.4) 0.211
Length of stay (d) 5.65 ± 0.74 3.72 ± 1.24 5.22 ± 0.88 0.000
Blood transfusion n (%) 6(2.8) 1(0.2) 4(1.8) 0.188
Complications n (%) 21(9.7) 30(6.8) 11(5.1) 0.165
Unplanned re-operation n (%) 5(2.3) 4(1) 2(0.9) 0.280
Haemoglobin decrease (>10 g/L), n (%) 26 26 24 0.012
(12.0) (5.9) (11.1)
Fees (RMB) 21334.69 ± 3006.73 33343.16 ± 3639.04 34563.45 ± 5198.03 0.000
Satisfaction score 89.84 ± 4.37 87.23 ± 5.99 92.29 ± 3.88 0.000
Measurement data between groups were expressed as the mean ± SD (¯x ± s). One-way Analysis of Variance was used to compare the
variables in different groups. Counting data were shown as the number and/or percentage (%), using the chi-square test (χ2). P < 0.05
illustrates statistical significance.
PCNL vs RIRS PCNL vs PNCFN RIRS vs PNCFN
One-stage stone-free 0.065 0.111 0.000
Operation time 0.000 0.000 0.000
Bleeding 0.000 0.056 0.000
Conversion to open surgery 0.078 0.703 0.181
Length of stay 0.000 0.006 0.000
Blood transfusion 0.099 0.801 0.142
Complications 0.586 0.350 0.685
Unplanned re-operation 0.147 0.253 0.985
Hemoglobin decrease >10 g/L 0.014 0.880 0.021
Hospitalization fees 0.000 0.000 0.001
Patient satisfaction(discharged for one month) 0.000 0.000 0.000
One-way Analysis of Variance was used to compare the measurement variables in different groups. Chi-square test (χ2) was used to
compare the counting variables in different groups.
P < 0.05 illustrates statistical significance.
Table 3. Comparison of the perioperative data between every two groups.
The Management of Kidney Stones 2-4 cm -Zhang et al.
Endourology and Stones diseases 30
Vol 18 No 1 January-February 2021 20
diameter of calculus, gender proportion, hydronephro-
sis, rate of urine leukocyte positive, rate of urine eryth-
rocyte positive, and the proportion of abnormal serum
creatinine showed no significant differences. The stone
locations of lower pole and multiple stones in group
PNCFN was higher than that in groups PNL and RIRS
(38.71 vs 34.10 vs 24.49%, 18.89 vs 15.20 vs 12.47%).
Renal pelvis stones frequency in group PNL, RIRS,
PNCFN were 24.42, 29.70, 18.89% respectively.
The perioperative-associated parameters of different
groups are shown in Table 2. Group PNCFN had higher
SFRs (80.2%, P = .00), better patient satisfaction (score
92.29, P = .00), but a longer operation time (131.88
min, P = .01). The length of stay in group PNCFN was
shorter than that in group PNL (multiple-tract was per-
formed for 102 (47.0%) cases in the PNL group) but
longer than that in group RIRS (average 5.22 vs 5.65
vs 3.72 d, P < .001). Haemoglobin decrease (> 10 g/L)
was higher in group PNL than those in groups RIRS
and PNCFN (P = .012). Increased hospitalization fees
(RMB) was observed in group PNCFN compared to
groups PNL and RIRS (average 34563.45 vs 21334.69
vs 33343.16 RMB, P < .001).
The reason for conversion to open surgery in group
PCNL was that 2 patients were morbidly obese; 1 case
of renal parenchymal laceration by multi-channel; and 1
case of anatomical abnormalities (renal neck stenosis).
1 case of ureteral avulsion injury and 1 case of intraop-
erative ureteral perforation necessitated conversion in
the group RIRS. 1 case of skeletal malformation and
2 case of ureteropelvic junction obstruction in group
PNCFN resulted in conversion. The rate of conversion
to open surgery, ratio of blood transfusion, incidence
of complications and rate of unplanned reoperation dis-
played no statistically significant differences.
The comparisons of the perioperative data between
every two groups are shown in Table 3. Compared
to group PNL, group PNCFN demonstrated a shorter
length of stay (P = .006) and a higher patient satisfac-
tion (P < .001), but a longer duration of operation (P
< .001) and a higher hospitalization fees (P < 0.001).
When comparing groups RIRS and PNCFN, group
PNCFN showed higher SFRs (P < .001) and patient
satisfaction rates (P < .001), but greater bleeding (P <
.001), longer length of stay (P < .001), and higher hae-
moglobin decrease (P < .001).
The treatment protocols for 2-4 cm renal calculi are
shown in Figure 1. The choice of PNL decreased
smoothly (17.51% to 9.22%), and RIRS showed a rap-
id growth trend (5.22% to 17.69%, peaking at 2012).
PNCFN continued to increase steadily (8.29% to
15.67%).
DISCUSSION
Guidelines recommend PNL as the first-choice treat-
ment for renal calculi larger than 2 cm(9). However, par-
allel calices calculi with the treatment of single-track
PNL was difficult. Multiple-access PNL increased
complications, such as haemorrhage.(10-12) The advan-
tages of RIRS include utilizing the inherent cavity of
the human body, low trauma, fast recovery, and better
curative effect(13). It can significantly reduce the inci-
dence of surgical trauma and complications and shorten
the average days of hospitalization(14). In our study, the
average length of stay was 3.72d (RIRS). However, due
to the limitation of lithotripsy efficiency, RIRS for renal
calculi larger than 2 cm needs to be performed in stag-
es, and the SFR is low. Xiaokun Zhao et al, reported a
92.0% SFR after 3 procedures for RIRS with holmium
laser lithotripsy (mean stone burden of 24.5 mm)(15). In
our study, the one-stage SFR was 66.7% (RIRS). More-
over, the success rate of RIRS was largely dependent on
the angle between the funnel and the pelvis (infundibu-
lopelvic angle, IPA). Petrisor et al. found that when the
IPA was between 30 and 90 degrees, the success rate of
RIRS was 74.3%, and when the IPA was less than 30
degrees, the success rate of flexible ureteroscopic litho-
tripsy became 0% (6).
The EAU and AUA guidelines recommendation is that
routine stenting is not necessary before RIRS. Howev-
er, pre-stenting facilitates RIRS management of stones,
improves the SFR, and reduces complications. In our
study, if ureteral access is not possible, insertion of a
6 Fr double-J stent 4 weeks before the second attempt
offers an alternative to dilation.
Over the last 10 years, living standards and the econ-
Figure 2. Patient Satisfaction
The Management of Kidney Stones 2-4 cm -Zhang et al.
Vol 18 No 1 January-February 2021 31
omy improved, causing people to be more engaged
health and healthcare consumers which lead to a rap-
id growth of less invasive RIRS (Figure 1). However,
there remain several controversial issues in the applica-
tion of flexible ureteroscopy, such as operation indica-
tion, operative skills, and cost efficiency. We focus on
the hot issues that puzzle clinicians most, and hope our
study will be able to help some urologists in clinical
practice. Our hospital did not introduce mini-percutane-
ous nephrolithotomy, super-mini percutaneous nephro-
lithotomy, or Chinese minimally invasive percutaneous
nephrolithotomy, which have improved smaller tracts
and are less invasive(16-18).
The use of flexible nephroscopy during PNL was
known for its higher SFRs, fewer interventions and
minimal bleeding(19). Improvements in design and novel
surgical instruments, such as flexible nephroscope and
the introduction of the holmium: YAG laser, increased
the SFRs for PNL(20-22). Williams et al. observed a high
SFR and low morbidity rate with staghorn stones fol-
lowing single-access PNL and flexible nephroscopy(23).
Our results showed that there was an 80.2% (174/217)
one-stage SFR for PNCFN versus 66.7% (294/441) for
RIRS (P < .001), indicating that PNCFN was an effec-
tive treatment protocol that provided more efficacy in
patients with 2-4 cm renal calculi.
Bleeding is a major and troublesome complication of
PNL. The volume of blood loss is associated with the
number of access points, stone size, and duration of
surgery 5,24. In our present study, the mean duration
was slightly longer in group PNCFN than that in group
PNL (131.88 versus 104.35, P = .001) as shown in Ta-
ble 2, whereas the mean bleeding was 54.17 (PNCFN)
versus 60.65 ml (PNL), which showed no statistically
significant differences (P = .056). This result may have
been due to the lower number of interventions that were
associated with flexible nephroscopy, or the use of a
smaller diameter instrument that could reach stones that
were inaccessible via rigid nephroscopy (with minimal
damage to renal parenchyma)19. Our puncture was
made through the fornix of calices. The fornix of the pa-
pilla is the preferred site for a puncture to the collecting
system(25). The principle behind this approach relies on
the anatomical distribution of the blood vessels within
the kidney, it is associated with less haemorrhagic risk
(26,27).
The patient satisfaction survey was relevant and mean-
ingful, and assessed patient satisfaction using an inde-
pendent, third-party survey center to eliminate observer
bias(28,29). Although it is a comprehensive data, there are
many influencing factors, however it can reflect the sat-
isfaction to some extent. In our study, the mean score
of patient satisfaction was the highest in Group PNCFN
92.29, as represented in Table 2, which was higher than
89.84 (PNL) and 87.23 (RIRS), and this result may have
been due to the high one-stage SFR (73.7% vs 80.2%),
less bleeding (54.17 vs 60.65ml), less complications
(11(5.1%) vs 21(9.7%) and the decreased length of stay
(5.22 vs 5.65) compared to PNL, although more instru-
ments were used and the expenses were slightly high-
er than those for PNL. Another crucial factor was that
there were no multi-channel cases in Group PNCFN.
To our knowledge, our study is the first to report the
comparison among PNL, RIRS and PNCFN. There are
no assessments of the three protocols based on patient
satisfaction by independent investigators.
The complications were low in the three groups, and
it showed no statistically significant differences, which
may be due to a small sample size. To clarify whether
the two were correlated, larger sample sizes are needed
to evaluate the long-term outcome of our study. Retro-
spective design is a drawback of our study, we do agree
that prospective and randomized design is needed in the
future studies.
When multiple treatment protocols compete in the
clinical setting, decisions of the optimal treatment op-
tion in an individual patient are mainly dependent on
medical factors, including procedural efficacy, success
rate and safety. From a broader perspective, these de-
cisions reflect comprehensive factors including the
above mentioned factors, as well as doctor`s prefer-
ence, cost-effectiveness, medical care status, and insur-
ance authorization. Therefore, identifying the changing
trends in the numbers or rates of certain treatments is
meaningful and may provide a comprehensive assess-
ment of the treatment of kidney stones 2-4 cm that can
be used in clinical management. In our study, a single
access percutaneous nephrolithotomy combined with
flexible nephroscopy was used, which gave full play to
the advantages of flexible and rigid nephroscopy. Sali-
ent advantages of our PNCFN include one-stage stone-
free rate of 80%, length of stay shortened to 5.22 days
and improved patient satisfaction. In addition, the cost
of the PNCFN was marginally higher than that of the
RIRS, which is also in favour of the promotion of the
PNCFN surgery in the primary hospitals.
As far as we know, our study is the first to report the
comparison among PNL, RIRS, and PNCFN at the
same time. There are no assessments of the three proto-
cols based on patient satisfaction by independent inves-
tigators in one study. Our study had certain limitations.
there may be a choice bias in this study. Fortunately, the
study has a large sample size so that this bias is effec-
tively reduced, and Table 1 shows no significant differ-
ence in the baseline data of each group.
CONCLUSIONS
The percutaneous nephrolithotomy combined with flex-
ible nephroscopy treatment on renal calculi of 2-4 cm
was associated with higher stone-free rates and better
patient satisfaction than RIRS and PNL.
ACKNOWLEDGEMENTS
We thank Mingquan Chen for editorial assistance with
our manuscript
FUNDING
The project was supported by the China Graduate Con-
test on Smart-city Technology and Creative Design
(Grant No.2018jspy108).
CONFLICT OF INTEREST
All authors declare that they have no conflict of interest
or financial ties to disclose.
REFERENCES
1. Türk C, Skolarikos A, Neisius A et al. EAU
Guidelines on Urolithiasis 2019. EAU
Guidelines Office, Arnhem, The Netherlands.
https://uroweb.org/guideline/urolithiasis/.
The Management of Kidney Stones 2-4 cm -Zhang et al.
Vol 18 No 1 January-February 2021 23Endourology and Stones diseases 32
2019
2. Saad KSM, Youssif ME, Hamdy SAIN et
al. Percutaneous Nephrolithotomy (PCNL)
Versus Retrograde Intra-renal Surgery (RIRS)
in Treatment of Large Renal Stones (>2cm) In
Pediatric Patients: A Randomized Controlled
Trial. J Urol 2015;194:1716-1720
3. Akman T, Sari E, Binbay M et al.
Comparison of outcomes after percutaneous
nephrolithotomy of staghorn calculi in those
with single and multiple accesses. J Endourol.
2010;24(6):955-60
4. Akman T, Binbay M, Sari E et al. Factors
affecting bleeding during percutaneous
nephrolithotomy: single surgeon experience. J
Endourol. 2011;25:327-33
5. Chen J, Zhou X, Chen Z et al. Multiple tracts
percutaneous nephrolithotomy assisted by
LithoClast master in one session for staghorn
calculi: report of 117 cases. Urolithiasis.
2014;42:165-9
6. Geavlete P, Multescu R, Geavlete B. Influence
of pyelocaliceal anatomy on the success of
flexible ureteroscopic approach. J Endourol.
2008;22:2235-9
7. Gokce MI, Gulpinar O, Ibis A et al. Retrograde
vs. antegrade fl exible nephroscopy for
detection of residual fragments following
PNL: A prospective study with computerized
tomography control. Int Braz J Urol.
2019;45:581-587
8. Sfoungaristos S, Mykoniatis I, Katafigiotis
I et al. Single lower calyceal percutaneous
tract combined with flexible nephroscopy:
A valuable treatment paradigm for staghorn
stones. Can Urol Assoc J. 2018;12:E21-E24
9. Assimos D, Krambeck A, Miller NL et al.
Surgical Management of Stones: American
Urological Association/Endourological
Society Guideline, PART II. J Urol.
2016;196:1161-9
10. El-Nahas A, Shokeir A, El-Assmy A
et al. 882 POST PERCUTANEOUS
NEPHROLITHOTOMY EXTENSIVE
HEMORRHAGE: A STUDY OF RISK
FACTORS. J Urology. 2007;177:576
11. Michel MS, Trojan L, Rassweiler
JJ. Complications in percutaneous
nephrolithotomy. Eur Urol. 2007;51:899
12. Bucuras V, Gopalakrishnam G, Jr WJ et al. The
Clinical Research Office of the Endourological
Society Percutaneous Nephrolithotomy Global
Study: nephrolithotomy in 189 patients with
solitary kidneys. J Endourol. 2011;25:11-7
13. Akman T, Binbay M, Ozgor F et al.
Comparison of percutaneous nephrolithotomy
and retrograde flexible nephrolithotripsy for
the management of 2–4cm stones: a matched-
pair analysis. Eur Urol Suppl. 2011;10:1384–
1389
14. Chen X, Li D, Dai Y et al. Retrograde intrarenal
surgery in the management of symptomatic
calyceal diverticular stones: a single center
experience. Urolithiasis. 2015;43:557-562
15. Huang Z, Fu F, Zhong Z et al. Flexible
ureteroscopy and laser lithotripsy for bilateral
multiple intrarenal stones: is this a valuable
choice? Urology. 2012;80:800-804
16. Zeng G, Zhu W, Liu Y et al. The new generation
super-mini percutaneous nephrolithotomy
(SMP) system: a step-by-step guide. Bju Int.
2017;
17. Zhu W, Li J, Yuan J et al. A prospective and
randomised trial comparing fluoroscopic, total
ultrasonographic, and combined guidance
for renal access in mini-percutaneous
nephrolithotomy. Bju Int. 2016;119
18. Huang Z, Fu F, Zhong Z et al. Chinese
Minimally Invasive Percutaneous
Nephrolithotomy for Intrarenal Stones in
Patients with Solitary Kidney: A Single-
Center Experience. Plos One. 2012;7:e40577
19. Gucuk A, Kemahli E, Uyeturk U et al. Routine
flexible nephroscopy for percutaneous
nephrolithotomy for renal stones with low
density: a prospective, randomized study. J
Urol. 2013;190:144-8
20. Albala DM, Assimos DG, Clayman RV et al.
Lower pole I: a prospective randomized trial
of extracorporeal shock wave lithotripsy and
percutaneous nephrostolithotomy for lower
pole nephrolithiasis-initial results. J Urol.
2001;166:2072-80
21. Wong C, Leveillee RJ. Single upper-pole
percutaneous access for treatment of > or
= 5-cm complex branched staghorn calculi: is
shockwave lithotripsy necessary? J Endourol.
2002;16:477-81
22. Gao X, Zeng G, Chen H et al. A novel
ureterorenoscope for the treatment of upper
urinary tract stones: initial experience from
a prospective multicentre study. J Endourol.
2015;29
23. Williams SK, Leveillee RJ. Management
of staghorn calculus: single puncture with
judicious use of the flexible nephroscope. Curr
Opin Urol. 2008;18:224-8
24. Maghsoudi R, Etemadian M, Kashi AH,
Ranjbaran A. The Association of Stone
Opacity in Plain Radiography with
Percutaneous Nephrolithotomy Outcomes and
Complications. Urol J. 2016;13:2899-2902
25. Basiri A, Kashi AH, Zeinali M et al. Ultrasound
- guided access during percutaneous
nephrolithotomy: entering desired calyx with
appropriate entry site and angle. Int Braz J
Urol. 2016;42:160-1167
26. Miller NL, Matlaga BR, Lingeman JE.
Techniques for fluoroscopic percutaneous
renal access. J Urology. 2007;178: 15-23
27. Sampaio FJ. Renal anatomy. Endourologic
considerations. Urol Clin N Am. 2000;27:585-
607
28. Nunley RM, Nam D, Berend KR et al. New
Total Knee Arthroplasty Designs: Do Young
Patients Notice? Clinical Orthopaedics and
Related Research®. 2015;473:101-108
29. Nam D, Nunley RM, Berend ME et al.
Residual Symptoms and Function in Young,
Active Hip Arthroplasty Patients: Comparable
to Normative Controls? J Arthroplasty.
2016;31:1492-7
The Management of Kidney Stones 2-4 cm -Zhang et al.
Vol 18 No 1 January-February 2021 33