Mini-percutaneous Nephrolithotomy vs Retrograde Intrarenal Surgery for Renal Stones Larger Than 10 mm: A Prospective Randomized Controlled Trial

Accepted Manuscript Mini-percutaneous nephrolithotomy versus retrograde intrarenal surgery for renal stones larger than 10 mm: a prospective randomized controlled trial Jeong Woo Lee, Juhyun Park, Seung Bae Lee, Hwancheol Son, Sung Yong Cho, Hyeon Jeong PII:

S0090-4295(15)00801-8

DOI:

10.1016/j.urology.2015.08.011

Reference:

URL 19365

To appear in:

Urology

Received Date: 12 June 2015 Revised Date:

14 August 2015

Accepted Date: 14 August 2015

Please cite this article as: Lee JW, Park J, Lee SB, Son H, Cho SY, Jeong H, Mini-percutaneous nephrolithotomy versus retrograde intrarenal surgery for renal stones larger than 10 mm: a prospective randomized controlled trial, Urology (2015), doi: 10.1016/j.urology.2015.08.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Mini-percutaneous nephrolithotomy versus retrograde intrarenal surgery for renal stones larger than 10 mm: a prospective

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randomized controlled trial

Jeong Woo Lee1, Juhyun Park2, Seung Bae Lee2, Hwancheol Son2, Sung Yong Cho2,

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Hyeon Jeong2

Department of Urology, Dongguk University Ilsan Hospital, Dongguk University

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College of Medicine, Goyang, Korea 2

Department of Urology, Seoul Metropolitan Government-Seoul National University

Boramae Medical Center, Seoul National University College of Medicine, Seoul,

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Korea

Runninghead: Mini-PCNL and RIRS for large renal stone Word count for the abstract: 241

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Word count for the manuscript: 2,745 (1 Figure, 2 Tables)

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Correspondence:

These two authors contributed equally to this article.

Sung Yong Cho, MD, PhD Department of Urology, Seoul Metropolitan Government-Seoul National Universit y Boramae Medical Center, 20, Boramae-ro 5-Gil, Dongjak-gu, Seoul, 156-707, Korea

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Hyeon Jeong, MD, PhD Department of Urology, Seoul Metropolitan Government-Seoul National Universit y Boramae Medical Center, 20, Boramae-ro 5-Gil, Dongjak-gu, Seoul, 156-707,

TEL: +82-2-870-2394, FAX: +82-2-742-4665

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E-mail: [email protected]

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Korea

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Keywords: mini-PCNL, RIRS, prospective, renal stone

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ACKNOWLEDGEMENTS

This study was supported by grant no. 16-2013-11 from the SK Telecom Research

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Fund. There are no financial or commercial interests about this paper.

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ABSTRACT

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OBJECTIVES: To compare mini-percutaneous nephrolithotomy (mini-PCNL) and retrograde intrarenal surgery (RIRS) in the management of renal stones larger than 10 mm in a single session.

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METHODS: Seventy patients presenting with renal stones >10 mm were randomized to a mini-PCNL or a RIRS group in a ratio of 1:1. Randomization was

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performed by a biostatistician and opened to the surgeon at the time of the patient’s admission on the day before surgery. Patient and stone characteristics, perioperative outcomes, and complications were compared between the two groups. The primary end point of “stone-free” which was defined as no residual stone or stones <2 mm on computed tomography within 3 months postoperatively.

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RESULTS: Thirty-five patients (Mini-PCNL) and 33 (RIRS) were included in the final analysis. Mini-PCNL and RIRS had a stone free rate of 85.7% and 97.0%, respectively (P=0.199). Operation time (P=0.148), hemoglobin decline (P=0.323),

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and hospital stay (P=0.728) were similar between the two groups. Pain visual

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analogue score at 1 hour postoperatively (P=0.029) and analgesic requirement (P=0.050) were higher in the RIRS group. Two patients in the mini-PCNL group and one in the RIRS group had minor pelvic or ureter perforation. One patient in each of the two groups had hypertension and urinary tract infection. CONCLUSIONS: Mini-PCNL and RIRS are safe and feasible surgical options to manage renal stones larger than 10 mm. RIRS produced a slightly higher stone free rate, but more immediate postoperative pain and higher analgesic requirement

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compared with mini-PCNL.

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INTRODUCTION

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Percutaneous nephrolithotomy (PCNL) is now the treatment of choice for large burden (>2 cm) renal stones because of the high rate of stone clearance [1,2]. However, considering the risk of surgical morbidities associated with PCNL, which

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include bleeding, pain, and urine leakage [3,4], minimally invasive procedures are getting more attention, especially miniaturized PCNL (mini-PCNL) and retrograde

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intrarenal surgery (RIRS).

Tract size is one of the important factors influencing surgical morbidities associated with PCNL [4,5]. The mini-PCNL technique (tract size ≤20 Fr) has been implemented with advances in technology. Mini-PCNL offers comparable stone free rates (SFR) compared with standard PCNL with less blood loss and less

standard PCNL [4,8].

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perforation [4,6,7]. Pain and urine leak are markedly less after mini-PCNL than

RIRS has gained much attention because it can lower the risk of significant

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morbidities associated with percutaneous approach [3]. The European Association

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of Urology guidelines recommend RIRS as the standard treatment option for small to medium-sized (≤2 cm) renal stones [2]. Encouraging surgical outcomes of RIRS in the management of larger (>2.5 cm) renal stones have been reported [9]. Few prospective randomized controlled trials have compared mini-PCNL and RIRS for large burden renal stones. The aim of this study was to compare SFR and surgical parameters between mini-PCNL and RIRS in the management of renal stones >10 mm in a single session.

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MATERIAL AND METHODS

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This prospective randomized controlled trial (NCT02067221) aimed to compare mini-PCNL and RIRS for renal stones >10 mm. The Institutional Review Board of Seoul Metropolitan Government-Seoul National University Boramae Medical

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Center approved the study (protocol number 16-2013-11). Between June 2014 and February 2015, 70 participants ≥20-years-of-age provided written informed consent.

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These enrolled patients were randomized into either a mini-PCNL (n = 35) or a RIRS group (n = 35) in a ratio of 1:1 [Figure 1]. Randomization was carried out by the Department of Biostatistics of our institution and opened to the operating surgeon at the time of the patient’s admission on the day before surgery. All

(Cho SY).

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procedures were electively performed in a single institution by a single surgeon

In the analysis of our database, the response within each treatment group was normally distributed and the standard deviation was 9. The true difference of

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surgical success rate was 6.5%. Type I error probability was 0.05 associated with

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the test of this null hypothesis. Therefore, we needed to study 31 subjects in each group to be able to reject the null hypothesis that the surgical success rates of mini-PCNL and RIRS groups were equal with a probability of 0.8. The follow-up rate of patients was estimated at 10%. Finally, the sample size was 35 cases in each group. All patients underwent history taking, physical examination, and laboratory tests including urinalysis, urine culture, complete blood count (CBC), renal function, and

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electrolyte determination. The size and location of all stones were evaluated via non-enhanced computed tomography (NECT). The mean Hounsfield unit was

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evaluated using an ellipsoid region of interest with axial images of CT. The inclusion criterion were a single or multiple renal stones (sum of the maximal length of stones, >10 mm). Patients with urogenital anomaly, solitary kidney, age <20

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years, or coagulopathy were excluded.

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Mini-PCNL

Under general anesthesia, patients were placed in the prone position. A percutaneous nephrostomy tube was inserted in the lower-pole calyx by an urologist or an experienced uro-radiologist. Calyceal puncture was carried out using a 22-gauge Skinny Needle (Cook Medical, Bloomington, IN, USA) under

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ultrasonography guidance. A 0.035-mm Terumo guidewire (Boston Scientific, Miami, FL, USA) was inserted through the calyceal puncture into the renal pelvis. The skin and fascia were incised and tract dilation was performed with a UltraxxTM balloon

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dilator (Cook Medical) of up to 18 Fr. A 15-Fr Nephroscope (Richard Wolf,

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Knittlingen, Germany) was inserted through the sheath and stone fragmentation was accomplished using a holmium:YAG laser using a 550- µm fiber (Trimedyne, Irvine, CA, USA). Holmium laser power was set to 40-50W. Stone fragments were removed using a 4-Fr grasping forcep (Richard Wolf) and a 6-Fr ureteral JJ stent was indwelled. A 16-Fr urethral Foley catheter was placed at the end of the operation.

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RIRS Under general anesthesia, patients were placed in the dorsal lithotomy position.

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Cystoscopic examination was routinely performed and a 0.035-mm Terumo guidewire (Boston Scientific) was inserted through the ureteral orifice under videoscopic guidance. Under C-arm fluoroscopic guidance, the Terumo Guidewire

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was exchanged with a Superstiff guidewire (Boston Scientific) using an openended 5-Fr ureteral catheter and a 14/16Fr or 12/14Fr ureteral access sheath

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(Cook Medical) was placed into the level of the ureteropelvic junction. A Flex-X2™ 7.5Fr flexible ureteroscope (Karl Storz, Tuttlingen, Germany) was passed through the access sheath and placed in the renal pelvis. The stones were fragmented with a 365- or 200-µm laser fiber. Holmium laser power was set to 10W. The repetition rate was 10 Hz and 15-20 Hz for the fragmentation and dusting mode, respectively.

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An endoscopic irrigation pump (Stryker, Kalamazoo, MI, USA) was utilized to maintain a constant intrarenal pressure of 100 mmHg throughout the procedure. Stone fragments were retrieved with a 1.9-Fr zero-tipped nitinol stone basket (Cook

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Medical). After laser lithotripsy, a 6-Fr JJ stent was routinely placed and was

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usually removed 1 to 2 weeks postoperatively. A 16-Fr urethral Foley catheter was inserted at the end of the operation. All patients were asked about the pain severity by visual analogue score (VAS; range: 1-10) 1 hour postoperatively and on the morning of the first operative day. Postoperative usage of analgesics used on an as-needed basis was recorded. On the first operative day, patients were rechecked concerning CBC, renal function, and kidney, ureter, and bladder X-ray. In the absence of complications, most

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patients were discharged after the Foley catheter was removed 1 day after surgery. The primary endpoint in this study was SFR in a single session. Prior to the 3

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month follow-up visit, all patients underwent NECT to assess for the presence of residual stone. Stone-free status was defined as no residual stones or stones <2 mm on NECT within 3 months postoperatively. The secondary outcomes were the

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intra-operative and postoperative parameters such as operation time, estimated blood loss, hemoglobin drop, VAS, analgesic requirement, hospital stay, and Complications

were

evaluated

according

to

the

Clavien

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complications.

classification of surgical complications [10].

Data were processed using the statistical software SPSS ver. 20.0 (IBM, Armonk, NY, USA). All parameters are reported as mean ± standard deviation or frequency (percentage). Continuous variables were analyzed by independent t-test or Mann-

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Whitney U-test, and categorical variables were assessed with the chi-squared test or Fisher’s exact test. All P values were estimated. P<0.05 was considered

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statistically significant.

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RESULTS

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Of the 70 randomized patients, 68 completed the study including mini-PCNL in 35 and RIRS in 33. Two patients from the RIRS group received mini-PCNL because of the allocation error and dropped out of the study.

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Patient and stone characteristics are shown in Table 1. The mean age, gender, body mass index, and the incidence of comorbidities were similar between the

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mini-PCNL and RIRS groups (P>0.05). Differences in stone characteristics including laterality, mean stone size, stone number, mean Hounsfield units, stone location, presence of staghorn stone, and stone composition were statistically insignificant between the two groups (P>0.05). However, the presence of hydronephrosis in the mini-PCNL group significantly less compared with the RIRS

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group (5/35, 14.3% versus 16/33, 48.5%; P=0.004). Seoul National University Renal Stone Complexity (S-ReSC) scores was 3.2 ± 1.9 in the mini-PCNL group and 2.1 ± 1.3 in the RIRS group (P=0.015).

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Table 2 presents the comparative data of intra-operative and postoperative

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parameters. In the mini-PCNL group, 32 (91.4%) patients underwent tubeless procedure. Three patients required nephrostomy tube for moderate intraoperative bleeding (n=1) and significant residual fragments (n=2). One patient underwent second mini-PCNL and 1 RIRS at 2 days after surgery. In the RIRS group, a ureteral access sheath (12/14 or 14/16 Fr) was placed in 32 (97.0%) patients. One patient underwent RIRS without access sheath due to ureteral narrowing. An intraoperative JJ stent was indwelled in 33 (94.3%) patients in the mini-PCNL

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group and routinely in all patients of the RIRS group. The mean JJ stent indwelling period was 10.0 ± 6.6 days in the mini-PCNL and 11.4 ± 8.8 days in the RIRS

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group, respectively (P=0.491). Mean operation times were shorter in the miniPCNL group than in the RIRS group, but the differences were not significant (76.1 ± 70.6 versus 99.6 ± 60.8 minutes; P=0.148). Mean estimated blood loss was

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significant higher in the mini-PCNL group than in the RIRS group (70.0 ± 105.2 versus 4.5 ± 26.1; P<0.001). However, there was no significant difference in mean

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hemoglobin drop in the both group (0.69 ± 0.98 versus 0.38 ± 0.97 g/dL for miniPCNL and RIRS groups, respectively; P=0.323). Mean VAS at 1 hour postoperatively in the mini-PCNL group was significantly lower compared with the RIRS group (4.2 ± 2.6 versus 5.7 ± 3.0; P=0.029). However, no significant differences between the both groups were noted in mean pain VAS on the first

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operative day morning (2.7 ± 2.1 versus 3.1 ± 2.0 for mini-PCNL and RIRS groups, respectively; P=0.383). Eleven (31.4%) patients in the mini-PCNL and 19 (57.6%) patients in the RIRS group required and took analgesics (P=0.050). Mean

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postoperative hospital stay was similar in the mini-PCNL (1.6 ± 1.1 days) and RIRS

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groups (1.5 ± 0.9 days) (P = 0.728). SFR in a single session was equivalent at the 3-month follow-up (30/35, 85.7% in the mini-PCNL group and 32/33, 97.0% in the RIRS group; P=0.199). Three patients in the mini-PCNL group and one patient in the RIRS group needed an auxiliary procedure. In the mini-PCNL group, one patient underwent second miniPCNL and two patients RIRS. In the RIRS group, one patient required SWL to remove residual fragments. There were no major complications (Clavien III or

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higher) in both groups. No patient required blood transfusion. Two patients in the mini-PCNL group and one in the RIRS group had a minor pelvic or ureter

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perforation, which was resolved by indwelling of a JJ stent. One patient in each group had hypertension that was controlled by nicardipine. Each group had one

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patient undergoing urinary tract infection that required antimicrobial treatment.

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COMMENT

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PCNL is the first choice for treating large burden (>2 cm) renal stones [2]. Despite high SFR, the limitation of PCNL is associated with significant complications. A prospective global study on PCNL involving 5,803 patients at 96 centers reported

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the 1-month SFR was 75.7% with a 14.5% complication rate. The distribution of scores in modified Clavien grades was I (11.1%), II (5.3%), IIIa (2.3%), IIIb (1.3%),

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IVa (0.3%), IVb (0.2%), and V (0.03%) [11]. Therefore, minimally invasive procedures are recently preferred much by urologists for treating renal stones. The treatment options for small renal stones are SWL, RIRS, and PCNL/miniPCNL. For renal stones <2 cm, European Association of Urology guidelines recommend SWL as the first-line treatment within the renal pelvis and upper or

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middle calices, but PCNL or RIRS for only lower pole because the efficacy of SWL is limited [2]. RIRS is not recommended as the first choice for stones in the renal pelvis and upper or middle calices. In a study that compared SWL, mini-PCNL, and

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RIRS for stones ≥1 cm in diameter, the authors reported mini-PCNL and RIRS had

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significant higher SFR compared to SWL in lower (77.3, 72.7, and 14.8%, respectively, P<0.0001) and non-lower (80.4, 69.2, and 39.3%, respectively, P<0.0001) pole stones [12]. Therefore, mini-PCNL and RIRS have recently been considered as attractive treatment modalities for small to medium-sized renal stones. In this study, we performed a prospective randomized controlled trial to compare mini-PCNL and RIRS for renal stones ≥1 cm in a single session. Mini-PCNL and RIRS have been established as acceptable modalities in the

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treatment of medium-sized (1-2 cm) renal stones. A prospective study reported that mini-PCNL represents a similar efficacy and is superior in terms of safety profile

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compared with standard PCNL [6]. A multicenter study reported SFR (defined by no residual stone on fluoroscopy for mini-PCNL and RIRS and X-ray KUB for SWL) after a single session were 83.6%, 86.1%, and 77.2% in the mini-PCNL, RIRS, and

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SWL groups, respectively [13]. In a prospective comparative study, SFR (defined as no stone visible on X-ray KUB and ultrasonography) was 100% and 96.88% for

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mini-PCNL and RIRS [14]. In a systematic review the literature of RIRS for large (>2.5 cm) renal stones encompassing 441 patients (10 studies) with a mean stone size of 2.9 cm, SFR and major complication rate with an average of 1.6 procedures was 89.9% and 1.9%, respectively [9]. In the present comparative study of the treatment of medium or large renal stones, both mini-PCNL and RIRS were

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feasible and effective modalities, with a single-session SFR of 85.7% and 97.0%, respectively, within 3 months follow-up NECT. Accumulating evidence supports that mini-PCNL requires shorter operation time

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compared with RIRS for 1-2 cm stones [13,14]. In contrast to these results, a

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prospective comparative study noted that mean operation time was longer for miniPCNL than for SWL and RIRS, but the differences were not significant (61.1 versus 43.6 and 47.5 minutes; P=0.23) [15]. In the present study, we observed no significant difference in mean operation time in the both groups (76.1 and 99.6 minutes; P=0.148). Mean stone size and number were greater in the mini-PCNL group, but differences were not significant. In our opinion, stone burden seems to influence operation times.

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Complications in PCNL increase with increasing size of the nephrostomy tract [4,5,7]. Mini-PCNL (categorized by tract size ≤20 Fr) has a similar SFR with lower

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complication rates compared with conventional PCNL (tract size of 30 Fr) [4,6]. The advantages of RIRS include acceptable SFR with lowered risk of complications related to percutaneous approach. In a prospective, randomized study of SWL,

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RIRS, and mini-PCNL for 1-2 cm radiolucent lower calyceal stones [15], Clavien I to II complications were more observed in mini-PCNL than in SWL and RIRS

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(24.3%, 7.1%, and 9.3%, respectively). Blood transfusion (13.3%) occurred in only mini-PCNL group. A higher complication rate for mini-PCNL than for RIRS has been described [13], with a blood transfusion rate of mini-PCNL group of 7.2%. Presently, mini-PCNL and RIRS was safe, as indicated by Clavien II complication rates of 11.4% and 9.1%, respectively. There were no blood transfusion or major

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complications (Clavien ≥III). In a comparative study between mini-PCNL and RIRS [14], there were significantly higher hemoglobin decline (P<0.001) and pain VAS (P<0.001) at 6, 24, and 48 hours, as well as analgesic requirement (P<0.003) in

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the mini-PCNL group compared to the RIRS group. In our prospective randomized

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comparative study, mean hemoglobin decline did not show any differences between the mini-PCNL and RIRS groups (0.69 and 0.38 g/dL, P=0.323). There was significantly lower pain VAS at 1 hour postoperatively in the mini-PCNL group compared to the RIRS group (4.2 and 5.7, respectively; P=0.029). However, mean pain VAS in the RIRS group had lower on the first operative day morning to a VAS similar to that of the mini-PCNL group (2.7 versus 3.1 for mini-PCNL and RIRS groups; P=0.383). The number of patients requiring analgesics was lower in the

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mini-PCNL group (P=0.050). These findings support that the tubeless approach is associated with the least amount of postoperative pain [16]. The irrigation

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pressures seem to be reliable factor on more pain and more analgesic requirement in the RIRS group.

Being a prospective randomized controlled design, there are some limitations in

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the present study. Because of the allocation error, two patients in the RIRS group did not receive the allocated intervention and dropped out of the study. The number

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of participants was relatively small. The maximal limit of stone size was not defined in the inclusion criteria. Stone size and number were higher in the mini-PCNL group than in the RIRS group, but the difference were insignificant. These factors may influence on a large discrepancy of the stone complexity and surgical outcomes between the both modalities. Further studies with a larger sample size and longer

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follow-up are necessary to confirm our findings.

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CONCLUSIONS

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Mini-PCNL and RIRS are safe and feasible surgical options for managing renal stones >10 mm. RIRS had slightly higher SFR, but more immediate postoperative pain and higher analgesic requirement compared with mini-PCNL. Although mini-

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PCNL and RIRS are still limited in use, the use of both is expanding in the management of large renal stone disease. Further prospective randomized

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controlled trials are needed to confirm the feasibility of mini-PCNL and RIRS for

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medium and large-sized renal stones.

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REFERENCES

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1. Preminger GM, Assimos DG, Lingeman JE, Nakada SY, Pearle MS, Wolf JS Jr. Chaper 1: AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173:1991-2000.

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2. Türk C, Knoll T, Petrik A et al. Guidelines on urolithiasis. European Urological Association Web site. http://www.uroweb.org/gls/pdf/22%20Urolithiasis_LR.pdf.

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Updated 2014.

3. Kirac M, Bozkurt ÖF, Tunc L, Guneri C, Unsal A, Biri H. Comparison of retrograde

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management of lower-pole renal stones with a diameter of smaller than 15 mm. Urolithiasis. 2013;41:241-246.

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4. Sabnis RB, Ganesamoni R, Sarpal R. Miniperc: what is its current status?. Curr Opin Urol. 2012;22:129-133.

5. Yamaguchi A, Skolarikos A, Buchholz NP et al. Operating times and bleeding

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complications in percutaneous nephrolithotomy: a comparison of tract dilation

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methods in 5,537 patients in the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study. J Endourol. 2011;25:933-939. 6. Mishra S, Sharma R, Garg C, Kurien A, Sabnis R, Desai M. Prospective comparative study of miniperc and standard PNL for treatment of 1 to 2 cm size renal stone. BJU Int. 2011;108:896-899. 7. Cheng F, Yu W, Zhang X, Yang S, Xia Y, Ruan Y. Minimally invasive tract in percutaneous nephrolithtomy for renal stones. J Endourol. 2010;24:1579-1582.

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8. De Sio M, Autorino R, Quattrone C, Giugliano F, Balsamo R, D’Armiento M. Choosing the nephrostomy size after percutaneous nephrolithotomy. World J Urol.

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2011;29:707-711. 9. Breda A, Angerri O. Retrograde intrarenal surgery for kidney stones larger than 2.5 cm. Curr Opin Urol. 2014;24:179-183.

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10. Dindo D, Demartines N, Clavien P-A. Classification of surgical complications: A new proposal with evaluation in a cohort of 6336 patients and results of a surgery.

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Ann Surg. 2004;240:205-213.

11. de la Rosette J, Assimos D, Desai M et al. The Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study: indications, complications, and outcomes in 5803 patients. J Endourol. 2011;25:11-17. 12. Kruck S, Anastasiadis AG, Herrmann TR et al. Minimally invasive percutaneous

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nephrolithotomy: an alternative to retrograde intrarenal surgery and shockwave lithotripsy. World J Urol. 2013;31:1555-1561. 13. Kiremit MC, Guven S, Sarica K et al. Contemporary management of medium-

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sized (10-20 mm) renal stones: a retrospective multicenter observational study. J

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Endourol. 2015;29:838-843.

14. Sabnis RB, Jagtap J, Mishra S, Desai M. Treating renal calculi 1-2 cm in diameter with minipercutaneous or retrograde intrarenal surgery: a prospective comparative study. BJU Int. 2012;110:E346-349. 15. Kumar A, Kumar N, Vasudeva P, Kumar Jha S, Kumar R, Singh H. A prospective, randomized comparison of shock wave lithotripsy, retrograde intrarenal surgery and miniperc for treatment of 1 to 2 cm radiolucent lower

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calyceal calculi: a single center experience. J Urol. 2015;193:160-164. 16. Desai MR, Kukreja RA, Desai MM et al. A prospective randomized comparison

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of type of nephrostomy drainage following percutaneous nephrostolithotomy: large

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bore versus small bore versus tubeless. J Urol. 2004;172:565-567.

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LEGENDS

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Figure 1. Flow diagram of the study.

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Table 1. Patient and stone characteristics

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P Variable Mini-PCNL (n=35) RIRS (n=33) Patient characteristics Mean age (years) 59.3 ± 13.3 55.8 ± 11.2 0.244 Gender (M:F) 28:7 28:5 0.753 Mean BMI (kg/m2) 26.3 ± 3.9 25.6 ± 5.1 0.707 Comorbidities Diabetes mellitus 14 (40.0) 9 (27.3) 0.312 Hypertension 17 (48.6) 19 (57.6) 0.478 Stone characteristics Laterality (right:left) 14:21 10:23 0.403 Stone size (mm) 39.1 ± 30.7 28.9 ± 17.5 0.102 Stone number 4.71 ± 6.29 2.54 ± 2.56 0.067 Hounsfield units 968.8 ± 383.1 931.3 ± 358.4 0.686 Stone location 0.742 Pelvis 6 (17.1) 9 (27.3) Upper calyx 1 (2.9) 1 (3.0) Lower calyx 14 (40.0) 10 (30.3) Multiple 14 (40.0) 13 (39.4) Staghorn 6 (17.1) 6 (18.2) 0.911 Stone composition 0.205 COM 24 (6.9) 15 (45.5) Uric acid 10 (28.6) 8 (24.2) Carbonate apatite 1 (2.9) 3 (9.1) Mixed 0 (0) 2 (6.1) Unknown 0 (0) 5 (15.1) Hydronephrosis 5 (14.3) 16 (48.5) 0.004 S-ReSC score 3.2 ± 1.9 2.1 ± 1.3 0.015 BMI, body mass index; COM, calcium oxalate monohydrate, S-ReSC, Seoul National University Renal Stone Complexity

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Table 2. Comparison of intra-operative and postoperative outcomes in the miniPCNL and RIRS groups.

Tubeless Access sheath usage Sheath size (12/14Fr:14/16Fr) Intraoperative JJ stenting JJ stent indwelling period (days) Mean operation time (minute) Mean estimated blood loss (mL)

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0.38 ± 0.97

0.493 0.491 0.148 <0.00 1 0.323

4.2 ± 2.6 2.7 ± 2.1 11 (31.4) 1.6 ± 1.1 30 (85.7)

5.7 ± 3.0 3.1 ± 2.0 19 (57.6) 1.5 ± 0.9 32 (97.0)

0.029 0.383 0.050 0.728 0.199

2 0 1 2

0 1 0 0

11 2 2 1 0

19 2 3 0 1

2 1 1 0

1 1 1 0

0.69 ± 0.98

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Mean drop in hemoglobin level (g/dL) Mean pain visual analogue score (range: 1-10) At 1 hour On the 1st operative day morning Analgesic requirement Mean hospital stay (days) Stone free (%) Auxiliary procedures Surveillance SWL Mini-PCNL RIRS Complications Grade I Pain Fever Nausea/Vomiting Transient hyperkalemia Transient tachycardia Grade II Minor pelvic/ureter perforation Hypertension requiring nicardipine Urinary tract infection Grade III - V

RIRS (n=33) 32 (97.0) 4:28 33 (100) 11.4 ± 8.8 99.6 ± 60.8 4.5 ± 26.1

RI PT

Mini-PCNL (n=35) 32 (91.4) 33 (94.3) 10.0 ± 6.6 76.1 ± 70.6 70.0 ± 105.2

SC

Variable

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

1