Impact of Vacuum-Assisted Mini-Endoscopic Combined Intrarenal Surgery for Staghorn Stones: Analysis of Perioperative Factors of Postoperative Fever and Stone-Free Status

Abstract

Background and Objective:

This retrospective cohort study aimed to evaluate the clinical outcomes of vacuum-assisted mini-endoscopic combined intrarenal surgery (vmECIRS) for staghorn stones.

Patients and Methods:

We analyzed a total of 61 cases treated with initial vmECIRS using 14F/16F ClearPetra^® percutaneous sheaths for staghorn stones. We primarily measured complications and stone-free rates (SFRs) to evaluate the safety and efficiency of vmECIRS. In addition, pre- and intraoperative factors in patients who experienced postoperative fever >38°C and achieved an initial stone-free status were evaluated.

Results:

The percentages of staghorn stones were 36.1% and 63.9% for complete and partial stones, respectively. The median stone volume was 8.48 cm³. The median operation time was 117 minutes, and the mean number of procedures was 1.54. Regarding postoperative complications, postoperative fever >38°C was reported in 18 patients (29.5%). The initial and final SFRs were 50.8% and 91.8%, respectively. Among patients with emerging fever >38°C, positive urine culture was the only significant risk factor in the multivariate analysis (odds ratio [OR], 7.500; 95% confidence interval [CI], 1.772–31.751; p = 0.006). Moreover, for achieving initial stone-free status, body mass index and stone volume were significant risk factors in the multivariate analysis (OR, 0.872; 95% CI, 0.776–0.980; p = 0.021; and OR, 0.882; 95% CI, 0.784–0.994; p = 0.039, respectively).

Conclusions:

These findings suggest that vmECIRS is safe and effective for treatment of staghorn stones. Although current guidelines suggest that percutaneous nephrolithotomy is the gold standard surgical technique for staghorn stones, vmECIRS could also be a treatment strategy.

The Clinical Trial Registration number (ID: 2022-05-17-1).

Introduction

Since Fernström and Johansson first reported percutaneous nephrolithotomy (PCNL) in 1976, it has been the standard treatment for kidney stones >2 cm, with a stone-free rate (SFR) ≥85%.¹ However, the SFR of PCNL for staghorn stones remains inferior at 56.9%.² With the recent advent of endoscopic combined intrarenal surgery (ECIRS) using a retrograde approach, along with technological innovations in equipment such as the flexible ureteroscope (fURS) and holmium laser, the SFR is expected to improve.

However, as the demand for minimally invasive PCNL (MIP) continues to drive the trend toward a smaller tract size, increased operative time, difficulty retrieving small fragments, and increased pressure in the renal collection system remain controversial.³ To overcome these limitations, mini-PCNL systems with aspirating sheaths have been developed. Therefore, in this study, we describe vacuum-assisted mini-ECIRS (vmECIRS) and evaluate its clinical results.

Materials and Methods

Study design and study patients

This retrospective cohort study was conducted between July 2019 and December 2021 at our institution after it received approval from our institutional review board (ID: 2022-05-17-1). Among 177 patients who underwent ECIRS, 61 patients treated intraoperatively with initial vmECIRS using a 14F/16F ClearPetra^® percutaneous sheath (Well Lead Medical Co., Ltd., China) for staghorn stones were included in the analysis. Therefore, cases without staghorn stones, in which the 14F/16F ClearPetra sheath was not used, were excluded.

Data collection

Patient data, including age; sex; body mass index (BMI); Eastern Cooperative Oncology Group Physical Status; patient comorbidity; preoperative pyuria; preoperative urine culture; preoperative hydronephrosis; preoperative pyelonephritis; preoperative stent placement; preoperative percutaneous nephrostomy; and stone demographics such as stone location, stone size, stone shape (partial staghorn stone defined as a branched stone that occupied part of the collection system and complete staghorn stone defined as a stone that occupied virtually all of the collection system⁴), and CT values, were collected from each patient's medical record.

In addition, surgical and clinical outcomes, including the number of percutaneous access tracts; SFR, defined as no fragments >4 mm on the kidney, ureter, and bladder radiograph (KUB) and ultrasonography (US) or low-dose CT (LDCT); operation time; postoperative complications classified according to the Clavien–Dindo grade⁵; and hospitalization days, were collected.

Outcome measure

The primary outcome measures were safety and effectiveness of vmECIRS for staghorn stones. Therefore, we evaluated the rates of postoperative complications and SFRs. The main postoperative complications were evaluated with or without fever >38°C and quick sequential organ failure assessment (qSOFA) score ≥2. Moreover, we evaluated the initial and final SFRs on postoperative day 7 and 3 months. While we defined SFR as no fragments >4 mm on KUB and US or LDCT, SFR is commonly evaluated using LDCT.⁶

Therefore, we evaluated the initial and final SFRs on KUB and US or LDCT separately. Moreover, regarding SFR on LDCT, stone-free status data were classified into three grades according to Endourological Society recommendations: Grade A (no stones on CT scan), absolutely stone free; Grade B (≤2-mm fragments), relatively stone free; and Grade C (2.1–4-mm fragments), relatively stone free.

Surgical steps

All surgeries for staghorn stones were performed under general anesthesia at our institution. Most patients were oriented in the modified Valdivia flank-free position, while some were oriented in the prone position. Two expert surgeons in endourological stone management performed all surgeries. All cases were administered antibiotics (cefotiam hydrochloride, 1 g) intravenously 30 minutes before the start of the surgery. If a prior urine culture was positive, efficient antibiotics were administered orally for 3 days preoperatively. The actual surgical steps of vmECIRS are described below.

Two surgeons worked together in concert during ECIRS; one surgeon manipulated the retrograde fURS, while the other performed the antegrade mini-PCNL using a ClearPetra percutaneous sheath with a vacuum system. First, to perform flexible ureteroscopy, a 6F semirigid ureteroscope (KARL STORZ, Tuttlingen, Germany) or a 4.5F semirigid ureteroscope (Richard Wolf, Knittlingen, Germany) was inserted into the bladder through the urethra. We then examined the bladder and confirmed the ureteral orifice.

Subsequently, a semirigid ureteroscope with a guidewire (Sensor™; Boston Scientific, Marlborough, MA) was routinely inserted into the ureter to observe the ureteral lumen size and the presence of ureteral stones before insertion of a urinary access sheath (UAS). After routine ureteral observation using a semirigid ureteroscope, the surgeon chose a suitable UAS size and length.

We preferred to use the 10F to 12F sheath (Proxis^®; BD Ltd., Franklin Lakes, NJ) or 9.5F to 11.5F sheath (Flexor^®; Cook Medical, Bloomington, IN) in our institution to prevent ureteral injury due to UASs whenever possible. The selected length of UAS was 45 to 46 cm in male patients and 35 to 36 cm in female patients. The UAS was placed around the ureteropelvic junction (UPJ).

Subsequently, the fURS (URF-P7; Olympus, Tokyo, Japan) was inserted through the UAS. Whenever possible, the fURS should be inserted into the renal pelvis to observe the puncture site during hydronephrosis. However, if observation of the puncture site is impossible owing to the effect of stones, only hydronephrosis should be performed from the UPJ.

Second, during PCNL, a 21-gauge needle was inserted under ultrasound and fluoroscopic guidance. Thereafter, the outflow of urine was checked, and a 0.018-inch lead wire was inserted. The 0.018-inch lead wire was guided as closely as possible to the ureter. For dilating the skin and subcutis bluntly and acutely, a 19-gauge metal dilater and a 5F dilater were inserted. After it was dilated from 6F to 12F, a dual-lumen ureteral access catheter was inserted and the safety guidewire was placed. The 15F/16F metal dilator was inserted to check for stones and bleeding from the puncture site using a miniature nephroscope (12F; KARL STORZ).

Finally, a 14F/16F vacuum-assisted ClearPetra access sheath was inserted. A continuous irrigation system (UROMAT^®; KARL STORZ) was used to maintain a clear surgical field in all cases. A 120-W holmium: YAG laser (VersaPulse PowerSuite; Lumenis, Yokneam, Israel) with a 550-μm end-firing laser fiber (Slim Line; Lumenis) was used to disintegrate the stone. A laser setting of 15 to 20 Hz and 1.5 to 2.2 J or 70 to 80 Hz and 0.3 to 0.5 J using MOSES™ technology (Lumenis) was used during lithotripsy depending on stone hardness and size.

Quarried fragments were removed using a ClearPetra system with continuous high-flow irrigation and vacuum fluid dynamics to attract and capture as many fragments as possible. In the PCNL procedure, the other surgeon performing flexible ureteroscopy was essentially helping to move the stones to a position where they can be approached using the ClearPetra sheath and occasionally break stones that cannot be reached from the PCNL side.

After all stone fragments were removed, a 6F ureteral stent and 14F nephrostomy catheter were placed in most cases.

Statistical analysis

Data were analyzed using StatView, version 5.0 (Abacus Concepts, Berkeley, CA). Continuous and nominal variables of the retrospectively collected data are described as median (interquartile range) and number and percentage (%), respectively. Additionally, the Mann–Whitney U test and Pearson's χ ² test for univariate analysis and logistic regression analysis for multivariate analysis were used to evaluate the factors related to fever >38°C and the SFR.

Two-sided values of p < 0.05 were considered statistically significant.

Results

Regarding patient demographics, the median BMI was 24.0 kg/m², while the rate of diabetes was 18.0%. The rates of preoperative pyuria, positive urine cultures, and pyelonephritis were 86.8%, 50.8%, and 18.0%, respectively. Regarding stone demographics, the percentages of staghorn stones were 36.1% and 63.9% for complete and partial stones, respectively. The median stone volume was 8.48 cm³ (Table 1).

Table 1.

Patient and Stone Demographics

<Patients, N = 61>
Age, years, median (IQR)	58.1 (50.0–67.1)
Sex, n (%)	M; 44 (72.1)
BMI, kg/m², median (IQR)	24.0 (21.3–24.0)
ECOG-PS, n (%)
0	49 (80.3)
1	7 (11.5)
2	2 (3.3)
3	3 (4.9)
4	0 (0)
5	0 (0)
6	0 (0)
Diabetes, n (%)	11 (18.0)
Preoperative pyuria, n (%)	53 (86.8)
Preoperative positive urine culture, n (%)	31 (50.8)
Preoperative hydronephrosis, n (%)	32 (52.4)
Grade 1	19 (31.1)
Grade 2	13 (21.3)
Grade 3	0 (0)
Preoperative pyelonephritis, n (%)	11 (18.0)
Preoperative stent placement, n (%)	47 (77.0)
Preoperative PNS	11 (18.0)
Stones
Staghorn stone, n (%)
Partial staghorn stone	39 (63.9)
Complete staghorn stone	22 (36.1)
No. of occupied calices with stones, n (%)
1	6 (9.8)
2	14 (23.0)
3	17 (27.9)
4	10 (16.4)
5	10 (16.4)
6	4 (6.6)
Stone volume, cm³, median (IQR)	8.48 (5.54–14.57)
CT value, HU, median (IQR)	1450 (1211–1614)

BMI = body mass index; ECOG-PS = Eastern Cooperative Oncology Group Physical Status; IQR = interquartile range; PNS = percutaneous nephrostomy.

The initial SFR was 50.8% within postoperative day 7, and the final SFR was 91.8% at 3 months postoperatively. Regarding the initial SFR, nine patients (14.8%) were evaluated using KUB and US, with stone-free status achieved in six patients (66.7%). On the other hand, 52 patients (85.2%) were evaluated using LDCT, with stone-free status achieved in 25 patients (48.1%): Grade A in 15 (28.8%), Grade B in 2 (3.8%), and Grade C in 8 (15.4%) patients.

Regarding the final SFR, 12 patients (19.7%) were evaluated using KUB and US, with stone-free status achieved in 11 patients (91.7%). On the other hand, 49 patients (80.3%) were evaluated using LDCT, with stone-free status achieved in 45 patients (91.8%): Grade A in 27 (55.1%), Grade B in 6 (12.2%), and Grade C in 12 (24.5%) patients.

The median operation time was 117 minutes, while a mean 1.54 procedures were performed before the final SFR was evaluated. Auxiliary procedures were used: extracorporeal shockwave lithotripsy in 0 cases, retrograde intrarenal surgery (RIRS) in 7 cases, and ECIRS in 26 cases.

Regarding postoperative complications, postoperative fever >38°C was reported in 18 cases (29.5%), of whom 6 (9.8%) experienced postoperative fever for only 1 day and 12 (19.7%) for >2 days. Only 1 patient developed urosepsis (1.6%), for which intensive care unit (ICU) management was required for 3 days. In Clavien-Dindo classification, the rates of Grade I, Grade II, and Grade IVa complications were 49.18%, 14.8%, and 1.6%, respectively (Table 2).

Table 2.

Surgical Outcome and Postoperative Complications

Operation time, minutes, median (IQR)	117 (92–138)
No. of percutaneous access tracts, n (%)
Single	56 (91.8)
Upper	4 (6.6)
Middle	19 (31.1)
Lower	33 (54.1)
Multiple	5 (8.2)
Upper+middle	2 (3.3)
Upper+lower	2 (3.3)
Middle+lower	1 (1.6)
Position, n (%)
Valdivia flank-free modified	59 (96.7)
Prone	2 (3.3)
Stone analysis, n (%)
CaOx	15 (24.6)
CaOx+CaP	24 (39.3)
CaOx+UA	4 (6.6)
CaOx+protein	1 (1.6)
CaOx+CaP+MAP	1 (1.6)
CaP	6 (9.8)
CaP+MAP	5 (8.2)
CaP+CaHPO4	1 (1.6)
UA	3 (4.9)
Cysteine	1 (1.6)
SFR, n (%)
Initial SFR	31 (50.8)
KUB and US: 9 (14.8)	6 (66.7)
LDCT: 52 (85.2)	25 (48.1)
Grade A	15 (28.8)
Grade B	2 (3.8)
Grade C	8 (15.4)
Final SFR	56 (91.8)
KUB and US: 12 (19.7)	11 (91.7)
LDCT: 49 (80.3)	45 (91.8)
Grade A	27 (55.1)
Grade B	6 (12.2)
Grade C	12 (24.5)
Mean No. of procedures	1.54
Auxiliary procedures, n
SWL	0
RIRS	7
Second-look ECIRS	26
Postoperative placement of nephrostomy, days, median (IQR)	10 (5–10)
Postoperative stent placement, days, median (IQR)	15 (11–21)
Hospitalization, days, median (IQR)	11.0 (7.0–12.0)
Clavien-Dindo grade, n (%)
Grade I	30 (49.18)
Grade II	9 (14.8)
Grade IIIa	0 (0)
Grade IIIb	0 (0)
Grade IVa	1 (1.6)
Grade IVb	0 (0)
Grade V	0 (0)
Postoperative complications, n (%)
qSOFA≧2	1 (1.6)
Fever (>38°C)
1 day	6 (9.8)
2+ days	12 (19.7)
Phone call	0 (0)
Emergency visit	0 (0)
Readmission	1 (1.6)

CaHPO₄ = calcium hydrogen phosphate dihydrate; CaOx = calcium oxalate, CaP = calcium phosphate; ECIRS = endoscopic combined intrarenal surgery; IQR = interquartile range; KUB = kidney, ureter, and bladder radiograph; LDCT = low-dose CT; MAP = magnesium ammonium phosphate hexahydrate; qSOFA = quick sequential organ failure assessment; RIRS = retrograde intrarenal surgery; SFR = stone-free rate; SWL = extracorporeal shockwave lithotripsy; UA = uric acid; US = ultrasonography.

We analyzed the pre- and intraoperative factors for patients who experienced postoperative fever >38°C and achieved an initial stone-free status. Emerging fever >38°C, diabetes, preoperative pyuria, and a positive urine culture were significant risk factors in the univariate analysis; of them, only positive urine culture was a significant risk factor in the multivariate analysis (odds ratio [OR], 7.500; 95% confidence interval [CI], 1.772–31.751; p = 0.006) (Table 3).

Table 3.

Pre- and Intraoperative Risk Factors for Patients with Postoperative Fever (>38℃)

			Univariate analysis^*	Multivariate analysis (odds ratio, 95% CI, p-value)^**
Variables related to fever	Fever (+), n = 18	Fever (−), n = 43	p-value
Age, years, median (IQR)	54.1 (50.0–71.9)	50.1 (50.1–66.2)	0.91
Sex, n (%)
Male	13 (72.2)	31 (72.1)	0.1
Female	5 (27.8)	12 (27.9)
Diabetes, n (%)
Present	6 (33.3)	4 (9.3)	0.04
Absent	12 (66.7)	39 (90.7)
Preoperative pyuria, n (%)
Positive	18 (100)	35 (81.4)	0.05
Negative	0 (0)	8 (18.6)
Preoperative positive urine culture, n (%)				7.500, 1.772–31.751, p = 0.006
Positive	15 (83.3)	16 (37.2)	<0.001
Negative	3 (16.7)	27 (62.8)
Preoperative pyelonephritis, n (%)
Present	5 (27.8)	6 (14.0)	0.2
Absent	13 (72.2)	37 (86.0)
Preoperative stent placement, n (%)
Present	16 (88.9)	31 (72.1)	0.15
Absent	2 (11.1)	12 (27.9)
Operation time, minutes, median (IQR)	116 (95.5–131.75)	117(92–138)	0.96

Pearson's chi-squared test, Mann–Whitney U test; ^**logistic regression analysis.

CI = confidence interval; IQR = interquartile range.

Moreover, in terms of achieving an initial stone-free status, BMI, number of occupied calices, and stone volume were significant risk factors in the univariate analysis; among them, only BMI and stone volume were significant risk factors in the multivariate analysis (OR, 0.872; 95% CI, 0.776–0.980; p = 0.021; and OR, 0.882; 95% CI, 0.784–0.994; p = 0.039, respectively) (Table 4).

Table 4.

Pre- and Intraoperative Factors for Patients Who Achieved Initial Stone-Free Status

			Univariate analysis^*	Multivariate analysis (odds ratio, 95% CI, p-value)^**
Variables related to initial SF status	Initial SF (+) n = 31	Initial SF (−) n = 30	p-value
Age, years, median (IQR)	54.1 (47.0–63.1)	60.1 (52.0–69.1)	0.1
BMI, kg/m², median (IQR)	22.8 (20.3–25.1)	26.1 (22.8–29.1)	0.02	0.872, 0.776–0.980, p = 0.021
Sex, n (%)			0.44
Male	21 (62.8)	23 (76.7)
Female	10 (37.1)	7 (23.3)
Preoperative PNS, n (%)			0.1
Present	8 (25.8)	3 (10.0)
Absent	23 (74.2)	27 (90.0)
Preoperative hydronephrosis, n (%)			0.71
Present	17 (54.8)	15 (50.0)
Absent	14 (45.2)	15 (50.0)
Preoperative ureteral stenting, n (%)			0.94
Present	24 (77.4)	23 (76.7)
Absent	7 (22.6)	7 (23.3)
No. of occupied calices with stone, n (%)
≤2	10 (32.3）	10 (33.3）	0.93
≥3	21 (67.7)	20 (66.7)
No. of occupied calices with stone, n (%)			0.03
≤3	23 (74.2)	14 (46.7)
≥4	8 (25.8）	16 (53.3)
Stone volume, cm³, median (IQR)	6.4 (4.1–10.3)	12.5 (8.1–15.7)	<0.001	0.882, 0.784–0.994, p = 0.039
CT value, HU, median (IQR)	1426 (1044–1549)	1519 (1291–1682.8)	0.14

Pearson's chi-squared test, Mann–Whitney U test.

Logistic regression analysis.

SF = stone-free.

Discussion

In this study, we evaluated the vmECIRS technique using a 14F/16F ClearPetra sheath. We focused on pre- and intraoperative factors for patients who experienced postoperative fever >38°C and achieved an initial stone-free status, respectively.

First, regarding postoperative fever >38°C, 18 patients (29.5%) developed postoperative fever (>38.0°C), 1 patient (1.6%) had a qSOFA score of ≥2, and 1 patient (1.6%) had severe sepsis. A preoperative positive urine culture was a significant risk factor in this study. The concept of sepsis has changed in recent years, and qSOFA is often used for early detection of fatal sepsis outside the ICU; thus, it was used in this study.

Chen et al retrospectively analyzed the medical records of 209 patients who underwent PCNL, of whom, 49 (23.4%) developed postoperative systemic inflammatory response syndrome (SIRS).⁷

In our study, we treated only staghorn stones, which are relatively large, with a median stone volume of 8.48 cm³. However, this can result in a low rate of infection. The ClearPetra system, which can maintain lower intrarenal pressure (IRP), may play a significant role during surgery. Zanetti and colleagues analyzed intraoperative IRP variations using a 16F ClearPetra sheath. They reported that the mean IRP during surgery was frequently lower than 40.78 cmH₂O (pyelovenous backflow threshold), while the cumulative time with IRP over this limit was short in most procedures.⁸

In addition, Lievore et al reported that mini-PCNL performed with continuous active suction is associated with lower rates of infectious complications, shorter operative time, and a lower patient effective dose than MIP.⁹ In our study, a preoperative positive urine culture was a significant predictive factor for postoperative fever (>38.0°C). Lai and Assimos reported that a preoperative urine culture, intraoperative stones, and collection system urine culture were predictive factors for postoperative infectious complications in PCNL.¹⁰

Second, the initial and final SFRs for staghorn stones were 50.8% (31 cases) and 91.8% (56 cases), respectively, while the mean number of procedures was 1.54. In this study, the risk factors for the initial SFR were significantly different in terms of stone volume and BMI. Currently, the definition of SFR remains controversial.^6,11,12 Therefore, we defined residual stones as those >4 mm in the present study.

Chen and colleagues reported a systematic review and meta-analysis of open vs PCNL for staghorn stone treatment. With PCNL, a meta-analysis of 4 studies evaluating 310 patients reported an initial SFR of 49%. Nine studies evaluating 804 patients reported that the final SFR was 82.7%.¹³ In the American Urological Association Guidelines, the final SFR for staghorn stones was the highest for PCNL (78%), while the average number of procedures was 1.9.⁴

The vmECIRS data at our hospital showed that the final SFR was 91.8% and initial SFR was 50.8% and the average number of procedures was 1.54, comparable with or better than that of other reports. One of the factors contributing to this result may be ECIRS itself. Keller and colleagues described the important role of ureteroscopy in the treatment of staghorn stones and reported the superiority of ECIRS over PCNL.¹⁴ Therefore, PCNL with simultaneous retrograde access can overcome the limitations of percutaneous management alone. The other factor may be the use of a ClearPetra sheath.

Zanetti and colleagues reported that by keeping the suction sheath in close contact with the stone, the vacuum held the stone in place during lithotripsy and directly suctioned the debris, thereby preventing fragment scattering.⁸ Furthermore, Chen et al reported comparing the effectiveness of a novel, flexible, vacuum-assisted ureteral access sheath (FV-UAS) with the traditional ureteral access sheath in simulating RIRS. Ultimately, FV-UAS could achieve a complete stone-free status after RIRS.¹⁵

In this study, we also found significant differences in stone volume and BMI as preoperative risk factors for an initial stone-free status. Regarding stone volume, Smith and colleagues studied data collected by the Clinical Research Office of the Endourological Society from November 2007 to December 2009 from 96 centers worldwide and developed a nomogram for effective PCNL. They concluded that stone burden was the best predictor of SFR.¹⁶

Regarding BMI, no studies to date have analyzed factors for stone-free status and BMI for staghorn stone treatment. However, Mithani et al noted that intraoperative blood loss was higher in patients with a higher BMI during PCNL,¹⁷ suggesting that a poor visual field due to intraoperative bleeding may be a factor preventing an initial stone-free status.

Our study had some limitations. First, this was a noncomparative retrospective cohort study. Therefore, future comparative studies such as randomized trials or matched retrospective trials between ECIRS and vmECIRS are needed.

Second, in our study, all patients were administered antibiotics (cefotiam hydrochloride, 1 g) intravenously 30 minutes before the start of the surgery. If a prior urine culture was positive, efficient antibiotics were administered orally for 3 days preoperatively. However, Sur and colleagues reported that administering prophylactic antibiotics for 7 days preoperatively decreased the risk of sepsis in moderate- to high-risk PCNL patients who had a positive preoperative urine culture or an existing indwelling urinary drainage tube. They also claimed that future guidelines should consider infection risk stratification for PCNL antibiotic recommendations.¹⁸

Third, we used qSOFA to diagnose sepsis in this study. However, the Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021 do not recommend using qSOFA vs SIRS as a single screening tool for sepsis or septic shock because the former is more specific, but less sensitive, than two of the four SIRS criteria for early identification of infection-induced organ dysfunction.¹⁹

Although a number of reports have evaluated the safety and efficiency of PCNL performed with continuous active suction,^20,21 to the best of our knowledge, no previous studies have examined the efficacy of vmECIRS on staghorn stones; thus, this study is expected to provide a novel perspective for endourologists.

Conclusions

The current study's findings suggest that vmECIRS is a safe and effective procedure for treatment of staghorn stones. Although current guidelines suggest that PCNL is the gold standard surgical technique for staghorn stones, vmECIRS could also be a treatment strategy.

Footnotes

Authors' Contributions

K.T. made a substantial contribution to conception and design of the work and data analysis or interpretation. T.I. performed supervision and critical revision of the manuscript. F.Y., M.F., and M. Fujita performed a critical revision of the manuscript.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Abbreviations Used

References

Ganpule

, Vijayakumar

, Malpani

, et al. Percutaneous nephrolithotomy (PCNL): A critical review. Int J Surg, 2016; 36(Pt D):660–664; doi: 10.1016/j.ijsu.2016.11.028

Desai

, De Lisa

, Turna

, et al. The clinical research office of the endourological society percutaneous nephrolithotomy global study: Staghorn versus nonstaghorn stones. J Endourol, 2011; 25(8):1263–1268; doi: 10.1089/end.2011.0055

, Hua

L-X

, Zhang

J-Z

, et al. Comparison of renal pelvic pressure and postoperative fever incidence between standard- and mini-tract percutaneous nephrolithotomy. Kaohsiung J Med Sci, 2017; 33(1):36–43; doi: 10.1016/j.kjms.2016.10.012

Preminger

, Assimos

, Lingeman

, et al. Chapter 1: AUA guideline on management of staghorn calculi: Diagnosis and treatment recommendations. J Urol, 2005; 173(6):1991–2000; doi: 10.1097/01.ju.0000161171.67806.2a

Dindo

, Demartines

, Clavien

P-A

. Classification of surgical complications: A new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg, 2004; 240(2):205–213; doi: 10.1097/01.sla.0000133083.54934.ae

Ulvik Ø, Harneshaug

J-R

, Gjengstø

. What do we mean by «stone free», and how accurate are urologists in predicting stone free status following ureteroscopy?. J Endourol, 2021; 35(7):961–966. doi: 10.1089/end.2020.0933

Chen

, Xu

Q-Q

, Li

J-X

, et al. Systemic inflammatory response syndrome after percutaneous nephrolithotomy: An assessment of risk factors. Int J Urol, 2008; 15(12):1025–1028; doi: 10.1111/j.1442-2042.2008.02170.x

Zanetti

, Lievore

, Fontana

, et al. Vacuum-assisted mini-percutaneous nephrolithotomy: A new perspective in fragments clearance and intrarenal pressure control. World J Urol, 2021; 39(6):1717–1723; doi: 10.1007/s00345-020-03318-5

Lievore

, Boeri

, Zanetti

, et al. Clinical comparison of mini-percutaneous nephrolithotomy with vacuum cleaner effect or with a vacuum-assisted access sheath: A single-center experience. J Endourol, 2021; 35(5):601–608; doi: 10.1089/end.2020.0555

10.

Lai

, Assimos

. Factors associated with postoperative infection after percutaneous nephrolithotomy. Rev Urol, 2018; 20(1):7–11; doi: 10.3909/riu0778

11.

Ermis

, Somani

, Reeves

, et al. Definition, treatment and outcome of residual fragments in staghorn stones. Asian J Urol, 2020; 7(2):116–121; doi: 10.1016/j.ajur.2019.12.013

12.

Opondo

, Gravas

, Joyce

, et al. Standardization of patient outcomes reporting in percutaneous nephrolithotomy. J Endourol, 2014; 28(7):767–774; doi: 10.1089/end.2014.0057

13.

Chen

, Feng

, Duan

, et al. Percutaneous nephrolithotomy versus open surgery for surgical treatment of patients with staghorn stones: A systematic review and meta-analysis. PLoS One, 2019; 14(1):e0206810. doi: 10.1371/journal.pone.0206810

14.

Keller

, De Coninck

, Doizi

, Traxer

. The role of ureteroscopy for treatment of staghorn calculi: A systematic review. Asian J Urol, 2020; 7(2):110–115. doi: 10.1016/j.ajur.2019.10.012

15.

Chen

, Li

, Gao

, et al. Novel flexible vacuum-assisted ureteral access sheath can actively control intrarenal pressure and obtain a complete stone-free status. J Endourol, 2022; 36(9):1143–1148. doi: 10.1089/end.2022.0004

16.

Smith

, Averch

, Shahrour

, et al. A nephrolithometric nomogram to predict treatment success of percutaneous nephrolithotomy. J Urol, 2013; 190(1):149–156. doi: 10.1016/j.juro.2013.01.047

17.

Mithani

, Khan

, El Khalid

, et al. Predictive factors for intraoperative blood loss during percutaneous nephrolithotomy. J Coll Physicians Surg Pak, 2018; 28(8):623–627. doi: 10.29271/jcpsp.2018.08.623

18.

Sur

, Krambeck

, Large

, et al. A randomized controlled trial of preoperative prophylactic antibiotics for percutaneous nephrolithotomy in moderate to high infectious risk population: A report from the EDGE consortium. J Urol, 2021; 205(5):1379–1386. doi: 10.1097/JU.0000000000001582

19.

Evans

, Rhodes

, Alhazzani

, et al. Surviving sepsis campaign: International guidelines for management of sepsis and septic shock 2021. Intensive Care Med, 2021; 47(11):1181–1247; doi: 10.1007/s00134-021-06506-y

20.

Zhu

, Wang

, Zhou

, et al. Comparison of vacuum-assisted sheaths and normal sheaths in minimally invasive percutaneous nephrolithotomy: A systematic review and meta-analysis. BMC Urol, 2021; 21(1):158; doi: 10.1186/s12894-021-00925-1

21.

Lai

, Chen

, Sheng, et al. Use of a novel vacuum-assisted access sheath in minimally invasive percutaneous nephrolithotomy: A feasibility study. J Endourol, 2020; 34(3):339–344; doi: 10.1089/end.2019.0652