Effects of vacuum-assisted access sheath in mini-percutaneous nephrolithotomy on early postoperative pain and analgesic requirement: a retrospective analysis

Abstract

Background/Objectives

This study aimed to evaluate the effect of vacuum-assisted access sheath use during mini-percutaneous nephrolithotomy (mini-PCNL) on early postoperative pain intensity and analgesic requirements in the treatment of renal pelvic stones.

Methods

A total of 150 patients who underwent mini-PCNL for a single renal pelvic stone ≥ 20 mm were retrospectively included. Patients who underwent standard mini-PCNL were classified as Group 1, while those treated with a vacuum-assisted access sheath were assigned to Group 2. Demographic characteristics, perioperative parameters, pain assessed by visual analog scale (VAS), and analgesic requirements were compared between the groups.

Results

The two groups were comparable in terms of mean age, body mass index, comorbidity status, ASA scores, degree of hydronephrosis, distance between skin puncture, fluoroscopy time, stone size, and stone density (p > 0.05). Operative time and length of hospital stay were significantly longer in Group 1 (77.97 ± 15.72 min and 3.28 ± 1.56 days, respectively) compared with Group 2 (p < 0.001). The incidence of high-grade fever and urinary tract infections requiring additional antibiotic therapy was significantly higher in Group 1 (p = 0.044 and p = 0.032, respectively). Hemoglobin decrease was also more pronounced in Group 1 (p < 0.001). Postoperative VAS scores were significantly lower in Group 2 than in Group 1 (p < 0.001). The absolute between-group differences in VAS at rest were 1.37 points at 1 h, 1.68 points at 6 h, and 1.81 points at 24 h. For dynamic VAS, the corresponding absolute differences were 2.38, 2.09, and 2.05 points, respectively. Furthermore, the number of patients requiring rescue analgesia was markedly higher in Group 1 (p < 0.001). In addition, Group 1 demonstrated a shorter mean time to rescue analgesia and higher analgesic dosage compared with Group 2 (p = 0.002 and p = 0.019, respectively). In multivariate analysis, vacuum-assisted access sheath use remained an independent predictor of both lower postoperative pain scores and reduced analgesic requirement, with an approximately 90% reduction in the odds of rescue analgesia use after adjustment for operative time and intraoperative remifentanil consumption.

Conclusion

Vacuum-assisted access sheath use was associated with lower early postoperative pain scores and reduced analgesic requirements; however, prospective controlled studies are needed to confirm these findings.

Introduction

Urolithiasis is one of the most prevalent urological pathology worldwide and is characterized by the formation of calculi within the urinary tract, including the kidneys, renal pelvis, ureters and bladder. A wide range of therapeutic approaches are currently available for the management of urolithiasis, encompassing pharmacological therapy, percutaneous nephrolithotomy (PCNL), ureteroscopy, extracorporeal shock wave lithotripsy and, in selected cases, open surgical interventions [1]. Over the past decades, technological advancements in endourology have substantially shifted clinical practice toward minimally invasive treatment modalities. Epidemiological data from the United States indicate an approximately 50% increase in the utilization of PCNL procedures, reflecting this global trend [2]. Although renal pelvic stones can be managed using various techniques, PCNL remains a cornerstone treatment, particularly for stones with a large burden or complex anatomy [3]. In line with this evidence, the guidelines of the American Urological Association recommend PCNL as the first-line therapeutic option for renal stones measuring greater than 20 mm in diameter [4].

Mini-PCNL was first introduced in 1998 by Jackman et al. as a less invasive alternative to standard PCNL [5]. Since its introduction, mini-PCNL has been associated with shorter hospital stays, reduced blood loss, and lower postoperative pain levels compared with conventional approaches [6, 7]. Mini-PCNL is generally defined as percutaneous nephrolithotomy performed using tract sizes ranging between 14 and 20 Fr, although variations exist across the literature [8]. Despite these advantages, this minimally invasive technique is not without limitations. Intrapelvic pressure is the fluid pressure inside the renal pelvis and calyces, typically measured during endourological procedures and it plays a critical role in postoperative outcomes. Increased intrapelvic pressure during the procedure may predispose patients to infectious complications, impaired endoscopic visibility, increased postoperative pain level and prolonged operative times, presenting notable challenges for surgeons [6, 7]. This situation may be related to increased intrapelvic pressure triggering pyelovenous and pyelolymphatic backflow and activating renal mechanoreceptors [7, 9]. As mini-PCNL has become increasingly integrated into routine urological practice, these drawbacks have prompted the development of innovative access sheath technologies aimed at minimizing procedure-related complications. In this context, vacuum-assisted access sheaths have emerged as a significant technological advancement by effectively reducing intrapelvic pressure, enhancing endoscopic visualization, and facilitating shorter operative durations, thereby offering important procedural advantages during mini-PCNL [9]. However, despite these potential benefits, the impact of vacuum-assisted access sheath use on postoperative pain outcomes in urolithiasis treatment has been investigated in only a limited number of studies. We hypothesized that the use of a vacuum-assisted access sheath during mini-PCNL, compared to the conventional sheath, would be associated with lower intrapelvic pressure, resulting in reduced postoperative pain and decreased analgesic requirement.

In this clinical study, we aimed to analyze the effectiveness of vacuum-assisted access sheath use on early postoperative pain intensity and analgesic requirements in patients undergoing mini-PCNL for renal pelvic stones. To the best of our knowledge, this study represents one of the few reports in the literature specifically focusing on postoperative pain outcomes in relation to vacuum-assisted sheath technology.

Materials and methods

Study design

A retrospective analysis was performed on 150 patients who underwent mini-PCNL at Kayseri City Hospital between January 2023 and June 2025. Patients aged between 18 and 70 years who underwent mini-PCNL under general anesthesia for a single renal pelvic stone measuring ≥ 20 mm were included in the study. Eligible patients had an American Society of Anesthesiologists (ASA) physical status classification of I–III and a body mass index (BMI) ranging from 18 to 35 kg/m².

Patients who underwent standard mini-PCNL were classified as Group 1, while those treated with a vacuum-assisted access sheath were assigned to Group 2. The choice of access sheath (conventional vs. vacuum-assisted) was based on surgeon preference and device availability during the study period. As this was a retrospective study, no randomization was performed, and potential selection bias cannot be excluded.

The following parameters were retrospectively documented and analyzed: patient age and sex, Charlson Comorbidity Index (CCI) scores, stone size and laterality, BMI, degree of hydronephrosis, distance between skin puncture, stone density, operative duration, stone-free rate, hemoglobin decrease, fluoroscopy time, visual analog scale (VAS) scores, rescue analgesia requirements, ASA scores, complications, intraoperative remifentanil consumption, and length of hospital stay.

Compliance with ethical standards

The study was approved by the Local Ethics Committee of Kayseri City Hospital (Approval No: 684, Date: December 2025). Due to the retrospective design of the study and the use of anonymized data, the requirement for informed consent was waived by the ethics committee. The study was conducted in accordance with the principles of the Declaration of Helsinki.

Surgical procedures

All patients underwent general anesthesia using the same type of medication. Preoperatively, sterile urine cultures were confirmed in all patients, and perioperative antibiotic prophylaxis was administered using a third-generation cephalosporin. All mini-PCNL procedures were performed by an experienced urology and anesthesia team. Following ureteral catheterization for retrograde pyelography in the supine position, patients were repositioned to the prone position. Percutaneous renal access was achieved under fluoroscopic guidance using an 18-gauge, 20-cm Chiba needle (Geotek, Turkey). The access tract was dilated using Amplatz renal dilator with a single-shot technique (Cook Medical). In Group 1, a conventional 18 F access sheath (Plastimed, Turkey) was placed, whereas patients in Group 2 received a 18 F ClearPetra^® vacuum-assisted access sheath (Well Lead Medical™, China). A 12 F mini-nephroscope (Karl Storz, Germany) was used to visualize the pelvicalyceal system. Stone fragmentation was performed using a holmium: YAG laser lithotripter (35 W; Quanta System™, 550-µm fiber) with energy settings of 0.6–1 J and a frequency of 12–18 Hz in long-pulse pulverization mode. In the conventional group, stone fragments were removed using graspers and baskets, whereas in the vacuum-assisted group, continuous active suction enabled simultaneous fragmentation and evacuation of stone fragments. Continuous saline irrigation was applied throughout the procedure, and a single percutaneous access tract was used in all patients. Irrigation was maintained using saline bags positioned approximately 1.5 m above the patient. In the vacuum-assisted system, suction was initiated at 200 mmHg and adjusted between 150 and 250 mmHg according to intraoperative visualization quality and efficiency of stone fragment clearance [10]. At the end of the procedure, a 4.7 Fr double-J ureteral stent was placed in all patients according to institutional routine, and no nephrostomy tube was used.

Anesthetic technique

All the patients who participated in the study were monitored with electrocardiogram, arterial blood pressure, arterial oxygen saturation and end-tidal carbon dioxide monitoring. After preoxygenation for 3–4 min general anesthesia was induced with intraveneous propofol 2 mg/kg and fentanyl 1.5 µg/kg and rocuronium 0.6 mg/kg according to standardized general anesthesia guidelines set by the institute. General anesthesia was maintained using 2% sevoflurane. Remifentanil infusions (0.2–1 Mcg/kg per minute) were used for analgesia.

Pain assessment

Postoperative pain was assessed using the VAS a standardized and validated 10-point self-reporting tool for pain intensity evaluation [11]. VAS assessment is routinely performed in our institutions as part of standard postoperative pain management protocols to guide analgesic treatment. On this scale, a score of 0 indicates the absence of pain, whereas a score of 10 represents the maximum imaginable pain. VAS scores were evaluated by a well-trained physician at postoperative 1, 6, and 24 h, both at rest and during coughing. However, the VAS is subjective and can be affected by anesthesia and analgesia protocols.

Patients with a VAS score of ≥ 4 were classified as experiencing moderate to severe pain. As part of the standard postoperative analgesia protocol, intravenous paracetamol was administered at a dose of 1 g. Patients whose VAS scores remained ≥ 4 despite paracetamol administration received rescue analgesia. Tramadol was used as the rescue analgesic agent at intravenous doses of 50, 100, or 200 mg, depending on clinical requirements. Patients with VAS scores of 4–5 received 50 mg of intravenous tramadol, those with scores of 6–7 received 100 mg, and those with scores ≥ 8 received 200 mg. This stepwise approach ensured consistency in analgesia delivery and minimized variability in postoperative pain management.

Exclusion criteria

Patients were excluded from the study if they had impaired renal function, structural urinary tract abnormalities, a history of previous stone surgery, stone localization outside the renal pelvis, a history of substance abuse, or the presence of endocrine or neurological disorders.

Statistical method

Descriptive statistics were presented as mean ± standard deviation for continuous variables and as number (n) and percentage (%) for categorical variables. The normality of continuous variables was assessed using the Shapiro–Wilk test. Intergroup comparisons of continuous variables that met the assumption of normal distribution were performed using the independent samples t-test. Categorical variables were compared using the chi-square test, or Fisher’s exact test when the expected cell counts were insufficient. All statistical analyses were conducted using two-tailed tests, and a p value of < 0.05 was considered statistically significant. Data analysis was performed using IBM SPSS Statistics for Windows, Version 27.0 (IBM Corp., Armonk, NY, USA).

Result

The mean age of the study population was 49.85 ± 12.07 years, and 32.7% of the patients were female. The two groups were comparable in terms of mean age and sex distribution (p = 0.197 and p = 0.325, respectively) (Table 1). All stones were unilateral, with 44.7% located on the right side, and moderate-grade hydronephrosis was observed in 70% of the cases. The mean stone size and mean Hounsfield unit values were 26.05 ± 6.11 mm and 823.59 ± 370.97, respectively. These parameters did not differ significantly between the groups (p = 0.711 and p = 0.966, respectively) (Table 2).

Table 1.

Comparison of demographic data and scores between groups

		Group		Test	Effect Size	%95 CI
		Group1 (n = 74)	Group2 (n = 76)
		Mean ± SD	Mean ± SD
Age (year)		48.55 ± 12.74	51.11 ± 11.33	0,197	-0.212	-0.532–0.110
BMI (kg/m2)		24.99 ± 2.83	25.57 ± 2.25	0,166	-0.225	-0.547–0.098
CCI		0.41 ± 0.81	0.46 ± 0.87	0,689	-0.066	-0.386–0.255
ASA		2.03 ± 0.47	2.12 ± 0.56	0,283	-0.176	-0.496–0.145
		n(%)	n(%)
Gender	Female	27(36.5)	22(28.9)	0.325#	0.325
	Male	47(63.5)	54(71.1)

Test: Independent samples t-test

#: Chi-square test

Abbreviations: BMI Body Mass Index, CCI Charlson Comorbidity Index, ASA American Society of Anesthesiologists

Table 2.

Comparison of preoperative, intraoperative, and postoperative parameters between the groups

		Group		Test	Effect Size	%95 CI	Absolute Mean Difference
		Group1 (n = 74)	Group2 (n = 76)
		Mean ± SD	Mean ± SD
Stone Largest Diameter (mm)		25.86 ± 5.86	26.24 ± 6.39	0.711	-0.061	-0.381-0.260
Stone Denstiy (Hounsfield unit)		822.28 ± 385.12	824.86 ± 359.21	0.966	-0.007	-0.327-0.262
Distance Between Skin Puncture (mm)		85.22 ± 7.9	86.05 ± 7.83	0.516	-0.106	-0.426-0.214
Total Fluoroscopy Time (sec)		66.65 ± 12.74	67.22 ± 14.26	0.795	-0.042	-0.636-0.278
Puncture Time (sec)		18.93 ± 2.79	19.63 ± 2.67	0.119	-0.256	-0.577-0.065
Duration of Surgery (min)		77.97 ± 15.72	58.36 ± 12.87	< 0.001*	1.367	1.010–1.721	19.61
Length of Hospital Stay (days)		3.28 ± 1.56	2.28 ± 0.79	< 0.001*	0.818	0.484–1.151	1.0
		n(%)	n(%)
Side	Left	40(54.1)	43(56.6)	0.756#
	Right	34(45.9)	33(43.4)
No Grade of hydronephrosis	Mild	21(28.4)	24(31.6)	0.669#
	Moderate	53(71.6)	52(68.4)

Test: Independent samples t-test

#: Chi-square test

* p < 0.05 indicates statistical significance

No patients in the study population were diagnosed with obesity. Body mass index and distance between skin puncture were similar between Groups 1 and 2 (p = 0.166 and p = 0.516, respectively). The mean Charlson Comorbidity Index (CCI) scores were 0.41 ± 0.81 in Group 1 and 0.46 ± 0.87 in Group 2, with no statistically significant difference observed (p = 0.689). Likewise, mean ASA scores were comparable between the two groups (p = 0.283) (Tables 1 and 2).

Blood transfusion was required in only one patient in each group, with no significant difference between the groups (p = 0.999). However, hemoglobin decrease was significantly greater in Group 1 compared with Group 2 (p < 0.001). Collecting system perforation occurred in a total of three patients, and no statistically significant difference was observed between the groups (p = 0.617). In Group 1, 11 patients developed a postoperative fever exceeding 38 °C. On the other hand, in Group 1, there were 7 patients with urinary tract infections requiring additional antibiotic therapy. Both the incidence of postoperative fever and urinary tract infections requiring additional antibiotics were significantly higher in Group 1 compared with Group 2 (p = 0.044 and p = 0.032, respectively). No life-threatening complications, such as adjacent organ injury, urinoma, or urosepsis, were observed in any of the patients. The stone-free rate achieved after a single surgical session exceeded 80% in both groups and did not differ significantly between the groups (p = 0.206) (Table 3).

Table 3.

Comparison of surgical outcomes and complication rates between the groups

	Group		Test	Effect Size	%95 CI	Absolute Mean Difference
	Group1 (n = 74)	Group2 (n = 76)
	Mean ± SD	Mean ± SD
Hemoglobin decrease (mg/dL)	1.83 ± 0.95	1.23 ± 0.89	< 0.001*	0.690	0.359–1.018	0.60
	n(%)	n(%)				Absolute Risk Difference
Fever (≥ 38°)	11(14.9)	3(3.9)	0.044#*	-0.188		%11
Urinary tract infection requiring additional antibiotics	7(9.5)	1(1.3)	0.032‡*	-0.181		%8.2
Collecting system perforation	2(2.7)	1(1.3)	0.617‡	-0.050
Blood Transfusion	1(1.4)	1(1.3)	0.999‡	-0.002
Stone-free rate by one surgery	61(82.4)	69(90.8)	0.206#	-0.123

Test: Independent samples t-test

#: Chi-square test

‡: Fisher’s exact test

* p < 0.05 indicates statistical significance

Puncture times in Groups 1 and 2 were both less than 1 min and did not differ significantly between the groups (p = 0.119). However, the mean operative time was significantly shorter in Group 2 (58.36 ± 12.87 min) compared with Group 1 (p < 0.001). Similarly, the length of hospital stay was significantly shorter in Group 2 than in Group 1 (p < 0.001). The mean intraoperative remifentanil consumption was 345.27 ± 66.81 Mcg in Group 1 and 271.71 ± 44.97 Mcg in Group 2, with a statistically significant difference between the groups (p < 0.001). Postoperative VAS scores were consistently higher in Group 1 across all evaluated time points (p < 0.001). The absolute between-group differences in VAS at rest were 1.37 points at 1 h, 1.68 points at 6 h, and 1.81 points at 24 h. For dynamic VAS, the corresponding absolute differences were 2.38, 2.09, and 2.05 points, respectively. The number of patients requiring rescue analgesia was significantly greater in Group 1 compared with Group 2 (p < 0.001). Moreover, Group 1 demonstrated a shorter mean time to rescue analgesia and required a higher analgesic dose than Group 2 (p = 0.002 and p = 0.019, respectively) (Table 4).

Table 4.

Comparison of postoperative pain levels and rescue analgesia requirements between the groups

		Group		Test	Effect Size	%95 CI	Absolute Mean Difference
		Group1 (n = 74)	Group2 (n = 76)
		Mean ± SD	Mean ± SD
VAS Rest	1. hour	3.16 ± 0.7	1.79 ± 0.85	< 0.001*	1.754	1.374–2.129	1.37
	6. hour	4.31 ± 1.24	2.63 ± 0.92	< 0.001*	1.542	1.175–1.905	1.68
	24. hour	3.77 ± 1	1.96 ± 0.87	< 0.001*	1.931	1.541–2.317	1.81
VAS Dynamic	1. hour	4.51 ± 1.59	2.13 ± 1.04	< 0.001*	1.779	1.399–2.156	2.38
	6. hour	5.04 ± 1.46	2.95 ± 1.15	< 0.001*	1.596	1.226–1.962	2.09
	24. hour	4.22 ± 1.29	2.17 ± 0.91	< 0.001*	1.838	1.453–2.207	2.05
The mean time to rescue analgesia (hour)		4.44 ± 2.24	8.77 ± 3.88	0.002*	1.010	0.680–1.540	4.33
Rescue analgesia dose (mg)		126 ± 48.13	75 ± 27.39	0.019*	0.918	0.490–1.150	51.0
		n(%)	n(%)				Absolute Risk Difference
Patients requiring rescue analgesia, n (%)		25(33.8)	7(9.2)	< 0.001#*	0.300		%24.6

Test: Independent samples t-test

#: Chi-square test

* p < 0.05 indicates statistical significance

Abbreviations: VAS Visual Analog Scale

Multiple linear regression analysis revealed that the model was statistically significant (F = 34.201, p < 0.001). The model explained 62.8% of the variance in the VAS variable (R² = 0.628, adjusted R² = 0.609). Examination of the regression coefficients indicated that group (β = −0.891, p < 0.001), BMI (β = 0.12, p = 0.025), and operation time (β = 0.204, p = 0.001) were significant predictors of the VAS score. Patients treated with a vacuum-assisted access sheath had, on average, 1.883 units lower VAS scores compared to those who underwent standard mini-PCNL (B = − 1.883; 95% CI: −2.198 to − 1.569). For each one-unit (kg/m²) increase in BMI, the VAS score increased by an average of 0.050 units (B = 0.050; 95% CI: 0.093 to 0.070). For each one-minute increase in operation time, the VAS score increased by an average of 0.012 units (B = 0.012; 95% CI: 0.001 to 0.025) (Table 5).

Table 5.

Results of multiple linear regression analyses between the mean VAS and other variables

Model	B	Std. Error	β (Beta)	t	p	Confidence Interval (%95)		VIF
						Lower	Upper
Constant	6.384	0.813		7.85	< 0.001	4.776	7.991
Group	-1.883	0.159	-0.891	-11.836	< 0.001*	-2.198	-1.569	2.161
Gender	-0.006	0.116	-0.002	-0.047	0.962	-0.236	0.225	1.018
Age	0.004	0.005	0.04	-0.766	0.445	-0.013	0.006	1.043
BMI	0.050	0.022	0.12	-2.271	0.025*	0.093	0.070	1.063
Hemoglobin	-0.017	0.063	-0.015	-0.274	0.785	-0.142	0.107	1.143
Operation Duration	0.012	0.004	0.204	-3.252	0.001*	0.001	0.025	1.497
Remifentanil	-0.001	0.001	-0.04	-0.647	0.519	-0.003	0.001	1.467
R = 0.792	R 2 =0.628		Adjusted. R2 = 0.609		Durbin Watson:1.467		F:34.201;p<0.001*

F: One-Way Analysis of Variance (ANOVA)

* p-value is significant at the 0.05 level

According to the test results, our model is significant (F:34.201; p<0.001)

All independent variables included in the model have VIF values less than 5

Durbin-Watson value: DW = 1.467

As a result of the multiple linear regression analysis, the model was found to be statistically significant (F = 34.201, p < 0.001). The model explains 62.8% of the variance in the VAS variable (R² = 0.628, Adjusted R² = 0.609)

Abbreviations: VAS Visual Analog Scale, BMI Body Mass Index

Multivariate logistic regression analysis showed that the model was statistically significant (Omnibus χ² = 19.797, p < 0.001) and demonstrated adequate goodness-of-fit (Hosmer–Lemeshow χ²(8) = 4.345, p = 0.825). The model had modest explanatory power (Cox & Snell R² = 0.124; Nagelkerke R² = 0.192). Group and intraoperative remifentanil consumption were identified as significant independent predictors of postoperative rescue analgesia requirement. After adjustment for operation time and intraoperative remifentanil use, patients in Group 2 had significantly lower odds of requiring postoperative rescue analgesia compared with those in Group 1 (OR = 0.096, 95% CI: 0.027–0.337, p < 0.001). This corresponds to an approximately 90.4% reduction in the odds of postoperative rescue analgesia requirement. In addition, higher intraoperative remifentanil consumption was associated with slightly lower odds of postoperative rescue analgesia requirement (OR = 0.992, 95% CI: 0.985–0.999, p = 0.020) (Table 6).

Table 6.

Results of multivariate logistic regression analyses between the rescue analgesia and other variables. Dependent Variable: Rescue Analgesia (0: No, 1: Yes)Covariates: Group, Operation Time, Intraoperative remifentanil consumption

Parameter	B	S.E.	p	Exp(B)	(%95) C.I. for EXP (B))
					Lower	Upper
Group	-2.347	.643	<0.001*	0.096	.027	.337
Operation Time	-.005	.015	0.719	0.995	.966	1.024
Remifentanil	-.008	.004	0.020*	0.992	.985	.999
Constant	1.432	1.599	0.370	4.188
R2=0.124 (Cox&Snell R Square)R2=0.192 (Nagelkerke)			χ2(8)=4.345; p=0.825(Homers&Lemeshow)		χ² = 19.797; p<.001*(Omnibus)

Multivariate logistic regression analysis demonstrated that the model was statistically significant (Omnibus χ² = 19.797, p < 0.001) and showed an adequate goodness-of-fit (Hosmer–Lemeshow χ²(8) = 4.345, p = 0.825). The explanatory power of the model was modest, with Cox & Snell R² of 0.124 and Nagelkerke R² of 0.192. Group and intraoperative remifentanil consumption were identified as significant independent predictors of postoperative analgesic requirement. Patients in the vacuum-assisted access sheath group had a significantly lower likelihood of requiring postoperative analgesia compared to the standard mini-PCNL group (OR = 0.096, 95% CI: 0.027–0.337, p < 0.001). This finding indicates that, after adjustment for operation time and intraoperative remifentanil use, patients treated with vacuum-assisted access sheath had approximately a 90.4% reduction in the odds of postoperative analgesic requirement. In addition, intraoperative remifentanil consumption was also significantly associated with postoperative analgesic requirement (OR = 0.992, 95% CI: 0.985–0.999, p = 0.020), suggesting that increasing remifentanil dose was associated with a slight reduction in postoperative analgesia need.

Discussion

In the present study, the use of a vacuum-assisted access sheath during mini-PCNL was associated with significantly lower postoperative pain scores, reduced analgesic requirements, shorter operative time, and decreased length of hospital stay compared to the conventional sheath group. In addition, lower rates of postoperative fever, urinary tract infection, and hemoglobin decrease were observed in the vacuum-assisted group. In this context, our study observed that the use of a vacuum-assisted access sheath during mini-PCNL was associated with better surgical outcomes due to less postoperative pain, shorter operation time, bleeding, and infectious pathologies.

Urolithiasis represents one of the most common disorders of the urinary tract and ranks as the third most prevalent urological disease worldwide. The global prevalence of kidney stones has been reported to range between approximately 1.7% and 8.8% [12]. Although multiple treatment strategies are available for the management of urolithiasis, PCNL is widely accepted as a standard endourological technique for the treatment of renal pelvic stones larger than 2 cm in adult patients. Nevertheless, PCNL is associated with a variety of potential complications, including postoperative fever, pain, bleeding requiring transfusion, colonic injury, pleural damage, and complicated urinary tract infections [13, 14]. In the present retrospective study, we demonstrated that one of the most clinically relevant complications of PCNL, postoperative pain, was significantly reduced through the use of a vacuum-assisted access sheath. This reduction in pain was accompanied by shorter hospitalization and a marked decrease in postoperative analgesic requirements, highlighting the potential clinical benefits of this technology.

Postoperative discomfort following PCNL is primarily related to both somatosensory and visceral pain mechanisms [15]. Moderate to severe pain has been reported in more than 50% of patients after PCNL [16]. Inadequate pain control not only negatively affects patients’ quality of life and limits daily activities but is also associated with impaired ventilation, prolonged hospital stay, and increased morbidity [15]. Pain following upper urinary tract surgery may arise from multiple factors, including neuropathic and inflammatory responses involving the skin, subcutaneous tissue, and musculature, as well as increased intraluminal renal pressure and mucosal irritation [17, 18]. Previous clinical studies have identified several determinants of postoperative pain following PCNL, such as operative duration, elevated intrarenal pressure, percutaneous tract size, and stone size and number [11, 15]. Renal mechanoreceptors are known to become activated when intrapelvic pressure exceeds approximately 30 mmHg, thereby contributing to pain perception [17, 19]. Moreover, elevated intrarenal pressure during lithotripsy may lead to adverse events such as retroperitoneal extravasation, perirenal fluid accumulation, acute absorption of irrigation fluid, and an increased risk of infectious complications. For these reasons, maintaining intrapelvic pressure at low levels is considered a critical aspect of PCNL procedures [15]. Within this framework, the use of vacuum-assisted access sheaths has gained increasing attention in recent years due to their ability to effectively limit intrarenal pressure. Despite the substantial number of studies evaluating postoperative pain after PCNL, only a limited body of literature has specifically addressed the impact of vacuum-assisted access sheath technology on pain outcomes within this surgical approach. Although intrarenal pressure level is a key factor discussed in relation to both infectious complications and postoperative pain, it was not directly measured in the present study. Therefore, the proposed mechanistic relationship between vacuum-assisted sheath use and reduced pain via intrarenal pressure modulation remains hypothetical. However, given the retrospective design of the study and the absence of multivariate analysis, these findings should be interpreted as associations rather than definitive causal relationships. Multiple perioperative factors, including operative time, intraoperative opioid consumption, and surgical complexity, may have contributed to the observed differences in postoperative pain.

Mini-PCNL has gained increasing popularity in recent years due to its association with reduced surgical trauma and lower morbidity rates. However, compared with standard PCNL, this approach also presents certain technical limitations, including challenges in the extraction of stone fragments, suboptimal utilization of irrigation flow, and reduced efficiency of endourological instruments [20]. In mini-PCNL, nephrostomy sheaths with diameters ranging from 16 F to 20 F are commonly used, a factor that is directly associated with elevated intrarenal pressure. Previous studies have demonstrated that intrarenal pressure exceeding 30 mmHg significantly increases the risk of procedure-related complications [3, 21]. In this context, technological advancements have led to the integration of vacuum-assisted access sheaths into routine clinical practice, offering substantial advantages by enabling continuous evacuation of stone fragments and irrigation fluid. Vacuum aspiration allows the nephroscope to move freely through a mobile, sealed valve mechanism while preventing excessive increases or decreases in intrarenal pressure. Furthermore, vacuum settings can be manually adjusted to maintain the collecting system under controlled negative pressure, facilitating simultaneous stone fragmentation and suction during the procedure.

Because the application of vacuum-assisted access sheath technology in mini-PCNL is relatively recent, the available evidence in the literature remains limited. In a feasibility study by Lai et al., the use of a vacuum-assisted access sheath was shown to reduce operative time by approximately 29.9% in patients undergoing mini-PCNL. The authors attributed this finding primarily to continuous evacuation of stone fragments and blood clots during lithotripsy, which significantly enhanced endoscopic visualization. In the same study, postoperative pain scores at 6 and 24 h were also reported to be lower in patients treated with vacuum-assisted access sheaths compared with those undergoing conventional procedures [11]. In the clinical studies conducted by Zanetti et al. investigating the effect of vacuum-assisted mini percutaneous nephrolithotomy on fragment clearance and intrarenal pressure control, they reported that in nearly two-thirds of the cases, stone fragments were removed without requiring additional interventions such as a basket. This situation provided safe and satisfactory stone clearance by maintaining an appropriate intrarenal pressure profile [22]. In another clinical study, Xu et al. reported that the use of a suction-evacuation nephrostomy sheath was more efficient in the removal of stone fragments compared to the conventional nephrostomy sheath, while simultaneously providing lower renal pelvic pressure and thereby ensuring a safer surgical procedure [21]. In a series of 104 cases, Lievore et al. reported that the use of a vacuum-assisted access sheath in mini-PCNL demonstrated high efficacy in fragment retrieval through active negative-pressure suction, and this was directly associated with shortened operative times [23]. Consistent with these findings, our study similarly demonstrated that vacuum-assisted access sheath use was associated with shorter operative duration and reduced postoperative pain. Additionally, the lower intraoperative remifentanil requirement observed in the vacuum-assisted group may be related to shorter operative time and improved surgical efficiency. Reduced nociceptive stimulation due to lower intrarenal pressure may also have contributed to decreased intraoperative opioid demand. However, differences in anesthetic management may represent a potential confounding factor influencing postoperative pain outcomes.

In a pediatric cohort, Collura et al. reported that vacuum-assisted mini-PCNL was both feasible and safe in children older than one year. Their study further documented that, in the treatment of pyelocaliceal stones measuring 2–3 cm, vacuum-assisted mini-PCNL allowed continuous irrigation of the collecting system, resulting in a clear surgical field and a stone-free rate of 100% [24]. In another comparative study, Szczesniewski et al. demonstrated that vacuum-assisted PCNL offered shorter operative times and reduced length of hospital stay compared with mini-PCNL, while stone-free rates and infectious complication rates were comparable between the techniques [25]. In our study, stone-free rates exceeded 80% in both groups, with no statistically significant difference observed. We believe that this outcome is related to the procedures being performed by an experienced urological team and to the selective inclusion of patients with a single renal pelvic stone.

In a large series of 912 patients, Du et al. reported that vacuum-assisted mini-PCNL for renal staghorn calculi resulted in lower intrarenal pressure, shorter operative times, reduced bleeding, and higher stone-free rates compared with standard PCNL and conventional mini-PCNL [26]. Although our analysis was limited to two mini-PCNL groups, hemoglobin decrease was found to be significantly lower in the vacuum-assisted mini-PCNL group. A meta-analysis conducted by Zhu et al. further demonstrated that vacuum-assisted sheath application in PCNL improved both safety and procedural efficiency compared with conventional sheaths. The authors also reported shorter operative times, higher stone-free rates, and reduced infectious complications associated with vacuum-assisted techniques [12]. Similarly, Marmiroli et al. showed that vacuum-assisted access sheath use during PCNL significantly reduced infectious complication rates, even in patients at high risk for infection, and served as an independent protective factor against postoperative infectious events [14]. In terms of healthcare economics, Lievore et al. reported a substantial reduction in total hospitalization costs associated with vacuum-assisted PCNL in a series of 225 patients [7]. Although a direct cost analysis was not performed in our study, the significantly shorter operative times and reduced length of hospital stay observed in the vacuum-assisted PCNL group suggest that this approach may offer meaningful benefits in terms of healthcare efficiency and economic sustainability. On the other hand, regardless of whether a conventional or vacuum-assisted access sheath was used, the length of hospital stay was moderately prolonged in both groups. The main reasons for the prolonged hospital stay are our national health insurance system, most patients’ reluctance to be discharged before full recovery, and the geographical challenges that make hospital access difficult.

Study limitations

This study has several limitations. First, its retrospective design, single-center setting, and relatively small sample size may limit the generalizability of the findings. Second, intraoperative opioid use was a confounding factor. İntraoperative opioid exposure (remifentanil consumption) differed between groups and may have influenced early postoperative pain perception and subsequent rescue analgesia requirement; although remifentanil was included in the multivariable models, residual confounding cannot be excluded. Third, the absence of randomization introduces a risk of selection bias. In addition, intrarenal pressure was not measured, and stone composition could not be evaluated, which might have provided further insight into the observed outcomes. Finally, postoperative pain assessment using the VAS is subjective and may be influenced by multiple patient-related and perioperative factors.

Conclusion

In recent years, the increasing prevalence and recurrence of renal stone disease have led to a substantial rise in the use of minimally invasive surgical techniques. The primary objective of clinicians is to achieve high surgical success while minimizing procedure-related complications. Within this context, maintaining postoperative pain at tolerable levels plays a critical role in improving patient compliance with treatment and follow-up protocols. In our study, vacuum-assisted access sheath use was associated with lower postoperative pain and analgesic requirements; however, prospective controlled studies are needed to confirm these findings. These findings suggest that vacuum-assisted access sheath technology may represent a valuable adjunct in mini-PCNL procedures, contributing to improved postoperative patient comfort and enhanced clinical outcomes.

Abbreviations

ASA

American Society of Anesthesiologists

BMI

Body mass index

CCI

Charlson comorbidity index

mini-PCNL

Mini-percutaneous nephrolithotomy

PCNL

Percutaneous nephrolithotomy

VAS

Visual analog scale

Authors’ contributions

HB conceptualized and designed the study, contributed to data collection, performed the analysis, and drafted the manuscript. VK contributed to study design, interpretation of the perioperative/analgesia outcomes, and critically revised the manuscript. Both authors read and approved the final manuscript.

Funding

The authors received no specific funding for this work.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Kayseri City Hospital Non-Interventional Clinical Research Ethics Committee (Decision No: 684, Decision date: 02 December 2025). The study was conducted in accordance with the Declaration of Helsinki. Due to the retrospective design and use of anonymized data, the requirement for informed consent was waived by the ethics committee.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.