Investigation of Predictors of Systemic Inflammatory Response Syndrome After Endourological Procedure of Upper Urinary Tract Stones

Abstract

Background:

In order to prevent infectious complications following endourological procedure of upper urinary tract stones, it is essential to determine which patients are at high risk of developing this complication. We aimed to identify predictors that may cause systemic inflammatory response syndrome (SIRS) after the endourological procedure of upper urinary tract stones.

Materials and Methods:

Patients who underwent percutaneous nephrolithotomy (PNL), flexible ureteroscopy (F-URS), or semirigid ureteroscopy (SR-URS) in our center between January 2011 and June 2020 were evaluated retrospectively. After surgery, patients were pursued for SIRS criteria. Logistic regression analyses were applied to identify predictors of SIRS.

Results:

A total of 1471 patients were included in the study. The rates of SIRS after PNL, F-URS, and SR-URS were 12.9%, 6.3%, and 1.7%, respectively. In multivariate analysis, predictors for SIRS were determined to be stone volume, operative time, and history of recurrent urinary tract infection (UTI) in the PNL group; ipsilateral stone surgery history, stone volume, and operative time in the F-URS group; and stone volume, operative time, and history of recurrent UTI in the SR-URS group.

Conclusion:

Stone volume and operative time were determined to be independent predictors of SIRS in endourological surgery of upper urinary tract stones.

Introduction

Endourological procedures have now almost fully replaced open surgery in the surgical treatment of urolithiasis and have gained substantial recognition in the latest guidelines of the European Association of Urology.¹ Although percutaneous nephrolithotomy (PNL), flexible ureteroscopy (F-URS), and semirigid ureteroscopy (SR-URS) are minimally invasive methods that are successfully applied in clinical practice, they can cause serious complications, such as bleeding and urosepsis.^2,3 Urinary tract infections (UTIs), which encompass a spectrum of severity ranging from fever to urosepsis and multiple organ failure, are the most common complications after endourological surgery of upper urinary tract stones, even where appropriate perioperative antibiotic prophylaxis has been administered.⁴ In a meta-analysis by De et al. comparing the postoperative complications of PNL and retrograde intrarenal surgery, the rates of fever were reported to be 3%–25% and 2%–28%, and the rates of sepsis were determined to be 0.5%–2% and 3–5%, respectively.⁵

Systemic inflammatory response syndrome (SIRS) is the first stage of urosepsis and can progress to multiple organ failure. It prolongs hospital stays and affects the prognosis. Due to its clear and specific diagnostic criteria, SIRS is an important index for the evaluation of infectious complications after endourological treatment of urinary stones.^6–8 In order to prevent infectious complications following endourological treatment of upper urinary tract stones, it is essential to determine which patients are at high risk of developing this complication. Despite the availability of studies in the literature on this subject,^6–12 there is heterogeneity in terms of centers, preoperative urine culture management, antibiotic treatment, surgical method, surgical team, and equipment. In the current study, we aimed to determine predictors that may cause SIRS after the endourological procedure of upper urinary tract stones at a single center.

Materials and Methods

After ethical committee approval of the Bakırköy Dr. Sadi Konuk Training and Research Hospital (Approval Number: 2022–350), the adult patients who underwent endourological procedure of upper urinary tract stones between January 2011 and June 2020 were retrospectively collected from a prospectively created database. Cases in which the ureteroscope could not be advanced due to narrow ureteral calibration in the first procedure and those in which a double-J (D-J) catheter was required for passive dilatation due to the inability to place the ureteral access sheath (UAS) were included, and the clinical data of the second procedure were considered in analyses. Patients with anatomical anomalies (horseshoe kidney, pelvic kidney, etc.), those with bilateral kidneys or ureteral stones, and those with missing follow-up data were not included. Further excluded were patients who underwent F-URS or SR-URS as an additional treatment method following shock wave lithotripsy or PNL, as well as those who underwent F-URS or SR-URS for diagnostic purposes. Last, patients with factors that predisposed them to infections, including immunosuppressive disease or medication, diabetes mellitus, and kidney failure, were not included.

The following parameters were examined: demographic data, body mass index, American Society of Anesthesiologists (ASA) score, ipsilateral stone surgery history, preoperative urine culture, history of recurrent UTI, stone characteristics (diameter, volume, and density), preoperative D-J stenting, time from preoperative bladder urine culture (PBUC) to surgery, surgical method, operative time, transfusion rate, postoperative SIRS, length of hospital stay (LOHS), and stone-free status. Recurrent UTIs were defined as the occurrence of UTIs at least three times a year or twice within the last 6 months.¹³ Noncontrast computed tomography (CT) was performed in all patients. Stone characteristics (diameter, volume, and density) were evaluated with CT.

All patients were evaluated with PBUC analysis. Appropriate antibiotic treatment at least 7 days before surgery was administered to patients with a positive PBUC result. Once a sterile urine culture was obtained according to the control PBUC, surgery was performed, and antibiotic treatment was continued until discharge from the hospital. Intravenous prophylactic antibiotics were administered during anesthesia induction in cases where the PBUC was sterile. In patients whose PBUC indicated contamination, if there was significant leukocyturia or UTI findings, ceftriaxone was administered for 48 hours, and a sterile urine culture was confirmed with the control PBUC. If there were no significant leukocyturia or UTI findings, intravenous prophylactic antibiotics were administered during anesthesia induction.

PNL technique

In our clinic, PNL procedures were undertaken with the prone method until 2019, after which there was a transition to the supine method. In both positions, punctures were performed under fluoroscopic guidance. In case of infected or pyuric urine during puncture, the operation was terminated, a nephrostomy was placed, and antibiotics were administered according to the results of the intraoperative urine culture. PNL was postponed until clear urine color at the nephrostomy site and sterile urine culture were observed. Tract dilation was performed using the Amplatz renal dilator set (Cook Medical, Bloomington, Indiana). A 24-Fr Amplatz sheath, a 19-Fr nephroscope (Karl Storz, Tuttlingen), and pneumatic lithotripter (Vibrolith, Elmed, Ankara) were used. A nephrostomy catheter was placed in all patients. In some cases, a D-J catheter was placed when deemed necessary, considering the complexity of the case.

F-URS technique

F-URS was preferred for the treatment of upper ureteral stones and kidney stones. Under general anesthesia, after the placement of guidewire (Sensor^TM, Boston Scientific, Marlborough, Massachusetts), diagnostic ureteroscopy was performed through a 7-F semirigid ureteroscope (Karl Storz). Upon the observation of no pathology in the ureter, a 12/14-Fr UAS (Plasti-med, Istanbul) was placed into the ureter over the guidewire under fluoroscopy. A flexible ureteroscope (Flex-X2, Flex XC, Karl Storz) was pushed forward through the UAS, and lithotripsy was performed using a 272-μm Holmium:YAG laser (Sphinx Lisa laser, Katlenburg). Laser settings were determined according to the hardness and size of the stone. A 4.8-Fr D-J catheter was placed in all patients.

SR-URS technique

SR-URS was generally preferred in the treatment of lower ureteral stones. Under spinal or general anesthesia, after the placement of guidewire (Sensor^TM, Boston Scientific), a 7-F semirigid ureteroscope (Karl Storz) was advanced along the ureter. Lithotripsy was performed using a 272-μm Holmium:YAG laser (Sphinx Lisa laser). A 4.8-Fr D-J catheter was placed in all patients with impacted stones. In the remaining cases, the decision to place the D-J catheter was determined according to operative time, complication, and/or ureteral edema.

Postoperative assessments

SIRS was defined as two or more of the following: body temperature >38°C or <36°C, white blood cell count >12,000/μL or <4000/μL, heart rate >90 beats/minute, and respiratory rate >20/minute or partial pressure of carbon dioxide <32 mmHg.¹⁴ Blood and urine cultures were taken from patients with fever or SIRS. Only patients who met the SIRS criteria within the postoperative first week were included in the study. The patients in each procedure group were further evaluated according to whether they developed SIRS.

F-URS and SR-URS patients without complications were discharged on the postoperative first day. Among PNL patients with clear urine color at the nephrostomy site, the first step was to clamp the nephrostomy catheter. After that, a nephrostomy catheter was removed in cases where there was no fever or pain. These patients were discharged after 1 day of observation.

The patients were evaluated in terms of D-J catheter removal and stone-free status in the postoperative first month. Stone-free status was evaluated by urinary system ultrasonography (patients with nonopaque stones or patients with suspicious kidney-ureter-bladder radiography) and/or kidney-ureter-bladder radiography (patients with opaque stones). If stone-free status could not be clearly determined by kidney-ureter-bladder radiography and/or ultrasonography, CT was performed. The presence of an asymptomatic, nonobstructive, and noninfectious clinically insignificant residual fragment smaller than 4 mm was defined as stone-free.

Statistical analysis

Statistical analysis was performed using SPSS version 21. Categorical variables were presented as numbers and percentages. Continuous variables were presented as mean and standard deviation. The Shapiro–Wilk test was used for the normality test for the continuous variables. The Pearson chi-square or Fisher’s exact test was used to compare percentages of categorical variables. An independent sample t-test or Mann–Whitney U test was used to compare the means of two independent groups. P < .05 was defined as significant. Univariate and multivariate analyses were undertaken to identify predicting factors of SIRS. The simultaneous inclusion of stone diameter and stone volume was avoided due to their high correlation, which could potentially lead to a multicollinearity problem. Another variable not included in multivariate analysis was LOHS, since it was not a preoperative or intraoperative variable.

Results

The study included 1471 patients, of whom 389 (26.4%) underwent PNL, 510 (34.7%) underwent F-URS, and 572 (38.9%) underwent SR-URS. The demographic and clinical characteristics of the patients are presented in Table 1. The overall stone-free rates were 75.8%, 81%, and 82.5% for PNL, F-URS, and SR-URS, respectively. SIRS occurred in 50 (12.9%), 32 (6.3%), and 10 (1.7%) patients following PNL, F-URS, and SR-URS, respectively. No infectious complications were observed in the postoperative follow-up of the remaining patients.

Table 1.

Demographic Data, Stone Characteristics, and Clinical Variables

Variables	PNL	F-URS	SR-URS
Number of patients	389	510	572
Age, mean ± SD, year	43.9 ± 14.0	38.3 ± 11.8	45.5 ± 15.7
Body mass index (kg/m²), mean ± SD	26.6 ± 3.1	25.0 ± 3.3	26.9 ± 3.3
Sex, n (%)
Male	250 (64.3)	312 (61.2)	390 (68.2)
Female	139 (35.7)	198 (38.8)	182 (31.8)
ASA score, n (%)
ASA I	142 (36.5)	179 (35.1)	208 (36.4)
ASA II	222 (57.1)	282 (55.3)	305 (53.3)
ASA III	25 (6.4)	49 (9.6)	59 (10.3)
Ipsilateral stone surgery history, n (%)	95 (24.4)	48 (9.4)	186 (32.5)
Recurrent UTI history, n (%)	51 (13.1)	96 (18.8)	51 (8.9)
Preoperative urine culture positivity, n (%)	61 (15.7)	136 (26.7)	79 (13.8)
Preoperative DJ stent, n (%)	24 (6.2)	40 (7.8)	63 (11)
Time from PBUC to surgery (day), mean ± SD	12.4 ± 5.4	11.8 ± 6.9	10.3 ± 5.6
Stone number, mean ± SD	1.42 ± 0.82	1.39 ± 0.71	1.09 ± 0.37
Stone diameter (mm), mean ± SD	24.5 ± 5.82	16.8 ± 4.2	11.2 ± 4.7
Stone volume (mm³), mean ± SD	2486 ± 1057	1216 ± 306	271 ± 40
Stone density (HU), mean ± SD	1000 ± 324	884 ± 315	951 ± 322
Operative time (min), mean ± SD	73.1 ± 18.8	63.9 ± 14.3	41.6 ± 10.3
Access number, mean ± SD	1.05 ± 0.22	N/A	N/A
Blood transfusion, n (%)	22 (5.7)	—	—
LOHS (day), mean ± SD	3.66 ± 1.62	1.39 ± 1.54	1.14 ± 0.68
Postoperative SIRS, n (%)	50 (12.9)	32 (6.3)	10 (1.7)
Stone-free status, n (%)	295 (75.8)	413 (81)	472 (82.5)

ASA, American Society of Anesthesiologists; DJ, double-J; F-URS, flexible ureteroscopy; HU, Hounsfield unit; LOHS, length of hospital stay; PBUC, preoperative bladder urine culture; PNL, percutaneous nephrolithotomy; SD, standard deviation; SIRS, systemic inflammatory response syndrome; SR-URS, semirigid ureterorenoscopy; UTI, urinary tract infection.

In the PNL group, the patients who developed SIRS had significantly higher rates or values for recurrent UTI history (P < .001), stone diameter (P < .001), stone volume (P < .05), operative time (P < .001), and LOHS (P < .001) than those without SIRS. In the F-URS group, the patients with SIRS had significantly higher rates or values for female patients (P < .05), ipsilateral stone surgery history (P < .001), and recurrent UTI history (P < .001), ASA III score (P < .05), stone diameter (P < .001), stone volume (P < .001), operative time (P < .001), and LOHS (P < .001) than those without SIRS. In the SR-URS group, the rate of recurrent UTI history (P < .05) and the values of stone diameter (P < .05), stone volume (P < .001), operative time (P < .001), and LOHS (P < .001) were significantly higher among the patients with SIRS than among those without SIRS. The time from PBUC to surgery did not significantly differ between the SIRS and non-SIRS groups for any of the three surgical methods. The results of the comparison between the SIRS group and the non-SIRS group are presented in Table 2.

Table 2.

Comparison of Patient Characteristics according to SIRS Development

Variables	PCNL	F-URS	SR-URS
Number (percentage) of patients
SIRS	50 (12.9)	32 (6.3)	10 (1.7)
Non-SIRS	339 (87.1)	478 (93.7)	562 (98.3)
Age, mean ± SD, n (%)
SIRS	44.7 ± 11.2	38.7 ± 11.7	43.6 ± 24.5
Non-SIRS	43.7 ± 14.4	39.6 ± 14.4	45.5 ± 15.5
Body mass index, mean ± SD, n (%)
SIRS	26.0 ± 2.5	25.8 ± 4.4	26.8 ± 2.1
Non-SIRS	26.7 ± 3.2	24.9 ± 3.2	26.9 ± 3.3
Female, n (%)
SIRS	12 (24)	19 (59.4)^*	4 (40)
Non-SIRS	127 (37.5)	179 (37.4)	178 (31.7)
ASA III, n (%)
SIRS	0 (0)	7 (21.9)^*	0 (0)
Non-SIRS	25 (7.4)	42 (8.8)	59 (10.5)
Ipsilateral stone surgery history, n (%)
SIRS	12 (24)	10 (31.3)^**	4 (40)
Non-SIRS	83 (24.5)	38 (7.9)	182 (32.4)
Recurrent UTI history, n (%)
SIRS	14 (28)^* ^*	13 (40.6)^**	4 (40)^*
Non-SIRS	37 (10.9)	83 (17.4)	47 (8.4)
Preoperative urine culture positivity, n (%)
SIRS	10 (20)	8 (25)	2 (20)
Non-SIRS	51 (15)	128 (26.8)	77 (13.7)
Preoperative DJ stent, n (%)
SIRS	6 (12)	4 (12.5)	2 (20)
Non-SIRS	18 (5.3)	36 (7.5)	61 (10.9)
Time from PBUC to surgery, mean ± SD
SIRS	11.2 ± 5.6	12.3 ± 3.9	11.3 ± 6.3
Non-SIRS	12.6 ± 5.3	11.8 ± 7.1	10.2 ± 5.5
Stone number, mean ± SD
SIRS	1.32 ± 0.55	1.43 ± 0.61	1.20 ± 0.63
Non-SIRS	1.43 ± 0.85	1.39 ± 0.72	1.09 ± 0.36
Stone diameter (mm), mean ± SD
SIRS	31.1 ± 8.23^**	20.3 ± 2.6^**	10.8 ± 4.3^*
Non-SIRS	23.5 ± 4.66	16.6 ± 4.2	15.7 ± 5.6
Stone volume (mm³), mean ± SD
SIRS	2812 ± 1056^*	1462 ± 192^**	356 ± 44^**
Non-SIRS	2437 ± 1050	1199 ± 305	270 ± 38
Stone density, mean ± SD (HU)
SIRS	936 ± 234	814 ± 296	953 ± 322
Non-SIRS	1010 ± 327	889 ± 316	798 ± 221
Operative time, mean ± SD (min)
SIRS	94.4 ± 8.2^**	72.6 ± 17.0^**	54.2 ± 6.1^**
Non-SIRS	69.9 ± 17.8	63.3 ± 14.0	41.4 ± 10.2
Access number, mean ± SD
SIRS	1.08 ± 0.27	—	—
Non-SIRS	1.05 ± 0.21
Blood transfusion, n (%)
SIRS	4 (8)	—	—
Non-SIRS	18 (5.3)
LOHS (day), mean ± SD
SIRS	5.16 ± 1.73^**	5.13 ± 4.55^**	3.6 ± 3.5 ^**
Non-SIRS	3.44 ± 1.49	1.14 ± 0.43	1.09 ± 0.4
Stone-free status, n (%)
SIRS	39 (78)	26 (81.3)	8 (80)
Non-SIRS	256 (75.5)	387 (81)	464 (82.6)

P < .05.

P < .001.

Statistically different values marked in bold. ASA, American Society of Anesthesiologists; DJ, double-J; F-URS, flexible ureteroscopy; HU, Hounsfield unit; LOHS, length of hospital stay; PBUC, preoperative bladder urine culture; PNL, percutaneous nephrolithotomy; SD, standard deviation; SIRS, systemic inflammatory response syndrome; SR-URS, semirigid ureterorenoscopy; UTI, urinary tract infection.

For all endourological treatment methods, recurrent UTI history, stone volume, and operative time were determined to be predictors of SIRS in univariate analysis. In addition to these variables, stone diameter was a significant predictor in univariate analysis for all three surgical methods (P < .001 for PNL and F-URS and P = .004 for SR-URS). Furthermore, in the F-URS group, female gender (P = .016), ASA III score (P = .020), and ipsilateral stone surgery history (P < 0.001) were significant predictors according to univariate analysis. In multivariate analysis, the predictive factors of SIRS were determined to be recurrent UTI history (P = .005), stone volume (P = .029), and operative time (P < .001) in the PNL group; ipsilateral stone surgery history (P < .001), stone volume (P < .001), and operative time (P < .001) in the F-URS group; and recurrent UTI history (P = .002), stone volume (P < .001), and operative time (P < .001) in the SR-URS group. Table 3 presents the results of univariate and multivariate binary logistic regression analyses.

Table 3.

Univariable and Multivariable Analyses of Predictive Factors for SIRS Development

	Univariable			Multivariable
	OR	95% CI	P	OR	95% CI	P
PNL
Recurrent UTI history	3.174	1.568–6.427	<0.001	4.151	1.542–11.178	0.005
Stone diameter	1.198	1.140–1.260	<0.001
Stone volume	1.003	1.000–1.001	0.020	1.001	1.000–1.001	0.029
Operative time	1.082	1.059–1.106	<0.001	1.098	1.067–1.129	<0.001
F-URS
Gender (female)	2.441	1.177–5.063	0.016	1.890	0.765–4.666	0.168
ASA III	2.907	1.187–7.120	0.020	1.581	0.515–4.857	0.423
Ipsilateral stone surgery history	5.263	2.323–11.922	<0.001	7.569	2.645–21.659	<0.001
Recurrent UTI history	3.256	1.547–6.853	0.002	1.554	0.614–3.937	0.352
Stone diameter	1.304	1.159–1.466	<0.001
Stone volume	1.004	1.002–1.005	<0.001	1.003	1.002–1.005	<0.001
Operative time	1.046	1.019–1.073	0.001	1.052	1.020–1.085	<0.001
SR-URS
Recurrent UTI history	7.305	1.991–26.802	0.003	33.97	3.797–303.891	0.002
Stone diameter	1.192	1.057–1.345	0.004
Stone volume	1.033	1.019–1.046	<0.001	1.046	1.026–1.065	<0.001
Operative time	1.080	1.036–1.127	<0.001	1.172	1.086–1.265	<0.001

Statistically different values marked in bold. ASA, American Society of Anesthesiologists; CI, confidence interval; F-URS, flexible ureteroscopy; HU, Hounsfield unit; OR, odds ratio; PNL, percutaneous nephrolithotomy; SIRS, systemic inflammatory response syndrome; SR-URS, semirigid ureterorenoscopy; UTI, urinary tract infection.

Discussion

There are many studies in the literature investigating infectious complications after endourological treatment of upper urinary stones. However, the designs of these studies exhibit heterogeneity, and they mostly focus on a single surgical procedure. Preoperative urine culture management, antibiotic treatment, surgical team, and equipment differ across studies; thus, the findings also vary. Fever is a nonspecific finding and may not always be associated with UTIs. When designing the current study, we planned to evaluate SIRS due to its clear and specific diagnostic criteria. In addition, to the best of our knowledge, this is the first study in which three endourological surgical techniques were compared after being performed at a single center by the same surgical team using the same preoperative urine culture management, antibiotic treatment, and equipment. On completion of the study, we determined that stone volume and operative time independently predicted SIRS in all three endourological surgical methods.

The reported incidence of SIRS after PNL varies between 9.8% and 27.4%.^8–11,15 Consistent with the literature, in the current study, we detected SIRS in 12.9% of the patients after PNL. The incidence of SIRS after F-URS has been reported to range from 8.1% to 17.9%.^6–8 In our study, SIRS occurred in 6.3% of the patients after F-URS. The relatively lower rate in our sample compared to the literature can be attributed to our preoperative urine culture management. In patients presenting with a positive PBUC result preoperatively, we did not perform surgery until we observed sterile urine culture in the control examination following appropriate antibiotic treatment. In addition, in the event of PBUC contamination, if there were significant leukocyturia in the urinalysis or UTI findings, we repeated the urine culture after 48 hours of ceftriaxone treatment and performed surgery after confirming the sterility of the urine culture. Furthermore, our findings may have been influenced by the exclusion of factors that predispose individuals to infections, such as diabetes mellitus.

Studies have generally investigated SIRS in patients undergoing F-URS or those undergoing both F-URS and SR-URS.^6–8,16,17 To the best of our knowledge, only Yee et al. evaluated the development of SIRS after SR-URS alone and reported this rate to be 8.6%.⁸ However, we consider that F-URS is riskier than SR-URS in terms of the risk of infectious complications and should be evaluated separately. This idea is supported by both our findings and those reported by Ye et al. (6.3% for F-URS versus 1.7% for SR-URS and 17.9% for F-URS versus 8.6% for SR-URS, respectively).⁸ Our rates may be lower since we generally preferred SR-URS in the treatment of lower ureteral stones. Additionally, in our study, we determined that recurrent UTI history, stone volume, and operative time were predictive factors of SIRS in the SR-URS group, which, to the best of our knowledge, has been demonstrated for the first time in the literature.

Concerning the literature on PNL on this subject, Korets et al., evaluating 204 patients who underwent PNL, reported that multiple accesses and stone burden predicted SIRS.⁹ In another study conducted with 303 patients who underwent PNL, Koras et al. determined that the presence of infectious stones, stone burden, and recurrent UTI history predicted SIRS.¹⁰ Chen et al., including 209 patients who underwent PNL in their sample, found the predictive factors of SIRS to be the number of tracts, receipt of a blood transfusion, stone size, and the presence of pyelocaliectasis.¹¹ In our study, we determined that recurrent UTI history, stone volume, and operative time were predictive factors of SIRS after PNL. Additionally, unlike the literature, we detected no significant difference between the patients who developed SIRS and those without this complication, according to the presence of multiple accesses. This may be due to the low number of patients with staghorn stones requiring multiple accesses in our PNL group.

Upon reviewing the literature pertaining to F-URS, it was observed that Baboudjian et al. conducted a study with 604 patients who underwent flexible URS and found that female gender, UTI history within the past 6 months, preoperative polymicrobial urine culture, and increased operative time were associated with postoperative UTIs.¹² In a study conducted by Zhong et al. with 260 patients who underwent flexible URS, female gender and stone size were determined to be the predictive factors of SIRS in univariate analysis and stone size in multivariate analysis.⁷ Mi et al., evaluating 216 patients who underwent F-URS, stated that stone size, operative time, preoperative urine culture positivity, and UAS diameter were factors that predicted SIRS according to multivariate analysis.⁶ In our study, we determined that ipsilateral stone surgery history, stone volume, and operative time were the predictive factors of SIRS after F-URS. Consistent with the literature, the number of female patients was significantly higher among those who developed SIRS (59.4%) than those without this complication (37.4%). However, no significant difference was detected in the multivariate analysis.

Similar to our study, Ye et al. evaluated the factors predicting SIRS in the endourological treatment of upper urinary stones (PNL, SR-URS, and F-URS) of upper urinary tract stones. Their multivariate analysis revealed that preoperative urine culture positivity and the type of operation (PNL) were predictive factors of SIRS.⁸ However, different from our study, the majority of their sample consisted of patients who underwent PNL, and the authors did not perform multivariate analysis separately for each surgical method. Consistent with that study and other previous research, we determined that the rate of SIRS was higher in the PNL group than in the F-URS and SR-URS groups (12.9%, 6.3%, and 1.7%, respectively). However, unlike the literature, we found no significant difference between the patients who developed SIRS and those without this complication in terms of preoperative urine culture positivity. This may have been influenced by our preoperative urine culture management and exclusion criteria, as we previously explained. Further studies comparing different preoperative urine culture managements can clarify this situation.

The most important limitation of our study is its retrospective design, which may have caused selection bias. In addition, although there are conflicting results in the literature concerning the relationship between struvite stones and infectious complications,^4,18,19 we did not evaluate the stone composition of the patients, which can be considered an important limitation. Another limitation is that we did not assess irrigation flow rate or renal pelvis pressure, especially in patients undergoing F-URS. Furthermore, despite the use of a thicker UAS having been shown to be advantageous in preventing postoperative infectious complications,²⁰ we used only 12/14-Fr UAS; therefore, we were not able to explore the relationship between SIRS and different UAS sizes. Nevertheless, our high patient volume and evaluation of all endourological surgical methods separately are the strongest aspects of our study.

Conclusion

In this study, we determined that stone volume and operative time were independent factors predicting SIRS in all three endourological surgical methods. It is necessary to provide these patient groups with preoperative information regarding possible infectious complications. Additionally, sterile PBUC should be ensured before surgery, and the diligent follow-up of patients should be undertaken to prevent postoperative infectious complications. Further research is necessary to obtain more conclusive findings.

Footnotes

Disclosure Statement

No competing financial interests exist.

Funding Information

This research did not receive any specific grant from public, commercial, or not-for-profit sectors’ funding agencies.

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