Perioperative predictors of urinary tract infections after percutaneous nephrolithotomy

Abstract

BACKGROUND

Urinary tract infections (UTIs) are the most common postoperative complications of percutaneous nephrolithotomy (PNL). Besides the significant threat to the patient's life, they represent a surgical, financial, and stressful burden to the healthcare systems. Duration of the procedure, bacterial load in urine, severity of obstruction, and presence of infected stone directly increase the incidence of UTI.

AIM

To identify the perioperative predictors of postoperative UTIs in patients undergoing PNL in Assiut University Urology Hospital, Assiut, Egypt.

METHODS

A prospective study was conducted at Assiut University Urology Hospital, Assiut University, Egypt, involving adult patients who underwent PNL from May 2022 to March 2023 for postoperative UTI. The sample size was calculated based on the previous studies and the PNL rate in our hospital, using Thompson’s equation. Patients who had other surgical procedures besides PNL, had immunosuppression, congenital kidney malformations, or refused to participate were excluded. Patients were recruited consecutively during the study duration. The Excel sheet was used for data collection, and the Statistical Package for the Social Sciences (SPSS) program, version 26, was used for statistical analysis. The authors analyzed the preoperative, operative, and postoperative variables using both univariate and multivariate analyses. The statistical cutoff point for significance was set at P < 0.05.

RESULTS

This study included 157 patients: 96 (61.1%) males and 61 (39.9%) females. The mean ± SD (range) age was 47.37 ± 12.47 (20-65) years. The mean body mass index ± SD (range) was 24.44 ± 2.84 (16.80-33.80) kg/m². Thirty-one patients (19.7%) had postoperative UTIs. The univariate analysis revealed that the presence of a history of pyuria (P = 0.026), diabetes mellitus (P = 0.010), large stone size (P < 0.001), multiple renal punctures (P = 0.001), prolonged operative time (P = 0.004), placement of a double-J stent (P = 0.027) or nephrostomy tube (P = 0.021), higher blood transfusion rate (P = 0.024), residual stones (P = 0.002), and prolonged urethral catheterization (P = 0.001) were associated with the incidence of UTIs. The multivariate analysis demonstrated that the presence of diabetes mellitus [odds ratio (OR) = 0.15, confidence interval (CI): 1.1-4.41], stone size (OR = 2.15, CI: 0.14-1.13), and residual stone (OR = 0.16, CI: 0.03-0.93) were independent predictors for postoperative UTIs.

CONCLUSION

Thirty-one out of 157 patients experienced UTIs following PNL. The presence of diabetes mellitus, larger stone size, and residual stones were identified as independent risk factors for postoperative UTIs after PNL. We suggest conducting further research to identify factors that may aid in the early detection of post-PNL UTI risks.

Key Words: Percutaneous nephrolithotomy; Perioperative predictors; Postoperative complications; Urinary tract infections; Urolithiasis

Core Tip: Percutaneous nephrolithotomy is the preferred treatment for kidney stones larger than 2 cm. It offers faster recovery and a higher stone removal rate. However, its complication profile remains significant, including hemorrhage and urinary tract infections. The current prospective study identified factors such as diabetes mellitus, history of preoperative pyuria, large stone size, multiple punctures, long operative time, intraoperative double-J stent placement, blood transfusion, residual stones, and extended urethral catheterization as influencing the risk of post-percutaneous nephrolithotomy urinary tract infection. Nonetheless, diabetes mellitus, larger stone size, and residual stones were independent predictors.

INTRODUCTION

Percutaneous nephrolithotomy (PNL) is the standard treatment for renal stones larger than 2 cm and staghorn calculi. It is less traumatic with quicker recovery compared with open surgery. Additionally, PNL has a higher rate of stone clearance than extracorporeal shock wave lithotripsy[1,2]. However, relatively higher perioperative complication rates have also been reported, including hemorrhage, blood transfusion, thoracic complications, embolization, organ injury, and urinoma[2]. Urinary tract infections (UTIs) are one of the most common PNL complications. Despite prophylactic antimicrobial treatment before PNL, the rate of postoperative UTIs remains high. Although severe UTIs and UTI-induced septic shock are less common (0.3%-4.7%), the mortality rate from septic shock can reach as high as 50%[3]. Risk factors for UTIs after PNL include preoperative bacteriuria, stone size, and operative time. Additionally, struvite and staghorn stones may harbor various organisms, increasing the risk of systemic dissemination and infectious complications during PNL[4].

Practically, the initial stage of UTIs often lacks typical symptoms, making early detection difficult. Therefore, the treatment of severe postoperative UTI is usually not started promptly, timely, or effectively. Treating patients within the first 6 hours of infection, including effective antibacterial therapy and maintaining circulatory perfusion, can efficiently reduce the mortality rate of UTIs[5,6].

On the other hand, nurses have a vital role in detecting early postoperative complications and preventing further sequels. They should emphasize to the patient the importance of immediately reporting symptoms. Monitoring for postoperative complications should involve careful observation of the wound, dressing, and drainage tubes or catheters, as well as infection prevention[7]. Additionally, adhering to infection control and sterile technique principles helps prevent nosocomial infections in the PNL operating room. This results in a shorter hospital stay for the patient and reduced costs for medical care and hospitals[5,7].

Despite the numerous predictors studied for reducing post-PNL UTIs, the associations between them have been largely inconsistent across different studies. These inconsistencies make it difficult to establish a universal set of reliable predictors for targeted interventions. Additionally, non-standardized definitions for post-PNL UTIs, risk severity of preoperative, intraoperative, or postoperative factors, mechanisms of organism release from stones, inconsistent preventive strategies, and the impact on patients’ quality of life contribute to the current information gap in the literature of post-PNL UTIs[8]. Moreover, combining the healthcare, nursing, and surgical factors is lacking in the literature[9,10]. The current study aimed to identify the perioperative predictors for post-PNL UTIs by evaluating the correlation between preoperative, operative, and postoperative variables.

MATERIALS AND METHODS

Study design

A prospective study was conducted at Assiut University Urology Hospital, Assiut University, Egypt. This study involved adult patients who underwent PNL from May 2022 to March 2023 to study the incidence and predictors of postoperative UTI.

Sampling and sample size

The target population was patients with kidney stones who attended the urolithiasis outpatient clinic for treatment. A consecutive sampling technique was employed to recruit participants in this study. The sample size of the current study was calculated using Thompson’s equation[11]. In this equation, the total population was estimated based on the number of patients admitted to Assiut Urology University Hospital between 2021 and the present for PNL (266 patients), with a 95% confidence interval (CI), a 5% error ratio, and a property availability ratio of 0.05. The assumptions of this sample included a property availability ratio of 0.50 and a medium effect size (Cohen’s h) of 0.41. Accordingly, 157 adult patients who underwent PNL were included in the current study. Based on the postoperative incidence of UTI, the patients were categorized into two groups: Patients with postoperative UTIs and patients without postoperative UTIs.

Inclusion and exclusion criteria

This study included adult patients aged 18-65 years, of male or female gender, who had kidney stones treated by PNL. However, patients with other surgical interventions combined with PNL, failed PNL procedure or conversion to open surgery, immunosuppression diseases, kidney congenital malformations, and those who refused to participate were excluded.

Preoperative workups

All patients underwent detailed history taking for age, body mass index, gender, educational level, occupation, marital status, residence, and special habits. Additionally, physical examination and surgical fitness workups were performed. Moreover, routine laboratory investigations included urinalysis, urine culture and sensitivity tests, serum creatinine, and hemoglobin levels. Furthermore, patients were evaluated for stones using abdominal ultrasonography, plain X-ray, kidney-ureter-bladder radiography, and non-contrast computed tomography (NCCT). The stone size was estimated by NCCT, considering the largest dimension of the stone and following the general size classification as medium-sized (10-20 mm) or large-sized (> 20 mm) stones[12,13].

Operative workups

The PNL technique was performed in this study as previously described by our institute[12]. The operative data included the surgical approach (supracostal vs infracostal), number of punctures (single or multiple), site of punctures (upper calyx, middle calyx, or lower calyx), operative time, intraoperative placement of double-J stent (JJ) and nephrostomy tube (NT), and the blood transfusion rate. Indications of JJ placement included expecting large residual stones, intraoperatively discovered kidney infections, infected stones, or bleeding. This was based on a predefined policy rather than the operator’s preferences.

Postoperative workups

The postoperative workups included assessments for early postoperative care, stone clearance, incidence and management of complications, including UTI, and length of hospital stay. Kidney-ureter-bladder and ultrasonography were performed during the first postoperative day for initial evaluation. The NT was removed on the first postoperative day, and the ureteral catheter was removed on the second day, provided there were no residual stones. In the absence of fever, pain, or urine leakage, patients were discharged on the third postoperative day. JJ removal was scheduled within 30-45 days after the procedure.

In cases of residual stones > 4 mm, a second-look PNL was performed on the same admission. The NCCT was done after three months to document the stone-free status in all patients. Exceptionally, if urinary leakage, fever, or persistent renal colic occurred, NCCT was performed at these presentations as well. Complications were managed by second-look PNL or other interventions rather than PNL, and all were considered as auxiliary procedures. Hence, the auxiliary procedure was defined as any extra procedure of the same primary treatment modality or a different modality, such as ureteroscopy and JJ placement for treatment of residual stones > 4 mm or complications.

Study outcomes

The primary outcome of the study was the incidence of UTI after PNL. It was defined as a clinical and laboratory diagnosis of infected urine or collection (within or outside the lumen of the genitourinary system) within 45 days of discharge from the hospital. At our institute, the policy is to remove the JJ within 4 weeks to 6 weeks after PNL[14]. Hence, this was the rationale for defining the upper limit of the time range of post-PNL UTI as 45 days. This definition considers the time range of JJ removal after PNL[14].

Approval and registration

The ethical committee of the Faculty of Nursing approved the proposal of the project from which this study was drafted. The institutional review board approval number is No. 3750011. Additionally, the project was registered in the ClinicalTrials registry (No. NCT05852483). This study was conducted in adherence with the ethical standards of the Declaration of Helsinki and its amendments. The participants provided informed consent to participate in the study.

Statistical analysis

The authors examined the collected data for accuracy, completeness, and consistency. They reviewed the data to ensure reliability, performing a double-check of the data range, type, and fitting for analysis. The illogical values, duplicates, and formatting errors were identified and corrected, ensuring data integrity before the final submission for statistical analysis.

Data analyses were performed using the SPSS program (Statistical Package for Social Science) version 26. Data presented as numbers and percentages or mean and standard deviation. The χ² test was used to compare the qualitative variables, including age categories, sex, educational level, occupation, residence, history of previous surgery, comorbidities, preoperative hydronephrosis, categorical operative variables (approach, number, and site of punctures), blood transfusion, and presence of residual stones. However, the independent-samples t-tests were used for continuous variables such as age, body mass index, hemoglobin, and serum creatinine levels, operative time, stone size, duration of urethral catheterization, and the length of hospital stay.

Additionally, the logistic regression analysis was performed to identify perioperative predictors of UTIs after PNL, including the presence of diabetes mellitus, history of preoperative pyuria, stone size, number of punctures, placement of JJ or NT, operative time, duration of urethral catheterization, blood transfusion, and residual stones. The Shapiro-Wilk test was used to test the skewness of the data. Additionally, variable multicollinearity was checked using the Belsley-Kuh-Welsch technique because of the potential similarity between the perioperative variables. Multivariate logistic regression analysis was used to evaluate the dependent and independent prognostic predictors of UTI after PNL. P-value is considered statistically significant when P < 0.05.

RESULTS

Descriptive variables

This study included 157 patients with a mean age (range) of 47.37 ± 12.47 (20-65) years. About 40% of patients were females. The remaining sociodemographic characteristics are demonstrated in Table 1.

Table 1 Sociodemographic characteristics of the studied patients (n = 157; Assiut, Egypt, 2026).

Variables	Values are represented as mean ± SD (range)/n (%)
Age (years)	47.37 ± 12.47 (20-65)
Age categories
20-29	19 (12.1)
30-39	40 (25.5)
40-49	38 (24.2)
50-59	40 (25.5)
60-65	20 (12.7)
Body mass index (kg/m2)	24.44 ± 2.84 (16.80-33.80)
Sex
Male	96 (61.1)
Female	61 (39.9)
Educational level
High education	42 (26.8)
Secondary education	32 (20.4)
Basic	30 (19.1)
Unable to read and write	53 (33.7)
Occupation
Working	36 (23)
Not-working	121 (77)
Marital status
Single	15(9.6)
Married	138 (87.9)
Widow/widower	4 (2.5)
Residence
Urban	39 (24.8)
Rural	118 (75.2)
Current smoker	46 (29.3)

Comparative outcomes

Post-PNL UTIs were diagnosed in 31 of 157 patients (19.7%). No significant differences were found in the sociodemographic characteristics between patients with and without post-PNL UTI (Table 2). Preoperatively, patients with post-PNL UTI had a higher rate of diabetes mellitus (P = 0.026), a history of preoperative pyuria in urinalysis (P = 0.010), and larger stone sizes (P < 0.001) (Table 3). Operatively, patients with post-PNL UTI experienced significantly higher rates of multiple renal punctures (P = 0.001), residual stones (P = 0.002), placement of a JJ (P = 0.027) or NT (P = 0.021), and intraoperative blood transfusions (P = 0.024). Additionally, they had a longer average operative time (P = 0.004). Postoperatively, however, they exhibited a significantly longer duration of urethral catheterization (P = 0.001), while their hospital stay was not significantly longer (Table 4).

Table 2 Comparison of the sociodemographic characteristics in both groups (n = 157; Assiut, Egypt, 2026)¹.

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Age groups
20-29	6 (19.4)	13 (10.3)	0.642
30-39	6 (19.4)	34 (27)
40-49	9 (29)	29 (23)
50-59	5 (16.1)	35 (27.7)
60-65	5 (16.1)	15 (12)
Mean age	42.13 ± 13.9	44.91 ± 12.1	0.273
Body mass index	24 ± 2.5	24.55 ± 2.9	0.344
Sex
Male	21 (67.7)	75 (59.5)	0.400
Female	10 (32.3)	51 (40.5)
Educational level
High	7 (22.6)	35 (27.8)	0.491
Secondary	5 (16.1)	27 (21.4)
Basic	9 (29)	21 (16.7)
Unable to read and write	10 (32.3)	43 (34.1)
Occupation
Office working	6 (19.4)	30 (23.8)	0.869
Not working	25 (80.6)	96 (76.2)
Marital status
Single	4 (12.9)	11(8.7)	0.224
Married	25 (80.6)	113 (89.7)
Widow/widower	2 (6.5)	2 (1.6)
Residence
Urban	7 (22.6)	32 (25.4)	0.745
Rural	24 (77.4)	94 (74.6)
Current smoker	10 (32.3)	36 (28.6)	0.686

¹χ² test for qualitative data between two or more groups.

UTIs: Urinary tract infections.

Table 3 Comparison of the preoperative data in patients with and without urinary tract infections (n = 157; Assiut, Egypt, 2026)¹.

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Previous urological surgery
Endourology	5 (16.1)	22 (17.5)	1.000
SWL	11 (100)	0 (0.0)	0.088
Open surgery	13 (41.9)	36 (28.6)	0.150
Comorbidity
Hypertension	4 (12.9)	19 (15.1)	0.759
Diabetes mellitus	5 (16.1)	6 (4.8)	0.026
Chronic kidney disease	2 (6.5)	2 (1.6)	0.124
Preoperative laboratory investigations
History of pyuria	23 (74.2)	61 (48.4)	0.010
Hemoglobin (g/dL)	13.19 ± 2.12	12.87 ± 2.24	0.489
Serum creatinine (mg/dL)	1.11 ± 0.59	1.17 ± 0.68	0.625
Preoperative imaging findings
Stone size (cm)	2.75 ± 0.9	2.2 ± 0.59	< 0.001
Hydronephrosis	16 (51.6)	56 (44.4)	0.473

¹χ² test for qualitative data between two or more groups.

SWL: Extracorporeal shockwave lithotripsy; UTI: Urinary tract infection.

Table 4 Comparison of the operative and postoperative variables for patients with and without urinary tract infections (n = 157; Assiut, Egypt, 2026)¹.

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Approach
Infracostal	26 (83.9)	113 (89.7)	0.363
Supracostal	5 (16.1)	13 (10.3)
Number of punctures
Single	5 (16.1)	63 (50)	0.001
Multiple	26 (83.9)	63 (50)
Site of puncture
Upper calyx	4 (12.9)	11 (8.7)	0.549
Middle calyx	11 (35.5)	37 (29.4)
Lower calyx	16 (51.6)	78 (61.9)
Operation time (minutes)	172.26 ± 35.47	153.10 ± 32.38	0.004
Intraoperative instrumentation
Double-J stent	11 (35.5)	22 (17.5)	0.027
Nephrostomy tube	30 (96.8)	100 (79.4)	0.021
Blood transfusion	27 (90)	88 (69.8)	0.024
Postoperative data
Residual stones	9 (29)	11 (8.7)	0.002
Urethral catheterization duration (days)	9.06 ± 5.63	6.29 ± 3.49	0.001
Length of hospital stay (days)	5.52 ± 3.53	4.43 ± 2.88	0.074

¹χ² test for qualitative data between two or more groups.

UTI: Urinary tract infection.

Multivariate analysis

By multivariable logistic regression analysis, the presence of diabetes mellitus [odds ratio (OR) = 0.15, CI: 1.1-4.41; P = 0.019], larger stone size (OR = 2.15, CI: 0.14-1.13; P = 0.036), and a higher rate of residual stones (OR = 0.16, CI: 0.03-0.93; P = 0.041) were independent predictors of post-PNL UTI. However, the effects of a history of preoperative pyuria (OR = 0.40, CI: 0.14-1.13; P = 0.083), insertion of NT (OR = 0.14, CI: 0.02-1.3; P = 0.084), and longer duration of urethral catheterization (OR = 1.1, CI: 0.99-1.22; P = 0.062) did not reach statistical significance (Table 5).

Table 5 Multivariate logistic regression analysis for the predictors (independent variables) of urinary tract infections after percutaneous nephrolithotomy (dependent variable) (n = 157; Assiut, Egypt, 2026).

Variables	OR1	95%CI	T2	VIF3	P value
Preoperative
Diabetes mellitus	0.15	(0.14-1.13)	0.85	1.18	0.019
History of pyuria	0.40	(0.14-1.13)	0.82	1.22	0.083
Stone size	2.15	(1.1-4.41)	0.55	1.82	0.036
Operative variables
Operation time	1.01	(0.99-1.02)	0.45	2.22	0.452
Multiple renal punctures	1.15	(0.44-3.02)	0.52	1.92	0.774
Blood transfusion	0.34	(0.09-1.3)	0.90	1.11	0.133
Intraoperative double-J placement	1.74	(0.38-7.86)	0.78	1.28	0.474
Nephrostomy tube insertion	0.14	(0.02-1.3)	0.70	1.43	0.084
Postoperative variables
Duration of urethral catheterization	1.1	(0.99-1.22)	0.81	1.23	0.062
Residual stones	0.16	(0.03-0.93)	0.65	1.54	0.041

¹Some odds ratios appear counterintuitive in direction (e.g., odds ratio < 1 for diabetes mellitus and residual stones despite being described as risk factors based on their P-values). This reflects coding direction in the regression model.

²Tolerance > 0.10 confirms the model is statistically sound.

³Variance inflation factor < 5 indicates that multicollinearity is not a concern.

CI: Confidence interval; OR: Odds ratio; T: Tolerance; VIF: Variance inflation factor.

DISCUSSION

PNL is associated with less trauma, high stone removal efficiency, mild postoperative pain, less bleeding, and quick recovery. It has now become the most common surgical method for treating upper urinary tract stones. However, UTIs are among the most common complications of PNL[15-17]. In the current study, the comparisons between patients with UTIs and the remaining cohort showed that the former had higher rates of diabetes mellitus, a history of preoperative pyuria, larger stone sizes, longer operative time, multiple punctures, placement of urinary tubes, blood transfusion, longer urethral catheterization, and hospital stay. Furthermore, many variables were reported as independent predictors of post-PNL UTI, including diabetes mellitus, larger stone size, and a higher rate of residual stones.

The current study revealed a statistically significant difference between the two groups in the history of pus cells in preoperative urinalysis. This finding was in agreement with previous studies[2,8,18], which reported a higher rate of post-PNL UTI in patients with positive vs negative urine cultures. Additionally, results of the current investigation suggest that the risk of post-PNL UTI in patients with a history of positive urine culture depends on the specific microorganisms found in their urine. Specifically, postoperative UTIs were reported in 9.7%-14.5% of patients with Gram-positive organisms and in 19.4%-23.8% of patients with Gram-negative organisms[8,18].

Additionally, the current results showed that the presence of diabetes mellitus was a risk factor for post-PNL UTI. The current finding was similar to that of Wong et al[19], who reported that diabetes mellitus is a predisposing factor for postoperative complications, such as infections and poor wound healing. Diabetes mellitus has been reported as a major risk factor for post-PNL UTI in several studies and meta-analyses[2,20,21]. It predisposes patients to infections due to biological alterations in the immunological cascades, which reduce the body’s ability to eliminate pathogens[22].

Moreover, the present study found that increasing stone size increases the risk of post-PNL UTI. This finding is consistent with previous studies[18,23,24]. Stones of a larger size can lead to urinary tract obstruction and increase the intracavity pressure above the obstruction. Additionally, large stones increase the difficulty of surgical procedures, prolong the operative time, and increase the risk of obstruction during and after the surgery. This may increase the likelihood of retrograde infections during surgical interventions[18,21].

Our results showed a statistically significant difference between the two groups regarding the number of punctures. This finding aligns with previous research reporting that multiple punctures can increase the potential of introducing more organisms into the system, raising the risk of septic complications[25,26]. The average number of punctures was higher in patients who experienced febrile complications. However, these findings contrast with other studies, which report that developing infectious complications after PNL is not related to having multiple punctures[27]. The current study demonstrated that the number of punctures increases the risk of post-PNL UTIs. These discrepancies may be due to differences in the studied populations, definitions of post-PNL UTI, and variables involved in these studies[3,21].

The current study showed that the prolonged operative time increased the risk of postoperative UTIs. This finding was consistent with Yang et al[28], who reported that the incidence of postoperative infections was higher in patients with longer operative times. Among patients with septic shock, the proportion of women and patients with longer operation times was larger. Lengthy operative time has been reported as an independent risk factor for infection after PNL[2,28].

The present study revealed statistically significant differences between the two groups regarding the intraoperative insertion of JJ and NT. These findings are consistent with the previous studies[8,21,29]. They reported a crucial role of these urinary catheters in post-PNL UTIs, as they can lead to acute pyelonephritis. Additionally, Scotland et al[30] reported that the incidence of UTIs related to ureteral stents ranged as 11%-45%, with a 50% mortality rate from sepsis. The urinary catheters predispose patients to UTIs by disrupting the natural valve-like action of the intramural ureter and by forming adhesive membranes on their surfaces[31-34].

Based on the current multivariate analysis, the presence of residual stones was an independent risk factor for postoperative UTIs. Similar to our finding, Degirmenci et al[35] found that the fragments remaining after PNL in large and complex stones may contain bacteria and endotoxins that reach the blood vessels through the damaged endothelium, resulting in the dissemination of microorganisms and eventually infectious complications. However, Erdil et al[27] found an insignificant association between residual stones and post-PNL UTIs. Practically, residual stone fragments may cause persistent UTIs by urinary tract obstruction or stone-adherent organisms. The residual fragments from patients with positive preoperative and intraoperative cultures may act as foci of infection. Then, they contribute to the development of postoperative infectious complications[21,35].

The current study revealed a statistically significant difference between the two groups in the duration of urethral catheterization. Our finding was consistent with Bozarth et al[36], who found that the longer the duration of urethral catheterization, the higher the catheter-associated UTI rate. This association is due to the prolonged use of urinary catheters, which disrupts the normal environment of the urethra. The immune system weakens phagocytosis of neutrophils, which affects the physiological role of the bladder in resisting bacteria, making it easier for bacteria to enter the bladder and ureter, resulting in UTI[36,37].

Studying the risk factors of post-PNL UTIs aims to reach consensus on the key factors. The overall outcomes should demonstrate the positive healthcare benefits in nursing practice and infection control measures throughout the operative and postoperative phases[14]. Nursing-related factors for preventing post-PNL UTIs include educating patients to recognize early signs of infection, proper catheter care, adherence to medications, and timely communication with healthcare providers[7,9]. However, we acknowledge that the large number of factors analyzed in the current study limited the combined study of the nursing-related factors.

Despite the current trial gathering the potential perioperative factors to reduce post-PNL UTI rates, there is a need for large-scale, randomized, and comparative studies to reach a stronger conclusion and solid consensus on the predictors of post-PNL UTIs[10]. Additionally, combined study designs for medical, surgical, and nursing-related factors can enhance the implementation of an enhanced recovery protocol after PNL[14]. Moreover, defining the factors responsible for the early detection of post-PNL UTIs may optimize the outcomes of intervention strategies for preventing post-PNL UTIs[20].

CONCLUSION

Thirty-one out of 157 patients experienced post-PNL UTIs within 45 days. UTIs are more common in patients with diabetes mellitus, preoperative history of pyuria, large stone size, multiple punctures, long operative time, intraoperative JJ or NT placement, blood transfusion, residual stones, and long duration of urethral catheterization. Among all these factors, only the existence of diabetes mellitus, larger stone size, and a higher rate of residual stones were independent predictors of post-PNL UTI. Certainly, identifying preoperative predictors may help prevent their role in post-PNL UTIs. Implementation of the enhanced recovery protocols is recommended. Additionally, a more detailed analysis of variables, such as the relationship between the intraoperative blood loss and duration of postoperative bleeding, is recommended. Also, studying the effects of the duration of removal of the JJ and NT is recommended. Furthermore, large-scale and randomized studies are recommended to establish a consensus on the major predictors of post-PNL UTIs, shorten the length of hospital stay, and reduce hospital readmission rates. As a result, patients’ outcomes can be remarkably improved, saving hospital resources.