Impact of Negative Pressure Suction on Irrigation Fluid Absorption and Postoperative Infection Risk During Flexible Ureteroscopic Lithotripsy: A Prospective Cohort Study
Conditions: Kidney Stones
Sponsor: Lanzhou University Second Hospital

Official Title: Impact of Negative Pressure Suction on Irrigation Fluid Absorption 
and Postoperative Infection Risk During Flexible Ureteroscopic Lithotripsy: A 
Prospective Cohort Study 
Date: December 1, 2025 
 
Objective:  
Based on the precise monitoring of irrigation fluid absorption during retrograde 
intrarenal surgery (RIRS) using an endoscopic surgical monitor, this study aims to 
investigate the impact of applying negative pressure suction technology during RIRS 
on the volume of irrigation fluid absorbed and the incidence of postoperative 
infections (fever, systemic inflammatory response syndrome [SIRS], and urosepsis). 
Significance: 
Currently, negative pressure suction technology is increasingly applied in RIRS. 
However, there are no international reports on whether negative pressure suction 
affects the volume of intraoperative irrigation fluid absorption. Our study will fill this 
research gap and provide robust clinical evidence for the rational application of 
negative pressure suction technology. 
Project Implementation: 
1. Study Population 
All subjects in this study will be patients with kidney stones treated at the Department 
of Urology, Lanzhou University Second Hospital, who meet both the inclusion and 
exclusion criteria. 
• Inclusion Criteria: 
1)Patients aged 18 years and older with kidney stones who meet the surgical 
indications for RIRS; 
2) Patients who have provided informed consent. 
• Exclusion Criteria: 

1) Concurrent combination with other surgical procedures, such as percutaneous 
nephrolithotomy (PCNL); 
2) Patients with malignancies, urinary tuberculosis, immune system diseases, or 
hyperthyroidism; 
3) Congenital renal anomalies, such as polycystic kidney disease or horseshoe kidney; 
4) Presence of untreated urinary tract infections; 
5) Inability to tolerate surgery due to severe cardiopulmonary dysfunction, hepatic or 
renal insufficiency, or coagulation abnormalities. 
• Withdrawal/Dropout Criteria: 
1) Surgery is not performed or is terminated early due to various reasons; 
2) Lack of valid monitoring records or missing key data; 
3) Temporary alteration of the surgical approach; 
4) Patient requests withdrawal from the study. 
2. Exposure and Outcomes 
• Exposure: Intraoperative application of negative pressure suction technology. 
• Primary Outcome: Volume of irrigation fluid absorption. 
• Secondary Outcomes: Postoperative fever (≥38°C), SIRS, urosepsis, postoperative 
pain requiring opioids, blood transfusion, renal artery embolization, Clavien-Dindo 
classification, and postoperative length of hospital stay. 
3. Study Content 
1) Effect of negative pressure suction on irrigation fluid absorption during RIRS: This 
study will establish a prospective cohort including eligible patients with kidney 
stones. By utilizing an endoscopic surgical monitor to precisely measure fluid 
absorption, we will compare the intraoperative irrigation fluid absorption between the 
exposure group (using a negative pressure suction ureteral access sheath) and the non-
exposure group (using a standard ureteral access sheath). We will analyze whether the 
negative pressure suction device can effectively reduce renal pelvic pressure, thereby 

decreasing the intravascular absorption of irrigation fluid, and evaluate its role in 
maintaining intraoperative hemodynamic balance. 
2) Correlation analysis between negative pressure suction and the risk of 
postoperative infectious complications: We will closely monitor and record infection-
related indicators in both groups postoperatively, including the incidence of 
postoperative fever (≥38°C), SIRS, and urosepsis. Through statistical analysis, we 
will explore whether the intraoperative application of negative pressure suction 
significantly reduces the risk of postoperative infectious complications by mitigating 
bacterial toxin reflux and lowering intrarenal pressure. Concurrently, combined with 
the patients’ preoperative urine culture results, we will analyze the protective efficacy 
of negative pressure suction under different infectious backgrounds. 
3) Comprehensive evaluation of the safety and recovery indicators of negative 
pressure suction following RIRS: In addition to infection indicators, we will 
systematically evaluate the impact of negative pressure suction on other postoperative 
complications and recovery metrics. Specifically, we will compare the two groups 
regarding postoperative pain severity (opioid requirement), bleeding risk (transfusion 
rate and incidence of renal artery embolization), overall complication severity 
(Clavien-Dindo classification), and postoperative length of hospital stay. This aims to 
comprehensively evaluate the clinical application value of this technology in 
enhancing surgical safety, alleviating patient suffering, and accelerating postoperative 
recovery. 
4) Subgroup analysis of populations benefiting from negative pressure suction under 
different clinical characteristics: Based on the collected cohort data, further subgroup 
analyses will be conducted according to factors such as stone size (e.g., >2cm vs. 
<2cm), stone CT value, surgical duration, or the presence of preoperative urinary tract 
infections. We will explore under which specific clinical scenarios the use of negative 
pressure suction can maximally reduce irrigation fluid absorption and lower infection 
risk, thereby providing clinicians with more precise surgical instrument selection 
strategies and individualized treatment recommendations. 
4. Data Collection 
Preoperative, intraoperative, and postoperative clinical data will be retrieved from the 
Hospital Information System (HIS) of Lanzhou University Second Hospital. 

Preoperative data include imaging and laboratory results, as well as baseline 
characteristics such as age, gender, and comorbidities. Urological CT or ultrasound 
results are collected to determine the location, size, and presence of staghorn calculi. 
Additionally, infection-related laboratory results, including white blood cell (WBC) 
count, routine urinalysis, and urine culture, will be collected. Intraoperative data 
include the surgical procedure details and duration. Postoperative data primarily 
consist of vital signs, nursing records, treatment records, postoperative laboratory and 
imaging results, and postoperative length of hospital stay. Postoperative complications 
such as fever, SIRS, urosepsis, blood transfusion, renal artery embolization, and pain 
requiring opioids will be assessed. SIRS is defined as meeting at least two of the 
following criteria: (1) Body temperature >38°C or <36°C; (2) Heart rate >90 
beats/min; (3) Respiratory rate >20 breaths/min or PaCO2 <4.3 kPa (32 mmHg); (4) 
WBC count >12×10^9/L or <4×10^9/L, or >10% immature neutrophils. 
5. Statistical Analysis 
Statistical analyses will be performed using IBM SPSS Statistics for Windows, 
Version 27.0 (IBM Corp., Armonk, NY, USA). A two-sided P-value < 0.05 will be 
considered statistically significant. Normality will be assessed using the Shapiro-Wilk 
test. Categorical variables will be presented as frequencies and percentages and 
compared using the Chi-square test or Fisher’s exact test. Continuous variables will 
be expressed as medians (interquartile ranges [IQR]) and compared using the Mann-
Whitney U test. If there are differences in baseline characteristics between the groups, 
Propensity Score Matching (PSM) will be employed to adjust for inter-group 
variables. A logistic regression model will be used to calculate the propensity score 
for each patient. Variables included in the propensity score model will consist of 
maximum stone diameter, presence of staghorn calculi, and surgical duration ≥2 
hours. Matching will be performed at a 1:1 ratio with a caliper width of 0.02 to 
maximize execution performance. The balance of variables between the groups before 
and after matching will be evaluated by comparing statistical significance. Subgroup 
analyses in the matched cohort will be based on age (<60 years vs. ≥60 years), gender 
(female vs. male), urine culture (positive vs. negative), and surgical duration (≥2 
hours vs. <2 hours). For subgroup analyses, a logistic regression model will be used to 
calculate the odds ratios (OR) and 95% confidence intervals (CI) for the primary 

outcome (postoperative fever ≥38°C), and interaction tests will be conducted across 
subgroups. 
6. Bias Control 
A comparative analysis will be conducted to determine if there are statistical 
differences in baseline data and clinical characteristics. If the baselines are consistent, 
subsequent statistical analyses will proceed directly; if inconsistent, Propensity Score 
Matching (PSM) or other statistical methods will be applied to ensure baseline 
comparability between groups before proceeding with further statistical analysis. 
7. Publication Plan 
The results of this research project may be published in medical journals. However, 
we will maintain the confidentiality of patient information as required by law. Unless 
mandated by relevant laws, patients’ personal information will not be disclosed. When 
necessary, government regulatory authorities, the hospital’s Institutional Review 
Board (IRB), and their authorized personnel may access patient records in accordance 
with regulations. 
Risks: 
This is an observational clinical study, and the patients’ routine diagnostic and 
treatment processes will not be affected by this research. The study only involves the 
collection and statistical analysis of patients’ clinical data and will not interfere with 
or influence patients’ treatment choices or processes. Therefore, this study poses no 
risk of personal injury to the patients. 
Compensation for Subjects: 
If the leakage of relevant clinical information or medical records causes related losses 
or adverse effects, and if it is related to this study, the sponsor will bear the 
corresponding responsibilities and provide financial compensation in accordance with 
relevant regulations.