Risk Factors for Postoperative Fever and Systemic Inflammatory Response Syndrome After Ureteroscopy for Stone Disease - Beyond the Abstract

With the rising prevalence of kidney stone disease worldwide, the volume of ureteroscopy for surgical stone management has also increased exponentially. Ureteroscopy is an ambulatory procedure with generally low overall complication rates ranging from 2.6%-3.5%; however, up to 6.6% of patients are seen in the emergency department (ED) postoperatively with 2.2% requiring admission. 1-4 One of the most common reasons for increased healthcare utilization following ureteroscopy is infectious complications; however, significant gaps remain in our understanding of which individuals are at highest risk of infectious complications following ureteroscopy. Defining the characteristics of those at risk is the critical first step towards reducing ED visits and readmissions, and therefore costs and burdens to patients and the healthcare system.

Prior studies have been limited to evaluating a small number of potential risk factors for infectious complications due to smaller sample sizes. In order to assess a larger number of potential risk factors, we conducted a large, retrospective cohort study of over 3000 ureteroscopy procedures performed for stone disease from 2008-2016 in our community-based health system.5 We used a combination of detailed, manual chart review and an automated data pull from our electronic health record system to assess patient, preoperative, intraoperative characteristics, and stone type. Variables were all selected a priori based on literature review and consultation with fellowship-trained endourologist. For patient characteristics, we selected age, sex, body mass index, estimated glomerular filtration rate, Charlson comorbidity index, prior urologic surgery, and prior stone surgery (ureteroscopy or percutaneous nephrolithotomy). For preoperative characteristics, we reviewed CT scans, renal ultrasounds, and plain x-rays for stone laterality, largest stone size, and stone location. We also included a preoperative urine culture, pre-stented patient status, and preoperative antibiotics. We were unable to determine the exact antibiotic regimen and length of treatment in our data, and this is an area for future study. For intraoperative characteristics, we reviewed operative reports and operating room billing records to determine the length of surgery, type of ureteroscope utilized (flexible, semirigid, or both), access sheath use, and stenting at the end of surgery.

We defined the outcome, infectious complications, as postoperative fever (temperature >100.4F) or Systemic Inflammatory Response Syndrome (SIRS) criteria plus immediate postoperative admission, hospital readmission within 7 days, or ED visit within 7 days. There are no standard definitions for post-ureteroscopy infectious complications and we chose to define the outcome in a way that would capture clinical significance. We found clinically significant postoperative fever or SIRS in 6.9% of procedures (229/3298). Of these procedures, 226 had an ED visit within 7 days and 75 were admitted to the hospital. Infectious complications tended to occur in older patients with higher body mass index, lower eGFR, and more medical complexity. Cases with increased stone complexity, positive preoperative urine cultures, pre-stented, and longer operative times were also associated with infectious complications on univariate analysis.

In building the predictive model, we entered all variables that were significant on univariate analysis into a backward elimination model to identify the most significant predictors. We found that female gender (adjusted OR 1.60, 95% CI 1.19-2.15), longer surgical time (adjusted OR 1.01, 95% CI 1.00-1.01), greater medical complexity with Charlson comorbidity index ≥2 (adjusted OR 1.86, 95%CI 1.29-2.67), and positive preoperative urine culture (adjusted OR 1.53, 95% CI 1.06-2.22) were most predictive of clinically significant infectious complications following ureteroscopy for stone disease.

Our study had notable strengths including the large cohort size which allowed for robust analysis of many predictors. We were able to accurately identify variables using a combination of data pull and meticulous chart review. Our patient population is very stable with a low out-migration rate, which we believe minimizes the chances that our outcome was underreported due to treatment at facilities outside our system. This study was conducted in a community-based practice which allows for reporting of real-world experience and outcomes.

In future work, we plan to further elucidate the role of preoperative urine cultures and antibiotics in postoperative infectious complications after ureteroscopy. As this was the one truly modifiable predictor in our study, we hope to determine whether new care processes are needed to select antibiotics, counsel specific patients, or manage the pathophysiology of certain combinations of urine bacteria and stone composition. Emerging evidence of the urinary microbiome may also play a role and requires future study.

Written by: Brant R. Fulmer, MD1; Jordan B. Southern, MD1; Marisa M. Clifton, MD1; Tullika Garg, MD, MPH1,2
1. Department of Urology, Geisinger, Danville, PA
2. Department of Epidemiology and Health Services Research, Geisinger, Danville, PA

References:
1. Turney BW, Reynard JM, Noble JG, et al: Trends in urological stone disease. BJU Int. 2011; 109: 1082–1087.
2. Mittakanti HR, Conti SL, Pao AC, et al: Unplanned Emergency Department Visits and Hospital Admissions Following Ureteroscopy: Do Ureteral Stents Make a Difference? Urology 2018; 117: 44–49.
3. Somani BK, Giusti G, Sun Y, et al: Complications associated with ureterorenoscopy (URS) related to treatment of urolithiasis: the Clinical Research Office of Endourological Society URS Global study. World J Urol 2017; 35: 675–681.
4. la Rosette de J, Denstedt J, Geavlete P, et al: The Clinical Research Office of the Endourological Society Ureteroscopy Global Study: Indications, Complications, and Outcomes in 11,885 Patients. Journal of Endourology 2014; 28: 131–139.
5. Southern JB, Higgins AM, Young AJ, et al: Risk Factors for Postoperative Fever and Systemic Inflammatory Response Syndrome After Ureteroscopy for Stone Disease. J. Endourol. 2018: end.2018.0789.

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