## 3 Results  
Figure 1 shows the incidence of ureteric stones and sepsis or APN by region in the United States. The incidence of sepsis or APN due to ureteric stones was 5-6% in most regions, with the highest in the pacific region at 7.21% and the lowest in the east-south region at 4.52%.  
Table 1 lists demographic patient characteristics. A total of 467,502 patients diagnosed with ureteral calculi, from a total of 1,713,248 patients with urinary stones, were treated from January 2003 to December 2017. Of these, 25,747 were diagnosed with sepsis or APN for an overall incidence of 5.51%. Ureteral calculi without sepsis or APN were common in men (64.38%), but ureteral calculi with sepsis or APN were more common in women (67.13%). There was a significant difference in the age between the nonsepsis or APN group and sepsis or APN group (50.5 vs. 56.8 years).  
Figure 1: Current status of ureteral calculi and sepsis or APN by region in the United States for 15 years.  
A total of 108,993 patients underwent surgical decompression, accounting for 23.31% of all ureteral calculi cases. A total of 97,890 patients (22.15%) with ureteral calculi without sepsis or APN and 11,103 patients (43.12%) with ureteral calculi with sepsis or APN underwent surgical decompression. Surgical decompression via retrograde double J stent insertion (22.03%, 42.62%) was more commonly performed than percutaneous nephrostomy (0.23%, 0.73%) in both groups.  
Patients with ureteral calculi were divided into the non-sepsis or APN group and sepsis or APN group. Risk factors (e.g., ischemic heart diseases, hypertension, diabetes mellitus, stroke, Alzheimer's disease, chronic kidney disease, chronic lower respiratory diseases, obesity, cancer, history of urinary tract infection (UTI), and history of uroilithiasis) were analyzed. All risk factors were found to be significant predictors of sepsis in this initial analysis.  
Table 2 shows a univariate analysis of patients after matching the cohorts by age by a 2:1 propensity score matching analysis. After correcting for age, all assessed risk factors were significant. History of UTI was present in 44.88% of patients with sepsis or APN but present in only 5.05% of patients without sepsis or APN.  
Table 3 demonstrates the multivariate analysis of risk factors significantly associated with sepsis or APN. The multivariate analysis using conditional logistic regression for the age-matched data revealed that history of UTI (OR 11.21, 95% CI 10.58-11.88, \(p<0.0001\)) and female sex (OR 2.74, 95% CI 2.63-28.5, \(p<0.0001\)) were associated with a higher risk of sepsis and APN. However, history of prior urinary stone disease (OR 0.89, 95% CI 0.86-0.93, \(p<0.0001\)) and history of cancer (OR 0.93, 95% CI 0.89-0.97, \(p=0.0008\)) were associated with decreased risk of sepsis and APN. Comorbidities, including a history of UTI, female sex, chronic kidney disease, Alzheimer's disease, stroke, diabetes mellitus,  
respiratory diseases, hypertension, overweightness and obesity, and age (in decreasing order of the size of the point estimate) were all associated with a higher risk of sepsis and APN. When more than one comorbidity was present, there was an additive effect with higher OR point estimates, rising to 11.31 (10.68-11.99) when three or more comorbidities were present.