Midstream Urine Culture Had a Higher Predictive Value of Post-PNL SIRS in Patients Without Upper Urinary Tract Obstruction

Introduction: Systemic inflammatory response syndrome (SIRS) is a common complication of percutaneous nephrolithotomy (PNL). Midstream urine culture (MUC) is reported to be associated with postoperative SIRS, but this correlation is uncertain, as MUC may not represent infection of obstructed urine in patients with upper urinary tract obstruction (UUTO). Instead, for patients without UUTO, positive MUC may be an indicator of intrarenal infection. The aim of this study was to investigate whether MUC had a higher predictive value in patients without UUTO. Materials and Methods The data of 175 patients who underwent PNL between September 2015 and June 2016 were retrospectively reviewed. Preoperative and intraoperative factors including MUC were collected and analyzed. The primary endpoint was development of SIRS. Subgroup analysis according to the presence of UUTO was conducted. Results Generally, patients who suffered SIRS had a higher incidence of positive MUC (56%[25/45] vs. 32%[41/130], p=0.005). Subgroup analysis showed that among patients without UUTO, positive MUC (75%[13/17] vs. 33%[13/39], p=0.003) was still associated with development of SIRS. Among patients with UUTO, however, there was no obvious correlation between positive MUC and SIRS. Multivariate analysis controlling for age, previous ipsilateral kidney surgery, multiple tracts, and blood creatinine conducted in patients without UUTO demonstrated that positive MUC (odds ratio [OR] = 6.419, 95% confidence interval [CI]: 1.424-28.942, p=0.016) was still associated with development of SIRS. The rate of positive urine culture was 37.7% (66/72), 72 isolates of 24 species were reported, including 6 patients with mixed infection and 2 patients with fungi infection. Gram-negative bacteria accounted for a large proportion of all isolates (68.1%), and Escherichia coli was the most common bacteria (34.7%). Conclusions MUC had a higher predictive value of post-PNL SIRS in patients without UUTO.