Group comparisons
The frequencies and rates of microorganisms grown in urine cultures are presented in Table 2. The PBUC analysis revealed positivity in 25 (19.4%) patients, and the most common microorganism was identified asEscherichia coli (9.3%). According to the perioperative RPUC, 35 (27.1%) patients had growth. Pseudomonas aeruginosa (10.1%) was the most common organism identified in the RPUC analysis. When the bacteriological analysis results of RPUC and PBUC were compared, it was observed that the same organism was isolated only from seven patients (14.3%). Growth was detected in both pelvic and urinary cultures of 12 (24.5%) patients. In addition, although the urine culture of 23 (46.9%) patients was negative, growth was detected in the pelvis culture (Figure 1). Even after adequate antibiotic administration, RPUC was positive for the same organism in 26.9% of the patients.
Table 3 presents the comparison of the factors associated with a positive RPUC. A higher rate of growth was seen in the RPUC of patients with preoperative hydronephrosis (p < 0.001 ). The ureteral wall was found to be thicker in RPUC-positive patients (p < 0.001). The presence or absence of growth was evaluated according to stone localization, and the subgroup analysis revealed less growth in lower, middle and upper pole stones while multicalyceal stones had significantly more growth (p = 0.011). Increased stone size and decreased preoperative pelvic urine density (HU) were found to be associated with a positive RPUC (p < 0.001 for both).
The multivariate analysis of factors associated with a positive RPUC is given in Table 4. Possible predictive markers in predicting a positive RPUC were evaluated using the multivariate logistic regression analysis. Preoperative renal pelvis urine density (OR): 0.848, p < 0.001) , grade ≥ 2 hydronephrosis (OR:18.970, p = 0.001 ) lower calyceal localization (OR: 0.033, p = 0.017 ) were determined to be independent predictive factors fora positive RPUC. However, stone size, stone density, and a positive PBUC were not independent markers for RPUC positivity. The ability of pelvis urine density to predict positive RPUC positivity was evaluated with the receiver operating characteristics analysis, in which the area under the curve value was determined to be 0.858 (0.780-0.936). The cut-off value of pelvis urine density in predicting RPUC positivity was 4.5, at which it had 80% sensitivity and 77.7% specificity (Figure 2).