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).