Patients with infected obstructed stones require urgent urinary drainage and appropriate antibiotic treatment to prevent 
urosepsis. Appropriate antibiotic treatment is determined by U/C derived from mid-urinary stream after empiric preoperative antibiotic treatment. In patients with 
completely obstructive stones, voided urine may not indicate the source of sepsis. In this study, we compared renal pelvis urine cultures (RPUC) to mid urinary 
stream culture (MUSC) in patients urgently stented for infected obstructing stones in our institution.

From 2018 to 2020, in patients who needed urgent stent placement, we obtained RPUC in addition to MSUC via a 6 Fr open-ended ureteral catheter 
passed proximal to the obstructing stone. We evaluated multiple variables including MSU and RPU analysis and culture, blood cultures ( BC), reason for 
stenting, stone size, operative time, length of admission, readmission rates, preoperative antibiotics susceptibility, and patients’ outcome.

From 2018 to 2020, 263 patients were urgently stented for urolithiasis , and 153 had possible UTI . In 112 of these 153 patients (73.2%), a RPUC was 
obtained in addition to a standard MUSC – this was our study group (SG).In our study group, RPUC were positive in 55 (49%) and U/C was positive in 41% (P= 
0.26). In SG, 26 patients (23.2%) had positive RPUC despite negative MUSC. In 29 patients both RPUC and MUSC were positive, with discording pathogens in 4 
samples (3.6%). Therefore RPUC identified bacteria, not found in MUSC in both of these groups (26.8%). In addition 15 patients (13%) had positive U/C and 
negative RPUC. Blood culture obtained in 88 patients and was positive in 34 (39%). Twenty of these 34 patients had positive RPUC, and with a 95% (19/20) 
concordance of pathogen growth between two cultures. The average operative time for the study group was 17.5 minute, compared to 18.8 minute for the patient 
with no RPU sampling with no statistically significant difference. Antibiotic susceptibility profiles were available for 53 patients. Empiric preoperative antibiotics 
were ineffective for the RPUC in 30.2% (16/53).

Sampling of urine from renal pelvis and sending for culture, adds valuable information which can save patients lives,  particularly  if  the bacteria in urine is resistant to empiric therapy selected  for stenting.

CONCLUSIONS: Renal pelvis urine culture identified pathogens not found in MSUC in 26.8 % of patients with infected obstructed stones. There was 30.2% 
resistance rate of RPU bacteria to empiric preoperative antibiotics and 95 % correlation of RPUC with blood culture in our patients. Based on our findings, we 
recommend renal pelvis urine sampling and culture in all patients with obstructed infected stones undergoing urgent stenting.