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Background: Urinary tract infection (UTI) after ureteroscopy (URS) has the potential for significant patient morbidity and mortality. Evidence based guidelines for obtaining preoperative urine cultures prior to ureteroscopy are lacking as little is known about the risk factors for developing a post-URS UTI. We sought to identify those patients at particular risk for developing a post-operative UTI, hence meriting further workup.
Methods: We reviewed our prospectively maintained patient registry to identify patients that underwent ureteroscopy for renal or ureteral stones. Risk factors included: GU history (chronic UTI’s, spina bifida, CIC); structural anomalies including primary obstructing megaureter (POM), ureteropelvic junction obstruction (UPJO), vesicoureteral reflux (VUR); previous stone surgery including any ESWL, PCNL, or URS; and stone incident factors such as presence of a preoperative stent, presence of and degree of hydronephrosis on diagnostic scan. UTI was defined as a positive urine culture in a symptomatic patient in the post-operative period. Univariate analysis with Fisher’s exact test was performed to evaluate risk for developing UTI. Logistic regression was used to adjust for age and gender for each variable that was significant on univariate analysis
Results: A total of 217 patients (125 females, 92 males) underwent 298 URS in our institution from January 2004-April 2013 and were included in our analysis. A total of 26 (8.7%) UTI’s occurred post operatively. Factors that were not found to be associated with a post-operative UTI included: presence of a preoperative stent, CIC, presence of and degree of hydronephrosis on diagnostic scan, VUR, POM, UPJO, gender, pre-operative antibiotic prophylaxis, and urosepsis at the time of stone diagnosis. Table 1 lists those risk factors found to be significantly associated with post-operative UTI.

Univariate analysis
Risk factor (RF)	# of Patients w/ RF	Number of UTI’s/RF	OR (CI)	*p-value
Previous stone surgery	159/298 (53.4%)	20/159 (12.6%)	3.18 (1.18-9.98)	0.01
Chronic UTI’s	68/298 (22.8%)	14/68 (20.5%)	4.68 (1.89-11.78)	<0.001
Spina bifida	26/298 (8.7%)	9/26 (34.5%)	7.84 (2.67-22.16)	<0.001
Bladder augment	13/298 (4.4%)	5/13 (38.5%)	7.75 (1.83-28.80)	0.003
Neurogenic bladder	48/298 (16.1%)	14/48 (29.2%)	8.07 (3.18-20.91)	<0.001
Positive pre-operative culture	26/298 (8.7%)	10/26 (38.5%)	n/a	<0.001

*p-value for Fisher’s exact test for positive UTI in risk factor group compared to no UTI in post-operative period

Multivariate analysis
Risk Factor (RF)	Odds Ratio (CI)	p-value
Previous stone surgery	2.67 (1.05-7.71)	0.05
Chronic UTI’s	2.96 (1.14-7.63)	0.02
Spina bifida	4.94 (1.43-16.55)	0.01
Bladder augment	3.36 (0.66-16.92)	0.14
Neurogenic bladder	7.38 (2.51-21.78)	<0.001
Positive pre-operative culture	6.19 (1.82-20.80)	0.023

-Multivariate analysis performed to control for age, gender
Conclusion: We have identified 6 patient risk factors that were associated with an increased risk of developing post-URS UTI. In particular, previous stone surgery, chronic UTI’s, spina bifida, neurogenic bladder, and positive pre- and intra-operative urine culture were significant risk factors in multivariate analysis. Patients with these risk factors warrant specific attention, including a dedicated preoperative urine culture and appropriate pre-operative and peri-operative antibiotics to prevent infection.