Abstract: We included 20 RCTs and two quasi-RCTs with 7711 participants, all of which compared antibiotic prophylaxis with placebo or no treatment control. We found no studies comparing antibiotic prophylaxis with non-antibiotic prophylaxis. Primary outcomes Systemic UTI: antibiotic prophylaxis may have little or no effect on the risk of systemic UTI compared with placebo or no treatment (risk ratio (RR) 1.12, 95% confidence interval (CI) 0.38 to 3.32; 5 RCTs; 504 participants; low-quality evidence); this corresponds to two more people (95% CI 12 fewer to 46 more) per 1000 people developing a systemic UTI. We downgraded the quality of the evidence for study limitations and imprecision. Symptomatic UTI: antibiotic prophylaxis may reduce the risk of symptomatic UTI (RR 0.49, 95% CI 0.28 to 0.86; 11 RCTs; 5441 participants; low-quality evidence); this corresponds to 30 fewer people (95% CI 42 fewer to 8 fewer) per 1000 people developing a symptomatic UTI when provided with antibiotic prophylaxis. We downgraded the quality of the evidence for study limitations and potential publication bias. Serious adverse events: the studies reported no serious adverse events in either the intervention group or control group and no effect size could be calculated. Antibiotic prophylaxis may have little or no effect on serious adverse events (4 RCTs, 630 participants; very low-quality evidence), but we are very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision. Secondary outcomes Minor adverse events: prophylactic antibiotics may have little or no effect on minor adverse events when compared with placebo or no treatment (RR 2.82, 95% CI 0.54 to 14.80; 4 RCTs; 630 participants; low-quality evidence). We downgraded the quality of the evidence for study limitations and imprecision. Localized UTI: prophylactic antibiotics may have little or no effect on the risk of localized UTI (RR 1.0, 95% CI 0.06 to 15.77; 1 RCT; 200 participants; very low-quality evidence), but we were very uncertain of this finding. We downgraded the quality of the evidence for study limitations and very serious imprecision. Bacterial resistance: prophylactic antibiotics may increase bacterial resistance (RR 1.73, 95% CI 1.04 to 2.87; 38 participants; 2 RCTs; very low-quality evidence), but we were uncertain of this finding. We downgraded the quality of the evidence for study limitations, indirectness, and imprecision. We were able to perform few secondary analyses; these did not suggest any subgroup effects. Antibiotic prophylaxis may reduce the risk of symptomatic UTI but not systemic UTIs. Serious and minor adverse events may not be increased with the use of antibiotic prophylaxis. The findings are informed by low- and very low-quality evidence ratings for all outcomes.

Plain-language summary: We found 22 studies with 7711 participants. These studies were published from 1971 to 2017. In these studies, chance decided whether people received an antibiotic or a placebo/no treatment. The evidence is current to 4 February 2019. Antibiotics given for UTI prevention before cystoscopy may have had little or no effect on the risk of developing a more serious infection that went into the bloodstream. They may have reduced the risk of infection when both serious infection that went into the bloodstream and infections limited to the bladder were taken together. None of the people included in the trials had serious unwanted effects. Therefore, we concluded that antibiotics given for prevention of UTIs may not cause serious unwanted effects but we are very uncertain of this finding. Antibiotics may also have had little or no effect on minor unwanted effects. They may also have had little or no effect on infections limited to the bladder taken alone, but we were very uncertain of this finding. People treated with antibiotics may have been more likely to have bacteria that were more resistant to antibiotics, but we are very uncertain of this finding. We rated the quality of the evidence as low or very low meaning that our confidence in the results was limited or very limited. The true effect of antibiotics for prevention of UTIs before cystoscopy may be quite different from what this review found.