Randomized trial of antibiotic prophylaxis for combined urodynamics and cystourethroscopy

OBJECTIVE: To determine the efficacy of prophylactic nitrofurantoin in preventing bacteriuria after urodynamics and cystourethroscopy. METHODS: We assumed that nitrofurantoin prophylaxis would decrease the rate of infection after urodynamics and cystourethroscopy from 19% to 5%. All women presenting for urodynamics and cystourethroscopy during a 27-month period were offered enrollment, and 142 were randomly assigned to receive two doses of long-acting nitrofurantoin 100 mg (n = 74), or two doses of placebo (n = 68). Nitrofurantoin and placebo capsules were identical, and subjects and physicians were masked to group assignment. Differences were assessed using Student t test for continuous data and chi2 analysis for dichotomous data. RESULTS: There were no statistical differences in demographic characteristics or final diagnoses between groups. Seven women (5%) who had bacteriuria on initial urine culture were not included in the final analysis. The frequency of bacteriuria in the postinstrumentation urine cultures was 6% overall, 7% in the treatment group, and 5% in the controls, a nonsignificant difference ([relative risk] 1.49, [confidence interval] 0.37, 5.95). The power of the study was 33% to detect a significant difference. CONCLUSION: Bacteriuria after combined urodynamics and cystourethroscopy was not improved by a 1-day course of nitrofurantoin.