Randomized trial of antibiotic prophylaxis for combined urodynamics and cystourethroscopy

To determine the efficacy of prophylactic nitrofurantoin in preventing bacteriuria after urodynamics and cystourethroscopy.

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.

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.

Bacteriuria after combined urodynamics and cystourethroscopy was not improved by a 1-day course of nitrofurantoin.