A Cochrane review [Abstract] 1 included 9 studies with a total of 3345 women. Vaginal oestrogens vs placebo reduced the number of women with UTIs in two small studies. The RR for one was 0.25 (95% CI 0.13 to 0.50, n=93, topical vaginal cream) and 0.64 (95% CI 0.47 to 0.86, n=108, oestrogen releasing ring) in the second. Two studies compared oral antibiotics vs vaginal oestrogens (cream or pessaries), though there was very significant heterogeneity. Vaginal cream reduced the proportion of UTIs compared to antibiotics in one study and in the second study antibiotics were superior to vaginal pessaries. Adverse events were vaginal bleeding or nonphysiologic discharge for the ring and vaginal irritation, burning and itching for the cream.
A systematic review 2 evaluated different interventions to prevent recurrent episodes of urinary tract infections (UTIs) in postmenopausal women. In two RCTs vaginal estrogen was effective compared to placebo (cream p<0.001, ring p< 0.008), but appeared to be inferior to continuous oral antibiotic suppression.
A meta-analysis 3 included 8 RCTs with a total of 4702 patients (2367 with estrogen and 2335 with placebo). Compared with placebo, vaginal estrogen significantly reduced recurrent UTIs (RR 0.42; 95% CI 0.30 to 0.59; 5 trials, n=1936) but oral estrogen showed no difference (RR 1.11; 95% CI 0.92 to 1.35, 3 trials, n=2766). Adverse events (vaginal discomfort, irritation, burning, and itching) were reported with vaginal estrogen with no significance increase in the vaginal estrogen group (RR 3.06; 95% CI 0.79 to 11.90).
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment) and by imprecise results (limited study size for each comparison), and upgraded by great magnitude of effect.
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