9.1 Introduction and Mechanism of Action

After menopause, oestrogen levels within a women’s body decrease. The vagina is normally colonised with Lactobacillus, a type of “good bacteria”, and their levels are maintained by oestrogen. Lactobacillus creates lactic acid, thus producing an acidic microenvironment within the vagina, protecting against harmful uropathogens from colonising. The loss of this oestrogen stimulation decreases the levels of lactobacillus within the vaginal wall epithelium, and thus the usual low pH acidic environment is lost, increasing the risk of UTIs in post-menopausal women.

Oestrogen replacement therapies are well established in treating menopausal and vaginal atrophy symptoms including dryness and dyspareunia (painful sexual intercourse) and systemic symptoms such as significant hot flushes. Their administration via the vaginal route has been shown both in cream and in ring pessary form to be effective at increasing blood oestrogen levels and combating menopausal symptoms.

9.2 Clinical Evidence

Their use in UTI prevention was reviewed in 2008 by a Cochrane study involving 3345 women. When comparing vaginal oestrogen and placebo, the authors reported vaginal oestrogen was effective at preventing recurrent UTIs, with a risk reduction of between 0.25 (95% CI 0.13–0.50) and 0.64 (95% CI 0.47–0.86) [1].

Preparations vary and often are dependent on clinician preference. Vaginal oestrogen can be applied in cream form (0.5 mg oestriol nightly for 2 weeks followed by twice a week for 8 months or even tablet form, such as Vagifem 1 tablet daily for 2 weeks, then 1 tablet twice a week) or as a pessary (a 12 weekly vaginal ring).

Side effects of vaginal oestrogen usage were mainly vaginal irritation (reported in 6–20% of women). Other side effects reported were breast tenderness, non-physiological discharge, burning and vaginal bleeding or spotting [2, 3].

Vaginal oestrogen replacement is currently recommended by both UK and EAU guidelines as a possible therapy in preventing UTI recurrences.

9.3 Oral Oestrogen

Until the late 1990s, oral oestrogen replacement (hormone replacement therapy) was the normal course of treatment for menopausal symptoms. However, later studies showed that this may actual cause more harm than good in patients, especially due to the significant side effects of high levels of oestrogen in the blood. These include higher risk of thromboembolic events (blood clots in legs, heart, lungs, etc.) and cancer.

Women in particular with underlying breast cancer or previous thromboembolic events should not be given oral oestrogen therapy due to increased risk of disease recurrence [4].

The above Cochrane review found that oral oestrogens did not reduce the risk of recurrent UTIs when used. Thus oral oestrogens are specifically NOT recommended in international guidelines in UTI prophylaxis [1].

From these findings, vaginal therapy gradually became the first line treatment and oral therapies were phased out.

Despite vaginal oestrogen replacement therapies inducing much lower (and safer) increases in blood oestrogen levels, patients with a history of breast cancer and clots often find the use of vaginal oestrogen replacement psychologically challenging.