Background: No official definition, but generally defined by most people as two or more episodes in six months or three or more per year. The only recommended prophylactic treatment currently is low-dose prophylactic antibiotics, which, based on one systematic review/meta-analysis, has a very good success rate with a NNT of 1.85 over a 6 – 12 month period (though unfortunately the studies on which this was based seem to have been of poor quality). The problem, of course, is our old bugbear of antibiotic resistance. This BMJ article discusses other methods.
Short version: Currently we don’t have much evidence to say that anything else works for prophylaxis. However, methenamine hippurate is looking promising, and topical vaginal oestrogens are probably helpful in post-menopausal women.
Methods discussed were:
Urinary alkalisation: No evidence as to whether or not it works because, in a recent review, none of 172 RCTs of the matter were good enough quality to include, which is a pretty scary comment on the state of our medical research today. Side-effects include nausea, flatulence, and mild diuresis. In practice, probably comes under the heading of ‘Might be worth a try’, but isn’t anything we can medically vouch for at this point.
Probiotics: Don’t seem to help, according to a recent Cochrane review, but again we have the problem of all the research being fairly poor quality, which means there may possibly be benefits that have been missed. Side-effects showed up in <5% of the women and included vaginal discharge, genital irritation, and diarrhoea. I’d file this as ‘Can’t hurt, but don’t expect too much’.
Chinese herbal medicine: Does seem to work according to a Cochrane review, but, again, problems with poor research; also, the existing research seems to have been in post-menopausal women and won’t necessarily apply to the pre-menopausal population. Not much work done on side-effects and, unfortunately, Chinese herbal medicine does have more potential for harm than the two above methods, so this is not one I’d recommend unless a lot more work gets done.
Methenamine hippurate: One trial of 30 people with recurrent UTI found this to be associated with a relative risk of UTI of 0.46, and several studies have found very low rates of adverse events; out of 2032 people in all studies in one Cochrane review, twelve had nausea, one had rash, one had diarrhoea, one had sore throat, and one had bladder ‘stinging’. Therefore, while there is not currently enough evidence to say this works, there is enough to be cautiously optimistic. Results of an ongoing multicentre RCT are awaited. Watch this space.
Cranberry juice: Seems, alas, to have been discredited; previous studies that showed benefits had a high dropout rate, and an updated Cochrane review did not see a statistically significant benefit. Another one bites the dust.
Oral immunostimulants: I’m not even sure what these are. Whatever they are, a meta-analysis of four RCTs found they helped, a further double-blind RCT found no effect, and the European Association of Urology supports their use, so overall it sounds as though they’re worth finding out about.
Topical vaginal oestrogen: In post-menopausal women, obviously. An analysis of two small RCTs did find a benefit, with a minority experiencing side-effects related to either hormonal (breast tenderness, vaginal bleeding, change in discharge) or local (vaginal irritation, burning or itching) effects.
Coming soon: Research papers on intravesical agents, vaccines, and D-mannose.