Urinary tract infection: prevention, and the one that needs a doctor

Urinary tract infection splits into uncomplicated cystitis — the common bladder infection — and pyelonephritis, which is a kidney infection and a medical emergency. Prevention is where plant preparations have some evidence; treatment is where they do not.

Cranberry has the largest evidence base, and the honest summary is mixed: older pooled analyses found no significant reduction in recurrent UTI in most populations, while more recent analyses and trials in specific groups (women with recurrent UTI, and children) have found a modest reduction. The mechanism is the A-type proanthocyanidins preventing bacterial adhesion to the urothelium, which is real and well characterised. Juice needs to be unsweetened and the volume is large; capsules are more practical. Cranberry is prevention, not treatment.

D-mannose is a sugar that binds the type 1 fimbriae of E. coli and prevents adhesion, and small trials have found it comparable to low-dose antibiotic prophylaxis for recurrent UTI. The trials are small and short. It is well tolerated and does not carry antibiotic resistance.

Bearberry (uva ursi) contains arbutin, which is hydrolysed to hydroquinone and has genuine urinary antiseptic activity. It is also hepatotoxic and carcinogenic in high or prolonged use, and it should not be used for more than a week or two, in pregnancy, or in children.

What actually reduces recurrence. Adequate fluid intake — a randomised trial found that drinking more water reduced recurrent cystitis in women who drank little. Post-coital voiding. Avoiding spermicide-containing contraception, which is a genuine risk factor. Treating vaginal atrophy in postmenopausal women with topical oestrogen, which a clinician can prescribe and which reduces recurrence substantially.

When it is not a prevention question. A UTI with fever, flank pain, vomiting or feeling systemically unwell is a kidney infection. A UTI in a man, a child, a pregnant woman, or someone immunosuppressed needs prompt medical care. And a UTI with confusion in an older adult is a medical emergency.