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Recurrent uncomplicated lower urinary tract infection — MSRA MCQ

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HardUrinary Tract InfectionsRecurrent uncomplicated lower urinary tract infectionMSRA

A 63-year-old postmenopausal woman is reviewed 2 weeks after completing culture-directed treatment for her fourth uncomplicated lower UTI in 12 months. She is now asymptomatic. Each episode was culture-confirmed Escherichia coli cystitis, with no fever, loin pain, vomiting, renal stones, catheter use or urinary tract abnormality. Renal tract ultrasonography was normal. Her infections have no relationship to sexual intercourse. Increased fluid intake, avoidance of delayed voiding and a 6-month trial of vaginal oestrogen have not reduced recurrence. She wishes to avoid long-term antibiotics. Her eGFR is 34 mL/minute/1.73 m², liver function is normal, and she has no gout, metabolic acidosis or sulfonamide treatment. She uses over-the-counter potassium citrate sachets most days because she believes they prevent urinary infections. What is the most appropriate prophylactic management now?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Stop potassium citrate sachets and start methenamine hippurate 1 g twice daily, with review within 6 months

Explanation lettering: B = shown as A · C = shown as B · A = shown as C · E = shown as D · D = shown as E

She is an appropriate candidate for methenamine hippurate: she is a non-pregnant woman with recurrent uncomplicated lower UTI, her current infection has been treated, and behavioural measures plus vaginal oestrogen have been ineffective. Single-dose antibiotic prophylaxis is not applicable because there is no identifiable trigger. NICE recommends considering methenamine hippurate as an alternative to daily antibiotic prophylaxis in this setting, at 1 g twice daily, and reviewing it within 6 months. The decisive additional issue is her potassium citrate use. Methenamine requires acidic urine to generate its antibacterial effect; alkalinising sachets reduce effectiveness. NICE specifically advises against potassium or sodium citrate UTI-relief sachets while taking methenamine, and the SmPC states that concurrent potassium citrate should not be used. Her eGFR of 34 mL/minute/1.73 m² does not itself preclude methenamine: the SmPC contraindicates severe renal failure below 10 mL/minute/1.73 m². A fails because citrate undermines methenamine. C is a reasonable later alternative if methenamine is ineffective or unsuitable, but is not preferred where an effective antibiotic-sparing option is appropriate. D is unsuitable without a sexual trigger. E incorrectly applies the renal threshold used for nitrofurantoin prophylaxis rather than methenamine.

Reference: Urinary tract infection (recurrent): antimicrobial prescribing — Recommendations (Last updated 12 December 2024) — https://www.nice.org.uk/guidance/ng112/chapter/recommendations Urinary tract infection (recurrent): antimicrobial prescribing — Methenamine hippurate (Last updated 12 December 2024) — https://www.nice.org.uk/guidance/ng112/chapter/Recommendations Hiprex 1 g Tablets — Summary of Product Characteristics (Updated 15 October 2025) — https://www.medicines.org.uk/emc/product/1530/smpc