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Acute pyelonephritis — MSRA MCQ

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ModerateUrinary Tract InfectionsAcute pyelonephritisMSRA

A 39-year-old non-pregnant woman was diagnosed with acute pyelonephritis 3 days ago after presenting with fever, rigors, dysuria and right loin pain. A midstream urine sample was obtained before treatment. She was haemodynamically stable, able to take oral medication and had no drug allergies, so was started on cefalexin 500 mg three times daily. She is contacted today with the urine culture result. Escherichia coli has been isolated and is resistant to cefalexin but susceptible to co-amoxiclav and ciprofloxacin. Her fever and loin pain resolved yesterday; she is now drinking normally and has no vomiting, systemic symptoms or features of sepsis. What is the most appropriate management now?

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

Reveal the answer and explanation

Correct answer: A — Stop cefalexin and change to oral co-amoxiclav in accordance with culture susceptibility

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

This is acute pyelonephritis rather than uncomplicated lower UTI, based on the initial fever, rigors and unilateral loin pain. Although she has improved clinically, the cultured organism is resistant to cefalexin. NICE advises reviewing treatment when culture results are available and changing to a susceptible, narrow-spectrum antibiotic where possible. For acute pyelonephritis, NICE specifically notes that treatment should be changed when the organism is resistant regardless of symptomatic improvement, because renal infection requires reliably active therapy to ensure cure. Co-amoxiclav is appropriate because susceptibility is confirmed. A is incorrect because symptomatic response does not remove the need to use an active agent in pyelonephritis. B would be inappropriate for the same reason: she has had only 3 days of inactive treatment for an upper UTI. D is incorrect because nitrofurantoin does not achieve adequate renal tissue concentrations and should not be used for pyelonephritis. E is unnecessary because she is clinically improving, can take oral medication and has no sepsis, vomiting, dehydration or other feature requiring admission.

Reference: Pyelonephritis (acute): antimicrobial prescribing (NG111) — Recommendations (31 October 2018; current NICE page checked 15 August 2026) — https://www.nice.org.uk/guidance/ng111/chapter/Recommendations Pyelonephritis (acute): antimicrobial prescribing (NG111) — Summary of the evidence (31 October 2018; current NICE page checked 15 August 2026) — https://www.nice.org.uk/guidance/ng111/chapter/summary-of-the-evidence