Pyelonephritis 🔥
UK guide to recognising and managing acute pyelonephritis / upper UTI in adults: NICE NG111 antibiotic pathways, MSU before antibiotics, referral criteria, and when nitrofurantoin is unsuitable.
📖 Definition & Presentation
- Acute pyelonephritis is infection of one or both kidneys, usually from bacteria ascending from the bladder.
- Typical features: flank/loin pain, fever, rigors, nausea or vomiting. Tenderness over the kidney may be present.
- Lower UTI symptoms (dysuria, frequency, urgency) may coexist but are not required for the diagnosis.
- Usual pathogens are Enterobacterales (commonly E. coli).
- This topic follows NICE NG111 for people without a catheter. Catheter-associated UTI needs a separate local pathway.
- People at higher risk of complications include those with known or suspected structural or functional genitourinary abnormality, diabetes, or immunosuppression.
🚨 Red Flags — Refer / Escalate
- Aged 16 years and over with symptoms or signs of a more serious illness (for example sepsis): refer to hospital / follow Trust sepsis pathway.
- Significantly dehydrated or unable to take oral fluids and medicines: consider hospital referral or specialist advice.
- Pregnancy: consider referral or specialist advice.
- Higher risk of complications (structural/functional GU abnormality, diabetes, immunosuppression): consider referral or specialist advice.
- Child or young person under 16 years: refer to hospital in line with NICE UTI in under 16s (and fever in under 5s if applicable).
- Inpatients: escalate for IV antibiotics, imaging, or urology if obstructed, septic, or not improving.
🔍 Assessment & Investigations
- Aged 16 and over: send MSU for culture and susceptibility before antibiotics are taken.
- Take account of previous urine culture results and recent antibiotic use when choosing empirical therapy.
- Vitals, NEWS2, and sepsis screen if systemically unwell (see Sepsis).
- Examine for loin tenderness, abdominal guarding, bladder fullness, and genital findings if relevant.
- Pregnancy test in people of childbearing potential.
- Bloods if unwell or admitted: FBC, U&E, CRP; lactate if sepsis suspected. Blood cultures if febrile/septic.
- Consider renal tract imaging (for example ultrasound) if obstruction, stones, abscess, or atypical course suspected; follow local protocol.
💊 Antibiotics — Non-pregnant adults 16+ oral (NICE NG111)
- Give oral antibiotics first line if the person can take oral medicines and severity does not require IV therapy.
- Confirm Trust AMS and local resistance data. See BNF for hepatic/renal impairment, pregnancy, and breastfeeding.
- Nitrofurantoin is NOT suitable in pyelonephritis (inadequate tissue levels).
- Co-amoxiclav and trimethoprim are first-choice oral options only when culture results are available and the isolate is susceptible.
- Ciprofloxacin only if other first-choice antibiotics are unsuitable. Follow MHRA fluoroquinolone restrictions (disabling and potentially long-lasting adverse effects).
- When culture results return, review choice and narrow spectrum if the bacteria are resistant to the current agent.
💊 Antibiotics — Non-pregnant adults 16+ IV (NICE NG111)
- Use IV antibiotics if vomiting, unable to take oral antibiotics, or severely unwell.
- Antibiotics may be combined if susceptibility or sepsis is a concern. Confirm Trust AMS / microbiology.
- Review IV antibiotics by 48 hours and step down to oral where possible.
- Second-choice IV antibiotics: consult local microbiologist.
💊 Antibiotics — Pregnancy (NICE NG111)
- For pregnant women aged 12 years and over. Prefer specialist / obstetric advice when unwell or unable to take oral therapy.
- Second-choice agents, or combining antibiotics if susceptibility or sepsis is a concern: consult local microbiologist.
- Review IV antibiotics by 48 hours and step down to oral where possible.
🔁 Reassessment & Follow-up
- Reassess if symptoms worsen at any time, or do not start to improve within 48 hours of taking the antibiotic.
- Consider alternative diagnoses, sepsis, and resistant organisms from previous antibiotic exposure.
- Address predisposing factors: stones, obstruction, incomplete emptying, catheter use, diabetes control.
- Document antibiotic start time, MSU sent, allergies, pregnancy status, and safety-net advice on discharge.
🩹 Supportive Care & Patient Advice
- Advise adequate oral fluids to avoid dehydration if able to drink.
- Paracetamol for pain; a low-dose weak opioid (for example codeine) may be added for people over 12 years if appropriate.
- Advise possible antibiotic adverse effects (particularly diarrhoea and nausea). Nausea with vomiting can also indicate worsening pyelonephritis.
- Seek medical help if symptoms worsen at any time, do not start to improve within 48 hours, or the person becomes systemically very unwell.
- Complete the full antibiotic course even if feeling better.
- Switch IV to oral when improving: see antibiotic IV-to-PO for inpatients.
Related NICE guidance
NICENICE NG111 — Pyelonephritis (acute): antimicrobial prescribing
Full guidance on nice.org.uk. BetterCall is not endorsed by NICE.
External resources
Note Template
Ready-to-use clinical note structure
🕒 08 / 10 / 2026 — 16:06 ATRP re: acute pyelonephritis / upper UTI Patient: [age] [sex] Admission Dx: [reason for admission] PMHx: [diabetes, structural/functional GU abnormality, immunosuppression, recurrent UTI, stones] 🧾 Hx: • Onset: flank/loin pain, fever, rigors, nausea/vomiting • Lower UTI symptoms: dysuria, frequency, urgency [Y/N] • Prior urine cultures / recent antibiotics • Catheter / obstruction risk / pregnancy: [Y/N] • Allergies: penicillin [Y/N — severity] fluoroquinolone [Y/N] 🩺 Exam: • Vitals: HR __ BP __ Temp __ NEWS __ • Loin tenderness / guarding: [side] • Hydration / able to take oral fluids and medicines: [Y/N] • Sepsis screen: [indicated / not] 🔬 Investigations: • MSU for C&S before antibiotics: [sent] • Bloods: FBC, U&E, CRP, lactate [if unwell] • Blood cultures: [if febrile/septic] • Pregnancy test: [result / N/A] • Imaging: [USS / CT / not indicated] 📋 Impression: Acute pyelonephritis / upper UTI — [community oral suitable / needs hospital / septic] 📌 Plan: • Antibiotics per HSE acute pyelonephritis v2.1: [cefalexin / ciprofloxacin / co-amoxiclav / trimethoprim if susceptible / local IV protocol] • Fluids, analgesia (paracetamol; avoid NSAIDs unless advised) • Review culture results; escalate if no response within 24 h • Referrals: [urology / microbiology / renal — or none] • Safety-netting: unable to drink, worsening systemic symptoms, pregnancy concerns 👤 [Your Name], [Role] IMC: _______
Educational reference only. Medical disclaimer