Pyelonephritis
Fever plus loin pain is an upper urinary tract infection — and sometimes much more. Send a urine culture before antibiotics, treat according to NICE and local guidance, decide oral or IV, and image when you suspect obstruction, an abscess or failure to improve. Built for revision, not live patient decisions.
Settle them, and check the basics
how sick?Red flags — what each should make you think
If someone with pyelonephritis isn't getting better within a day or two of the right antibiotic, assume something is blocked or there is a collection, and image the kidneys. Antibiotics alone don't fix an obstructed, infected kidney.
First actions
- 🧪Urine culture
- 🩸Bloods + cultures
- ℞Antibiotics
- IVFluids
- 🤰Pregnancy test
- USSImaging if
Understand the patient
who · which antibioticAntibiotics (NICE NG111, adults 16+, not pregnant) — follow local policy
- Oral first-choice: cefalexin (7–10 days), or co-amoxiclav (only if culture-sensitive), trimethoprim (only if culture-sensitive, 14 days), or ciprofloxacin (7 days; consider safety warnings)
- IV options (severely unwell/can't take oral): amoxicillin (only if culture-sensitive) + gentamicin, co-amoxiclav, cefuroxime, ceftriaxone, ciprofloxacin, or gentamicin per local policy
- Review with culture results, switch IV to oral at 48 h if improving
- Pregnancy: oral cefalexin, or IV cefuroxime if severely unwell — admit/obstetric input
Who needs admission?
- Sepsis or significantly unwell, vomiting or unable to take oral antibiotics
- Pregnancy
- AKI, obstruction, single kidney, transplant, immunosuppression
- Failed outpatient treatment
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Known stones, colicky pain, AKI, not improving.
CT KUB / USS (hydronephrosis).
Urgent decompression + antibiotics. See the renal colic page.
Diabetic, very unwell, not responding.
CT (gas in renal parenchyma).
IV antibiotics, urology — drainage or nephrectomy.
Fever persisting despite antibiotics, flank mass.
CT with contrast.
Drainage + prolonged antibiotics.
Hypotension, high lactate, confusion.
NEWS2, lactate.
Sepsis bundle; critical care if not responding.
Investigate — what to order, when, and what it tells you
test with a question in mindUrine
Bloods
Imaging
How the plan comes together
disposition · handoverhome
Well, tolerating oral antibiotics, not pregnant, no obstruction: course per NICE, safety-net (worsening, vomiting, not improving in 48 h), check culture results.
admit
Septic, vomiting, pregnant, AKI, obstruction, or high-risk patient.
Hand over: antibiotic and time, culture sent, imaging plan.
Culture first, the right antibiotic for the right duration, and image the patient who doesn't improve. Pregnancy and stones change the plan. Nicely done getting here.
Clerking template
copy or downloadPyelonephritis — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 10 knownFrequently asked questions
quick answersWhat are the red flags for pyelonephritis?
- Sepsis, hypotension — think urosepsis
- Known stones, AKI, single kidney — think infected obstructed kidney
- Diabetic, very unwell — think emphysematous pyelonephritis
- Not improving after 24–48 h — think abscess / obstruction
- Pregnant — think admit, different antibiotics
- Male — think consider prostatitis
What is the initial management of pyelonephritis?
- Urine culture — before antibiotics
- Bloods + cultures — FBC, U&E, CRP, lactate if unwell
- Antibiotics — oral if well; IV if unwell, vomiting or septic — per NICE NG111/local policy
- Fluids — if dry or hypotensive
- Pregnancy test — women of childbearing age
- Imaging if — obstruction suspected, not improving, or recurrent
Always alongside senior support and your local guideline.
What diagnoses must you not miss in pyelonephritis?
- Infected obstructed kidney — stone + fever
- Emphysematous pyelonephritis — diabetic · gas
- Renal / perinephric abscess — persistent fever
- Urosepsis — shock
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for pyelonephritis?
- Urine — Always, before antibiotics.
- Bloods — FBC, U&E, CRP, cultures, lactate.
- Imaging — Suspected obstruction, no improvement within 24–48 h, recurrent, male, or stones.
Admit or discharge: how is the plan decided for pyelonephritis?
- Home — Well, tolerating oral antibiotics, not pregnant, no obstruction: course per NICE, safety-net (worsening, vomiting, not improving in 48 h), check culture results.
- Admit — Septic, vomiting, pregnant, AKI, obstruction, or high-risk patient.
Is there a clerking template for pyelonephritis?
Yes — there is a free clerking template for pyelonephritis on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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