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Pyelonephritis

Updated Nov 3, 2026Adults, not pregnant · ED management14 sources · 7 checked in PubMed2 figuresIDSA 2025 · IDSA/ESCMID 2010

Bottom line

  • Pyelonephritis is a complicated UTI. The 2025 IDSA guideline calls a UTI complicated when signs suggest spread beyond the bladder, especially fever.1 Flank pain, costovertebral angle tenderness, chills and rigors count.2
  • Send a urine culture with susceptibilities in every patient, and narrow to a targeted drug when results return.3,1
  • Choose the empiric drug by sepsis first, then resistance risk. Avoid any class a previous urine isolate resisted, and avoid fluoroquinolones after any use in the past 12 months.1
  • Fluoroquinolone resistance is common. Across 15 US emergency departments, 22.1% of E. coli were resistant.4 Where resistance may exceed 10%, the 2010 guideline gives one IV dose of ceftriaxone 1 g before oral therapy.3
  • Short courses work. For patients who improve, give 5–7 days of a fluoroquinolone or 7 days of another effective agent, and 7 days for gram-negative bacteremia.1

First steps

  1. Recognize it. A UTI with fever, flank pain, costovertebral angle tenderness, chills or rigors has spread beyond the bladder. Treat it as a complicated UTI.1,2
  2. Screen for sepsis. The guideline uses the Sepsis-3 definition and accepts SOFA, qSOFA or SIRS to identify it. Sepsis changes the empiric choice.1
  3. Send a urine culture with susceptibilities.3
  4. Look back. Check earlier urine cultures and any fluoroquinolone in the past 12 months. Avoid drugs those point against.1
  5. Choose and give the empiric antibiotic (tables below).1,3
  6. Image selected patients: a history of stones, urine pH ≥ 7.0, or eGFR ≤ 40.5
FIG 1 · Decision flowCited
  1. UTI with fever, flank pain, CVA tenderness, chills or rigors. Treat it as a complicated UTI.1,2 Send a urine culture with susceptibilities.3
  2. Look back at earlier urine cultures and any fluoroquinolone in the past 12 months. Avoid drugs those point against.1
  3. Is there sepsis?
    Sepsis or septic shock
    Third- or fourth-generation cephalosporin, carbapenem, piperacillin-tazobactam or a fluoroquinolone.1
    With a local antibiogram from the past 12 months, aim for ≥ 90% susceptibility in shock and ≥ 80% without.1
    No sepsis
    Third- or fourth-generation cephalosporin, piperacillin-tazobactam or a fluoroquinolone, in preference to a carbapenem.1
  4. Well enough to go home on oral antibiotics?
    Yes
    Ceftriaxone 1 g IV once where fluoroquinolone resistance may exceed 10%, as it does in many US emergency departments.3,4
    Then ciprofloxacin 500 mg twice daily for 7 days or levofloxacin 750 mg daily for 5 days, unless the look-back rules them out. TMP-SMX only if the isolate is known to be susceptible; an oral beta-lactam only after IV ceftriaxone.3,1
    Not nitrofurantoin or oral fosfomycin.2 Make sure someone acts on the culture: many resistant infections are first treated with an inactive drug.6
  5. No, admitted
    Admitted: start IV therapy chosen from local resistance data, then narrow to the culture result.3,1
  6. History of stones, urine pH ≥ 7.0 or eGFR ≤ 40?
    Yes
    Image the urinary tract. Without any of the three, urgent findings such as pyonephrosis or abscess were very unlikely.5
  7. Either way
    Not improving promptly? Look for a source that needs control.1
  8. Switch to oral once improving, taking oral medication, with an effective oral drug.1
  9. Course: 5–7 days of a fluoroquinolone or 7 days of another agent, from the first effective dose; 7 days for gram-negative bacteremia. Men with suspected prostatitis may need 10–14 days.1 The 2010 guideline used 14 days for TMP-SMX.3
FIG 1Pyelonephritis in the emergency department. Drawn for this page from the IDSA 2025 and IDSA/ESCMID 2010 guidelines. Each box carries its own citations.1,3

Diagnosis and imaging

  • What makes a UTI complicated: systemic illness (fever, flank pain, chills, rigors, CVA tenderness), upper tract obstruction, kidney involvement, or an indwelling catheter, nephrostomy or ureteral stent. Diabetes, immune compromise or a urologic condition alone do not.2
  • The 2025 classification relies on what is visible at the bedside, such as vital signs and catheters, not on findings that need a urologic workup.1
  • Culture every patient. The urine culture and susceptibilities guide the switch to a targeted drug.3,1

Who needs imaging

In a prospective study of adults with febrile UTI at 8 Dutch emergency departments, a rule of any of: a history of stones, urine pH ≥ 7.0, or eGFR ≤ 40 predicted findings worth imaging for. For urgent findings (pyonephrosis or abscess), the negative predictive value was 99% in derivation (n = 346) and 100% in validation (n = 131). Positive predictive value was low (10–11%). Using the rule could have cut imaging by 40%.5

When a patient does not improve promptly on effective therapy, look for a source that needs control.1

Four contrast CT images of the abdomen, axial and coronal, showing a patchy, poorly enhancing left kidney with stranding of the surrounding fat beside a normally enhancing right kidney
FIG 2Acute left pyelonephritis on contrast CT. The left kidney (right of each image) enhances unevenly, with wedge-shaped areas of poor perfusion and stranding in the fat around it. The right kidney is normal. Top row arterial phase, bottom row portal venous phase.Hellerhoff · Wikimedia Commons · CC BY-SA 4.0

Antibiotics

SituationEmpiric choice (IDSA 2025)Strength
Sepsis or septic shockThird- or fourth-generation cephalosporin, carbapenem, piperacillin-tazobactam or fluoroquinolone, over newer agents, cefiderocol, plazomicin or older aminoglycosidesConditional, very low to moderate
No sepsisThird- or fourth-generation cephalosporin, piperacillin-tazobactam or fluoroquinolone, over carbapenems, newer agents or older aminoglycosidesConditional, very low to moderate
Earlier resistant urine isolateAvoid that drug; the most recent culture is the best guideConditional, very low
Fluoroquinolone in the past 12 monthsAvoid fluoroquinolonesConditional, very low
Sepsis, with a local antibiogram from the past 12 monthsPick a drug with ≥ 90% susceptibility in shock, ≥ 80% without shockConditional, very low
Allergy, contraindications, interactionsAccount for themGood practice

From the IDSA 2025 complicated UTI guideline.1 The guideline's dose tables were not available as text, so the doses below come from the 2010 guideline and the FDA labels.

DrugAdult doseCourseNotes
Parenteral
Ceftriaxone1 g IV once, before oral therapySingle doseWhere fluoroquinolone resistance may exceed 10%, with TMP-SMX of unknown susceptibility, or with an oral beta-lactam.3 Label: usually 1–2 g once daily, no more than 4 g a day.7
Ciprofloxacin IV400 mg IVFirst doseOptional single dose before oral ciprofloxacin.3
Oral
Ciprofloxacin500 mg twice daily7 daysGuideline regimen for outpatients.3,8 Label UTI dose: 250–500 mg every 12 hours.9
Levofloxacin750 mg once daily5 daysLabeled 5-day regimen for acute pyelonephritis. Adjust for creatinine clearance under 50 mL/min.3,10
TMP-SMX160/800 mg (1 DS tablet) twice daily14 days (2010)Only if the isolate is known to be susceptible.3,11
Oral beta-lactamsNo dose given here10–14 days (2010)Less effective than other agents. Give an IV ceftriaxone dose first.3 Short-course data are limited, and higher doses may be needed.1
Nitrofurantoin, oral fosfomycinNot for pyelonephritis—May not reach adequate levels in the kidney or blood.2

Unreviewed doses. Verify against the current label and your institution's protocol before giving anything.

Resistance in US emergency departments

  • 2013–2014, a US emergency department network, 521 adults with culture-confirmed pyelonephritis: E. coli fluoroquinolone resistance was 6.3% in uncomplicated and 19.9% in complicated cases, up to 50% at one site. ESBL production was 2.6% and 12.2%.6
  • 2018–2020, 15 US EDs, 3,779 patients with UTI: E. coli fluoroquinolone resistance was 22.1% (10.5–29.7% by site), and 7.4% of uropathogens produced ESBL.4
  • Risk factors miss many. About 37% of patients with fluoroquinolone-resistant E. coli or an ESBL organism had no documented risk factor.4 A third of ESBL infections occurred without antibiotic, healthcare or travel exposure.6
  • Inactive first drugs are common. 75.9% of ESBL and 45.3% of fluoroquinolone-resistant infections were first treated with a drug the organism resisted.6

Why TMP-SMX is not given blind: in a US outpatient trial, 18% of E. coli resisted it. Clinical cure was 83% with 14 days of TMP-SMX and 96% with 7 days of ciprofloxacin, and resistance predicted TMP-SMX failure.12

How long, and when to switch to oral

  • Improving on effective therapy: 5–7 days of a fluoroquinolone (conditional, moderate certainty) or 7 days of a non-fluoroquinolone (conditional, very low), rather than 10–14 days. Count from the first day of effective therapy.1
  • Gram-negative bacteremia from the urine: 7 days rather than 14 if improving (conditional, low).1
  • Switch IV to oral once the patient is improving, can take oral medication and has an effective oral option. This applies with bacteremia too.1
  • Men with febrile UTI and suspected acute bacterial prostatitis may benefit from 10–14 days, though evidence is lacking.1

What the trials show

  • Ciprofloxacin 7 vs 14 days (248 Swedish women, oral 500 mg twice daily): short-term cure 97% vs 96%, noninferior. No vaginal candidiasis after week 1 with 7 days, versus 5 cases with 14.8
  • Levofloxacin 750 mg for 5 days vs ciprofloxacin for 10 days (1,109 enrolled with complicated UTI or pyelonephritis): eradication 88.3% vs 86.7% in evaluable patients, noninferior.13
  • 7 vs 14 days for gram-negative bacteremia (604 inpatients, 68% urinary source, stable for 48 hours): the composite poor outcome occurred in 45.8% vs 48.3%, noninferior.14
Guidelines disagree

The 2010 guideline gives TMP-SMX for 14 days and oral beta-lactams for 10–14 days.3 The 2025 guideline suggests 7 days for any effective non-fluoroquinolone in a patient who is improving, but rates that evidence very low certainty, and notes most duration trials studied fluoroquinolones.1

Disposition

  • Home: some patients can be treated entirely with oral antibiotics as outpatients.1 In the US outpatient trial, women went home on oral antibiotics with or without a single IV first dose.12
  • Admitted: start an IV regimen chosen from local resistance data, then adjust to susceptibilities.3
  • Before discharge, make sure the culture result will reach someone who can change the drug.3,6
  • Return if not improving. Prompt failure should trigger a search for a source that needs control.1

Neither guideline gives explicit admission criteria. Sepsis care follows the empiric choices above.1

Pitfalls

  • Treating pyelonephritis with nitrofurantoin or oral fosfomycin.2
  • Reaching for a fluoroquinolone without asking about use in the past 12 months, or checking earlier cultures.1
  • Assuming no risk factors means a susceptible organism. About 37% of resistant cases had none documented.4
  • Starting TMP-SMX or an oral beta-lactam without a first IV dose of ceftriaxone when susceptibility is unknown.3
  • Discharging without a culture, or without anyone to act on it.3,6
  • Imaging every patient. A simple rule could have avoided 40% of scans.5

How strong is the evidence?

Every 2025 recommendation is conditional, with certainty from very low to moderate. The duration trials mostly studied fluoroquinolones when resistance was less common. They mostly excluded patients with catheters, severe sepsis, immune compromise, urinary abscess, chronic kidney disease, prostatitis, complete obstruction or recent urologic procedures.1 The imaging rule was derived and validated in Dutch emergency departments only.5 The resistance figures come from US ED networks and vary widely by site.6,4

On-shift teaching

Questions to ask a learner at the bedside. Tap a question to see the answer. Every answer uses facts cited above.

Q1Under the 2025 IDSA guideline, what makes a UTI complicated? Does diabetes alone count?
Signs that infection has spread beyond the bladder, especially fever.1 That includes flank pain, chills, rigors and CVA tenderness, plus obstruction, kidney involvement or an indwelling catheter, nephrostomy or stent. Diabetes, immune compromise or a urologic condition alone do not.2
Q2Which three findings suggest a febrile UTI needs imaging?
A history of stones, urine pH ≥ 7.0, or eGFR ≤ 40. Without any of them, urgent findings had a negative predictive value of 99–100%.5
Q3Your patient took levofloxacin for sinusitis 6 months ago. Does that change your choice?
Yes. The guideline suggests avoiding fluoroquinolones after any use in the past 12 months. Without sepsis, choose a third- or fourth-generation cephalosporin or piperacillin-tazobactam.1
Q4Why is TMP-SMX not a good blind choice?
In a US outpatient trial, 18% of E. coli resisted it, and clinical cure was 83% versus 96% with ciprofloxacin.12 The 2010 guideline uses it only for a known susceptible isolate, with a first IV dose of ceftriaxone 1 g if susceptibility is unknown.3
Q5How short can a fluoroquinolone course be?
5–7 days. Ciprofloxacin for 7 days matched 14 days (cure 97% vs 96%), and levofloxacin 750 mg for 5 days matched 10 days of ciprofloxacin.8,13,1
Q6How often did US ED patients with resistant pyelonephritis get an inactive first drug?
75.9% of ESBL and 45.3% of fluoroquinolone-resistant infections.6 That is why every patient needs a culture, and someone needs to act on it.3

References

Evidence base

What this page is built on

14 sources, cited 91 times. Dots are sources, filled by how far each was read; stronger color means a larger share of the citations. Tap a tier to see its sources.

Read in full · 7Abstract read · 7Record only · 0Link checked · 0

Checked by the writer, not a physician. The dots show how each source was read, not that anyone has confirmed the claims.

How this page was made
  • Written from scratch. No source text was copied; facts are restated and cited.
  • Anchored on the IDSA 2025 complicated UTI guideline, read on the IDSA website. Its classification boxes and dose tables are published as images and could not be read, so the definitions come from an emDocs summary and the doses from the 2010 IDSA/ESCMID guideline (full text read) and FDA labels on DailyMed.
  • Trial and cohort results were checked against their PubMed abstracts.
  • Covers non-pregnant adults. Pyelonephritis in pregnancy and in children is managed differently and is not covered here.
  • Figure 1 was drawn for this page from cited guidance. Figure 2 is an openly licensed image from Wikimedia Commons, credited under it, and keeps its own license.
  • Not for clinical use.
Not for clinical use

AI-generated draft. Not reviewed by a physician. This page is for education only and may contain errors, including in doses. Do not use it to diagnose, treat or make decisions about any patient. Rely on your own clinical judgment, your institution's protocols and current drug labeling. Reading this page does not create a physician-patient relationship. Full terms