Pyelonephritis
Fever, loin pain and UTI symptoms. Culture first, the right antibiotic for the right length, and scan anyone not improving.
A 32-year-old woman has 2 days of burning urine, then fever with rigors and right loin pain. Temperature 39.2 °C, pulse 112, BP 104/66. Right renal angle tenderness. Urine dipstick: leucocytes and nitrites positive.
Can she go home on tablets?
- Sepsis screenLow BP, high lactate, confusion: sepsis pathway.
- Pregnancy testIn every woman of child-bearing age. Changes the drugs.
- Urine culture before the first doseAnd blood cultures if febrile and admitted.
- Creatinine and sugarAKI and diabetes change everything.
- Antibiotic for the right lengthUsually 7–10 days, depending on the drug.
- Scan if not improving or obstructedUltrasound within 24 hours if no better in 48–72 hours, or if stone suspected.
- Check the culture resultSwitch to the narrowest effective drug.
- Septic or low BP
- Obstruction on scan or known stone
- Diabetic and very unwell
- Pregnant
- Single kidney or transplant
- Not improving after 48–72 hours
- Infected obstructed kidney
- Emphysematous pyelonephritis
- Renal or perinephric abscess
- Ectopic pregnancy
- Appendicitis
- Lower lobe pneumonia
| Typical course | 7 days (fluoroquinolone) to 10–14 days (beta-lactam) |
| No better at 48–72 hours | Ultrasound for obstruction or abscess |
| Infected and obstructed kidney | Urological emergency: drain within hours |
| Diabetic, very unwell, gas on imaging | Emphysematous pyelonephritis: urology now |
| Pregnant | Admit for IV treatment in most cases |
Check every dose against a current drug reference and your hospital protocol.
On this page
Who needs admission?
- Not septic
- Can keep fluids and tablets down
- Not pregnant
- No obstruction or abnormal urinary tract
- Reliable follow-up
- Septic or vomiting
- Pregnant
- Diabetic and unwell, or kidney injury
- Stone or obstruction
- Male with complicated infection
- Failed oral treatment
Antibiotics
Resistance to ciprofloxacin and co-trimoxazole, and ESBL-producing E. coli, are common in Pakistan. Use your hospital antibiogram, send a culture before the first dose, and change once sensitivities are back.
- Pregnancy: admit, IV ceftriaxone, avoid fluoroquinolones and nitrofurantoin (nitrofurantoin does not reach kidney tissue). Discuss with obstetrics.
- Nitrofurantoin and fosfomycin are for lower UTI only. They do not treat pyelonephritis.
- Men: treat as complicated; look for prostatitis and obstruction.
- Kidney function: adjust doses for creatinine clearance.
When it is not getting better
- Check the cultureIs the bug resistant?
- Ultrasound kidneysHydronephrosis, abscess, stone.
- Obstructed and infectedUrology for nephrostomy or stent within hours. Antibiotics alone will fail.
- Diabetic with gasCT shows emphysematous pyelonephritis: urology now.
- AbscessLarger collections need drainage.
Frequently asked questions
What is the treatment of pyelonephritis?
Antibiotics guided by local resistance and urine culture: oral cefalexin, ciprofloxacin or co-amoxiclav for mild cases, or IV ceftriaxone (or meropenem for ESBL) in admitted patients, for 7–14 days depending on the drug. Scan if not improving.
How long is antibiotic treatment for pyelonephritis?
Usually 7 days for a fluoroquinolone and 10–14 days for a beta-lactam, depending on the drug and response.
When is pyelonephritis treated IV?
When the patient is septic, vomiting, pregnant, diabetic and unwell, has kidney injury, or has an obstructed or abnormal urinary tract.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A woman at 20 weeks of pregnancy has pyelonephritis. What is the best management?
Answer: Admit for IV ceftriaxone. Pyelonephritis in pregnancy is usually treated in hospital with IV antibiotics.
- No antibiotics until culture: Treat now.
- Trimethoprim at home: Not suitable for pyelonephritis in pregnancy.
- Oral ciprofloxacin at home: Avoid in pregnancy.
- Oral nitrofurantoin: Doesn't reach kidney tissue.
2. A patient with pyelonephritis is still spiking 39 °C on day 3 of IV ceftriaxone. What is the next step?
Answer: Ultrasound of the kidneys. Failure to improve within 48–72 hours needs imaging and review of the culture result.
- Add paracetamol and wait a week: Delay.
- Stop antibiotics: No.
- CT head: Not relevant.
- Discharge on oral antibiotics: Still febrile.
3. Why are nitrofurantoin and fosfomycin not used for pyelonephritis?
Answer: They don't reach adequate levels in kidney tissue. These drugs concentrate in urine but not in kidney tissue; they are for lower UTI only.
- They cause kidney failure: Not the reason.
- They are banned in Pakistan: No.
- They only work against Gram-positive bacteria: Not true.
- They are too expensive: Not the reason.
4. A 28-year-old woman has fever 39 °C, loin pain, rigors and vomiting with nitrite-positive urine. She is not pregnant. What is appropriate?
Answer: IV ceftriaxone. Acute pyelonephritis: fever, loin pain, rigors, vomiting, CVA tenderness. Send urine culture; treat with antibiotics achieving renal tissue levels — IV ceftriaxone or gentamicin if unwell/vomiting, then oral by sensitivities (ciprofloxacin, co-amoxiclav, co-trimoxazole) for 7–14 days. Nitrofurantoin and fosfomycin don’t reach therapeutic renal levels. Image (ultrasound) if no response in 48–72 h, sepsis, stones or men — exclude obstruction/abscess.
- Nitrofurantoin for 3 days: Nitrofurantoin does not reach kidney tissue.
- No antibiotics until culture: Waiting for culture delays treatment.
- Fosfomycin single dose: Fosfomycin is for cystitis only.
5. A 26-year-old woman has fever of 39 °C, right loin pain, rigors and vomiting. Urine dipstick is positive for nitrites and leucocytes. Why is nitrofurantoin NOT suitable?
Answer: Poor kidney tissue and blood levels. Nitrofurantoin concentrates in the bladder urine but achieves very low levels in renal tissue and blood, so it does not treat pyelonephritis. Options include cefalexin, co-amoxiclav (if the organism is susceptible) or ciprofloxacin, guided by culture; admit for IV antibiotics if she is vomiting or septic.
- It is too broad-spectrum: Nitrofurantoin is actually narrow-spectrum; the problem is that it only reaches useful levels in the bladder.
- It is unavailable orally: It is an oral drug.
- It is ineffective against E. coli: It covers most E. coli well in the bladder.
6. What is the most common cause of traveller's diarrhoea?
Answer: Enterotoxigenic E. coli. ETEC produces heat-labile toxin (raises cAMP) and heat-stable toxin (raises cGMP), causing watery diarrhoea without blood. It is usually self-limiting; treat with fluids, and in severe cases azithromycin or a fluoroquinolone.
- Shigella dysenteriae: Causes bloody dysentery.
- Vibrio cholerae: Causes rice-water stools in outbreaks; less common in travellers.
- Entamoeba histolytica: Causes bloody diarrhoea and liver abscess.
- Clostridioides difficile: Follows antibiotic use.
7. In the collecting duct, which cells secrete hydrogen ions to acidify the urine?
Answer: α-intercalated cells. Principal cells reabsorb Na⁺ through ENaC and secrete K⁺ (aldosterone-regulated) and reabsorb water through aquaporin-2 inserted in response to ADH (V2 receptors). α-intercalated cells secrete H⁺ via apical H⁺-ATPase and H⁺/K⁺-ATPase and return bicarbonate to blood (failure causes distal RTA). β-intercalated cells secrete bicarbonate in alkalosis. Juxtaglomerular cells secrete renin; podocytes form the filtration slit diaphragm.
- Principal cells: Na⁺, K⁺ and water.
- β-intercalated cells: Secrete bicarbonate.
- Juxtaglomerular cells: Secrete renin.
- Podocytes: Filtration barrier.
References and dose sources
- NICE NG111: Pyelonephritis (acute), antimicrobial prescribing
- IDSA guideline: uncomplicated cystitis and pyelonephritis in women (Clin Infect Dis 2011)
- NICE NG253 — suspected sepsis in over 16s
- Cefalexin (cephalexin) dosing: Drugs.com: Cephalexin dosage (see also our cefalexin (cephalexin) dose page)
- Ciprofloxacin dosing: Drugs.com: Ciprofloxacin dosage (see also our ciprofloxacin dose page)
- Co-amoxiclav (amoxicillin with clavulanic acid) dosing: Drugs.com: Amoxicillin/clavulanate dosage (see also our co-amoxiclav (amoxicillin with clavulanic acid) dose page)
- Ceftriaxone dosing: Drugs.com: Ceftriaxone dosage (see also our ceftriaxone dose page)
- Meropenem dosing: Drugs.com: Meropenem dosage (see also our meropenem dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.