Acute pyelonephritis is an infection of one or both kidneys usually caused by bacteria travelling up from the bladder.

Supporting advice:

• Drink adequate fluids to avoid dehydration
• Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are generally not recommended for people with acute pyelonephritis because of concerns about renal safety

In people aged 16 years and over with acute pyelonephritis, obtain a midstream urine sample before antibiotics are taken and send for culture and susceptibility testing.

In children and young people under 16 years with acute pyelonephritis, obtain a urine sample before antibiotics are taken and send for culture and susceptibility testing in line with NICE CG54 Urinary tract infection in under 16s: diagnosis and management (August 2007 [updated October 2018]).

For children under 5 years with acute pyelonephritis who present with fever refer to NICE NG143: Fever in under 5s: assessment and initial management (November 2019)

When results are available:

• review antibiotic choice and
• change antibiotic if bacteria resistant and symptoms not improving

Referral and seeking specialist advice

Refer people aged 16 years and over with acute pyelonephritis to hospital if they have any symptoms or signs suggesting a more serious illness or condition (for example, sepsis, or acute prostatitis in men/people with prostates).

Consider referring or seeking specialist advice for people aged 16 years and over with acute pyelonephritis if they:

• have recurrent infections or
• are pregnant or
• are men, following a single episode without an obvious cause or
• have a higher risk of developing complications (for example, people with known or suspected structural or functional abnormality of the genitourinary tract or underlying disease [such as diabetes or immunosuppression])

Refer children and young people with acute pyelonephritis to hospital in line with NICE CG54 Urinary tract infection in under 16s: diagnosis and management (August 2007 [updated October 2018]).

Seek specialist advice if the patient cannot take oral antibiotics to explore options for giving intravenous antibiotics at home or in the community, rather than in hospital, where this is appropriate e.g. via outpatient or home parenteral antibiotic therapy service where available

Antibiotics for non-pregnant women and men aged 16 years and over

Offer an antibiotic to people with acute pyelonephritis; taking into account the considerations when prescribing antibiotics.

• The risk of developing complications is higher in people with known or suspected structural or functional abnormality of the genitourinary tract, or immunosuppression

1st line

Cefalexin

• 1g three times a day for 7 to 10 days

See section: 5.1.2 Cephalosporins, carbapenems, and other beta-lactams

If 1st line has failed, will not work due to resistance, or is unsafe to use in an individual patient

Ciprofloxacin

• 500mg twice a day for 7 days
• Systemic fluoroquinolones must now only be prescribed when other commonly recommended antibiotics are inappropriate (see MHRA Drug Safety Updates below)
• Patients should be advised to stop treatment at the first signs of a serious adverse reaction, such as tendinitis or tendon rupture, muscle pain, muscle weakness, joint pain, joint, feet, or abdomen swelling, peripheral neuropathy, rapid onset of shortness of breath, new-onset of heart palpitations, and central nervous system effects: including new or worsening depression or psychosis, and to seek immediate medical attention.

Drug Safety Updates for Ciprofloxacin (refer to 5.1.12 Quinolones for further details).

• MHRA Drug Safety Update (November 2018): Systemic and inhaled fluoroquinolones: small increased risk of aortic aneurysm and dissection; advice for prescribing in high-risk patients.
• MHRA Drug Safety Update (December 2020): Systemic and inhaled fluoroquinolones: small risk of heart valve regurgitation; consider other therapeutic options first in patients at risk.
• MHRA Drug Safety Update (September 2023): Fluoroquinolone antibiotics: suicidal thoughts and behaviour.
• MHRA Drug Safety Update (January 2024): Fluoroquinolone antibiotics: must now only be prescribed when other commonly recommended antibiotics are inappropriate.

Alternative option (use only if culture results available and susceptible):

Co-amoxiclav

• 500/125mg three times a day for 7 to 10 days

Trimethoprim

• 200mg twice daily for 14 days

See sections: 5.1.1 Penicillins and 5.1.8 Sulfonamides and trimethoprim

Antibiotics for pregnant women aged 12 years and over

Consider referring or seeking specialist advice for pregnant women aged 12 years and over

Cefalexin

• 1g three times a day for 7 to 10 days

Consult local microbiologist if cefalexin is not suitable.

Trimethoprim may be considered or advised by specialists. It is recommended that women who need to take trimethoprim during the first trimester also take high dose folic acid (5mg daily) until week 12 of pregnancy. Avoid trimethoprim if the woman has a low folate status or is on a folate antagonist (e.g. antiepileptic or proguanil)

See section: 5.1.2 Cephalosporins, carbapenems, and other beta-lactams, 5.1.8 Sulfonamides and trimethoprim, and Resources for: contraception for drugs with teratogenic potential, and prescribing in pregnancy and lactation

Antibiotics for children and young people under 16 years

Children under 3 months of age

Infants and children under 3 months with a possible UTI should be referred to a paediatric specialist.

Children aged 3 months and over

Consider referring or seeking specialist advice for children aged 3 months and over

Cefalexin

• 3 months to 11 years:
  • 25mg/kg two to four times a day for 7 to 10 days
  • Maximum 1g per dose four times a day
• 12 to 15 years
  • 1g three times a day for 7 to 10 days
  • Maximum 1g per dose four times a day

Alternative option (use only if culture results available and susceptible):

Co-amoxiclav

• Use only if culture results available and susceptible
• Children and young people aged 3 months and over (doses given three times a day for 7 to 10 days):
  • 3 to 11 months: 0.25ml/kg (125/31 suspension) (dose doubled in severe infection)
  • 1 to 5 years: 5ml or 0.25ml/kg (125/31 suspension) (dose doubled in severe infection)
  • 6 to 11 years: 5ml or 0.15ml/kg (250/62 suspension) (dose doubled in severe infection)
  • 12 to 15 years: 250/125mg or 500/125mg

See section 5.1.1 Penicillins and 5.1.2 Cephalosporins, carbapenems, and other beta-lactams