What is the treatment for a kidney infection?

Treatment of Kidney Infection (Acute Pyelonephritis)

For a kidney infection (acute pyelonephritis), treatment with a lipid-soluble antibiotic such as trimethoprim-sulfamethoxazole or a fluoroquinolone for 7 days is recommended as first-line therapy, with adjustments based on local antimicrobial susceptibility patterns.

Diagnosis and Initial Assessment

• Key diagnostic features:

  • Flank pain (nearly universal)
  • Fever (though may be absent early)
  • Increased white blood cell count (>11 × 10^9/L)
  • Elevated C-reactive protein (≥50 mg/L)
  • Positive urinalysis
  • Compatible clinical history

• Essential initial tests:

  • Urine culture (obtain BEFORE starting antibiotics) 1
  • Blood cultures (if upper UTI or kidney cyst infection is suspected) 1

Outpatient Treatment Algorithm

First-line therapy (for uncomplicated pyelonephritis):

1. Oral fluoroquinolones (if local resistance <10%):

   • Ciprofloxacin 500 mg twice daily for 7 days 2
   • Levofloxacin 750 mg once daily for 5 days 3

2. Alternative first-line options:

   • Trimethoprim-sulfamethoxazole (based on local susceptibility) 1
   • Fosfomycin (based on local susceptibility) 1

If local fluoroquinolone resistance >10%:

• Initial dose of long-acting parenteral antibiotic (ceftriaxone) followed by oral therapy 4, 5

Inpatient Treatment Considerations

• Indications for hospitalization:

  • Severe illness/sepsis
  • Inability to tolerate oral medications
  • Suspected complications
  • Pregnancy (high risk of severe complications) 5

• Inpatient regimens:

  • Parenteral antibiotics initially (fluoroquinolones, aminoglycosides, or cephalosporins) 4
  • For suspected multidrug-resistant organisms: antibiotics with activity against extended-spectrum beta-lactamase-producing organisms 5

Special Considerations

Kidney Cyst Infections

• For patients with ADPKD and kidney cyst infection:
  • Use lipid-soluble antibiotics for better cyst penetration (trimethoprim-sulfamethoxazole or fluoroquinolones) 1
  • Longer treatment duration (4-6 weeks) is recommended 1
  • Higher doses may be necessary (e.g., ciprofloxacin 750 mg twice daily) 6

Important Caveats

• Fluoroquinolones carry risks of tendinopathies and aortic aneurysms/dissections 1
• Rising resistance to fluoroquinolones and third-generation cephalosporins is a concern 7
• Patients should show clinical improvement within 48-72 hours; if not, consider imaging and alternative diagnoses 5
• If concurrent urinary tract obstruction is present, urgent decompression is necessary 5

Follow-up

• Reassess clinical response in 48-72 hours
• No routine imaging is necessary unless symptoms fail to improve or recur after initial improvement 4
• Adjust antibiotics based on culture and sensitivity results when available

This approach prioritizes effective antimicrobial therapy while considering local resistance patterns and the patient's clinical status, with the goal of minimizing morbidity and mortality from kidney infections.