What antibiotics are recommended for treating an infected kidney stone?

Antibiotic Treatment for Infected Kidney Stones

For infected kidney stones, intravenous antimicrobial therapy with a fluoroquinolone, an aminoglycoside (with or without ampicillin), an extended-spectrum cephalosporin, or a carbapenem is recommended, with the choice based on local resistance patterns and tailored according to culture results. 1

Initial Assessment and Treatment Approach

• Infected kidney stones represent a urologic emergency when causing obstructive pyelonephritis, as this can rapidly progress to sepsis 2
• Complete stone removal is the mainstay of treatment for infected stones 2
• Always obtain urine culture before initiating antibiotics, but do not delay treatment in patients with signs of sepsis 1, 3

Empiric Antibiotic Selection

For hospitalized patients with severe infection/sepsis:

• First-line IV options:
  • Fluoroquinolone (e.g., ciprofloxacin)
  • Aminoglycoside with or without ampicillin
  • Extended-spectrum cephalosporin (e.g., ceftriaxone)
  • Carbapenem (e.g., meropenem) for suspected multi-drug resistant organisms 1, 3

For mild-moderate infection (outpatient management):

• Oral ciprofloxacin (500 mg twice daily) for 7 days if local resistance <10% 1
• Oral trimethoprim-sulfamethoxazole (160/800 mg twice daily for 14 days) if the pathogen is known to be susceptible 1
• Oral β-lactams are less effective but can be used if other options aren't available 1

Dosing Considerations

• Fluoroquinolones:

  • Ciprofloxacin: 500 mg twice daily (oral) or 400 mg IV initially
  • Levofloxacin: 750 mg daily for 5-7 days 3

• Carbapenems (for multi-drug resistant infections):

  • Meropenem: 1g IV every 8 hours
  • Dose adjustment based on renal function:
    • CrCl 26-49 mL/min: 1g q12h
    • CrCl 10-25 mL/min: 500mg q12h 3

Duration of Therapy

• For pyelonephritis with urinary stones: 10-14 days of therapy is recommended 1
• For complicated UTI with stones: 7-14 days depending on clinical response 3
• Shorter courses (5-7 days) may be effective with fluoroquinolones if good clinical response and the stone has been removed 3

Antibiotic Resistance Considerations

• Local resistance patterns should guide empiric therapy 1, 3
• Avoid fluoroquinolones if local resistance exceeds 10% 1
• Avoid trimethoprim-sulfamethoxazole if local resistance exceeds 20% 1, 3
• Multi-drug resistant organisms are increasingly common in urinary stone patients (32.7% in one study) 4
• Extended-spectrum beta-lactamase (ESBL) producing E. coli and K. pneumoniae are common in stone patients 4

Prophylaxis for Stone Procedures

• For patients undergoing percutaneous nephrolithotomy (PCNL) with large stones (≥20 mm) or dilated pelvicalyceal systems:
  • Ciprofloxacin 250 mg twice daily for 1 week before the procedure significantly reduces the risk of upper tract infection and sepsis 5

Key Clinical Pearls

• Nitrofurantoin and ciprofloxacin show better sensitivity profiles against uropathogens in stone patients 4
• High resistance to ampicillin, penicillin, and trimethoprim-sulfamethoxazole has been observed in stone patients 4
• Female sex, history of UTI, and previous antibiotic use are risk factors for infected stones 4
• Complete stone removal is essential for definitive treatment of infection stones 2

Follow-up

• Monitor clinical response within 48-72 hours of initiating antibiotics 3
• Consider follow-up urine culture after completing antibiotic therapy in complicated cases 3
• Assess for complete stone clearance with appropriate imaging 6