What is the treatment for pyelonephritis (infection of the kidney) diagnosed by ultrasound?

Treatment of Pyelonephritis Diagnosed by Ultrasound

For patients with pyelonephritis diagnosed by ultrasound, the recommended first-line treatment is a fluoroquinolone such as oral levofloxacin 750 mg once daily for 5 days or ciprofloxacin 500 mg twice daily for 7 days, provided local resistance rates are below 10%. 1

Initial Assessment and Treatment Selection

• Obtain urine culture and susceptibility testing before initiating antibiotic therapy to guide subsequent treatment 1, 2
• For outpatient treatment of uncomplicated pyelonephritis, a once-daily oral fluoroquinolone is the preferred first-line therapy where local resistance rates are <10% 1
• If fluoroquinolone resistance rates exceed 10%, administer an initial intravenous dose of a long-acting parenteral antimicrobial (ceftriaxone 1g) before starting oral therapy 1, 2
• Trimethoprim-sulfamethoxazole (160/800 mg twice daily for 14 days) is appropriate only if the uropathogen is known to be susceptible 1

Inpatient Treatment Recommendations

• Hospitalization is indicated for patients with complicated infections, sepsis, persistent vomiting, failed outpatient treatment, or extremes of age 2, 3
• For hospitalized patients, initial intravenous antimicrobial options include 1:
  • Fluoroquinolones (ciprofloxacin 400 mg IV twice daily or levofloxacin 750 mg IV once daily)
  • Aminoglycosides with or without ampicillin
  • Extended-spectrum cephalosporins (ceftriaxone 1-2 g daily)
  • Extended-spectrum penicillins
  • Carbapenems (for suspected multidrug-resistant organisms)

Duration of Therapy

• For fluoroquinolones: 5-7 days (levofloxacin 750 mg once daily for 5 days or ciprofloxacin 500 mg twice daily for 7 days) 1, 4
• For trimethoprim-sulfamethoxazole: 14 days 1
• For β-lactam antibiotics: 10-14 days 1

Special Considerations

• Oral β-lactam agents are less effective than fluoroquinolones for pyelonephritis and should be used with caution 1
• If an oral β-lactam must be used, administer an initial IV dose of ceftriaxone 1g 1
• Nitrofurantoin and oral fosfomycin should be avoided for pyelonephritis due to insufficient efficacy data 1, 2
• Patients with diabetes and chronic kidney disease are at higher risk for complications including renal abscesses and emphysematous pyelonephritis 2

Monitoring and Follow-up

• Most patients should respond to appropriate therapy within 48-72 hours 5
• If symptoms persist after 72 hours of treatment, consider imaging studies (preferably CT scan) to evaluate for complications 1, 2
• Repeat urine culture 1-2 weeks after completion of antibiotic therapy 3
• Treatment failure may be due to resistant organisms, underlying anatomic abnormalities, or immunosuppression 3

Common Pitfalls to Avoid

• Using oral β-lactams as monotherapy without an initial parenteral dose can lead to treatment failure 1, 2
• Failing to consider local resistance patterns when selecting empiric therapy 1
• Delaying appropriate antibiotic therapy, which can lead to complications including renal scarring, hypertension, and end-stage renal disease 2
• Using nitrofurantoin or fosfomycin for pyelonephritis, which are ineffective for kidney infections 1, 2

Recent Evidence on Antimicrobial Resistance

• A 2021 study showed high resistance rates to commonly used antibiotics, with E. coli resistance rates of 55% for cotrimoxazole, 48% for ciprofloxacin, and 34.4% for ceftriaxone 6
• This highlights the importance of obtaining cultures and susceptibility testing to guide therapy 1, 6