What is the recommended treatment for pyelonephritis (infection of the kidney) in pregnancy?

Treatment of Pyelonephritis in Pregnancy

Pregnant women with pyelonephritis should receive intravenous antibiotics initially, with ceftriaxone being a preferred first-line agent, followed by oral antibiotics to complete a 10-14 day course. 1, 2

Initial Assessment and Management

• Diagnosis confirmation: Obtain urine culture before starting antibiotics to identify the causative organism and its susceptibility pattern 1
• Initial hydration: Administer 1L of normal saline IV over 4 hours 3
• Blood cultures: Consider obtaining blood cultures as bacteremia occurs in approximately 8-14% of cases 3, 2

Antibiotic Therapy

Inpatient Management (Preferred Approach)

Most pregnant women with pyelonephritis should be managed as inpatients, particularly those in the late second and third trimesters 4.

First-line parenteral options:

• Ceftriaxone (intramuscular or intravenous) 2, 5
• Cefazolin (intravenous) 2
• Ampicillin plus gentamicin (intravenous) - use with caution due to aminoglycoside nephrotoxicity risk 2, 1

Duration of parenteral therapy:

• Continue until patient is afebrile for 48 hours 5
• Then transition to oral antibiotics

Oral Antibiotic Options

After clinical improvement, transition to:

• Cephalexin 500 mg every 6 hours to complete a 10-14 day total course 3, 2, 5

Outpatient Management Considerations

Outpatient treatment may be considered for select patients in the first or early second trimester (<24 weeks) who:

• Are clinically stable
• Can tolerate oral intake
• Have no comorbidities
• Have reliable follow-up 4, 5

Outpatient regimen:

• Two doses of intramuscular ceftriaxone followed by oral cephalexin for 10 days 5

Treatment Considerations

• Antibiotic selection: Consider local antimicrobial resistance patterns when choosing empiric therapy 4, 6
• Common pathogens: Escherichia coli is the predominant organism (70-86% of cases) 3, 2, 6
• Resistance concerns: Approximately 12% of uropathogens may be resistant to cefazolin 5
• Treatment failure: If clinical worsening or prolonged fever occurs, consider changing antibiotics based on culture results 5

Follow-up and Monitoring

• Obtain follow-up urine culture 5-14 days after completion of therapy 2, 5
• Monitor for recurrent infection throughout pregnancy (occurs in approximately 6% of cases) 2
• Be vigilant for potential complications including preterm labor 2

Pitfalls and Caveats

• Aminoglycosides (gentamicin) carry risk of nephrotoxicity and ototoxicity and should be used cautiously 1
• Fluoroquinolones should be avoided in pregnancy due to potential fetal risks
• Inadequate treatment duration increases risk of recurrence
• Failure to obtain pre-treatment cultures may lead to inappropriate antibiotic selection if the patient doesn't respond to empiric therapy
• Approximately 5-10% of patients may have persistent positive cultures after treatment, requiring reassessment 2, 5