What is the treatment for pyelonephritis (kidney infection) during pregnancy?

Treatment of Pyelonephritis in Pregnancy

Pregnant women with pyelonephritis should be hospitalized and treated with intravenous antibiotics, specifically ceftriaxone 1-2g daily or an extended-spectrum cephalosporin/penicillin, avoiding fluoroquinolones due to fetal safety concerns. 1

Initial Management and Hospitalization

• Most pregnant women with pyelonephritis require inpatient management with intravenous antimicrobial therapy, particularly those presenting after the first trimester or with severe symptoms 1, 2
• Selected low-risk patients in the first or early second trimester (before 24 weeks) may be candidates for outpatient management with intramuscular ceftriaxone followed by oral cephalexin, though this requires careful patient selection 3, 2
• All patients should receive initial intravenous hydration (typically 1L normal saline over 4 hours) 4

Antibiotic Selection: Critical Pregnancy-Specific Considerations

The choice of antibiotics differs significantly from non-pregnant patients because fluoroquinolones—the first-line agents for uncomplicated pyelonephritis—are contraindicated in pregnancy. 1

Recommended First-Line Agents:

• Ceftriaxone 1-2g IV daily (preferred due to once-daily dosing and safety profile) 1
• Cefotaxime 2g IV three times daily 1
• Cefepime 1-2g IV twice daily 1
• Piperacillin/tazobactam 2.5-4.5g IV three times daily 1
• Aminoglycosides (gentamicin 5mg/kg daily or amikacin 15mg/kg daily) with or without ampicillin 1

Agents to AVOID in Pregnancy:

• Fluoroquinolones (ciprofloxacin, levofloxacin) are contraindicated despite being first-line in non-pregnant patients 1
• Nitrofurantoin and fosfomycin have insufficient efficacy data for pyelonephritis treatment 1

Diagnostic Workup

• Obtain urine culture and antimicrobial susceptibility testing in all cases before initiating empiric therapy 1
• Perform urinalysis assessing white blood cells, red blood cells, and nitrites 1
• Use ultrasound or MRI (NOT CT) for imaging if complications are suspected, to avoid radiation exposure to the fetus 1
• Consider imaging immediately if clinical deterioration occurs or if fever persists beyond 72 hours of appropriate therapy 1
• Blood cultures should be obtained as bacteremia occurs in approximately 14% of pregnant patients with pyelonephritis 4

Duration and Transition of Therapy

• Continue IV antibiotics until the patient is afebrile for 24-48 hours 4, 3
• Transition to oral therapy to complete a 10-14 day total course 1, 3
• Oral options after IV therapy include cephalexin 500mg every 6 hours 4, 3
• Tailor antibiotic selection based on culture and susceptibility results once available 1

Post-Treatment Surveillance: A Critical Difference from Non-Pregnant Patients

Unlike non-pregnant women, pregnant patients require ongoing surveillance after treatment due to high recurrence risk. 1, 5

• Obtain repeat urine culture 5-14 days after completing therapy to confirm bacterial clearance 3, 6
• Recurrent pyelonephritis occurs in 7-8% of pregnant patients even with close surveillance 5
• Pyelonephritis occurring in the first trimester has higher relapse rates and warrants particularly close follow-up 6, 5
• Some evidence suggests treating even low-level bacteriuria (<10^5 CFU/mL) with gram-negative organisms in high-risk pregnant patients to prevent recurrence 5

Special Considerations and Common Pitfalls

Bacteremia Recognition:

• Approximately 14% of pregnant patients with pyelonephritis have concurrent bacteremia, which mandates IV therapy and cannot be predicted by presentation characteristics 4

Resistance Patterns:

• E. coli causes 86% of cases but up to 12% may be resistant to first-generation cephalosporins like cefazolin 3
• Base empiric therapy on local resistance patterns and adjust based on culture results 1

Distinguishing from Asymptomatic Bacteriuria:

• Asymptomatic bacteriuria (ASB) in pregnancy requires only 4-7 days of treatment, not the 10-14 days needed for pyelonephritis 1
• Do not confuse Lactobacillus (normal vaginal flora contamination) with pathogenic bacteriuria requiring treatment 7

Monitoring for Complications:

• Pyelonephritis increases risk of preterm delivery and low birth weight 1
• Untreated asymptomatic bacteriuria progresses to pyelonephritis in 20-35% of pregnant women, emphasizing the importance of prenatal screening 1

When to Escalate Therapy:

• Switch to broader coverage (e.g., gentamicin or carbapenem) if clinical worsening occurs or fever persists beyond 72 hours 1, 3
• Carbapenems should be reserved for culture-confirmed multidrug-resistant organisms 1

Algorithm Summary

1. Hospitalize (with rare exceptions for carefully selected first-trimester patients) 1, 2
2. Obtain urine culture and blood cultures before starting antibiotics 1, 4
3. Initiate IV ceftriaxone 1-2g daily (or alternative extended-spectrum cephalosporin/aminoglycoside) 1
4. Provide IV hydration 4
5. Continue IV therapy until afebrile 24-48 hours 4, 3
6. Transition to oral cephalexin to complete 10-14 days total 1, 3
7. Obtain repeat urine culture 5-14 days post-treatment 3, 6
8. Maintain surveillance throughout remainder of pregnancy 6, 5