What's the next step for a patient with a urinary tract infection (UTI) who has been taking nitrofurantoin for 4 days, with improved symptoms but persistent radiating pain from the back to the left leg?

Management of Persistent Back Pain in a Patient with UTI on Nitrofurantoin

The patient's back pain radiating to the left leg despite 4 days of nitrofurantoin treatment strongly suggests pyelonephritis, requiring immediate evaluation for upper urinary tract infection and a switch to a more appropriate antibiotic regimen.

Clinical Assessment

• Radiating pain from back to left leg in a patient with UTI is highly concerning for pyelonephritis (upper urinary tract infection), which requires different management than uncomplicated cystitis 1
• Nitrofurantoin is not appropriate for pyelonephritis as it does not achieve adequate tissue concentrations in the kidney parenchyma 1
• Persistent or worsening symptoms after 4 days of treatment indicate treatment failure or progression to upper urinary tract infection 1

Immediate Next Steps

1. Obtain urine culture and antimicrobial susceptibility testing before changing antibiotics 1

   • This is essential when symptoms do not resolve or recur within treatment period
   • Previous culture results (if available) should guide empiric therapy while awaiting new results

2. Evaluate for upper urinary tract involvement 1

   • Check for fever (>38°C), chills, flank pain, costovertebral angle tenderness
   • Assess for signs of systemic illness including nausea, vomiting

3. Consider imaging of the upper urinary tract 1

   • Ultrasound is recommended to rule out urinary tract obstruction or kidney stones
   • More advanced imaging (CT scan) may be needed if fever persists after treatment change

Treatment Recommendations

• Switch from nitrofurantoin to an appropriate antibiotic for pyelonephritis 1

  • Oral options (for mild-moderate cases):
    • Ciprofloxacin 500-750 mg twice daily for 7 days
    • Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days
    • Levofloxacin 750 mg daily for 5 days

• Consider hospitalization if patient has severe symptoms, inability to maintain oral hydration, or signs of sepsis 1

• For outpatient management, ensure close follow-up within 48-72 hours to assess response to new treatment 1

Important Considerations

• Nitrofurantoin is specifically contraindicated for pyelonephritis and should not be continued 1

  • It concentrates in the bladder but achieves poor tissue penetration in the kidneys 2
  • It can cause serious adverse effects including pulmonary toxicity with continued use 3, 4

• Fluoroquinolones and cephalosporins are the only recommended oral antibiotics for pyelonephritis 1

  • Local resistance patterns should guide the choice between these options

• If symptoms worsen or do not improve within 72 hours of appropriate antibiotic therapy, further evaluation is necessary 1

Prevention of Recurrence

• After successful treatment of the acute episode, evaluate for risk factors for recurrent UTI 1
• For patients with recurrent UTIs, consider prophylactic strategies based on individual risk factors 1
• Ensure adequate fluid intake as this may reduce the risk of recurrent UTI 1