What is the most appropriate management for a patient with persistent fever and flank pain despite appropriate antibiotic therapy for pyelonephritis?

Management of Persistent Fever and Flank Pain in Pyelonephritis

Kidney ultrasound is the most appropriate management for a patient with persistent fever and flank pain despite 5 days of appropriate antibiotic therapy for pyelonephritis. 1, 2

Rationale for Imaging

• Persistent fever after 72 hours of appropriate antibiotic treatment for pyelonephritis warrants imaging to rule out complications such as urinary tract obstruction, renal abscess, or stone disease 1
• The European Association of Urology guidelines specifically recommend additional investigations when a patient remains febrile after 72 hours of treatment or if there is clinical deterioration 1
• Ultrasound is the preferred initial imaging modality to evaluate for complications of pyelonephritis, including obstruction, abscess formation, or renal stones 2

Diagnostic Algorithm for Persistent Pyelonephritis

1. First-line imaging: Kidney ultrasound

   • Evaluate for urinary tract obstruction or renal stone disease 1, 2
   • Assess for potential abscess formation 3
   • Non-invasive and does not expose the patient to radiation 1

2. If ultrasound is inconclusive and symptoms persist:

   • Consider contrast-enhanced CT scan for better visualization of potential complications 1
   • CT is particularly indicated when abscess is suspected 1, 3

Why Other Options Are Less Appropriate

• Changing antibiotics (Option B): Not indicated as the urine culture shows E. coli susceptible to the current antibiotic; changing therapy without identifying a complication would be premature 2, 4
• Repeat urine culture (Option C): Not the priority when fever persists despite appropriate antibiotic therapy; imaging should be performed first to rule out complications 1, 5
• Continue observation (Option D): Inappropriate when fever persists beyond 72 hours of appropriate therapy; complications need to be ruled out 1, 4

Common Pitfalls in Managing Persistent Pyelonephritis

• Failure to consider complications such as renal or perinephric abscess in patients with persistent symptoms despite appropriate antibiotic therapy 3, 6
• Delaying imaging studies in patients who remain febrile after 72 hours of treatment 1
• Changing antibiotics without first ruling out anatomical complications that may require drainage 4, 6
• Not recognizing that persistent fever may indicate obstructive pyelonephritis, which can rapidly progress to urosepsis if not promptly identified and addressed 1

In conclusion, for a 48-year-old woman with persistent fever and flank pain after 5 days of appropriate antibiotic therapy for pyelonephritis, kidney ultrasound is the most appropriate next step to evaluate for potential complications requiring intervention.