In a 26‑year‑old woman with bladder infection, bilateral pyelonephritis, cystitis, and gastritis receiving intravenous ceftriaxone (or levofloxacin) and ondansetron, is the lack of fever a reassuring sign?

Absence of Fever in Bilateral Pyelonephritis: Clinical Significance

The lack of fever in a patient with bilateral pyelonephritis is NOT necessarily reassuring and should prompt heightened vigilance, as fever is a typical presenting feature of pyelonephritis and its absence may indicate either early disease, atypical presentation, or potentially concerning immunologic factors.

Understanding the Clinical Context

Pyelonephritis classically presents with fever (>38°C), chills, flank pain, nausea, vomiting, or costovertebral angle tenderness 1. The absence of fever in your patient with documented bilateral pyelonephritis represents an atypical presentation that warrants careful consideration.

Key Clinical Considerations:

Why absence of fever matters:

• Fever is one of the cardinal signs used to differentiate upper tract infection (pyelonephritis) from lower tract infection (cystitis) 2
• Up to 20% of pyelonephritis patients may lack typical symptoms, but this doesn't make the infection less serious 3
• The patient is already receiving appropriate IV antibiotics (ceftriaxone or levofloxacin), which may be suppressing fever

Critical monitoring parameters:

The 2024 EAU guidelines emphasize that additional imaging should be considered if the patient remains febrile after 72 hours of treatment, or immediately if there is deterioration in clinical status 1. This same vigilance applies to afebrile patients—you must monitor for:

• Clinical deterioration (worsening pain, hemodynamic instability, altered mental status)
• Response to therapy within 48-72 hours (improvement in symptoms, ability to tolerate oral intake)
• Signs of complications: obstructive pyelonephritis can rapidly progress to urosepsis 1

Current Treatment Assessment

Your antibiotic regimen is appropriate:

• Both ceftriaxone (1-2g daily) and levofloxacin (750mg daily) are guideline-recommended first-line IV therapies for hospitalized pyelonephritis 1
• Recent evidence shows ceftriaxone may have superior microbiological response compared to levofloxacin (68.7% vs 21.4% pathogen eradication) 4

What You Should Do Now

Immediate actions:

1. Ensure imaging has been performed to rule out obstruction or complicating factors, particularly given bilateral involvement 1

2. Monitor closely for clinical response over the next 48-72 hours:

   • Improvement in flank pain
   • Resolution of nausea/vomiting (hence the ondansetron)
   • Ability to maintain oral intake
   • Stable vital signs

3. Review culture results when available and adjust antibiotics accordingly 1

4. Consider complicating factors that may explain atypical presentation:

   • Immunosuppression
   • Diabetes mellitus
   • Anatomic abnormalities
   • These would classify this as complicated UTI requiring longer treatment 1

Red flags requiring immediate escalation:

• Hemodynamic instability
• Worsening pain despite therapy
• Oliguria or rising creatinine (ceftriaxone can cause urolithiasis and post-renal failure 5)
• Altered mental status (ceftriaxone can cause encephalopathy 5)
• Lack of clinical improvement by 72 hours

Bottom Line

The absence of fever is not reassuring—it's simply atypical. What matters most is the overall clinical trajectory over the next 48-72 hours. With bilateral pyelonephritis, appropriate IV antibiotics, and close monitoring, most patients improve. However, maintain a low threshold for repeat imaging if there's any clinical deterioration or failure to improve, as bilateral involvement and atypical presentation increase the risk of complications including progression to urosepsis 1.