From the Guidelines
Pyelonephritis can present with signs and symptoms even when urine cultures show no bacteria, and empiric antibiotic therapy should still be initiated in suspected cases despite negative cultures. Common signs of pyelonephritis include flank pain, fever above 38°C (100.4°F), chills, nausea, vomiting, and costovertebral angle tenderness, as well as urinary symptoms like frequency, urgency, and dysuria 1. Laboratory findings often show elevated white blood cell count, C-reactive protein, and erythrocyte sedimentation rate. Sterile pyuria in pyelonephritis can occur due to prior antibiotic use, fastidious organisms that don't grow on standard culture media, or non-infectious causes of inflammation.
Diagnosis and Treatment
The diagnosis of pyelonephritis typically involves urinalysis, including assessment of white and red blood cells and nitrite, as well as urine culture and antimicrobial susceptibility testing 1. Imaging studies such as ultrasound or CT scan may be necessary to rule out complications like abscess formation or obstruction. For suspected pyelonephritis despite negative cultures, empiric antibiotic therapy should still be initiated. Typical regimens include:
- Fluoroquinolones (ciprofloxacin 500mg twice daily for 7 days)
- Trimethoprim-sulfamethoxazole (160/800mg twice daily for 14 days)
- A third-generation cephalosporin like ceftriaxone (1-2g daily) 1
Patient Management
Patients should increase fluid intake, take antipyretics for fever, and seek immediate medical attention if symptoms worsen despite treatment. It is essential to identify predisposing factors to avoid future recurrences and to tailor treatment based on local resistance patterns and susceptibility results 1.
Key Considerations
The choice of antibiotic regimen should be based on local resistance data and tailored on the basis of susceptibility results 1. In regions with low levels of fluoroquinolone resistance, fluoroquinolones are the preferred antimicrobial class for oral therapy 1. However, in areas with high resistance rates, alternative agents such as cephalosporins or carbapenems may be necessary 1.
From the Research
Signs of Pyelonephritis
- Fever, although it may be absent early in the illness 2
- Flank pain, which is nearly universal, and its absence should raise suspicion of an alternative diagnosis 2
- Positive urinalysis confirms the diagnosis in patients with a compatible history and physical examination 2
- Laboratory evidence of urinary tract infection, such as urine culture with antimicrobial susceptibility testing 3
Causative Organisms
- Escherichia coli is the most common pathogen in acute pyelonephritis 2, 4, 5
- Increasing rate of E. coli resistance to extended-spectrum beta-lactam antibiotics 2
- Other uropathogens, such as Enterococcus faecalis, may also be present, although less commonly 4
Antibiotic Susceptibilities
- Approximately 50% of E. coli infections are resistant to ampicillin 4
- First and third generation cephalosporin resistance is <5%, although the latter has increased over the last decade 4
- Fluoroquinolones, such as levofloxacin, have been shown to be effective in treating acute pyelonephritis, with a high microbiologic response rate and good tolerability 5