Diagnosis and Treatment of Suspected Pyelonephritis in a 16-Year-Old Female
This 16-year-old female with 6 days of fever, vomiting, and urinary symptoms most likely has acute pyelonephritis (upper urinary tract infection), and should be started immediately on empiric antibiotic therapy after obtaining urine culture, with consideration for hospitalization given the prolonged fever duration.
Clinical Presentation and Diagnosis
The combination of prolonged fever (6 days), vomiting, and urinary symptoms (micturition issues) strongly suggests pyelonephritis rather than simple cystitis. 1, 2
Immediate Diagnostic Steps
Obtain urine culture and antimicrobial susceptibility testing before initiating antibiotics - this is mandatory in all suspected pyelonephritis cases to guide definitive therapy. 1
Perform urinalysis with microscopy to evaluate for pyuria, hematuria, nitrites, and leukocyte esterase. 1 The presence of pyuria is expected with UTI, and its absence suggests an alternative diagnosis. 3
Obtain a complete blood count with differential to assess for leukocytosis and left shift, which helps evaluate infection severity. 1
Collect urine via catheterization if clean-catch is unreliable - bag collection has false-positive rates of 12-83% and should never be used for culture. 4, 2 Catheterization has 95% sensitivity and 99% specificity. 4
Key Diagnostic Considerations
Escherichia coli is the predominant pathogen in both complicated and uncomplicated UTI, though Klebsiella and Proteus appear with increased frequency in complicated cases. 5, 6
Bacteriuria is more specific and sensitive than pyuria for detecting UTI, even in young women. 7
Diagnosis requires pyuria and at least 50,000 CFU/mL of a single pathogen in an appropriately collected specimen. 2
Imaging Requirements
Perform renal and bladder ultrasound within 24-48 hours to rule out urinary obstruction, stones, abscess, or anatomic abnormalities. 1
If fever persists beyond 72 hours of appropriate antibiotic therapy, obtain a contrast-enhanced CT scan of the abdomen/pelvis to evaluate for complications such as abscess formation. 1
Antibiotic Therapy
Initial Empiric Treatment
For severe pyelonephritis with prolonged fever and vomiting, initiate intravenous therapy:
Cefepime 2 grams IV every 12 hours is the preferred initial regimen. 1
Alternative: Ceftriaxone 1-2 grams IV once daily if cefepime is unavailable. 1
Oral Therapy Options (if patient can tolerate oral intake and appears non-toxic)
Ciprofloxacin 500-750 mg orally twice daily for 7-14 days is appropriate for uncomplicated pyelonephritis when fluoroquinolone resistance is low in your area. 8, 3 However, fluoroquinolone resistance is increasing worldwide, which complicates treatment choices. 3
Cefixime 400 mg orally once daily can be used for susceptible organisms, though it is primarily indicated for uncomplicated UTI rather than pyelonephritis. 9
Treatment Duration and Transition
Total antibiotic duration should be 7-14 days, with transition to oral therapy based on culture sensitivities and clinical improvement. 1, 2, 5
Adjust antibiotics according to sensitivity testing of the isolated uropathogen once culture results are available. 2
Hospitalization Criteria
This patient likely requires admission given:
Prolonged fever (6 days) suggests failure of outpatient management or delayed presentation. 2
Inability to retain oral intake (vomiting) necessitates IV fluids and parenteral antibiotics. 2
Patients with signs of pyelonephritis who fail to respond within 48 hours should be considered for admission. 2
Supportive Care
Administer IV fluids at maintenance rate with adjustments based on clinical status and strict intake/output monitoring. 1
Use acetaminophen for fever management and ondansetron for nausea/vomiting control. 1
Consider ketorolac for flank or abdominal pain management. 1
Monitoring and Follow-Up
Acute Phase Monitoring
Monitor vital signs every 4 hours including temperature, blood pressure, heart rate, respiratory rate, and oxygen saturation. 1
Perform daily weight monitoring to assess fluid status. 1
Repeat CBC and CRP at 48-72 hours to assess response to therapy. 1
Post-Treatment Follow-Up
Obtain follow-up urine culture 1-2 weeks after completing antibiotics to document clearance. 1
Ultrasound of kidneys and bladder should be performed after the first febrile UTI to detect anatomic abnormalities. 2
Counsel patient to seek prompt medical evaluation for future febrile illnesses and obtain urine specimens at onset of subsequent febrile episodes. 2
Critical Pitfalls to Avoid
Do not delay antibiotic initiation - delays in treating pyelonephritis increase the risk of renal scarring, which occurs in approximately 15% of children after their first UTI episode. 2, 6
Do not rely on bag urine specimens - the 12-83% false-positive rate leads to overtreatment. 4, 2
Do not assume negative dipstick rules out UTI in patients with high pretest probability based on symptoms. 7
Do not treat asymptomatic bacteriuria if discovered incidentally, as this is common in women and does not require antibiotics. 5, 7
Recognize that antimicrobial resistance is increasing to fluoroquinolones, beta-lactams, and trimethoprim-sulfamethoxazole, making culture-guided therapy essential. 3, 7