What is the workup for acute pyelonephritis (infection of the kidney)?

From the Guidelines

The workup for pyelonephritis should begin with a thorough history and physical examination, followed by urinalysis and urine culture to confirm the diagnosis, as recommended by the European Association of Urology guidelines 1. The diagnosis of pyelonephritis typically involves:

• Urinalysis to assess white and red blood cells and nitrite
• Urine culture and antimicrobial susceptibility testing to guide antibiotic therapy
• Evaluation of the upper urinary tract via ultrasound to rule out urinary tract obstruction or renal stone disease
• Additional investigations, such as a contrast-enhanced computed tomography scan, if the patient remains febrile after 72 hours of treatment or if there is a deterioration in clinical status Key considerations in the management of pyelonephritis include:
• Prompt initiation of empiric antibiotic therapy, with options including fluoroquinolones, such as ciprofloxacin 500mg twice daily or levofloxacin 750mg daily, or beta-lactams like ceftriaxone 1-2g daily 1
• Treatment duration, which is typically 5-7 days for fluoroquinolones and 7 days for dose-optimized β-lactams, as recommended by the Wikiguidelines group consensus statement 1
• Imaging studies, such as renal ultrasound or CT scan, to identify structural abnormalities, obstructions, or complications that might require additional interventions
• Patient education on increasing fluid intake and seeking follow-up care if symptoms persist despite appropriate antibiotic therapy.

From the FDA Drug Label

Dosing and initial route of therapy (i.e., I.V. or oral) for complicated urinary tract infection or pyelonephritis should be determined by the severity of the infection. In the clinical trial, pediatric patients with moderate to severe infection were initiated on 6 to 10 mg/kg I. V. every 8 hours and allowed to switch to oral therapy (10 to 20 mg/kg every 12 hours), at the discretion of the physician. The mean duration of treatment was 11 days (range 10 to 21 days). Uncomplicated and Complicated Urinary Tract Infections (including pyelonephritis) caused by Escherichia coli or Klebsiellapneumoniae, when the infection is severe, or caused by Escherichia coli, Klebsiellapneumoniae, or Proteus mirabilis, when the infection is mild to moderate, including cases associated with concurrent bacteremia with these microorganisms

The workup for pyelonephritis involves determining the severity of the infection and choosing an appropriate antibiotic regimen.

• Initial assessment: Evaluate the severity of the infection to determine the initial route of therapy (I.V. or oral).
• Antibiotic selection: Choose an antibiotic such as ciprofloxacin or cefepime, considering the suspected or confirmed causative microorganisms.
• Dosage and duration: For ciprofloxacin, the dosage is 6 to 10 mg/kg I.V. every 8 hours, with a possible switch to oral therapy (10 to 20 mg/kg every 12 hours) at the discretion of the physician. The mean duration of treatment is 11 days (range 10 to 21 days) 2.
• Considerations: Take into account the patient's renal function and adjust the dosage accordingly, as well as consider the potential for drug-resistant bacteria and maintain the effectiveness of the chosen antibiotic 3.

From the Research

Diagnostic Approach

• The diagnosis of pyelonephritis typically involves a combination of history, physical examination, urinalysis, and urine culture 4, 5, 6, 7, 8.
• Urine culture with antimicrobial susceptibility testing should be performed in all patients and used to direct therapy 4, 5, 7.
• Imaging studies, such as contrast-enhanced computed tomography, are not necessary unless there is no improvement in the patient's symptoms or if there is symptom recurrence after initial improvement 5, 6, 7.

Treatment Options

• Outpatient oral antibiotic therapy with a fluoroquinolone is successful in most patients with mild uncomplicated pyelonephritis 4, 5, 6, 7.
• Other effective alternatives include extended-spectrum penicillins, amoxicillin-clavulanate potassium, cephalosporins, and trimethoprim-sulfamethoxazole 4, 5, 6.
• Inpatient treatment is recommended for patients with severe illness, complicated infections, sepsis, persistent vomiting, failed outpatient treatment, or extremes of age 4, 5, 6, 7.
• The standard duration of therapy is seven to 14 days, and urine culture should be repeated one to two weeks after completion of antibiotic therapy 4, 8.

Special Considerations

• Pregnant patients with pyelonephritis are at significantly elevated risk of severe complications and should be admitted and treated initially with parenteral therapy 7.
• Patients with concurrent urinary tract obstruction should be referred for urgent decompression 7.
• Patients with suspected complicated pyelonephritis require the standard assessment plus blood cultures and urinary tract imaging, preferably a computed tomography (CT) scan 6.