Is a computed tomography (CT) scan of the abdomen necessary in a young, healthy patient with likely acute pyelonephritis and Escherichia coli (E. coli) bacteremia who is improving with intravenous (IV) antibiotics?

From the Guidelines

A CT abdomen is generally not necessary in a young, healthy patient with likely pyelonephritis and E. coli bacteremia who is improving with IV antibiotics. The recommended approach is to continue IV antibiotic treatment, typically with a fluoroquinolone like ciprofloxacin 400 mg IV every 12 hours or a third-generation cephalosporin like ceftriaxone 1-2 g IV daily, as supported by the most recent guidelines 1. Treatment duration should be 7-14 days, depending on clinical response.

If the patient shows consistent improvement (decreasing fever, reduced flank pain, improving urinary symptoms, and normalizing white blood cell count), imaging can be deferred. Clinical improvement suggests that the infection is responding appropriately to antibiotics and there are likely no complications requiring surgical intervention. This approach is supported by the 2022 update of the ACR Appropriateness Criteria for acute pyelonephritis, which states that CT of the abdomen and pelvis is not beneficial in the initial imaging evaluation for the first-time presentation of suspected APN in an uncomplicated patient 1.

However, a CT scan should be considered if:

• The patient's condition worsens or fails to improve after 48-72 hours of appropriate antibiotic therapy.
• There are signs of urinary obstruction or renal abscess.
• The patient has a history of urinary tract abnormalities or recurrent infections. The rationale for this approach is that uncomplicated pyelonephritis in young, healthy individuals typically responds well to antibiotics alone, as nearly 95% of patients with uncomplicated pyelonephritis become afebrile within 48 hours after appropriate antibiotic therapy, and nearly 100% become afebrile within 72 hours 1. Unnecessary imaging exposes the patient to radiation and increases healthcare costs without providing significant additional benefit in straightforward cases.

From the Research

Necessity of CT Scan in Acute Pyelonephritis

• A computed tomography (CT) scan of the abdomen is not necessary in a young, healthy patient with likely acute pyelonephritis and Escherichia coli (E. coli) bacteremia who is improving with intravenous (IV) antibiotics 2, 3, 4.
• Imaging, usually with contrast-enhanced computed tomography, is only necessary unless there is no improvement in the patient's symptoms or if there is symptom recurrence after initial improvement 2.
• Simple pyelonephritis of the young female without febrile UTI history requires little imaging 3, 4.
• Extensive imaging workup is mandatory in the male, the elderly, when treatment is not rapidly effective or in case of early relapse 3, 4.

Patient Characteristics and Imaging Needs

• Young, healthy patients with acute pyelonephritis and E. coli bacteremia who are improving with IV antibiotics do not require a CT scan 2.
• Patients with severe illness, complications, or those who do not respond to initial empiric antibiotic regimens may require further evaluation, including imaging studies 2, 5.
• Patients with urinary tract abnormalities, diabetes, or immunocompromised status may require more extensive imaging workup 3, 4.

Treatment and Management

• Acute pyelonephritis caused by highly virulent uropathogens in an otherwise healthy woman may be considered an uncomplicated infection 5.
• The optimal treatment duration for acute uncomplicated pyelonephritis has not been established, but 10- to 14-day regimens are recommended 5.
• Antimicrobials that attain high renal tissue levels, such as fluoroquinolones, trimethoprim-sulfamethoxazole, or aminoglycosides, are preferred for pyelonephritis 5.