American Board of Internal Medicine (ABIM) Certification Practice Exam

What imaging method is preferred if symptoms and fever persist longer than 72 hours in patients hospitalized with pyelonephritis?

1. Magnetic Resonance Imaging

2. Ultrasonography

3. X-ray

4. CT scan

The correct answer is: CT scan

In cases of pyelonephritis, especially when symptoms and fever persist beyond 72 hours despite treatment, a CT scan is the preferred imaging method. This is because a CT scan provides detailed cross-sectional images of the kidneys and surrounding structures, enabling the identification of complications such as abscess formation, obstruction, or other anatomical anomalies that may not be evident through other imaging modalities. Ultrasonography, while useful for assessing kidney size and presence of hydronephrosis, may lack the sensitivity needed to detect all potential complications. Magnetic Resonance Imaging is typically not utilized in acute pyelonephritis cases due to cost, availability, and the fact that it generally does not add significant value over a CT scan. X-rays are limited in their ability to provide the necessary detail for evaluating renal pathology. In summary, a CT scan is the best imaging choice for evaluating persistent symptoms in pyelonephritis as it comprehensively assesses the kidneys and surrounding tissues for underlying issues that may require additional management.