American Board of Internal Medicine (ABIM) Certification Practice Exam

In the case of acute or chronic osteomyelitis, what is the next best choice of imaging study when MRI with contrast is contraindicated?

1. X-ray

2. Contrast-enhanced CT

3. Ultrasound

4. Plain CT scan

The correct answer is: Contrast-enhanced CT

When assessing acute or chronic osteomyelitis, if an MRI with contrast is contraindicated, a contrast-enhanced CT scan is often considered the next best imaging modality. This is primarily due to several factors regarding how osteomyelitis is characterized and diagnosed through imaging. A contrast-enhanced CT scan provides detailed cross-sectional images of the bone and surrounding soft tissues, making it particularly useful for identifying abscesses, bone destruction, and changes in the medullary cavity that are indicative of osteomyelitis. The use of contrast enhances the visibility of vascular structures and lesions, helping to differentiate between normal and infected tissue. This level of detail is essential for evaluating the extent of infection and guiding management decisions. Other imaging modalities, such as plain X-rays, might not show early changes of osteomyelitis, which can lead to misdiagnosis or delayed treatment. Ultrasound lacks the specificity needed for detailed bone assessment and is typically not a first-line diagnostic tool for osteomyelitis. While a plain CT scan can provide some information, it does not have the same contrast enhancement as a contrast CT, which significantly improves the diagnosis and evaluation of infectious processes. Thus, in cases where MRI with contrast is not an option, a contrast-enhanced