American Board of Internal Medicine (ABIM) Certification Practice Exam

Which imaging feature is typical of diffuse idiopathic skeletal hyperostosis?

1. Spinal fractures

2. Flowing osteophytes

3. Disk herniations

4. Bone cysts

The correct answer is: Flowing osteophytes

Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by a distinctive radiological feature known as "flowing osteophytes." These osteophytes are abnormal bony outgrowths that form along the anterior and lateral aspects of the thoracic spine, creating a "flowing" appearance on imaging studies. This radiologic finding is integral to the diagnosis of DISH and helps differentiate it from other conditions such as ankylosing spondylitis, which may exhibit different patterns of bone formation and even fusion but not the same osteophyte pattern. The presence of "flowing osteophytes" is significant because it reflects the underlying pathophysiology of DISH, which involves ossification of the anterior longitudinal ligament and periosteal new bone formation, leading to the characteristic appearance on X-rays or CT scans. Recognizing this feature is essential for clinicians to correctly identify DISH and manage it appropriately. Other listed conditions, while they reflect different spinal pathologies, do not exhibit the specific imaging hallmark of flowing osteophytes associated with DISH. For example, spinal fractures typically manifest as acute changes in bone architecture rather than the gradual ossification seen in DISH. Disk herniations and bone cysts have entirely different