Diffuse idiopathic skeletal hyperostosis (DISH) is a condition where there is flowing ossification of the anterior longitudinal ligament involving the thoracic spine and enthesopathy (e.g. at the iliac crest, ischial tuberosities, and greater trochanters). There is no involvement of the sacroiliac synovial joint.

Ankylosing spondylitis (AS) is a very close differential diagnosis, however, the following points favor the diagnosis of diffuse idiopathic skeletal hyperostosis:

• old age of the patient (AS involves the middle-aged males)
• bulky syndesmophytes
• sparing the synovial portion of sacroiliac joint (they are ankylosed in AS)
• calcification of the bridging sacroiliac ligament (typical of DISH)

Chalk stick or carrot stick fractures are fractures of a fused spine, classically seen in diffuse idiopathic skeletal hyperostosis and ankylosing spondylitis.

The hyperintense signal of intervertebral discs may be due to the presence of mobile protons (liquid state or milk of calcium) in calcium ¹.