Presentation
Abdominal pain. Suspecting an appendicitis we performed an US, and later a CT scan with this incidental finding.
Patient Data
In this CT scan with bone window, we can see a well-defined lesion with gas density in the right sacrum that corresponds to an intraosseous pneumatocyst, an incidental finding.
Case Discussion
A well-defined bone lesion with very low density (approximately gas) suggests an intraosseous pneumatocyst. Differential diagnosis should consider osteomyelitis and osteonecrosis.
Restricting oneself to a subjective assessment on a bone window, intraosseous lipoma might be volunteered as the diagnosis, illustrating the importance of measuring the attenuation of the lesion, showing it is gas, and not fat.