Intraosseous pneumatocysts of the ilium. Findings on radiographs and CT scans

CT scans demonstrated a localized collection of gas adjacent to a normal sacroiliac joint in 5 patients. In each case the lesion was sharply demarcated by a thin sclerotic rim. A benign bone cyst was confirmed histologically in 2 cases. The radiologist should be aware of this appearance so as to avoid invasive procedures based on a misdiagnosis of infection or neoplasm.