Pyogenic sacroiliitis. An absolute indication for computerized tomographic scanning.

Pyogenic sacroiliitis (PSI) resulted from direct injection of a foreign substance, pumice, in a 32-year-old woman and was complicated by iliopsoas abscess. The symptoms of PSI are unspecific, and similar complaints may accompany such conditions as herniated disc and arthritis. Results of physical examination may be misleading, especially if movements that stress the sacroiliac joint are omitted. Early roentgenograms are normal and rarely aid in the diagnosis. Scintiscanning with gallium and technetium may indicate an inflammatory pelvic focus. These methods lack specificity, however, and may underestimate the extent of disease. The computerized tomographic (CT) scan was effective in detecting interosseous gas with an associated soft tissue abscess. It also proved invaluable in precisely delineating the location and extent of the lesion in and around the sacroiliac joint, facilitating use of the most expeditious surgical approach. Through follow-up CT studies the course and end results of therapy can be objectively determined.