Figure 14. CT was done for an 11-year-old girl with fever and chest pain. (a) An axial image just below the carina shows linear periosteal reaction at the vertebral end of the left 5th rib adjacent to a large extrapleural collection which is contiguous with necrotic mediastinal and left hilar lymph nodes. Caseous collections in the anterior chest wall partially encircle the sternum without evidence of bone erosion. Florid periosteal reaction was seen along the posterior aspect of the 4th to 8th ribs on the left side. (b) A reconstructed image in the coronal plane shows the extent of the thoracic paravertebral abscess from the level of D1 to D10. Periosteal reaction is seen to cause expansion of the vertebral ends of the adjacent ribs.