Postoperative CT changes: Numerous small centrilobular densities are seen throughout the right lung on the lung windows of non-high-resolution CT images obtained at two adjacent levels (A & B). Also note mild, central bronchial wall thickening in the right lung.

A

On both images they appear as somewhat ill-defined densities a few millimeters in size clustered around several arteries (for example, see circled area and compare right and left sides). Also on image B there is a suggestion of "tree-in-bud" seen as a tiny branching V- or Y-shaped density (arrow).

B

Centrilobular nodules: Centrilobular densities can best be appreciated on high-resolution CT scans, but can also sometimes be seen on regular CT images, as in this case. The location of the nodules can be inferred as centrilobular if they are near small vascular branches, surround or obscure the centrilobular artery, or are centered 5 to 10 mm from the pleural surface. These densities may appear as a rosette of small opacities, and if associated with filling or thickening of the bronchiole will result in a tree-in-bud appearance.

Differential diagnosis: The differential diagnosis for centrilobular densities generally falls into the category of peribronchiolar disease, but may include perilymphatic or perivascular disease. Centrilobular densities due to peribronchiolar diseases may be seen with bronchopneumonia (particularly in regions peripheral to frank consolidation), bronchiectasis, cystic fibrosis, bronchogenic spread of tuberculosis, bronchiolitis obliterans, cryptogenic organizing pneumonia (BOOP), respiratory bronchiolitis, and hypersensitivity pneumonia.

Reference:

Webb W, Müller N, Naidich D: High-resolution CT of the Lung, 2nd ed. Philadelphia, Lippincott-Raven Publishers, 1996, pp 98-103.

Discussion

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