Interstitial Disease

The reticular appearance refers to a collection of innumerable small linear opacities that together produce an appearance resembling a “net”. The pattern can be fine, medium or coarse. Fine and medium patterns are shown here. Reticular patterns represent interstitial lung disease.
End stage interstitial lung disease can result in the so-called “honeycomb” appearance. The honeycomb appearance is due to shadows of air space 5-10 mm in diameter and 2-3 mm in wall thickness.

Bilateral interstitial and alveolar infiltrates with typical sparing of apices. Arrow showing pneumothorax.

Peribronchial cuffing (arrow) occurs when interstitial fluid accumulates around a bronchus. Peribronchial cuffing is present if the bronchial wall is thicker than the tracing of a well-sharpened pencil. [Courtesy of Dr. N. Jaffer]

Kerley B lines represent thickened connective tissue planes, for example due to edema of the septal lines of secondary lobules. They are most commonly due to pulmonary edema or lymphangitic carcinomatosis. Kerley B lines are horizontal, <2 cm long and 1 mm thick, at periphery of lung and reaching the lung edge.

The left image (a) shows mildly reduced lung volumes, hazy opacifications and reticulation, primarily in the lower lobes. The right image (b), taken about 9 months later, shows progression of the reticulation, volume loss and some nodularity. [Courtesy of Dr. Ted Marras]

“Silhouette sign” (loss of normally appearing profiles). Unilateral localized infiltrate involving lingula and obliterating left heart border.