Diseases with normal CXR

Diseases with normal CXR : serious resp. disease may have normal CXR, sometimes only possible to detected abn. By compare with prev. Or later examinations, e.g.:
1- obst. Air way dis. As asthma, emphysema.
2- small lesions: us. Impossible to see solitary lung mass or consolidation less than 1 cm.
Even 2 – 3 cm CA lung may very difficult to identify.
Endobronchial lesions as CA, can not dx. On routine films unless cause collapse or consolidation.
3- pulm. Emb. Without infarction even with life threatening emb.
4- infections: as in patient with miliary TB.
5- diffuse pulm. Fibrosis
6- pleural abn.: as dry pleurisy.
Small pl. fluid may be impossible to dx. On PA and lateral films
7- med. Masses: plain CXR very insensitive to dx. Med. Masses, LNs, med. Fluid collections.

Abn. Chest: if the abn. Surrounded on all sides by aerated lung, it must arise within the lung.
If the shadow has broad base, smooth convex border projecting into the lung, well defined outline, so it is pl., extrapl. Or med. In origin.
Silhouette sign: invaluable sign for localizing dis. From plain CXR.
Intrathoracic lesion touching heart, aorta or diaph. Obliterate their borders
It has two important applications:
1- localize shadow by observing which border is obliterated, e.g.: loss of heart border means the shadow in ant. Half of the chest, loss of diaph. Outline indicate the dis. Of pl. or in lower lobes.
2- it makes possible on occasions to dx. Disorders as consolidation or collapse even when its presence is uncertain, when it is in contact with med. Or diaph., losing their sharp outlines.

Radiological signs of lung dis. :
Air space filling: means replacement of air in alveoli by fluid or rarely by other materials.
The fluid either exudate : often called consolidation, or transudate: pulm. Edema.
Signs of consolidation: 1- a shadow with ill defined borders except when in contact with fissure.
2- air bronchogram: if alveoli filled with fluid, the air within bronchi contrasts with fluid in adjacent lung.
3- silhouette sign: i.e. loss of visualization of adjacent med. Or diaph. Outline.
Consolidation of a whole or majority of a lobe is virtually diagnostic of bacterial pneumonia.
Lobar consolidation produce opaque lobe except for air bronchogram.
Patchy consolidation: one or more patches of ill defined shadowing, is usually due to: pn., infarction, contusion, and immunological disorders.
Cavitation(abscess formation) : within consolidated areas in the lung may occur with many bact. And fungal infections, occasionally in infarction and Wegener granulomatosis.
Abscess formation only recognizable once there is communication with bronchial tree, allowing liquid Centre to coughed up and replaced by air, the air then seen as transradiancy within consolidation, and air fluid level may be present.
CT is better and more sensitive than plain CXR for cavitation