Reticular — lung parenchyma replaced by many thin-walled cysts (lesions less than 10 mm in diameter), hence the term "honeycomb" lung, these microcysts may be barely perceptible, round or oval, giving the lung the radiologic appearance of a fine network.

Seen in disseminated interstitial diseases such as eosinophilic granuloma of the lung, scleroderma, pneumoconiosis (diseases caused by inhalation of organic or inorganic matter), idiopathic pulmonary fibrosis, sarcoidosis, and other, less common disorders.

Miliary, Nodular — numerous discrete, tiny (< 5 mm), uniform densities; evenly distributed throughout the lungs; quite uniform in size.

Seen in miliary tuberculosis, other fungal diseases (histoplasmosis), pneumoconiosis, histiocytosis X (early stage), pulmonary hemosiderosis (late stage) and primary amyloidosis.

Reticulonodular — mixture of the two previously described patterns.

May predominate in one or another portion of the lung in the diseases described.

Kerley's Lines — most commonly encountered in CHF and interstitial pulmonary edema; may be quite transient in these conditions.

May represent a constant, irreversible finding in other interstitial disease, esp. pneumoconiosis, lymphatic spread of neoplasm, lymphatic mitral valve disease, and COPD.

Kerley B Lines — usually < 2 cm in length and about 1 mm in thickness.

Not confined to the margins of the lung.

Attributed to increased tissue and/or fluid accumulation in interlobular septa; also referred to as septal lines.

Kerley A Lines — usually ~ 4 cm in length, relatively straight, linear densities.

Tend to be oriented perpendicular to the nearest pleural surface.

Attributed to increased tissue and/or fluid accumulation in communicating lymphatics between veins and bronchi.

Exaggerated Bronchovascular Markings — ill-reputed sign; lacks specificity in terms of pathologic correlation.

May refer to a lack of crispness of the margins of structures initially giving rise to the linear densities within aerated lung. Caused by excessive tissue or fluid displacing air-filled lung from the interstitial structures.

• Inability to detect radiologic signs of alveolar consolidation on abnormal CXRs such as the air bronchogram sign.

• Majority of interstitial diseases are chronic. Principal exceptions are viral pneumonia, drug-induced pneumonia, and pulmonary edema.


Viral Pneumonia

Patchy alveolar consolidation usually; rarely a predominance of interstitial abnormalities.

Drug-Induced Pneumonia

Nitrofurantoin-Induced Pneumonia

Interstitial lung changes, principally a basal reticular infiltrate.

Presents acutely with chills, fever, quite severe dyspnea, and nonproductive cough within hours or days of the initiation of nitrofurantoin therapy.

Likely to have moderate peripheral eosinophilia.


Pulmonary Edema

Mixed alveolar and interstitial edema.

Apical redistribution of blood flow — results in increased size of upper lung vasculature and background veiling of the pulmonary parenchyma initially.

Subpleural edema, peribronchial cuffing, bronchiolar cuffing, hilar haziness, haziness of vessel detail, reticular pattern, and basilar septal lines.

Kerley B lines are present at the periphery of the lung bases and may be quite prominent — represent thickened interlobular septa.

Usually, enlargement of the heart (if cardiogenic in origin) and redistribution of the pulmonary vasculature (appears esp. engorged in the upper lung zones).

Idiopathic Pulmonary Fibrosis (Hamman-Rich disease)Reticular pattern (honeycombing).

Most common "etiology" of disseminated pulmonary fibrosis.

Differential Diagnosis of Interstitial Lung Disease

Pneumoconiosis Primary Lung Diseases




Histiocytosis X

Coal Worker's pneumoconiosis



Lymphangitic carcinomatosis

Organic dusts (pigeons, turkey, duck, chicken, humidifier) Lipoidosis



Cystic fibrosis

Chemotherapeutic agents (busulfan, bleomycin, methotrexate)

Antibiotics (nitrofurantoin, sulfonamides, INH)

Alveolar Filling Disease

Diffuse alveolar bleeding (Goodpasture'sAmiodarone syndrome, lupus, mitral stenosis, Penicillamine idiopathic pulmonary hemosiderosis)

Lupus-like reactions (hydralazine, procainamide)

Alveolar proteinosis


Alveolar cell carcinoma

Eosinophilic pneumonia

Connective Tissue Disease

Lipid pneumonia

Systemic lupus erythematosus

Rheumatoid arthritis

Infectious Diseases


Miliary tuberculosis


Some fungal and viral infections

Other Cardiovascular Diseases

Idiopathic pulmonary fibrosis

Interstitial pulmonary edema

Bronchiolitis obliterans organizing

Pulmonary hemosiderosis 2° to mitral pneumonia stenosis

Lymphocytic interstitial pneumonia


Pulmonary Sarcoidosis — lymphadenopathy always precedes or presents concurrently with pulmonary changes of the disease.

± Hilar and paratracheal adenopathy.

Intrathoracic lymphadenopathy (75%)

Diffuse parenchymal disease (50%)

Exclusively hilar lymphadenopathy initially (33%)

Pulmonary disease without hilar lymph node enlargement (25%)

Lung involvement varies from a miliary nodular pattern, to a reticulonodular pattern, to a purely reticular pattern (honeycombing).

Occasionally patients exhibit mx. large granulomas simulating metastatic neoplasm.

Likely that a miliary nodular form precedes the reticular pattern.

Progression to marked pulmonary fibrosis of bullous emphysema with disabling functional impairment, development of cor pulmonale, and death occurs in a small % of cases.

Majority of patients remain relatively asymptomatic.


Great majority of patients with abnormal pulmonary function studies do not exhibit radiologically

discernible pulmonary changes.

?? Relatively fine network of reticular infiltrates (honeycombing); generally restricted to the lower lung zones.

Radiologic demonstration of abnormalities of esophagus, duodenum, small bowel, or terminal phalanges more likely to be seen.

Recurrent or chronic aspiration of ingested material may be underlying cause of pulmonary fibrosis.

Histiocytosis X — includes Letterer-Siwe disease, Hand-Schüller-Christian disease, and eosinophilic granuloma. Only eosinophilic granuloma occurs in adults.

Coarse, reticular interstitial pattern.

Individual cysts comprising the coarse reticular or honeycomb pattern are generally less than 5 mm in greatest dimension, although large cysts of up to 6 cm in diameter have been reported.

Pneumothorax = relatively frequent complication.

2/3 deny dyspnea; 2/3 have dry cough; systemic symptoms = lassitude, weight loss, and less

commonly, fever may predominate in 1/3.

Diabetes insipidus may be and associated disorder.

Systemic form — ? involvement of bone, liver, CNS, kidneys, and alimentary tract.





A. ECG leads

B. Endotracheal tube — positioning

C. CVP and PA lines


Air bronchogram — Surrounding consolidation will sometimes allow more peripheral bronchi to be seen as tubular or branching lucencies. Normally only the trachea, mainstem bronchi, and occasionally the origins of the lobar bronchi, are visible on CXRs as air-filled tubular structures. Visualization of the more peripheral bronchi with air in them is usually not possible.

Alveolar (consolidative) densities — An abnormal density caused by the collapse or, more often, the filling of air spaces with abnormal material (blood, pus, water, protein, or cells). Alveolar densities characteristically have irregular, hazy margins except where they are bounded by a pleural surface. (Also referred to as "acinar pattern".) Segmental distribution and air bronchograms are also characteristic of this pattern.

Atelectasis — Collapse and volume loss are synonymous terms. Very small areas of atelectasis often produce a linear shadow, which is often, but not always, horizontal. This is referred to as "plate-like", "linear", or "subsegmental" atelectasis. Lobar and total lung atelectasis also occur. These larger varieties of atelectasis are usually associated with increased density in the involved portion of lung so that there is, in fact, consolidation present as well. To diagnose atelectasis, there must be a specific evidence of volume loss such as displacement of a fissure, the mediastinum, or a hilum. Elevation of the hemidiaphragm and decreased space between ribs can also be signs of atelectasis.

Bleb — A small, thin-walled, air-containing structure. This term is frequently reserved for such small areas which are frequently intrapleural. This term may be used synonymously with "bulla" but often is reserved for smaller air spaces.

Bronchiectasis — Dilatation of a bronchus or bronchi, usually secreting large amounts of offensive pus. Dilatation may be in an isolated segment or spread throughout the bronchi.

Bulla — See "bleb" or "cavity." These abnormal air spaces may or may not be associated with diffuse pulmonary emphysema.

Caseous — cheese-like.

Cavity — Another form of air space in the lung. This term is usually reserved for those which are the result of tissue necrosis, unlike bullae. Thickness and irregularity of the walls often the distinguishing feature separating cavities from bullae or blebs.

Consolidation — Filling of pulmonary air space with some abnormal material. May also be referred to as "alveolar disease."

Density — A nonspecific term that can be used to describe any area of whiteness on the chest film. Normal structures such as the heart as well as abnormalities in the lungs may be called densities. This term is often used when the nature or cause of an abnormal shadow is not known. It is a useful term in that situation, since other terms (e.g., "mass" or "infiltrate") frequently imply more specific entities which may or may not be present.

Extra-pleural — Anything that is outside both the parietal and the visceral pleura but that impinges on the lungs. The heart is the most obvious example. Since normal or abnormal structures in this location are separated by two layers of pleura from the lung, the margins of these densities are characteristically sharp and smoothly tapering.

Hilum (pleural = hila.) — "lung root;" medusa-like tangle of arteries and veins on either side of the heart shadow. Irregular medial shadow in each lung where the bronchi and pulmonary arteries enter. Other structures in these areas, particularly lymph nodes, are normally so small as to be inapparent. The normal hilar shadow is almost entirely composed of the central pulmonary arteries. R hilar vessels seem to extend out farther than those on the L because a part of the L hilum is obscured by the shadow of the more prominent L side of the heart. The L hilum on a normal CXR is a little higher than the R one because of the slightly higher take-off of the L pulmonary artery.

Interminate or mixed lung disease — This category of diffuse lung disease is frequently used when the radiographic criteria to designate a specific pattern (consolidative, interstitial, etc.) may not be present, or when there may be elements of several types of diffuse lung disease in the same patient.

Infiltrate — A poorly defined abnormal pulmonary density or any such density sharply bounded by pleura and fissures. This is a confusing term, since it may be used to indicate any abnormal lung density or, by others, as a synonym for consolidation. Synonymous with "fluid density."

Interstitial — The portion of the pulmonary parenchyma that consists of the actual lung tissue as opposed to the air spaces. Includes alveolar walls, septa, bronchovascular structures, and pleura. Involvement of this tissue is a frequent form of diffuse lung disease.

Kerley's lines — most commonly encountered in CHF and interstitial pulmonary edema; may be quite transient in these conditions; may represent a constant, irreversible finding in other interstitial disease, esp. pneumoconiosis, lymphatic spread of neoplasm, lymphatic mitral valve disease, and COPD.

Kerley B (septal) lines — usually < 2 cm in length and about 1 mm in thickness; not confined to the margins of the lung; attributed to _ tissue and/or fluid accumulation in interlobular septa; thickening of interlobular septa for any reason may allow them to be seen as narrow, straight shadows, especially at the periphery of the bases; another form of interstitial abnormality.

Kerley A lines — Usually ~ 4 cm in length, relatively straight, linear densities; tend to be oriented perpendicular to the nearest pleural surface; attributed to _ tissue and/or fluid accumulation in communicating lymphatics between veins and bronchi.

kVp — Peak kilovoltage; the peak voltage across the radiographic tube. An increase in this factor allows increased tissue penetration by higher energy roentgens.

Lingula — (tongue-shaped) area of left lung adjacent to the left ventricle not a separate lobe.

Lucency — An increase in blackness of an area on the radiograph. In the lung, it may imply that air is being trapped, that lung tissue has been destroyed, or that there is decreased blood supply. Artifacts, changes in position, and soft tissue abnormalities can also cause areas of lucency.

milliampere/seconds (mAs) — This is the amount of current through the radiographic tube. The amount of current and the length of time during which the current flows control the quantity of x-rays generated. Increasing the mA causes an increase in patient exposure to ionizing radiation and produces more x-rays to create an image on the film.

Mass — A solid-appearing, reasonably well-defined soft tissue density usually larger than 3 or 4 cm in diameter.

Mediastinal — Referring to the structures or a lesion between the lungs. Unless the lungs are actually invaded by a mediastinal lesion, the lesion's x-ray shadow will be extra-pleural and, therefore, usually will have sharp demarcation from the lung.

Miliary — A form of diffuse lung disease consisting of countless very tiny nodular densities.

Nodule — A well-defined, more or less round density in the lung; smaller than a mass. No rigid size distinction between a "mass" and "nodule" is possible.

Opacity — Synonym for "density."

Pleural — Refers to an abnormality arising in the pleura or pleural space. Most commonly this is free of loculated fluid.

Pneumothorax — Free air in the pleural space; may be modified by the following descriptive terms" hydro-, pyo-, hemo-, chylo-, tension.

Pulmonary edema — defined radiographically as diffuse, bilateral consolidation by fluid' other materials can fill air spaces bilaterally and give the same radiographic pattern.

Reticular — A fine branching pattern with lines radiating in all directions; one of the signs of the interstitial pattern.

Segmental — Limited to specific bronchopulmonary segments or lobes. Segmental distribution of disease usually indicated bronchial or vascular involvement and is most common in consolidation.

Septal lines — see Kerley B lines.

Silhouette sign — Normally an interface is seen between areas of different density as between shadows of the heart and lung. Loss of air on the pulmonary side, usually because of consolidation, may cause obliteration or "silhouetting" of this normal interface. This sign is useful in localizing an abnormality or confirming the presence of abnormality. Occasionally the silhouette sign will be the only definite indication of consolidation next to the heart or diaphragm.


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  Pneumonia Pulmonary Infarct ARDS Pneumo-








Emphysema Bronchitis Pleural Effusion Pericardial




Air visible

Air occluded

Masses nearby


Intercostal Spaces












Increased density between gastric bubble and diaphragm boarder


Lungs (consolidation)

Fluid changes




Homogeneous density

Patchy infiltration (heterogeneous)

Complete density





  Pneumonia Pulmonary Infarct ARDS Pneumo-








Emphysema Bronchitis Pleural Effusion Pericardial


Area involved






Diagnostic Changes

Air bronchogram

Kerley B lines


Volume changes


Overinflated (one side)

Underinflated (one side)

No inflation

Overinflated (lobe)

Underinflated (lobe)

Hyperinflated (both)

Underinflated (both)



Use of expiratory film

Gravity changes

Air at apexes

Fluid at bases

Noticeable structures



Old scarring





  Pneumonia Pulmonary Infarct ARDS Pneumo-








Emphysema Bronchitis Pleural Effusion Pericardial



Increased density

Kerley lines (A)

Vascular signs of collapse

Heart / Mediastinum

Silhouette Sign

Disappeared (anterior)

Hazy (posterior)

Increased Borders

Aortic knob

Pulmonary artery

Left ventricular border

Right ventricular border

Triangular shape

Signs of Shift


Nonsymmetrical clavicles





  Pneumonia Pulmonary Infarct ARDS Pneumo-








Emphysema Bronchitis Pleural Effusion Pericardial



Hilar Region

Butterfly effect



Symmetrical - elevated

Symmetrical - depressed



Not visible








Fluid density (white)

Air density (black)


....................................1. Up

2. Down


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