Common lung radiographic syndromes

2021-07-03 10:03 AM

On the straight film, standing position, the fluid concentrates at the bottom of the lung for a dark, uniform blur; whose upper limit is an indistinct fuzzy curve.

Pleural effusion

Free pleural effusion

Fluid in the pleural cavity (between parietal and visceral leaves) is concentrated in the low area. On the straight film, standing position, the fluid concentrates at the bottom of the lung for a dark, uniform blur; whose upper limit is an indistinct fuzzy curve, concave up and inward, that is the radiographic Damoiseau curve; not clearly see the diaphragm, the heart border; The translation changes position according to the patient's position.

When the amount of fluid is small, only the oblique angle of the diaphragm is seen, it is seen earlier on the slant film at the posterior costal angle, the earliest is in the supine position with horizontal X-rays.

Abdominal ultrasonography shows pleural effusion earlier on radiographs, with echogenic hollowness on the diaphragm.

When multiple mediastinal fluids are pushed to the opposite side, the diaphragm is pushed down, and the remaining lung field is too bright due to compensatory ventilation.

The film has taken in the supine position, pleural fluid in the lower part of the back, shown on straight film as a limited, indistinct cloud in the middle of the thorax.

On computed tomography (CT) scan, pleural fluid is deposited in the lower part, in the posterior chest wall, crescent-shaped with fluid density (from -10 H to +20 H). When the amount of fluid is high, the lung parenchyma is forced inward, called passive atelectasis, the lower lobe may collapse completely and become submerged in fluid.

Magnetic resonance imaging also showed a crescent of fluid in the lower part of the chest. The cause of pleural effusion can be pleurisy, pleural tumor, thoracic trauma, effusion due to heart disease, kidney disease. On normal lung radiographs, the types of fluid cannot be distinguished. Ultrasound can distinguish clear or non-clear fluid due to pus, computed tomography and magnetic resonance can detect fluid and blood.

Free pleural effusion diagnosisbook

Figure: Free pleural effusion.

Localized pleural effusion

Fluid may be localized to the diaphragm, chest wall, mediastinum, or interlobar fissure, with little or no movement when changing the patient's position. The shading of localized fluid usually has a sharply rounded base, a fuzzy upper margin, and a greater height than width. It should be differentiated from pleural tumors.

Fluid is localized in the presence of pulmonary fibrosis, interstitial edema, or pleural adhesions.

 Localized pleural effusion sites diagnosisbook

Figure: Localized pleural effusion sites.
(a. the apex of the lung; b. posterior chest wall; c. lateral chest wall; d. minor interlobar fissure; e. major interlobar fissure; f. supradiaphragmatic)

Focal pleural effusion diagnosisbook

Figure: Focal pleural effusion.


Air enters the pleural space due to damage to the lung and viscera or from damage to the chest wall and parietal leaflet. Negative pressure between the two pleura pulls air in. The image is too bright in the apex and axillary region, no blood vessels can be seen, the visceral leaf can be seen as a very thin blurred line separating the pneumothorax and the lung parenchyma that is passively pushed and collapsed. Air may be in the mediastinal pleura within the apical region. 

When the pneumothorax is small, it is easy to detect when taking a lung scan during expiration.

Valved pneumothorax is an emergency requiring drainage. Due to a valved pleural perforation, air enters the pleural space during inspiration and cannot escape during expiration. The air pressure in the pleural space gradually increases, pushing the adjacent organs: the intercostal space is wide, the mediastinum is pushed to the opposite side, the diaphragm is lowered, the lung parenchyma is collapsed gradually around the umbilicus.

Usually, there is a small horizontal level of fluid at the diaphragmatic costal angle, which is the physiological amount of fluid in the pleural cavity, when seen a lot, it must be suspected of hemothorax, a complication of pneumothorax.

If the patient's condition is severe and must be taken in the lying position, pneumothorax is difficult to detect. Air concentrated in the anterior chest wall is not visible, sometimes a focal area of ​​light is visible, or the mediastinum border is abnormally clear. If the X-ray can be obtained in the supine position, then on exhalation, the pneumothorax will be easier to see. Computed tomography (CT) is very sensitive to the detection of pneumothorax, which is essential in critically ill patients to make decisions about drainage therapy.

Pneumothorax and pneumothorax with valve diagnosisbook

Figure: Pneumothorax (left), pneumothorax with valve (right).

Localized Pneumothorax: When pleural adhesions are present, or lung elasticity is reduced, the air is localized to the chest wall anterior, posterior, lateral, or apical, above the diaphragm, which is easier to detect on radiographs. while breathing out.

The common cause of pneumothorax is the rupture of subpleural air bubbles (spontaneous pneumothorax); It may also be due to trauma.

Effusion - pneumothorax

The presence of fluid and air in the pleural space. Diagnosis is easy, on an upright chest x-ray, the patient stands with a horizontal level of fluid. The lung parenchyma collapses around the hilum, protruding from the fluid surface like a rock. If the effusion-pneumothorax is localized, multiple levels of fixed fluid may be seen.

On computed tomography, the lung was found floating on the surface of the fluid. Computed tomography is useful to differentiate focal pneumothorax from multiple peripheral lung abscesses.

The usual cause is air entering during pleural aspiration. In addition, it may be due to thoracic trauma, due to the rupture of a lung abscess into the pleura.

Pleural tumor

Primary pleural tumor

Primary pleural tumors are mainly mesotheliomas, which can be benign or malignant, diffuse or localized. The diffuse type is always malignant.

Malignant mesothelioma may present with irregular thickening of the pleura or diffuse nodularity; irregular border opacity; more or less pleural effusion. No calcification, no cavernous ulceration. There may be opacities in the lung parenchyma, chest wall bone lesions. Computed tomography is the best lesion assessment.

Benign mesothelioma usually presents with basal shading, solitary, well-defined boundaries, and more or less arc-shaped. No calcification is possibly associated with pleural effusion.

Pneumothorax and pleural tumor diagnosisbook

Figure: Pneumothorax (left), pleural tumor (right).

Secondary pleural tumor

Metastatic pleural opacities are the most common pleural malignancies, often originating from tumors of the lung, breast, gastrointestinal tract, and kidney. Presented as opacities, sometimes bilateral, adjacent to the peripheral pleura or mediastinal pleura, diaphragm, and interlobar fissure. Possibly diffuse pleural thickening. Pleural effusion or combination. May be associated with chest wall injury.

Pleural lymphoma presents as a focal pleural thickening or subpleural opacities, usually arising from a lymphoid mass in the mediastinum.

The contact angle is obtuse and sharp diagnosisbook

Figure: The contact angle is obtuse and sharp.

Abnormal shading in the mediastinum

Abnormal shading in the mediastinum is characterized by uniform shading; external limits are clear and continuous, convex to the lung, the angle of contact with the mediastinum is an obtuse angle; The inner limit is not visible because the shadow is mixed with the shadow of the mediastinum.

Computed tomography is a very effective mediastinal study technique.

Mediastinal division

The anterior mediastinum is bounded anteriorly by the sternum, posteriorly by the anterior border of the trachea, and posterior border of the heart.

The mediastinum is limited posteriorly by an anterior bordering plane of the vertebral bodies.

The posterior mediastinum is limited to the posterior arches of the ribs.

The mediastinum is divided into three levels: superior, middle, and inferior, by two planes crossing the superior border of the aortic arch and the inferior border of the tracheobronchial junction.

The division of the anterior, middle, and posterior mediastinum and the upper, middle, and lower mediastinum

Figure: The division of the anterior, middle, and posterior mediastinum and the upper, middle, and lower mediastinum.

The nature of mediastinal lesions may be related to their location.

The most common types of mediastinal tumors in adults are:


Type tumor

Mediastinum anterior upper floor

Thyroid goiter

Mediastinum anterior to the middle and lower levels

Thymus tumor

posterior mediastinum

Nerve tumor

Middle and anterior mediastinum

Bronchial cocoon

Mediastinal enlargement is the most common cause of mediastinal opacity and can be found anywhere in the mediastinum.

Common mediastinal tumor locations diagnosisbook

Figure: Common mediastinal tumor locations.
(1. goiter; 2. thymoma; 3. pleuritic cyst; 4. tracheobronchial junction; 5. neuroma)

Abnormal light in the mediastinum

Except for tracheal balloons, mediastinal luminosity can be caused by pneumomediastinum, pneumopericardium, or esophageal abnormalities.

Mediastinal pneumothorax

On straight film, one or two sides of the luminosity are shown along the mediastinal border, on slant film, there is luminescence behind the sternum, anterior border of the trachea, surrounding the aortic arch.

Continuous diaphragmatic sign on straight film. Signs of a prominent thymus gland in young children.

The image of pneumomediastinum usually does not move with changing patient position. Pneumomediastinum is often associated with subcutaneous pneumothorax, or sometimes with pneumothorax.

Causes: Pneumothorax, tracheobronchial rupture, esophageal perforation, facial surgery, neck and chest surgery, perforation of retroperitoneal hollow viscera: duodenum, colorectal.

 Mediastinal shadow on straight lung film diagnosisbook

Figure: Mediastinal shadow on straight lung film.
(1. brachiocephalic trunk; 2. superior vena cava; 3. right atrium; 4. right diaphragmatic angulation; 5. inferior vena cava; 6. left subclavian artery; 7. node aorta; 8. left ventricle; 9. left-diaphragm fat mass; 10. pulmonary artery [pulmonary hilum])


The luminosity surrounds the heart, does not reach the aorta, and is mobile, with persistent diaphragmatic signs

Causes: Chest trauma, pericardial procedures, anaerobic pericarditis.

Esophageal abnormalities

Esophageal enlargement, diaphragmatic hernia, esophageal diverticulum.

In addition, mediastinal light may be due to mediastinal abscess.

Pneumococcal syndrome

A collection of symptoms reflecting damage to the alveoli, where the air in the alveoli is replaced by fluid or by healthy or malignant cells.

Types of damage

Alveolar opacities (alveolar opacities): Round, translucent margins, about 5 - 10 mm in diameter.

The marginal opacity is indistinct, possibly with a markedly linear interlobular fissure limitation; may have a triangular base at the periphery, or have a watermark of butterfly wings in the hilum on both sides.

Pneumothorax injury characteristics

Alveolar nodules.

The lesion margin is blurred unless leaning against the interlobar fissure.

Tends to focus on broader lesions.

May form triangular, lobular, or lobar opacities. (systematic blur)

There may be a butterfly shape with two opacities on either side of the hilum, not extending to the periphery and apex of the lung. The mechanism of formation is unknown.

Tracheobronchial branch in shadow.

Spread quickly, disappear quickly, under 48 hours.

The main causes of the pneumococcal syndrome

Bacterial or viral pneumonia.       

Pulmonary tuberculosis.

Lung fungus.

Lung parasitic infection.

bronchiole-bronchial cancer.        

Lung metastasis.

Primary lymphoma.                   

Pulmonary edema

Pulmonary infarction.                                 

Hemorrhage in the alveoli... 

Tracheobronchial branch sign in the pneumothorax and kerley lines

Figure: Tracheobronchial branch sign in the pneumothorax (left), Kerley lines (right).

Interstitial syndrome

The interstitial organization includes the connective tissue surrounding the bronchi and blood vessels, the interlobular septa, the subpleural organization of the pleura, and the alveolar wall. Normally, interstitial tissue is not visible on chest radiographs and on computed tomography (some basal lobules can be seen on computed tomography) Interstitial tissue is visible only when thickened by fluid or infiltrated cells. cell.

Types of damage

Short opacities are Kerley lines, due to the thickening of the interlobular septum, seen in the periphery. Depending on the location, Kerley road is also called Kerley A, B, C, D, from 1 to 10mm long.

Long blurred lines due to fibrous lines and atelectasis.

The vascular surrounds of the bronchi are thickened, making their edges indistinct.

The pleural border, due to the thickening of the subpleural interstitial tissue, is often associated with the Kerley B opacities, adjacent to the pleura at the base of the lung.

Glass opacity image due to the dense presence of microscopic opacities, showing decreased lung brightness, still visible vascular branches, on chest radiograph as well as on computed tomography, different from coagulated pneumothorax The pulmonary features do not show vascular branches.

Small opacities (1-7mm): clear margins, no tendency to focus, visible only when >3mm in size, usually mainly in the basal area and due to hematogenous spread of infected lesions or tumors (TB, metastatic schizophrenia)

Sometimes it is difficult to distinguish between opacities and pneumothorax, when these two syndromes coexist, computed tomography helps to differentiate well.

Matte mesh, thick or thin, thin mesh hard to detect; Reticular opacity in the elderly is normal.

Large opacities (7 - 20 mm) and opacities (> 20 mm) are usually of hematogenous origin and are seen predominantly at the base (bubble sign).

Honeycomb opacity: irreversible, thick mesh-like opacity caused by thickening of the fibrous interstitial tissue, creating polygonal shapes surrounding some alveoli that have destroyed their walls and filled with gas.

Features of interstitial tissue damage

Clear blur.


There are no lobes or lobes.

No tracheobronchial branches.

Slow progress.


Cancerous lymphadenitis, lymphoma.

Infectious diseases (tuberculosis, fungi, viruses, parasites).

Pulmonary disease.

Early-stage acute pulmonary edema.

Bronchiolitis obliterans, idiopathic interstitial fibrosis, ...

Schematic image of interstitial lesions on computed tomography film

Figure: Schematic image of interstitial lesions on computed tomography film.
(1. pleural effusion; 2. Kerley lines; 3. perivascular and bronchial opacities; 4. opacified glass, visible blood vessels; 5. reticular opacities; 6. interstitial nodular opacities; 7. honeycomb shape)

Bronchial syndrome

Bronchial syndrome is a collection of radiological manifestations of bronchial disease, including signs directly associated with bronchial thickening or dilation or stasis, and indirect findings related to ventilation consequences. or circulation of bronchial obstruction.

Direct sign

Bronchial wall thickening:

Normally, the bronchial wall is only seen in the main bronchus and in the para hilum lobe bronchi. On computed tomography scans with thin slices, segmental bronchial and subsegmental bronchi will be seen (2/3 of the lung).

Bronchial wall thickening due to edema of the peribronchial interstitial, cellular infiltration in the bronchial mucosa, or fibrosis.

Train track shape, thick-walled circle, circular opacification of adjacent blood vessels (unusual double-barreled gun shape).

Dirty lung shape: due to diffuse bronchial wall thickening but not directly visible. Computed tomography allows showing thickening of the small bronchi with or without bronchiectasis.


Railroad, double-barreled gun with a bronchus larger than the accompanying artery.

The bronchial walls are irregularly thick, not parallel.

Pseudo-honeycomb image: grid-like blur but localized and not visible in the periphery.

The figure of small cysts with fluid levels.

Causes of bronchiectasis: Benign tumor, bronchial malignancy, primary infection, cavernous tuberculosis, bronchial foreign body.

Bronchial stasis:

Due to increased bronchial secretion or impaired bronchial motility, resulting in dilated bronchi filled with mucus, common causes are bronchial asthma, chronic bronchitis. Bronchial stagnation produces palmar-shaped or Y-, V-shaped, or nodular opacities.

Indirect signs

Atelectasis due to complete bronchial obstruction:

Typically, there will be clear border shadows, smaller in size than normal lung areas, triangular in shape, apex toward the hilum; the branches of the blood vessels close; with indirect signs of atelectasis: retraction of the interlobular groove, hilum, mediastinum, diaphragm; intercostal stenosis; The healthy lung area is too bright to compensate.

Pneumothorax due to incomplete bronchial stenosis:

Increased volume of lung area corresponding to bronchi, overexposed image with sparse blood vessels. Indirect signs of pulmonary distension: the interlobar fissure is pushed toward the healthy side; The diaphragm is pushed down, the intercostal space is wide, the mediastinum is pushed to the opposite side on expiration.

Expiratory scans are easier to detect on plain chest radiographs as well as computed tomography. 

Left lung collapse due to complete obstruction of the main bronchus, left pleural effusion

Figure: Left lung collapse due to complete obstruction of the main bronchus (left), left pleural effusion (right).

Vascular syndrome

Includes pathological changes in the aperture, number, and distribution of blood vessels in the lungs; These changes may be localized or diffuse and are detectable on plain chest radiographs.

Focal aperture increase: pulmonary aneurysm; pulmonary artery-venous fistula.

Diffuse increase in aperture: fever, exercise, pregnancy, left-right shunt (ventricular septal defect, atrial septal defect, ductus arteriosus). In addition, it can be caused by fever, exertion, pregnancy.

Pulmonary artery redistribution: a decrease in blood volume in one lung area will lead to increased perfusion in another nearby area or in the other lung (because pulmonary venous hypertension causes edema of the interstitial tissue at the base, so the vascular network increases ascending to the top of the lung, extensive alveolar dilatation, etc.).

Increased central vascular diameter and decreased peripheral vascular diameter, associated with long-term pulmonary hypertension. Usually secondary to chronic bronchopulmonary disease, long-term left-right shunt, long-term mitral stenosis.

Focal or diffuse reduction in aperture produces an overexposed lung that can be compared with the contralateral lung. There are three main causes: stenosis of the pulmonary artery; pneumothorax causes a decrease in blood flow to or destruction of the pulmonary capillary network: alveolar dilation, pulmonary distension; Increased pressure in the pleural space: pneumothorax.

Parenchymal syndrome

The pathological images of lung parenchymal origin do not belong to interstitial, alveolar, bronchial, vascular syndrome due to too localized or too diffused lesions.

Lonely circular watermark

Larger than 3 cm usually malignant lesions can be primary or secondary.

The border of the benign lesion is continuous, if the border is not clearly defined, irregular, or has a spiky appearance, it is usually a malignant lesion.

Calcified watermarks are usually benign.

Combined lesions: converging vascular opacities due to arteriovenous fistulas, large opacities with small satellite opacities are inflammatory lesions.

Multi-drive round watermark

Usually unequal in size, the most common is metastasis.

Cave figure

Parenchymal necrosis damage, if connected to the bronchi, will form caverns.

Lung abscess image:

An overexposed image in the pneumonia opacity, possibly with fluid levels.

The inner limit is uniform, the outer limit is fuzzy.

Cave picture:

There is usually little fluid level because the cavernous tubercle is usually located in the upper lobe, and fluid drains out easily.

Bronchial drainage can be seen.

Many small opacities can be seen around the cavern (satellite).

Cavity due to malignant lesions:

The inside edge of the cave is irregular, waterlily shaped; a clear outer edge.

Bright silhouette

Well demarcated, no blood vessels, the wall is a thin border.

The surrounding parenchyma is normal, with fluid or opacity due to superinfection.

Cause: Alveolar dilatation, acquired bronchial obstruction

Image is too bright: diffuse or focal

Pneumonia after bronchial obstruction with valves.

Pulmonary artery stenosis

Compensatory ventilation.

Idiopathic interlobular alveolar dilatation at the base of the lung.

Central lobular alveolar dilatation due to chronic bronchitis.

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Category: Lung disorders