Helpful Radiological Signs in CXR

A. Almasi MDIran University of Medical Sciences

Department of Radiology

Mass vs Infiltrate/ Consolidation1. First of all, you should be able to detect an abnormality

2. Then you should describe your findings

3. Putting together your different findings you can come to a diagnosis• In each of the cases below, there is an abnormal opacity in the left upper lobe (1)• In the case on the left, the opacity would best be described as well-defined.  The

case on the right has an opacity that is poorly defined (2)• Therefore the left radiograph depicts a mass and the one on the right is an air

space disease (3)

Silouhette Sign

• By studying the borders of the heart, diaphragm and the aorta we can determine the anteroposterior position of a lesion on a frontal CXR.

• The border of the anatomic organ is obscured only if it is in contact with the lesion (i.e. in the same anteroposterior position).

Silhouette Sign• For the heart, the silhouette

sign can be caused by an opacity in the RML, lingula, anterior segment of the upper lobe, anterior mediastinum, and anterior portion of the pleural cavity

• This contrasts with an opacity in the posterior pleural cavity, posterior mediastinum, of lower lobes which cause an overlap and not an obliteration of the heart border

Silhouette sign in an anteriorly located mass

(bronchogenic carcinoma)

Silhuette sign in a posteriorly located lesion (lower lobe pneumonia); not obscuring the right heart border

Silhouette sign in an anterior lesion obscuring the PA but not the aortic knob

Air Bronchogram

• Visible air-filled bronchus in a background of airless parenchyma

• Most commonly seen in pneumonia and pulmonary edema

• Its presence confirms the intrapulmonary location of the lesion

Air bronchogram in pneumonia

Air Bronchogram

Causes of an air-bronchogram

Common • Expiratory film • Consolidation (air space

disease) • Cardiogenic pulmonary

edema• Hyaline membrane

disease

Rare• Lymphoma• Alveolar cell

carcinoma• Sarcoidosis• Fibrosing alveolitis• Alveolar proteinosis• ARDS• Radiation fibrosis

Air-space (acinar/alveolar) pattern or consolidation or infiltration

• Acinus is the functional unit of the lung and is defined as all the airways located distal to a terminal bronchiole.

• Acinar pattern appears when the distal airways and the alveoli are filled with fluid (transudate, exudate or blood).

• Fluid-filled acini form nodular shadows 4-8mm in diameter (acinar shadows).

• An air-filled acinus surrounded by fluid-filled acini produces air-acinogram

• These acinar shadows can coalesce into larger ill-defined homogenous or patchy opacities which are well-defined adjacent to the fissures.

• Vascular markings are usually obscured.• Air-bronchogram is characteristic

Air-space pattern characteristics

• Ill-defined nodular shadows 4-8mm in diameter

• Coalescence of these acinar nodules• Ill-defined borders of larger opacities

except where limited to a fissure• Air-bronchogram• Air-acinogram

Acinar nodules in a case of diffuse TB (bronchial spread)

Coalescing acinar nodules in pulmonary contusion (hemorrhage)

Alveolar filling pattern in a case of diffuse TB

Sharp border of an alveolar shadow confined to the minor fissure in RUL pneumonia

Typical air-space pattern in pneumonia

Common causes of an air-space pattern (Consolidation)

• Pulmonary edema: cardiogenic/noncardiogenic• Pneumonia/pneumonitis• Aspiration • Hemorrhage

Pulmonary edema

• Two basic types: –cardogenic edema: increased hydrostatic

pulmonary capillary pressure–noncardogenic edema: either altered

capillary membrane permeability or decreased plasma oncotic pressure.  

Cardiogenic Pulmonary Edema• Would you favor pneumonia or CHF in this patient? Why?

What pattern is shown?

Fat Embolism (ARDS)

• Mostly peripheral distribution of the opacities contrasts with the central bat wing pattern seen in cardiogenic pulmonary edema

• Normal heart size is another suggestive evidence

Pulmonary Hemorrhage

Congestive Heart Failure• Cardiomegaly: the earliest CXR finding• Cephalization: when the pulmonary capillary wedge

pressure (PCWP) 12-18 mmHg pulmonary venous hypertension (PVH) grade I

• Interstitial edema: PCWP 18-24 mmHg, Kerley lines and peribronchial cuffing (thickening), PVH grade II

• Alveolar edema: PCWP > 24 mmHg, PVH grade III often in a classic perihilar bat wing pattern of density. Pleural effusions also often occur.

• CXR is important in evaluating patients with CHF for development of pulmonary edema and evaluating response to therapy as well.

Kerley B lines• These are horizontal lines less than 2cm long, commonly found in the lower

zone periphery.  These lines are the thickened, edematous interlobular septa. • They are found in interstitial pulmonary edema, but are also seen in

lymphangitis carcinomatosa, lymphoma and other diseases too.

PVH grade I

PVH grade II

Peribronchial cuffing

PVH grade III

Solitary Pulmonary Nodule• A solitary nodule in the lung can be totally innocuous or potentially a fatal

lung cancer• Rule out presence of multiple nodules first• After detection, the initial step in analysis is to compare the film with prior

films if available.  A nodule that is unchanged for two years is almost certainly benign

• If the nodule is completely calcified or has central or stippled calcium it is benign

• If the nodule is indeterminate after considering old films and calcification, subsequent steps in the work-up include ordering a CT to find subtle calcification

• Nodules with irregular calcifications or those that are off center should be considered suspicious, and need to be worked up further with a PET scan or biopsy 

• The patient may choose to have an indeterminate nodule removed if there is no evidence of spread on CT as this would diagnose and treat a cancer if present

Solitary Pulmonary Nodule• This patient clearly has a solitary lung nodule present on chest x-ray. 

Can you tell which lobe it's in? 

Solitary Pulmonary Nodule• PA and Lateral of a subtle right lower lobe

cancer.  Can you find it in the frontal projection?

Interestitial lung disease• Correlation between the CXR and severity

of the symptoms is poor• HRCT can detect interstitial changes in

earlier stages• Different patterns on CXR:

– Miliary– Ground-glass – Reticular – Reticulonodular– Honeycomb

Different patterns of interestitial involvement of the lungs

• Miliary pattern: 2-4mm well-defined nodules most often seen with TB

• Ground-glass opacity: low density opacity which does not obscure the vascular pattern of the lungs. It may be due to either an interestitial disease or mild alveolar filling

• Reticular pattern: fine irregular network of lines unlike vessels which bifurcate

• Reticulonodular pattern: presenting as reticulations plus nodules <1cm in between

• Honey combing: a network made of thin-walled cysts measuring less than one centimeter in diameter and implying end-stage lung fibrosis

The most common causes of miliary pattern

1) TB

2) Silicosis

3) Coal worker’s pneumoconiosis

4) Metastases

5) Sarcoidosis

Miliary pattern in TB

Ground glass density/opacity in usual interstitial pneumonitis

Reticulonodular pattern in idiopathic pulmonary fibrosis

Honeycomb pattern in longstanding RA with reumatoid nodules

Atelectasis/Collapse/Volume Loss

• Passive collapse: due to pleural effusion or thickening or pneumothorax

• Cicatrisation collapse: due to fibrosis (e.g. IPF, TB)

• Adhesive collapse: due to lack of surfactant• Resorption collapse: due to bronchial obstruction.

This has a lobar pattern

Anatomy of the Fissures

Radiological Signs of Atelectasis• Direct signs

– Displacement of interlobar fissures– Loss of aeration– Vascular and bronchial signs (crowding of vascular

markings, airbronchogram)

• Indirect signs– Elevation of a hemidiaphragm– Mediastinal displacement– Hilar displacement – Compensatory hyperinflation

Adhesive Atelectasis due to RDS

Passive Atelectasis due toPneumothorax

Cicatrisation Atelectasis due to TB

RUL Atelectasis

RUL Atelectasis

RUL Atelectasis

RUL Consolidation• Lobar consolidation

usually indicates bacterial pneumonia

RUL Consolidation

Thymus Sail Sign

Left Upper Lobe Atelectasis

LUL Atelectasis

LUL Consolidation

LUL Atelectasis

LUL Atelectasis

Middle Lobe Atelectasis• Right middle lobe atelectasis may cause minimal changes on the frontal chest

film. A loss of definition of the right heart border is the key finding. Right middle lobe collapse is usually more easily seen in the lateral view.  The horizontal and lower portion of the major fissures start to approximate with increasing opacity leading to a wedge of opacity pointing to the hilum.  Like other cases of atelectasis, this collapse may by confused with right middle lobe pneumonia.

RML Atelectasis• Right middle lobe collapse can be difficult to detect in the PA film. • The right heart border is indistinct on the PA film. • The lateral CXR shows a marked decrease in the distance between

the horizontal and oblique fissures.

Middle Lobe Consolidation

RML Consolidation vs Collapse

Left Lower Lobe Collapse

Left Lower Lobe Collapse

Left Lower Lobe Consolidation

Right Lower Lobe Collapse

Right Lower Lobe Collapse

Right Lower Lobe Consolidation

Pleural Diseases

• Pleural Effusion• Subpulmonic Effusion • Pleural Thickening • Pleural Calcification • Pneumothorax • bronchopleural fistula

Normal Pleural Space

• Visceral pleura is adherent to the lung• Space between visceral and parietal

pleura is a potential space• Infoldings of visceral pleura form

fissures.• Normally there are 2-10 cc of fluid in the

pleural space.

Appearances of Pleural Effusions

• Blunting of Costophrenic angle

• Meniscus sign• Subpulmonic

effusion• Layering

• Loculated• Laminar effusion• Opacified

hemithorax• Air-fluid levels

Blunting of Costophrenic Angle

• Normally there are 2-10cc of fluid in thepleural space

• When >75cc accumulate, the posteriorcostophrenic (CP) sulci, seen on thelateral film, become blunted

• When 200-300cc accumulate, the CPsulci on the frontal film become blunted

Blunting of the CP Angle

Normal Rt costophrenic angle

• When 200-300cc of fluid accumulate in pleural space, the usually acute costophrenic angle becomes blunted

Blunted Lt costophrenic angle

Meniscus Sign

• Pleural fluid tends to rise higher along itsedge producing a meniscus shape medially and laterally.

• Usually only lateral meniscus can be seen• The meniscus is a good indicator of the

presence of a pleural effusion.

Meniscus Sign

•Fluid rises higher along the edge of a pleural effusion producing an upside down “U” or meniscus shape.

Loculated Effusion

• Occurs secondary to adhesions which formbetween visceral and parietal pleura.

• Adhesions more common with blood(hemothorax) and pus (empyema).

• Loculated effusions have unusual shapes or positions in thorax e.g. remain at apex on erect films.

Loculated Effusion

• A loculated effusion has an unusual shape (lentiform) or position in the thoracic cavity

• This is a loculatedempyema

Laminar Effusion

• A laminar effusion collects in the loose connective tissue between the lung and the visceral pleura.

• It is not usually free-flowing.• It usually occurs with CHF or lymphangitic

spread of malignancy

Laminar Effusion

•A laminar effusion collectsbetween the lung and thevisceral pleura in the looseconnective tissue of thesubpleural space

•Laminar effusions areusually seen with CHF orlymphangitic spread oftumor

Effect of Position - Layering

Supine Erect• In the supine position, the fluid layers out posteriorly and

produces a haziness, especially near the bases. • In the erect position, the fluid falls to the bases.

Lateralized Diaphragmatic Dome in Subpulmonic Effusion

NormalSubpulmonic PE

Right Lateral Decubitus

Subpulmonic Effusion presenting as increased distance between stomach gas

and diaphragm

Subpulmonic PE Previously Normal Film

Deep Sulcus Sign

Pneumothorax

Hydropneumothorax

• If both a pneumothorax and a pleuraleffusion occur together, it is called ahydropneumothorax.

• A hydropneumothorax is usually due totrauma, surgery or bronchopleural fistula

• It is characterized by an air-fluid level inthe hemithorax.

Hydropneumothorax• A straight edge, indicative of a

fluid interface, in this case an air-fluid interface, is seen on the right.

• In order to have anair-fluid level in thepleural space, theremust be a pneumothorax present.

Y=4.2+[4.7 x (A+B+C)]

Barotrauma

Unilateral White Hemithorax