Module 1

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Welcome CME module 1

Systematic Evaluation of Lung Consolidation

Welcome to the online CME module 1.

In this module we will emphasize on Systematic Evaluation of Lung Consolidation using chest imaging.

• Interpret lung consolidation
• Differential diagnosis of lung consolidation

At the end of this module you will be able to interpret ‘lung consolidation and understand the differential diagnosis of consolidation using chest X-Ray’

Alveoli filled with fluid, pus, blood, cells (including tumor cells)

Consolidation divided in to segmental, non-segmental and interstitial patterns.

• Segmental, affecting several focal areas of the lung
• Non-segmental,where the consolidation is located in a defined portion of the lung, such as a specific lobe or lobes, and
• Interstitial, affecting the lung fields diffusely

However, it is important to recognize that while some patterns of consolidation tend to occur with certain diagnoses, different causes of consolidation may present with different or multiple patterns on chest imaging.

• An ill-defined homogeneous opacity obscuring vessels
• Silhouette sign: loss of lung/soft tissueinterface
• Air-bronchograms
• Extension of opacity to the pleura or fissure, but not crossing it
• No volume loss

Several radiographic features are characteristically found with lung consolidation:

• An ill-defined homogeneous opacity that obscures the normal vascular pattern in the affected area of the lung,
• Silhouette sign, which is the loss of the normal borders between thoracic structures, such as the usual interface of lung with the diaphragm, heart, or other mediastinal structures,
• Air-bronchograms, in which the outline of the air-filled bronchus becomes visible because it is surrounded by alveoli filled with fluid, pus or other material
• Extensionof the increased opacity to the pleura or fissure, but not crossing it, and
• No evidence of volume loss in the lung.

This pneumonia is typically multifocal and centered in distal airways.

Radiographic opacities are normally heterogenous and distributed along the course of the airways.

Firstly, we will discuss Bronchopneumonia,which classically presents with a segmental pattern on chest radiography.

Bronchopneumonia may be caused by aspiration of secretions from the upper portions of the airway, with consolidation being typically multifocal and centered in distal airways. Radiographic opacities are normally heterogenous and distributed along the course ofthe airways

• Single lobe involvement
• Unilateral
• Air-bronchograms may be present
• Air bronchogram:

Lobar pneumonia is a classic non-segmental process as it differs radiographically from bronchopneumonia with consolidation being localized to either a specific lung lobe or entire lung instead of more diffusely. The most common cause of lobar pneumonia isStreptococcus pneumoniae, although Haemophilus influenzae, Moraxella catarrhalis, Klebsiella pneumoniae, Legionella pneumophila, and Mycobacterium tuberculosis may also present with a lobar pattern.

In this type of consolidation, the key findings of X-ray and CT-scan are:

• It usually involves a single lobe
• It is often unilateral
• Because of alveolar opacities occurring within a well-defined area, air-bronchograms may be present

It’sa type of pulmonary infection that is caused by Gram-negative bacilli and is an important cause of severe community-acquired pneumonia.

The chest X-ray reveals consolidation present in left lower lung lobe, with an air-bronchogram present.

Fibrosis and cavitation

Paratracheal bulging

There is also ipsilateral hilar enlargement due to lymphadenopathy.

This frontal chest radiograph shows right-sided paratracheal bulging (arrows), suggestive of mediastinal lymph node enlargement.  

Advanced cases may also show non-segmental, lobar fibrosis and cavitation.

This frontal radiograph shows a mass of soft-tissue opacity with an air-crescent sign (arrowheads) in the left upper lobe, caused by air outlining the infectious mass making it visible within the cavity.

There are also focal fibrotic and nodular areas of increased opacity (arrows) in the inferior aspect of the mass.

Increased density

Increased density with ill-defined borders in the left lungthe heart silhouette is still visible, which means that the density is in the lower lobe

Organizing pneumonia is a patchy process that involves proliferation of granulation tissue within alveolar ducts, alveolar spaces, and surrounding areas of chronic inflammation. Although a number of diseases may cause this pattern, including acute infections and autoimmune disorders, the term cryptogenic organizing pneumonia is used only in those who do not have a clear cause.

The X-ray and CT scan reveal increased density with ill-defined borders in the left lung; the heart silhouette is still visible, whichmeans that the density is in the lower lobe. The consolidation in organizing pneumonia can be migratory and is often seen in the lower lobes.

It is often associated with a vasculitic process such asgranulomatosis with polyangiitis (previously known as Wegner’s granulomatosis) which can present with acute shortness of breath.

As one can see, in this chest radiograph there is the presence of several cavitating lung lesions.

Radiological features that are suggestive of the presence or the development of a BPF include: (1) steady increase in intrapleural air space, (2) appearance of a new air fluid level, (3) changes in an already present air fluid level, (4) development of tension pneumothorax, and (5) a drop in the air fluid level exceeding 2cm

In this chest X-ray, findings includeconsolidation with a cavity in the right upper lobe (arrow). There are patchy and nodular areas of increased opacity in the left middle lung zone (arrowheads).

• Cardiac heart failure
• Viral infection
• Pneumocystis Pneumonia (PCP) Mycoplasma pneumonia

Chest X-ray findings:

• Involves interstitial space
• Ground glass appearance
• Bilateral & symmetrical enlargement of lymph nodes of pulmonary hila

The interstitium of the lung consists of structures that support the airways and includes the pulmonary vessels, bronchi, and connective tissue. Disease processes that cause a relative thickening of the interstitium (as opposed to opacification of the lung parenchyma) are seen as a predominance of interstitial markings on chest imaging.

An interstitial pattern on chest radiography may be caused by:

• Cardiac heart failure leading to edema in the interstitial spaces
• Infection, including by organisms such as viruses, Pneumocystis carinii pneumonia (PCP), and Mycoplasma pneumonia

This chest X-ray is of apatient who presented with a nonproductive cough and fever.

Chest X-rayfindings include:

• Involvement of the interstitial space
• Ground glass appearance
• Bilateral & symmetrical

UIP is a form of diffuse parenchymal lung disease and is a histological pattern of interstitial pulmonary inflammation and fibrosis.

Pulmonary fibrosis causes reticular (net-like) shadowing of the lung peripheries which is typically more prominent towards the lung bases.

It may cause the contours of the heart to be less distinct or ‘shaggy.’

Chest X-rays can be helpful in monitoring the progression of pulmonary fibrosis.

• Consolidation is the radiological term used to describe increased lung density on radiographic imaging.

• Any pathologic process that fills the alveoli with fluid, pus, blood, cells or protein can result in diffuse, lobar, or multifocal ill-defined opacities, and diseases that lead to thickening of the interstitium may lead to characteristic patterns of consolidation on chest imaging.

• The differential diagnosis of multifocal consolidation is wide and can be challenging.

• Certain factors help the radiologist reach the correct diagnosis. Non-radiological factors include the general clinical picture of the patient and if the patient is acutely breathless.

• Radiologically, the distribution of consolidation, appearance on previous imaging and certain associated features are very important for diagnosis.