Module 1: Systematic Evalution Of Lung Consolidation(v2)

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Welcome CME module 1

Systematic Evaluation of Lung Consolidation

Dear Doctor,

Welcome to the online CME module 1.

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

2Key Objectives:

  • 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’

3Consolidation

Increasing pulmonary attenuation and obscuring the margins of adjacent airways and vessel.
Consolidation is an alveolar-filling process that replaces air within the affected airspaces, increasing pulmonary attenuation and obscuring the margins of adjacent airways and vessels on radiographs
4

 


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

In consolidation the alveoli and possibly the interstitial spaces are filled with fluid, pus, blood, cells (including tumor cells) or other substances.
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Consolidation divided in to segmental, non-segmental and interstitial patterns.

Based upon distribution pattern, consolidation can be divided into following:

  • 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.

6Radiographic features of lung consolidation

Key features:

  • 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
Lung consolidation

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.
7Bronchopneumonia1,2,3

This pneumonia is typically multifocal and centered in distal airways.

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

Let’s start with reviewing the potential causes of the different types of lung consolidation.

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

8Lobar pneumonia1,2,3,4

X-ray findings with lobar pneumonias are typically:

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

Next, we will consider several processes that tend to present with a more non-segmental, lobar radiographic appearance.

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
9Legionella pneumophila2,5

Lobar consolidation of the left lower lung with an air-bronchogram within the homogeneous airspace consolidation
This is an example of pneumonia caused by Legionella pneumophila infection presenting with a non-segmental, lobar pattern on chest radiography.

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.

10Mycobacterium tuberculosis3,5


Fibrosis and cavitation

Paratracheal bulging

Mycobacterium tuberculosis infection may also present with a non-segmental, lobar pattern. This image shows patchy consolidation with linear and nodular opacities in the posterior segments of the right upper lobes and superior segments of the lower lobes, primarily on the right.

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.

11Aspergilloma5

A mass of soft-tissue opacity with an air-crescent sign (arrowheads) in the left upper lobe. There are also focal fibrotic and nodular areas of increased opacity.
Aspergilloma is a less common cause of non-segmental, lobar consolidation, usually caused by infection with the fungus Aspergillus fumigatus within an existing cavitary lesion.

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.

12Organizing pneumonia

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

Several other less common disorders may present with a non-segmental, lobar radiographic pattern. One is organizing pneumonia.

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.

13Pulmonary haemorrhage

The presence ofcavitating lung lesions
Pulmonary haemorrhage typically results in air space consolidation that may occur in one or more areas across the lung fields.

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.

14Bronchopleural fistula

Patchy and nodular areas of increased opacity in the left middle lung zone
A bronchopleural fistula is a connection between the pleural space and the lung that may occur post-traumatically or with certain infections.  

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).

15Dilated Lung Hilum

Heart EnlargementInterstitial consolidationInterstitial pneumonia or edema is caused due to:

  • 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 last pattern of consolidation is Interstitial.

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
16Usual interstitial pneumonia

UIP is a histologic pattern of interstitial pulmonary inflammation and fibrosis.On a chest X-ray, UIP manifests as a reticularpattern, particularly at the lung bases.
UIP (Usual interstitial pneumonia)

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.

Key points: To summarize,

  • 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.

References:

  • Walker CM, Abbott GF, Greene RE, Shepard JA, Vummidi D, Digumarthy SR. Imaging pulmonary infection: classic signs and patterns. American Journal of Roentgenology. 2014 Mar;202(3):479-92.PMID: 24555584.
  • Haroon A, Higa F, Haranaga S, Yara S, Tateyama M. Differential diagnosis of non-segmental consolidations. J Pulmon Resp Med S. 2013;8:2.
  • Al-Ani Z, Suut S, Khan AN. Multifocal Lung Consolidation: Differential Diagnosis & The Role of Imaging.
  • Reynolds JH, Banerjee AK. Imaging pneumonia in immunocompetent and immunocompromised individuals. Curr OpinPulm Medicine. 2012;18:194-201 PMID: 22388581
  • Kim HY, Song KS, Goo JM, Lee JS, Lee KS, Lim TH. Thoracic sequelae and complications of tuberculosis. Radiographics. 2001;21:839-58.PMID: 11452057
  • Grottola A, Forghieri F, Meacci M, Fabio A, et al. Severe pneumonia caused by Legionella pneumophila serogroup 11, Italy. Emerg Infect Dis. 2012;18:1911.PMID: 23092583
  • Usual interstitial pneumonia. Available at: https://radiopaedia.org/articles/usual-interstitial-pneumonia. Accessed on 7-05-2018.

MCQS:

Which of the following help differentiate between massive lung consolidation and pulmonary fibrosis on a plain chest X-ray?

A.Radiographic evidence of lung scarring

B.Presence of pleural effusion

C.Evidence of infection or airway blockage

D.All the above

Pulmonary fibrosis (scarring of the lung) has a very different appearance than lung consolidation (formation of dense lung, usually due to infection or blockage) or effusion (fluid in the chest cavity around the lung)

What are the radiological signs of lung consolidation?

A.Obscuring of the normal pulmonary vasculature

B.Presence of air-bronchograms

C.Extension of opacities to the pleural surface

D.All the above

The key-findings of consolidation on the chest X-ray are:

  • Ill-defined homogeneous opacity obscuring vessels
  • Silhouette sign: loss of lung/soft tissue interface
  • Air-bronchogram
  • Extention to the pleura or fissure

Which of the following organisms typically present with a lobar pattern of consolidation?

A.Streptococcus pneumoniae

B.Klebsiella pneumoniae

C.Legionella pneumophila

D.All the above

Streptococcus pneumoniaeis the most common cause of lobar community-acquired pneumonia, although Klebsiella pneumoniae and Legionella pneumophila typically present with a lobar

Which of the following is a common cause of an interstitial pattern of consolidation?

A.Diabetes

B.Hypertension

C.Heart failure

D.None of the above

Common causes of an interstitial pattern of consolidation include

  • Heart failure
  • Viral infection
  • Pneumocystic carinii pneumonia (PCP)

Which of the following may increase density of the alveoli or interstitium leading to radiographic consolidation?

A.Pus

B.Blood

C.Fluid

D.Cells

E.All the above

In consolidation the alveoli may be filled with fluid, pus, blood, cells (including tumor cells) or other substances.

What is most common cause of acute lung consolidation on chest imaging?

A.Infectious pneumonia

B.Tuberculosis

C.Neoplasm

D.None of the above

Consolidation must be present to diagnose pneumonia: the signs of lobar pneumonia are characteristic and clinically referred to as consolidation.

The pathologic process leading to organizing pneumonia is which of the following?

A.Non-infectious pneumoni

B.Infectious pneumonia

C.Both

D.None of the above

Cryptogenic organizing pneumonia (COP), also known as bronchiolitis obliterans organizing pneumonia, is a form of non-infectious pneumonia.

Which of the following is a primary or reactivation radiological findings may be observed in Mycobacterium tuberculosis lung infection?

A.Airspace consolidation in the upper lobes

B.Architectural distortion in the lower lobes

C.Cavitary lesion

D.All of the above

Key radiological observation in Mycobacterium tuberculosis

  • Airspace consolidation in the upper lobes
  • Lower lobes with architectural