ecr 2007: march 9 - 13 vienna, austria ct imaging of the spectrum of diseases causing air trapping...

ECR 2007: March 9 - 13

Vienna, Austria

CT imaging of the spectrum of CT imaging of the spectrum of

diseases causing air trappingdiseases causing air trapping

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CT imaging of the spectrum of diseases

causing air trapping

Authors:

Juntima Euathrongchit,

MD.

Nisa Muangman, MD.

Jeffrey P Kanne, MD.

Eric J Stern, MD.

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Siriraj Hospital

CMU

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Objective

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To systemically review the CT

imaging spectrum of diseases

causing air trapping

Objective Index Definition Causes Reference

Index

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• Definition

• Causes of air trapping:

– The airway disease

– The lung parenchymal disease

– The cardiovascular disease

– Miscellaneous

• Reference


DefinitionHome How to show

Air TrappingAir Trapping

A condition that there is an abnormal retention of gas within a lung or part of a lung, especially during or after expiration [1].


ExhaleExhale

Definition: air trapping

Normal breathingNormal breathing

Lung attenuation normally increases during exhalation (ovals) The anterior arching of the posterior membrane confirms exhalation (arrow)

InhaleInhale


Exhale

Definition: air trapping

• Note the mostly normal right lung with patchy areas of low attenuation during expiration

• CT images show that the lingula does not increase in attenuation as expected indicating air trapping (oval)

•Diagram shows air trapping in LUL.

Air trappingAir trapping

Inhale


Definition: normal vs air trapping

CT images compare between normal breathing and air trapping.

• Note the mostly normal right lung with patchy areas of low attenuation during expiration.

• The lingula does not increase in attenuation as expected indicating air trapping.

Normal vs Air trapping


Definition: normal vs air trapping

Cine images show normal breath and air trapping, which is accentuated on expiration

Normal breathing Air trapping


Causes

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Air trapping fromAir trapping from

The airway diseaseThe airway disease

• The lung parenchymal diseaseThe lung parenchymal disease

• The cardiovascular diseaseThe cardiovascular disease

MiscellaneousMiscellaneous

Causes Reference

Causes: airway disease

Airway diseaseAirway disease

• Both large and small airway diseases are Both large and small airway diseases are

the main causes of air trapping on CT.the main causes of air trapping on CT.

• The small airway or bronchiolar diseases The small airway or bronchiolar diseases

are more common than diseases of are more common than diseases of

bronchi.bronchi.

Small airway diseaseSmall airway disease Large airway diseaseLarge airway diseasevs



•Inflammation is the most common cause of bronchiolar

disease, referred to as bronchiolitis.

•Bronchiolar disease can be grouped into four categories:

(i) Tree-in-bud pattern;

(ii) Poorly-defined centrilobular opacities;

(iii) Decreased lung attenuation or air trapping; and

(iv) Focal, diffuse ground-glass opacity, consolidation or both [2].

Causes

Small airway (bronchiolar) disease



Air trapping pattern is still seen in all groups :-

Constrictive bronchiolitis (obliterative bronchiolitis)

Swyer Jame syndrome

Asthma.

Sarcoidosis

Extrinscic alveolitis

Infectious bronchiolitis

Diffuse panbronchiolitis

Small airway (bronchiolar) diseaseSmall airway (bronchiolar) disease


Causes: airway disease - Small airway - BO

Constrictive bronchiolitis (obliterative Constrictive bronchiolitis (obliterative

bronchiolitis) 1bronchiolitis) 1

• Most common cause of air trapping pattern

• Due to bronchiole narrowing or obliteration from

concentric fibrosis involving exclusively the

submucosal and peribronchiolar

tissues of terminal and respiratory

bronchioles [2].



Constrictive bronchiolitis (obliterative bronchiolitis) 2Constrictive bronchiolitis (obliterative bronchiolitis) 2

Table: Etiology of obliterative bronchiolitis.

Post infectious BO - Bacterial, Mycoplasma, viral (esp. Measles, Respiratory

Syncytial virus, Adenovirus, Influenza, Parainfluenza and

Cytomegalovirus),

- Sequela of PCP, HIV, viral infection or both in AIDS

Toxic fume BO - Exposure gas: Nitrogen dioxide (Silo-filler’s lung), sulfur dioxide, ammonia, chlorine, phosgene and ozone

Idiopathic

BO associated with connective tissue disease

RA, Polymyositis

BO associated with drug therapy Penicillamine, Gold

BO as a complication of lung or bone marrow transplantation

Chronic lung allograft rejection

Neuroendocrine hyperplasia (carcinoid)Children surviving bronchopulmonary dysplasia (BPD)



Constrictive bronchiolitis (obliterative bronchiolitis) 3Constrictive bronchiolitis (obliterative bronchiolitis) 3


Air trapping on expiratory HRCT images, clinical characteristic, and physiologic

features often are diagnostic for obliterative bronchiolitis.

On dynamic CT scanning, look for small caliber and paucity of vessels within the

low attenuation regions, reflecting hypoxic reflex vasoconstriction, consequent to

bronchiolitis and impaired ventilation

Causes: airway disease - Small airway - SJS

Swyer Jame syndrome 1Swyer Jame syndrome 1


• Post-infectious obliterative bronchiolitis occurs in infancy or

early childhood, before the age of 8 and full alveolar

developmenti. • Many organisms implicated: adenovirus, measles virus, B.

pertussis, M. tuberculosis, and Mycoplasma. • Classic chest radiograph findings are a unilateral

hyperlucent lung with attenuated ipisilateral peripheral and

central pulmonary arteries and a small or normal

hemithorax.• HRCT shows focal, patchy, or diffuse air trapping.[3]

Causes: airway disease - Small airway - SJS

Swyer Jame syndrome 2Swyer Jame syndrome 2


Note radiolucent area of air trapping in the RUL with mild dilatation of the RUL bronchi with peribronchial wall thickening (arrow)

Causes: airway disease - Small airway - asthma

AsthmaAsthma


A reversible reactive small airways disease, occurring in up to 5% of A reversible reactive small airways disease, occurring in up to 5% of

adults and 10% of children [4]. adults and 10% of children [4].

HRCT: - Bronchial wall thickening (the most common finding), HRCT: - Bronchial wall thickening (the most common finding),

- Narrowing of bronchial lumen, bronchiectasis - Narrowing of bronchial lumen, bronchiectasis

- Mosaic perfusion and air trapping on expiratory CT scans - Mosaic perfusion and air trapping on expiratory CT scans

[5-7].[5-7].

- Full inspiratory CT scan may be normal. - Full inspiratory CT scan may be normal.

- Full expiratory HRCT examination may show patchy air - Full expiratory HRCT examination may show patchy air

trappingtrapping

Causes: airway disease - Small airway - asthma

AsthmaAsthma


Coronal, sagittal and axial images show prominent peribronchial wall (arrow) and air trapping in left lung apex and RML (oval) on expired phase (cine images)

expired

Causes: airway disease - Small airway - sarcoidosis

Sarcoidosis 1Sarcoidosis 1


• Systemic disease of unknown etiology characterized by noncaseating granulomata

• Chest involved in about 90% of cases [9]

• Characteristic HRCT findings are small perilymphatic nodules in peribronchovascular, subpleural, and interlobar septal distributions and mediastinal and hilar lymphadenopathy

• Air trapping is caused by bronchial or bronchiolar obstruction from endobronchial granulomata or enlarged peribronchial lymph nodes

• 89 -95 % of cases show air trapping [10, 11]

Causes: airway disease - Small airway -sarcoidosis



• Air trapping can occur at multiple airway levels: sublobular,

subsegmental, and segmental bronchi

• Air trapping may be the result of accumulation of

secretions in large and small airways, bronchial

hyperactivity from chemical mediators, and pulmonary

fibrosis.



L hilar N

Subcarinal NSubcarinal N

Precarinal NPrecarinal N

APW NAPW N

Typical finding: Diffuse small nodules, subpleural nodules (arrow) and nodules along interlobar fissure (yellow box), predominately. Note mediastinal and hilar adenopathy




CT upper lung fields show heterogeneous attenuation of lung CT upper lung fields show heterogeneous attenuation of lung parenchyma corresponding to the air trapping (mosaic perfusion) at the parenchyma corresponding to the air trapping (mosaic perfusion) at the low density areas.low density areas.


Causes: airway disease - Small airway - HP

Extrinsic allergic alveolitis 1Extrinsic allergic alveolitis 1

• Also known as hypersensitivity pneumonitis • Characterized by a type IV hypersensitivity reaction

to inhaled, primarily organic, particles• Two most common forms are farmer’s lung and bird

breeder’s lung.• The combination of clinical antigen exposure,

characteristic signs and symptoms, and distinctive HRCT findings are often diagnostic




• HRCT (subacute):

– Diffuse poorly-defined centrilobular nodules and patchy ground-glass

opacities, correlating with interstitial pneumonitis, cellular bronchiolitis,

and small noncaseating granulomata

– Most common affects mid and upper lungs.

– Air trapping may also be present

– The most common HRCT patterns are decreased attenuation and mosaic

perfusion (86%), ground-glass opacity (81%), small nodules (54%), and a

reticulation (36%) [12]




Diffuse groundglass opacities in both lungsNote a few areas of air trapping in both upper lobes (arrow)


Causes: airway disease - Small airway – infectious bronchiolitis

Infectious bronchiolitisInfectious bronchiolitis


• A form of follicular bronchiolitis causing by viral or Mycoplasma pneumoniae

infection in the general population [2]. • Immunocompromised patients and those with poor airway clearance are also

at risk for fungal infection • Iinfectious bronchitis and bronchiolitis are increasingly being recognized as

causes of acute lung symptoms in AIDS.

Radiologic findings:

- Bronchial wall thickening on chest radiograph

- Small centrilobular nodules and tree-in-bud opacities, representing inflammed

bronchioles impacted with debris [2]

Causes: airway disease - Small airway – infectious bronchiolitis

Infectious bronchiolitisInfectious bronchiolitis


Coronal and sagittal reconstruction images and cine axial images show tree in bud pattern in both lungs and mild heterogeneous attenuation of lung parenchyma

Causes: airway disease - Small airway - DPB

Diffuse panbronchiolitisDiffuse panbronchiolitis

Typically seen in Southeast Asia Typically seen in Southeast Asia

patients. patients.

The characteristic feature on The characteristic feature on

HRCT : HRCT : “tree-in-bud”“tree-in-bud” of secretion of secretion

filled dilated bronchiole. filled dilated bronchiole.

Otherwise: Otherwise:

- bronchiolectasis, - bronchiolectasis,

- bronchiectasis, and - bronchiectasis, and

- mosaic opacities. [7]- mosaic opacities. [7]


Causes: airway disease - large airway


• Large airway (bronchial) diseaseIt could be from

• Endobronchial tumor: primary vs secondary

• Bronchiectasis

• Tracheobronchomalacia

Causes: airway disease - large airway – endobronchial tumor

Endobronchial tumor

Most significant cause of air trapping. Endobronchial

tumor could be from :-

– Primary tumor such as bronchogenic carcinoma,

carcinoid or adenoid cystic carcinoma, etc.

– Metastasis from breast, colon, GU, melanoma,

Kaposi’s sarcoma.

Large airway (bronchial) disease


Causes: airway disease - Large airway: primary tumor

Primary tumor: Bronchogenic carcinoma 1

• The most common cause of cancer-related death worldwide

• No good effective screening method to early diagnosis

• The radiologic features depend on location and size of the lesion.

• Tumor may intrinsically occlude central airways or extrinsically

compress the airway lumen, resulting in obstructive pneumonitis,

which is more common than air trapping.

• When the tumor involves the adjacent pulmonary artery, the

supplied parenchyma may have lower attenuation because of

hypoperfusion



Bronchogenic carcinoma 2


Axial lung images at the arch and carinal level and cine axial mediastinal images, closed up at the endobronchial mass (squamous cell CA) in the left main bronchus (arrow), producing air trapping in LUL (oval)


Bronchogenic carcinoma 3


Axial and coronal show LLL bronchial obstruction by tumor (arrow), resulting of obstructive pneumonitis distally and lucent area of air trapping in superior segment of LLL (oval).Note paraseptal emphysema at both lung apices.


Primary tumor: Carcinoid, Adenoid cystic adenoma 1

Carcinoid tumor : An uncommon lung neoplasm, approximately 0.5 – 2.5% of all lung tumors [13], mainly in female with mean age of 45 years old. In spite of a neuroendocrine tumor, carcinoid syndrome is a rare, unless it has liver metastases. There are two kinds of carcinoid, typical one that is much more common than atypical one, divided by basic histopathology.

Usually tumor is located centrally and shows large and chunky calcification up to 39% of lesions as demonstrated by CT scans. When a carcinoid tumor partially occludes a bronchus, it can cause expiratory air trapping on dynamic CT [13].

Adenoid cystic carcinoma and Mucoepidermoid carcinoma: rare conditions. Only a report case of them reveal the mimic MacLeod’s syndrome or unilateral hyperlucent lung [14] [15].



Primary tumor: Carcinoid, Adenoid cystic adenoma 2


A small well defined intrabronchial tumor (caricinoid) presented at the right intermediate bronchus (arrow). Note groundglass opacity at posterior portion of the both hemithorax could be aspiration.

Causes: airway disease - Large airway: metastasis

Metastatic diseases

Endobronchial or endotracheal metastases:• Rare conditions. The incidence from autopsy shows widely

range from 2% to 50% [16].

• The common primary tumors are carcinoma from the

breast, colorectum, and kidney as well as melanoma.

• The airway obstruction is an important mechanism for

radiologic findings, which are included atelectasis,

obstructive pneumonitis or air trapping.


Causes: airway disease - Large airway: metastasis

Metastatic diseases


Metastatic breast carcinomaLymphatic metastasis at the right hilum with bronchial invasion, resulting of segmental atelectasis and bronchiectasis of RLL. Also note multifocal lucency areas of air trapping in RLL

Bronchiectasis 1

• An irreversible dilation of the bronchi resulting from destruction of the

elastic and muscular components [20]. There are both congenital and

acquired causes of bronchiectasis.

• Air tapping or atelectasis of the affected lobe are commonly present.

• Three categories based on the morphology of dilated bronchi :

– cylindrical bronchiectasis (mild)

– varicose bronchiectasis (moderate)

– cystic bronchiectasis (sever form disease)

Causes: airway disease Large airway - bronchiectasis


Bronchiectasis 2

HRCT is a standard technique to diagnose bronchiectasis

HRCT shows :

- loss of normal tapering of bronchus and bronchial wall thickening

- tram-track appearance when scan plane is parallel to the dilated bronchus

- signet ring pattern when plane is perpendicular to the bronchus

- bead-like appearance in varicose type

- cystic dilatation of the bronchi, sometimes filled with liquid



Bronchiectasis 3



• Two levels of thin slice CTA demonstrate – tram-track of dilated RUL

bronchi– Signet ring sign in RLL

(arrow) with small fluid-filled dilated bronchus (ovals)

• Two levels of thin slice CTA demonstrate – tram-track of dilated RUL

bronchi– Signet ring sign in RLL

(arrow) with small fluid-filled dilated bronchus (ovals)

Bronchiectasis 4


• Thin slice CTA demonstrate – tram-line of dilated bronchi in LUL and signet ring pattern in the apical

segment of RUL (arrow).– General heterogeneous attenuation of lung parenchyma and illdefined low

density areas of air trapping, peripherally

• Thin slice CTA demonstrate – tram-line of dilated bronchi in LUL and signet ring pattern in the apical

segment of RUL (arrow).– General heterogeneous attenuation of lung parenchyma and illdefined low

density areas of air trapping, peripherally


Bronchiectasis 5


Ring = dilated bronchiSignet = correlated pulmonary artery

String of pearlString of pearlString of pearlString of pearl


Bronchiectasis 6


Marked dilatation Marked dilatation of bronchi, containing of bronchi, containing

variable amounts of variable amounts of pooled secretionspooled secretions

HRCTHRCT: cluster of grapes : cluster of grapes with air-fluid levelwith air-fluid level

Associated with obliterative & Associated with obliterative & inflammatory bronchiolitis (85%)inflammatory bronchiolitis (85%)


Tracheobronchomalacia 1• Characterized by increased tracheal and bronchial compliance, which can

result in a functional obstruction or stenosis. Disease is usually focal but

can be be diffuse.

• Acquired tracheobronchomalacia is more common than congenital

– Most common: ischemic necrosis from an overinflated endotracheal tube

balloon cuff

– Other causes include trauma, radiation therapy, tracheaoesophageal fistula,

Wegener granulomatosis, and relapsing polychondritis

• On expiratory CT scan, tracheobronchomalacia is characterzied by

collapse of the airway with approximately 60-100% loss of full inspiratory

cross-sectional area [20].

Causes: airway disease Large airway - Tracheomalacia


Tracheobronchomalacia 2

• Air trapping in tracheobronchomalacia was reported by J Zhang and colleagues [24].

• They found that most tracheobronchomalacia cases in their hospital show air trapping, and the lobular pattern is the most commonly seen on dynamic expiratory CT scans. Though the control group shows lobular air trapping, the degree or score of air trapping is more severe in tracheobronchomalacia patients.

• The cause of air trapping in tracheobronchomalacia is unclear, but it may reflect chronic small airways disease due to abnormal respiratory mechanics related to excessive central airways collapse.





Note the marked difference in size of the tracheal lumen during inspiration (arrow) and expiration (double arrow)

Inspired vs expired




Volume rendered 3D reconstruction of the trachea from a patient with tracheomalacia

Note the near complete collapse of the trachea, and a small diverticulum arising from the right main bronchus, inferiorly







Causes


Causes: lung parenchyma

II Air trapping associated with lung parenchymal II Air trapping associated with lung parenchymal

diseasedisease

– Lung emphysema

– Cystic disease: Cystic disease:

• CCAM, , LAM, , Langerhan’s histiocytosis

– Infiltrative disease: Infiltrative disease:

• Thalassemia, , Intralobar pulmonary sequestration


Causes: lung parenchyma – emphysema

Lung emphysema 1

• An abnormal, permanent enlargement of the air spaces distal

to the terminal bronchioles accompanied by destruction of the

alveolar wall and without obvious fibrosis.

• Three main types classified by anatomical structure involved:

– centrilobular

– panlobular

– paraseptal



Lung emphysema 2

Centrilobular emphysema the most common form, associated with cigarette smoking, localized at upper lobe, predominately.


RUL shows lucent area at the centrilobular area, representing of centrilobular emphysema (oval).Note central artery is seen in these lucent areas (arrow).


Lung emphysema 3

Panlobular emphysema

• Associated with alpha-1-antitrypsin deficiency

• Basal predominant

• Can mimic the air trapping of obilterative bronchiolitis



Lung emphysema 3


picture

Multiple areas of lucency with accenuated of blood vessels at lower lung fields, mainly medially (rectangle)


Lung emphysema 4

Paraseptal emphysema• Subpleural location• Can coalesce and form

bullae, which can rupture and lead to spontaneous pneumothorax

HRCT showed multiple air filled rather rectangular shape along the subpleural area, medially (arrow)


Causes: lung parenchyma : cystic lung - CCAM

Congenital cystic adenomatoid malformation (CCAM)1or Congenital pulmonary airway malformation (CPAM)

- Congenital hamartoma of the developing lung parenchyma and terminal respiratory

tract associated with intercommunicating cysts of various sizes. A localized lobar

lesion is common without zone preference. Three types of CCAM have been

described, based on the cystic size.

• Type 1 CCAM, the most common form (about 50% of cases), composed of one or more large cysts (2–10 cm) and sometimes associated with air trapping.

• Type 2 CCAM (~ 40%) consist of multiple uniform smaller cysts (0.5–2 cm).

• Type 3 CCAM (~10%) appear as large solid masses but have multiple tiny cysts on microscopic examination [25].

CCAMs have communicate with the bronchial tree (unlike pulmonary sequestrations) and the cystic components fill with air within hours or days of birth.



Congenital cystic adenomatoid malformation 2

• The radiologic findings vary with the type of malformation, the number and size of cysts, and the amount of fluid within them.

• The most common findings are numerous air-containing cysts with expansion of the ipsilateral hemithorax and contralatearl displacement of the mediastinum.

• Occasionally, one cyst may be as large as single large lucent area, similar to congenital lobar hyperinflation.

• Almost all cases present in the neonatal period; however, some may present in adulthood when they become infected

• Adults with CPAM usually have lower lobe lesions, and the findings at CT can mimic cystic bronchiectasis, intralobar pulmonary sequestration, intrapulmonary bronchogenic cyst, or pneumatocele



CCAM 3


picture

CPAM type 1: Note multicystic lesion, vary in size (oval). There is air fluid level in some

cysts (arrow). Opacities in the RLL.

"Courtest of Dr. Nestor L. Muller, Vancouver BC"

Causes: lung parenchyma : cystic lung - LAM

Lymphangioleiomyomatosis (LAM) 1

A rare cystic lung disease with unclear etiology affecting

almost exclusive women of child-bearing age

Characterized by progressive proliferation of smooth muscle

in the airways, arterioles, venules, and lymphatic vessels

of the lung parenchyma, resulting in progressive shortness

of breath, lung cysts, pneumothorax, hemoptysis, and

chylous pleural effusion




HRCT scans show multiple small round well-define thin wall cysts that are fairly uniform in size and throughout the lungs [26]. The lung volume in LAM is increased.

Air trapping at expiratory CT is not common with LAM unless in severe case that there are multiple cysts instead of identification of the normal lung tissue[26].

Both pathology and imaging findings of LAM can not be differentiated with cystic lung disease of tuberous sclerosis. However, pleural effusion is much common with LAM. Extrathoracic manifestation of LAM are including renal angiomyolipoma, retroperitoneal cystic mass of lymphangioleiomyoma, lymphadenopathy, and chylous ascites[26].




Thin slice CT image at the Thin slice CT image at the carinal level shows rather carinal level shows rather uniform multiple cysts in uniform multiple cysts in both lungs, in severe case.both lungs, in severe case.





In this case, showing classical feature of LAM, left In this case, showing classical feature of LAM, left chylous effusion in childbearing aged woman, and chylous effusion in childbearing aged woman, and multiple small cysts (arrow)multiple small cysts (arrow)

Causes: lung parenchyma : cystic lung - LCH

Langerhan’s cell histiocytosis 1

LCH – A non-neoplastic proliferation of antigen presenting cells (Langerhans

cells) in the lungs that leads to destruction of the lung parenchyma and

airflow obstruction

Almost all cases of pulmonary LCH are associated with cigarette smoking

and more common in Caucasians.

Radiologic characteristic findings of LCH includ poorly defined centrilobular

nodules, some of which are cavitated, and cysts of varying sizes and

shapes with an upper lung predominance



Langerhan’s cell histiocytosis 2

In the early stage, chest radiography shows multiple small

nodules, which are less than 5 mm in diameter in an upper

lung predominance [28]. Cavitary nodules are identified in

approximately 10% of cases by HRCT.

In advanced disease, a reticulonodular pattern develops and

progresses to a coarse reticular pattern



Langerhan’s cell histiocytosis Langerhan’s cell histiocytosis 33

• The The most common HRCT findings include cysts and most common HRCT findings include cysts and centrilobular nodules with an upper zone centrilobular nodules with an upper zone predominancepredominance

• Cysts are usually up to 10 mm in diameter and have Cysts are usually up to 10 mm in diameter and have bizarre shapesbizarre shapes

• Relative focal air trapping can be seen in the cystic Relative focal air trapping can be seen in the cystic areas of the lung parenchyma on expiratory CT areas of the lung parenchyma on expiratory CT scans [29]scans [29]



Langerhan’s cell histiocytosis Langerhan’s cell histiocytosis 44


Note multiple small centrilobular nodules scattering in both upper lung fields with small cysts

Causes: lung parenchyma: Infiltrative disease - Thalassemia

Thalassemia 1• A common inherited disorder of hemoglobin synthesis with

varying severity, most common in southeast Asia and Africa.

• Pek-Lan Khong et al [30] studied the CT findings of β-thalassemia major patients and found that air trapping was the predominant thin-section CT finding in 24%, and patients had reduced FEV 25%-75%. Hepatic iron overload was not a common finding. The relationship between iron deposition in the lungs and pulmonary dysfunction is unclear.



Thalassemia 2

The proposed mechanisms of airway obstruction in β-thalassemia include:

• Oxidative damage as a result of free iron deposition within the airway epithelium.

• Bronchial hyperactivity and chronic immunologic response related to blood transfusion

• Disproportionate and/or excessive alveolar growth relative to airway growth caused by hypoxemia or hypoxia, a chronic abnormality in patients with β-thalassemia major.



Thalassemia 3 Case B-thalassemia, thin slice CT scan showed lucency area of air trapping at bilateral posterior basal segment and right anterior basal segment (oval). Note extramedullary hematopoeitic tissue (arrow)


Causes: lung parenchyma: Infiltrative disease - sequestration

Intralobar pulmonary sequestration 1Intralobar pulmonary sequestration 1

• Pulmonary sequestration - An abnormal development of lung forming a non-function mass that does not directly communicate with the airway and has its own blood supply from a systemic artery (usually a branch of the thoracic or abdominal aorta). Lung sequestrations can be divided into intralobar and extralobar types, based on their relationship to the pleura [25].

• Intralobar sequestration (ILS) is most common in the lower lobes. It lacks its own visceral pleural but has its own systemic arterial supply and drains to the pulmonary veins.

• Extralobar sequestration (ELS) has its own pleura and drains through the systemic veins.




• Frequently, ELS occurs on the left (Rokitansky’s lobe) and up to 15% can are within or below the diaphragm

• ILS may present in both childhood and adulthood, and, unlike ELS is often detected perinatally. Both ELS and ILS can communicate with the foregut and are sometimes referred to as bronchopulmonary foregut malformations. Communication with the upper gastrointestinal tract is uncommon, but can be shown by barium swallow [25].

• Diagnosis can be made by CT or MRI by demonstrating the origin and course of the anomalous systemic vessel(s) supplying the sequested lung.

• Inspiratory and expiration HRCT scans of ILS typically show a non-segmental focal mass, containing soft tissue, and cysts surrounded by low attenuation lung parenchyma (Fig) in a lower lobe. Although, there is no communication between ILS and the tracheobronchial tree, the collateral air-drift and fistula to the bronchi are causes of air-trapping on expiratory HRCT.




CT shows lucent area of air trapping (oval) with feeding artery from the aorta (arrow)


Causes







Causes: Cardiovascular


Cardiovascular causes:Cardiovascular causes:

– Pulmonary Thromboembolism

– Pulmonary arterial hypertension

Causes: cardiovascular - PE

Pulmonary thromboembolism 1

A serious condition that requires proper treatment to reduce morbidity and mortality.

CT pulmonary angiography is the most common examination of choice

Demonstration of intraluminal filling defect is diagnostic




Air trapping can occur in both acute and chronic pulmonary thromboembolism [31, 32].

There are several proposed mechanisms of bronchoconstriction in acute pulmonary embolism including:

• Release of bronchoactive amines such as serotoin and prostaglandins

• Change in parasympathetic nervous system tension, which controls the bronchial smooth-muscles [31].




In chronic PE, regional hyperventilation and low alveolar carbon dioxide tension were suggested as causes of regional bronchoconstriction and air trapping.

• Recently, however, more complex mechanisms have been proposed:

– Increase of endothelial-1 and decreased nitric oxide lead to bronchoconstriction and suppress bronchodilatation, respectively [32]

– Weakness of the bronchial wall due to redirection of blood flow from the bronchial arteries to the ischemic lung and compression of the bronchi by the adjacent deformed pulmonary arteries [32].




PE 4

Coronal reformatted images show eccentric filling defect of clots in the right lower pulmonary branch (arrow)

Relative lucent of mosaic perfusion at the anterior basal segment of RLL (oval)




Multisegmental luncency areas of air trapping in the upper lobes. Note slightly decreased size of the vessels within these lucent areas

Causes: cardiovascular - PAH

Pulmonary arterial hypertension 1

PAH - condition defined by systolic pulmonary arterial pressure

exceeding 30 mmHg of mean pulmonary arterial pressure exceeding 18

mmHg [33].

• Etiologies can be grouped into three major categories:

– Pre-capillary

– Capillary

– Post-capillary causes

• Chest radiograph may show markedly enlarged central pulmonary

arteries with rapid tapering of the peripheral branches

• Other findings depend on cause of PAH



Pulmonary arterial hypertension 2

• Air trapping is uncommon in PAH

• May be seen with– Chronic pulmonary embolism (pre-capillary)– Emphysema (capillary)



Pulmonary arterial hypertension 3: Marked enlarged pulmonary trunk (arrow) and heterogeneous attenuation of lung parenchyma. Note low density area of air trapping (oval)


picture

PA

PA

Causes







Causes: Miscellaneous

Miscellaneous

• Normal variant in the health and normal pulmonary function test

• Mimic diseases: Groundglass pattern

- PCP, Alveolar proteinosis


Causes: miscellaneous - normal

Normal variant in the health and normal pulmonary function test 1

Air trapping, particularly lobular, can be seen in normal adults, and many studies show varying in frequency of air trapping in healthy people with normal pulmonary function test, ranging from 40 to 80% [34].

Webb et al. [35] found that the lingular segments of the LUL are common locations of air trapping in normal adults He postulated that lingular bronchial length and alignment of those bronchi relative to the pleura made them more prone to dynamic compression.

Tanaka N. et all [34] studied the frequency of air trapping, overall 64% in asymptomatic subjects with normal pulmonary function test in groups of non smoking and smoking. Air trapping are also seen in both with various degrees and no significant difference between them in the distribution, which is common seen in lower lobes and dependent areas. However, two of non-smoker found air trapping in non dependent lung, while it is not seen in the smoker group. Potential reasons for the high prevalence of air trapping in patients with normal pulmonary function are extensive difference in local lung compliance or muscle tone of small air-ways without small-airway disorder, or presence of a small-airway disorder that is too mild to be detected by percent predicted MEF50% testing.




Various degrees of air trapping including the lobular, mosaic or extensive type can be observed in subjects with normal pulmonary function. However, most of reports mentioned that lobular air trapping is the most common one. Webb et al [35] suggested that lobular air trapping was caused by regional differences in lung compliance and the phenomenon of interdependence of adjacent lung units: Because of interdependence, a lung region that is less compliant than the lung parenchyma that surrounds it will show relative air retention during expiration, with less of an increase in lung attenuation than that of the surrounding lung. Mastora et al (16) believed that lobular air trapping was never caused by small airway diseases because the frequency of lobular air trapping in their study was not significantly different among smokers, ex-smokers, and nonsmokers.





HRCT shows mild lucent lingular segment of LUL and RML on expired view.

Inspired Expired

Causes: miscellaneous: Mimic diseases - PCP

Pneumocystis carinii pneumonia (PCP) 1Pneumocystis carinii pneumonia (PCP) 1

• Pneumocystic jiroveciPneumocystic jiroveci is classified as a primitive fungus and is classified as a primitive fungus and is one of most common causes of pulmonary infection in is one of most common causes of pulmonary infection in immunocompromised hosts, espeically those with AIDS.immunocompromised hosts, espeically those with AIDS.

• Ground-glass opacity is the usual finding on CT and often Ground-glass opacity is the usual finding on CT and often

has a patchy or geographic distribution with lower lung has a patchy or geographic distribution with lower lung predominately. However, the upper lung zone is involved in predominately. However, the upper lung zone is involved in the severe cases or patients who receive aerosolized the severe cases or patients who receive aerosolized pentamidine prophylaxis [36]. pentamidine prophylaxis [36].




• With progression, lung consolidation developsWith progression, lung consolidation develops

• Pneumatoceles may develop during the acute phase or during Pneumatoceles may develop during the acute phase or during resolutionresolution

• Less common findings include:Less common findings include:– Reticulation and septal thickeningReticulation and septal thickening

– CavitationCavitation

– Focal massesFocal masses

– Miliary diseaseMiliary disease

– Pleural effusionPleural effusion

– Lymphadenopathy [36]Lymphadenopathy [36]




Thin slice CT chest at the atrial level, there are diffuse groundglass opacities with small left pneumothorax (arrow)




Thin slice CT chest at the aortic arch level, there are diffuse groundglass opacities with interlobular, intralobular septal thickening of crazy paving pattern. No multiple small pneumatocele in both lungs (arrows).


Causes: miscellaneous: Mimic diseases - PAP

Pulmonary Alveolar Proteinosis 1

• A condition characterized by accumulation of periodic acid-shiff (PAS) staining phopholipid-rich material in the alveoli

• Most commonly occurs between 20 and 50 years old.

• Dyspnea and nonproductive cough are the most common associated symptoms. Pleuritic chest pain, malaise, and low-grade fever are less common [37].

• Increased incidence of Nocardia infection [38].




• The classic radiographic findings are a pulmonary edema like pattern

with bilaterally, symmetric perihilar ground-glass opacity or

consolidation.

• HRCT typically shows patchy ground-glass attenuation with

superimposed intra- and interlobular septal thickening (crazy-paving

pattern) [37].




HRCT at mid thoracic level, there are bilateral groundglass opacities with inter and intralobular septal thickening (oval). Note relativehypodensity at bilateral subpleural areas, especially RML.


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The end


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