RESPIRATORY SYSTEM:
METHODS OF INVESTIGATOINS:
1. PLAIN FILMS: INCLUDES
a) PA , lateral.
b) AP, supine, decubitus, oblique.
c) Inspiratory-expiratory.
d) Loardotic, apical, penetrated.
2. FLUOROSCOPY: for assessing the chest wall, diaphragmatic motion and for demonstrating of
mediastinal shift in cases of air trapping.
3. CT scan: indications:
a) To exclude metastatic disease.
b) Assessment of masses.
c) Assessment of diffuse infiltrative lung diseases.
d) Arterial assessment (pulmonary emboli, aortic dissection).
e) CT guided lung biopsy (peripheral masses).
4. TOMOGRAPHY: used when CT scan exam. are not available. Linear tomography used to
improve visualization and better localization of a peripherally located lesion, and to evaluate the
hilum and proximal air-ways. It’s helpful in n on-cooperative child due to movement and poor
inspiration, also to differentiate pleural from pulmonary lesions by rotating the patient and noting
movement of the lesion.
5. BRONCHOGRAPHY: occasionally bronchography is used to investigate recurrent hemoptysis
and to demonstrate BPF (broncho-pleural fistula). HRCT is now widely preferred over
bronchography.
6 .US: only useful for assessing g superficial pulmonary, pleural based, and chest wall lesions. It’s
helpful in diagnosis and localization of pleural effusion and collections and their drainage
percutaneously, for subphrenic collections, in differentiating solid from cystic mass, and for
studying the movement of diaphragm. Finally biopsy of the pleura and chest wall lesions may be
performed with US guidance using fine or cutting needle.
6- MRI: has a limited role in a assessing the respiratory system due to susceptibility artifact from
the large volume of air. The main advantage of MRI include multiplanar facility and high intrinsic
soft tissue contrast discrimination, allowing vascular structures and lesions in the mediastinal and
hilar regions to be defined separately from other tissues, in particular A.P window and subcarinal
space, without need for contrast-medium administration. Disadvantage of MRI include respiratory
and cardiac motion artifacts and inability to visualize small branching pulmonary vessels and
bronchi and lung parenchyma. These structures, however, are better depicted on HRCT.
7- ANGIOGRAPHY:
a) Pulmonary angiography: the main indications are:
 Diagnosis of pulmonary embolism.
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 Evaluation of pulmonary hypertension.
 Diagnosis of vascular lesions , e.g. pulmonary hypolasia, AVM, pulmonary artery
aneurysm.
 Therapeutic procedure, e.g. emboliztion of pul. AVM.
b) Bronchial angiography: angiography followed by embolization of bronchial and intercostal
branches for life- threatening or recurrent severe hemoptysis usually due to bronchectasis or
myecetoma, when surgery is contraindicated.
8- RADIONUCLIDE STUDIES: Tc99 - labeled agents or radioactive gases are used to investigate
regional ventilation (V), and perfusion (Q) in the lung (VQ) imaging. Positron emission
tomography (PET) imaging is increasing being used for staging of lung tumors and detection of
residual or recent disease after treatment.
 Viewing the PA film: before a diagnosis can be made, an abnormality, if present, must be
identified. Knowledge of the normal appearance of chest radiograph is essential. In addition
the examiner must develop a routine which insure that all areas of radiograph are not
missed. The order in which one looks at the structures is not important. What matters is to
follow a routine. A suggested scheme is presented below:
1- Request form: name, age, date, sex and clinical information.
2- Technical factors: adequate inspiration, patient position, rotation, film centering, optimum
exposure or under- , over- exposure, collimation of radiation.
3- Trachea: position, outline.
4- Heart and mediastinum, size, shape, displacement.
5- Diaphragms: outline, shape, relation, positions.
6- Below diaphragms: gas shadows (stomach or free peritoneal gas), any calcifications.
7- Lungs: local, generalizes abnormality, comparison of the translucency and vascular marking.
8- Hila: density, position, shape.
9- Hidden areas: Apices, posterior salcus, mediastinum and posterior cardiac, hila, behind bones.
10- Pleural spaces: position of fissures, costo-phrenic and cardio-phrenic angles, calcifications,
and thickenings.
11-soft tissue shadows: notice mastectomy, gas densities, and calcifications.
12-bones: missing bone (congenital, cliedo-cranial dysplasia or iatrogenic e.g. rib resection), bone
destruction.
Important radiological signs:
1- Silhouette sign: is the loss of an interface by adjacent disease and permits localization of a
lesion or a plain film by studying the diaphragms, cardiac and aortic outlines. These structures are
normally seen because the adjacent lung is aerated and the difference in radiodensity is
demonstrated .when air in alveolar spaces is replaced by fluid or soft tissue, there is no longer
difference in radiodensity between that part of the lung and adjacent structures. Therefore, the
silhouette is lost and the silhouette sing is positive. Conversely if the border is retained and the
abnormality id superimposed, the lesion must be lying either anterior or posterior.
Hilum overlay sin: helps to distinguish a large heart from mediastinal mass. With the latter, the
hilum is seen through the mass whereas in the former the hilum is displaced so that only its lateral
border is visible.
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2- Air-bronchogram sign: is important sign showing that an opacity is intrapulmonary. The
bronchus if air filled, but not fluid filled, becomes visible when air is displaced from the
surrounding parenchyma. Frequently seen as scattered linear lucencies rather than continuous
branching structures. It’s most commonly seen in pneumonic consolidation and pulmonary edema.
An air bronchogram is not seen within plural fluid, and rarely within pulmonary tumors, with
exception of alveolar cell CA and rarely lymphoma.
3- Air-space (acinar -alveolar) pattern: when the distal airways and alveoli are filled with fluid,
whether its transudate, exudates, or blood, the acinus forms a nodular 4-8 mm. shadow. These
shadows coalesce into fluffy ill-defined round or irregular cotton-wool shadows, non-segmental,
homogeneous or patchy but frequently well-defined adjacent to fissures. A ground glass
appearance or a generalized haze may be seen with bat’s wing or butter fly perihelar distribution.
Causes of air space filling:
 Pulmonary Edema:
a- Cardiac.
b- Non- cardiac: (without cardiomeally): U DOPA: (uremia, drugs, over hydration,
pulmonary hemorrhage acute arrhythmia). Others: aspiration, drowning, trauma).
 Infecting: located or generalized.
 Neonatal: hyaline membrane dis., aspiration.
 Alveolar blood: hemorrhage, pulmonary infraction (PE).
 Tumors: alveolar cell CA, lymphoma, leukemia.
4- diffuse lung disease: is non- homogenous and includes various patterns such as linear, septal
lines, miliary, reticulo-nodular, nodular, honeycomb shadowing, cystic, peri-bonchial cuffing and
the ground-glass pattern, care is necessary to avoid mistaken normal vascular marking (tapering
peripherally) from early interstitial changes.
 Miliary pattern: is a wide spread small discrete opacities of similar size (2-4 mm). Most
commonly seen with TB. Dense opacities occur with calcifications and metallic dust
inhalation disease.
 Ground glass shadowing: is a fine granular pattern which obscures the normal anatomical
details, such as the vessels and diaphragm, it may be seen with an interstitial or air-space
disease.
 Reticulo-nodular shadowing: is more common than reticular or nodular shadowing a lone.
The nodules are less than 1 cm in diameter, ill-defined and irregular border.
 Honey-comb shadowing: is a result of parenchymal destruction leading to end stage
pulmonary fibroses with the formation of thin walled cysts, the wall being 2-3 mm thick,
when these cysts are 5-10 mm in size, the term honey-comb shadowing is used. This
condition is associated with increased risk of pneumothorax, often of the tension type.
 Kerley lines:
-kerley A lines: are 1-2 mm thick non-branching lines radiating from the hilum, 2-6 cm
long, represents thickened deep interlobular septa.
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- Kerley B lines: are transverse non-branching 1-2 mm thick lines at the lung bases
peripheral, perpendicular to the pleura and parallel to the diaphragm, 1-3 cm long, represent
thickened interlobular septa.
Pulmonary infections:
Pneumonia: usually implies an infection by pathogenic organism resulting in consolidation of
lung, where as pneumonitis tends to refer to those inflammatory processes that primarily involve
the alveolar wall, e.g. fibrosing alveolitis.
Classification of pneumonia:
1- according to pathogens:
A. bacterial pn. include: streptococci pn. (Pnemococcus), staphylococcus, pseudomonas,
klebsiella, and other G-ve, anaerobes, legionella, mycoplasma pn. TB.
B. viral pn. Influenza, varicella, herpes zoster, rubeola, CMV. Coxackie…. etc.
C. fungal pn. Histoplasmosis, aspergillosis, candidiasis, coccidioidomycosis … etc.
D. parasitic pn. : Pneumocystis carinii, toxoplasma gondii.
2- according to Distribution:
A. lobar pn. (Alveolar pn.): infection primarily involves alveolus. Spread through pores of kohns
and canals of Lambert through out a segment and ultimately an entire lobe. Bronchi are not
primarily affected and remain air filled, therefore:
- Air bronchogram common.
- No volume less (because airways are patent).
- Expansion of lobe + bulging of fission (klebsiella + staph).
- Lung necrosis + cavitations.
Organisms commonly show lobar pn. Strepto pn., Klebs. , Staph., and H. influenza.
B. broncho-pn. (Lobular pn.): primarily affect bronchi and adjacent alveoli, shows combination
of interstitial + alveolar dis. (injury Starts in the air ways and involve the bronchovoscular bundle,
spill into alveoli.
- Volume loss may occur secondarily to bronchial narrowing + mucus plugging as bronchi fill with
exudates.
- Bronchial spread results in multifocal patchy consolidation in segmental distributions.
Organisms: pseudomonas, staphylococcus, klebsiella, legionella, anaerobes,and mycoplasma.
C. diffuse opacities: reticulo nodular, interstitial peri-bonchial area of inflammation, usually
bilateral parahilar peribonchil cuffing (thickening) + interstitial pattern.
- Hyper aeration + air trapping.
Org.: viruses, mycoplasma, PCP.
3- According to Acquisition of pneumonia:
a- community acquired pneumonia: streptococcus pneumonae, mycoplasma, viruses, mortality
10%.
b- Hospital acquired pn. (Nosocomial pn.) Incidence 1% mortality 35%. Organisms:
1- G -ve (>50%), klebsiella. pseudomonas arogenosa, E.coli, enterobacter, proteus.
2- G +ve (10%): MRSA (methicillin resist staph aureus, strepto. Pn. H. influenza.
3- Vancomycin resistant enterococcus.
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4- Pn. In immunocompromized patient.
- G-ve bacteria are the most common.
- TB.
- Fungal.
- PCP.
5- Aspiration associated Pn. (chemical pn.).
6- Endemic pn:
- Fungal: histoplasmosis, blastomycosis, coccidioidomycosis.
- Viral.
Tuberculosis: affect 10 million people world wide. Mycobacterium TB. responsible for most cases
of infection. (≥ 95) while only fewer than 5% are caused by atypical mycobacterium (m. avium,
intracellulare, m. kanasasii, m.xenopi …etc.
Mycobacterium is acid fast aerobic rods staining red with carbol-fuchsin.
Susceptible people: immunocompromized (HIV), racial different immigrants from Indian
subcontinent, blacks, infants, pubertal adolescents, elderly, alcoholics, diabetics, silicosis, measles,
sarcoidosis.
At risk people: immunocompromized, minorities, poor, alcoholics, immigrant’s prisoners, elderly,
nursing home resident (medical personnel), and homeless.
 Positive PPD + tuberculin test: 3 weeks after infection.
 Negative PPD tuberculin test:
1- Overwhelming TB infection (miliary TB).
2- Sarcoidosis.
3- Corticosteroid therapy.
4- Pregnancy.
5- Infection with atypical mycobacterium TB.
* Primary pulmonary TB: caused by inhalation of infected airborne droplet.
- Age: most common in infants + childhood, increasing in adults.
- Subclinical (asymptomatic) in 91%, usually heal without complications.
- Symptomatic in 5 – 10%.
Radiological Findings:
1- Pulmonary consolidation: (1-7 cm), most commonly is subpleural in the well ventilated lower
lobe (60%). This area of peripheral consolidation called Gohn focus.
2- Spread of infection from this area along the draining lymphatic’s to regional L.N. (hilar +
paratracheal 95%). This combination is called primary complex.
3- Gaseous necrosis.
4- Pleural effusion 10%.
Out come of infection:
1- Complete healing.
2- Progressive primary TB.
3- Miliary TB, uncontrolled massive hematogeneous dissemination overwhelming host defense
mechanism.
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4- Post primary TB: reactivation TB.
Complications:
1- Bronchopleural fistula + empayema.
2- Fibrosis mediastinitis.
Post primary pulmonary TB (reactivation TB, recrudescent TB):
Predominantly in adolescent + adults.
Etiology:
1- Reactivation of focus acquired in childhood (90%).
2- Continuation of initial infection (progressive primary TB (rare).
3- Initial infection in individuals vaccinated with BCG.
* Site: 85% in apical + posterior Segment of upper lobes (in comparison to histoplasmosis occur
in anterior segment), 20% in superior Segment of lower lobes, 5% mixed location.
Radiographic features:
1- Exudative TB:
-patchy or confluent air space disease commonly involving two or more segments (earliest
finding).
- Adenopathy: uncommon.
- Thin walled cavitations, with smooth inner surface.
- Air-fluid level suggests superimposed bacterial infection.
- Air crescent sign suggests mobile intracavitory myecetoma (asperagiloma).
2- Fibrocalcific TB.:
a- parenchymal disease: sharply circumscribed linear densities radiating to hilum.
- Thick walled irregular cavities.
- Cicatrisation + atelectasis: volume losing affected lobe.
b- Airway bronchial stenosis
- Traction bronchectasis in apical posterior Segment of upper lobes.
- persist segmental or lobar collapse.
- Lobar hyper infection.
c- Pleural extension:
- Pleural thickening (apical cap).
- Air-fluid level in pleural space (BPF).
- Rim enhancing / calcific soft tissue mass of chest wall.
- Fistulation to skin.
d- L.A.P.: - enlarged L.N. With central low attenuation (necrosis).
- Calcific hilum/ mediastinal L.N.
f- Rasmussen aneurysm: aneurysm of terminal branches of pulmonary artery within the wall of
TB cavity.
Miliary TB: massive hematogeneous dissemination of organism any time after primary infection.
- Radiographically identifiable after 6wks post hematogeneous dissemination.
- Generalized granulamatous interstitial small foci of pinpoint to 2-4 mm size (of similar size).
- Rapid complete clearing with appropriate treatment.
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Hydatid disease (lung echinococcosis):
Is the most common site of secondary involvement in children and 2nd most frequent site in
adults. The source is from hematogeneous spread from liver lesions. Frequency 15-25% of hated
disease
Clinical findings:
* Asymptomatic.
* Eosinophilia (<25%).
* Sudden cough attacks, hemoptysis, chest pain, fever.
* Expectoration of cyst fluid/ membrane, scolices.
* Positive casoni skin test is 60%.
* Hypersensitivity reaction (if cyst rupture occurs).
Location: lower lobes in 60%, bilateral in 20%.
- Solitary (70-75%)/ multiple (25-30%) sharply circumscribed.
- Spherical/ avoid masses.
- Size 1-120 cm in diameter (16-20 weeks doubling times).
- Cyst communication with bronchial tree:
* Meniscus sign (double arch sing) (moon sins), (crescent sing) 5%: thin radiolucent crescent
in upper most part of cyst.
* Air-fluid level: rapture of all cyst walls with air entering endocyst.
* Combo sign: air fluid level inside endocyst + air between endocyst and pericyst (onion peel
appearance).
* Water lily sign: completely collapsed crumpled membranes floating on the cyst fluid.
* Mass within cavity: crumpled membranes falls to most dependent part of cavity after
complete expectoration of cyst fluid.
-hydropneumothorax.
- Calcification of cyst wall 0.7%
- Rib + vertebral erosion (rare).
- Mediastinal cyst.
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Collapse (atelectasis): partial or complete loss of volume of a lung is referred to as collapse or
atelectasis.in comparison with consolidation, in which a diminished air in the lungs is associated
with normal lung volume.
Mechanism of collapse:
1. Relaxation or passive collapse: in which the lung tend to retract toward its hilum when air
or increased fluid collects in the pleural space.
2. Cicatrisation (fibrosis) collapse: the normal lung expansion depends upon a balance
between outward forces in the chest wall and opposite elastic forces in the lungs. When the
lung is abnormally stiff, this balance is disturbed.
3. Adhesive collapse: the surface tension of the alveoli is decreased by surfactant. If this
mechanism is disturbed, as in RDS, collapse of alveoli occurs.
4. Resorption collapse: in acute bronchial obstruction the gases in the alveoli are steadily
absorbed by the blood in the pulmonary capillaries and not replaced causing alveolar
collapse.
Radiological signs of collapse:
The radiological appearance in pulmonary collapse depends upon the mechanism of collapse, the
degree of collapse, the presence or absence of consolidation, and the pre-existing state of pleura.
Direct signs of collapse:
1-displacement of interlobar fissure: this is the most reliable sign, and the degree of displacement
will depend on the extent of collapse.
2- Increased density of lobe: may not be apparent until collapse is almost complete.however, if the
collapsed lung is adjacent to mediastinum or diaphragm, Silhouette sign will be positive.
3-vascular and bronchial redistribution: crowding of vessels seen in the collapsed lobe, and if air
bronchogram seen, crowding of bronchi is visible.
Indirect sins of collapse:
1-elevation of hemidiaphragm: seen in lower lobe collapse, but rare in other lobes collapse.
2-mediastinal displacement: in upper lobe collapse the trachea is often displaced to the affected
side, and in lower lobe collapse the heart may be displaced.
3-hilar displacement: hilum may be elevated in upper lobe collapse, and depressed in lower lobe
collapse.
4-compensatory hyperinflation: the normal part of the lung may become hyperinflated and appear
hyertransradiant, with its vessels widely spaced than in the corresponding area of the contralateral
lung. if there is considerable collapse of lung, compensatory hyperinflation of the contralateral
lung may occur with herniation across the midline.
 RUL collapse: radiopaqe shadow in the right upper zone, upward elevation of minor fissure
(on PA and LAT.), and anterior displacement of major fissure (on LAT. view).
 RML collapse: minor and lower half of major fissure move toward each other, best seen on
lateral view, silhouetting of the right cardiac border (on PA view).
 RLL collapse: elevation of the rt. Hemidiaphragm, depression and rotation of the rt. Hilum.
 LUL collapse: lt. upper zone haziness, silhouetting of aortic knuckle (on PA view).
 LLL collapse: silhouetting and elevation of the lt. Hemidiaphragm, retrocardiac radiopacity
(on PA view), and spine sign positive (on LAT. View).
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