Chest CT’

Lecture No. 6 (Dated 22nd August 2020) for 8th & 9th Semester Students of MBBS

Dr. Rajesh Sharma

Professor of Radio diagnosis
lung field abnormalities -Atelectasis
CT scans show direct and indirect signs of lobar collapse:
Direct signs include:
§ Displacement of fissures
§ Opacification of the collapsed lobe.
Indirect signs include the following:
§ Displacement of the hilum
§ Mediastinal shift toward the side of collapse
§ Loss of volume in the ipsilateral hemithorax
§ Elevation of the ipsilateral diaphragm
§ Crowding of the ribs
§ Compensatory hyperlucency of the remaining lobes
Atelectasis can be sub-categorized by morphology as follows:
§ linear(plate, band, discoid, subsegmental) atelectasis
§ lobaratelectasis
§ Segmentaland subsegment alatelectasis
§ Round atelectasis
 lung field abnormalities -Atelectasis
Complete atelectasis: Characterized by:
§ Opacification of the entire hemithorax
§ An ipsilateral shift of the mediastinum.

CT: Demonstrates the mediastinal shift to the left and the collapsed left lung (A) surrounded by pleural
effusion. A central hilar mass (M) with complete obliteration of the left bronchus and main left pulmonary
artery can be noted ( arrows)
 lung field abnormalities -Atelectasis
Lobar Atelectasis: Right upper lobe collapse:

Increased density in the upper medial aspect of the right

hemithorax
§ Appears as a right paratracheal opacity
§ Elevation of the minor fissure, appears concave
laterally.
§ Elevation of the right hilum
§ Hyperinflation of the right middle and lower lobe
§ Right diaphragmatic tenting (next) Post contrast axial CT scan at the level of
§ The Golden S-sign (or reverse S-sign of Golden) (next) the tracheal bifurcation shows a mass
§ Non-specific signs : obliterating the right upper lobe bronchus
Elevation of the hemidiaphragm and Right upper lobe atelectasis.
Crowding of the right sided ribs
Shift of the mediastinum and trachea to the right
Lobar Atelectasis -Right upper lobe collapse

Right upper lobe collapse: Coronal CT reveals

Post-contrast sagittal reformat images the Golden S-sign; a reverse S shaped curve
in lung window settings show collapse of the horizontal fissure. The supero-lateral
of the right upper lobe with pulling up concave segment of the S is formed by the
of the otherwise horizontal minor elevated horizontal fissure(red arrow). The
fissure which now appears concave infero-medial convex segment is formed by
superiorly the central tumour or lymph node
enlargement.
 Lung field abnormalities -Atelectasis
Right middle lobe collapse:
§ Axial and coronal images: a triangular opacity along the right heart border, with
the apex pointing laterally, is a characteristic finding. This appearance resembles
a tilted ice-cream cone.
§ Sagittal image: obliquely oriented triangular opacity with apex pointed toward
hilum
§ Non-specific signs may be subtle or absent due to its small size
§ Right middle lobe syndrome are the combination of: right middle lobe collapse
and bronchiectasis
Axial coronal Sagittal
 Lung field abnormalities -Atelectasis
Right lower lobe collapse:
§ It collapses downwards, posteriorly and medially
towards the posterior mediastinum and spine.
§ The right hilum is depressed
§ Non-specific signs :
Elevation of the hemidiaphragm
Shift of the mediastinum to right
Crowding of the right sided ribs
Right
lower lobe
collapse:
Coronal CT image revealed a large
increase
right hilar mass (yellow arrow)
density at
resulting in right lower lobe
right lower
atelectasis(red arrow)
lobe
 Lobar Atelectasis -Right lower lobe collapse
§ On the Sagittal view there is posterior displacement of the oblique fissure.
§ There is opacity seen at the level of the ‘mediastinal wedge’, which is the region of the
posterior costophrenic sulcus
Sagittal reformatted CT image demonstrating that
the right lower lobe collapses posteriorly (black
arrows). This causes the so called ‘mediastinal
wedge’. The horizontal fissure can be seen on the
image separating the right upper and middle lobes
(white arrow). RLL, right lower lobe; RML, right
middle lobe; RUL, right upper lobe.
 lung field abnormalities -Atelectasis
Left upper lobe collapse:
§ The left upper lobe predominantly lies in the anterior and
superior part of the left hemithorax. It collapses medially and
anteriorly
§ A wedge-shaped triangular opacity, apex at the hilum and base
at the chest wall
§ Endobronchial obstruction
§ Elevation of the left hilum
§ Hyperinflation of the left lower lobe
§ Non-specific signs :
§ Elevation of the hemidiaphragm
§ ‘Peaked' or 'tented‘ hemidiaphragm: Juxtaphrenic peak (next)
§ Crowding of the left sided ribs
§ Shift of the mediastinum to left Axial CT slice demonstrating left upper lobe
collapse. The collapsed lung is draped over
the anterior aspect of the hemithorax
(yellow arrow). Note the left pleural effusion
in this patient (red arrow)
Lobar Atelectasis -Left upper lobe collapse
Juxtaphrenic peak (Kattan's sign):
§ It is a small sharply defined shadow which projects cranially from the medial two thirds of the diaphragmatic
surface usually close to the crest of the diaphragm
§ commonly seen in upper lobe collapse but may also be seen in middle lobe collapse

left upper lobe collapse: Coronal CT image

Coronal CT image revealed left upper
revealed triangular opacity with upward
lobe collapse. Juxtaphrenic peak sign
displacement of the major fissure (red arrow).
(red arrow)
Juxtaphrenic peak sign (blue arrow)
Lobar Atelectasis -Left upper lobe collapse
Lingular collapse:
§ The lingular segment of the left upper lobe is analogous to the middle lobe
§ It does not have its own bronchus, and is therefore commonly collapsed together with
the left upper lobe
§ The lingual collapses inferiorly and medially

Right middle lobe and lingual

distribution of
nontuberculous mycobacterial
infection. Axial (A) and
coronal (B) CT images show
advanced cylindrical
bronchiectasis and atelectasis
of the right middle lobe and
lingula in a “Lady Windermere
syndrome” distribution.
lung field abnormalities -Atelectasis
Left lower lobe collapse:
§ Triangular opacity in the posteromedial aspect of left lung
§• left hilum will be depressed
§ Non-specific signs indicating left sided atelectasis :
Elevation of the hemidiaphragm
Crowding of the left sided ribs
Shift of the mediastinum to left

Complete collapse of the left

lower lobe due to a mucous plug
Coronal CT reformatted
image demonstrating left
lower lobe collapse.
lung field abnormalities -Atelectasis
Round atelectasis; also known as folded lung or Blesovsky syndrome:

§ Causes: asbestosis is the most common cause,

pneumoconiosis, exudative pleuritis, tuberculosis,
hemothorax, cardiac surgery, in chronically dialyzed
patients
§ Usually2.5–8 cm peripheral round, ovaor fusiform lesion of
soft tissue density, with air bronchogram
§ Sub pleural location, acute angle between the mass and
the pleura, thickening of adjacent pleura
§ Typically found in lower lung lobes, particularly in posterior
Sagittal projections. Round atelectasis
regions with “comet tail” sign. Displacement of
§ The volume of the affected lobe is reduced the oblique fissure and reduced volume
§ Comet tail sign (next) of the lower lobes.
§ Pleural effusion
 Atelectasis -Round atelectasis
Comet tail sign:
§ Consists of a curvilinear opacity that extends from a subpleural "mass"toward the ipsilateral hilum.
§ The bronchovascular bundles appear to be pulled into the mass and resemble a comet tail.
§ Adjacent pleural thickening
§ On administration of IV contrast, homogenous enhancement is seen. This, however may also be
seen in carcinomas and hence cannot be used as a differentiating feature.

Pleural effusion and

rounded atelectasis
(RA) affecting most of
the lower right lobe
and adjacent to the
distorted and displaced
oblique fissure. Air
bronchogram in
proximal part of RA is
also visible
 lung field abnormalities -Atelectasis
Segmental atelectasis:
§ Collapse of one or several segments of a lung lobe.
§ It is a morphological subtype of lung atelectasis.
§ Its radiographic appearance can range from being a thin linear to a wedge shaped
opacity then does not abut an interlobar fissure.

CT: the segmental atelectasis is located

within the anterior segment of the left
upper lobe. Bronchial wall thickening with
partial narrowing of the left upper
bronchus and adjacent bullae indicates the
compressive nature of the atelectasis.
 lung field abnormalities -Atelectasis
Plate-like/ subsegmental /discoid atelectasis:
§ Seen in smokers, elderly, after abdominal surgery, patients in the ICU and in pulmonary embolism .
§ linear shadows of increased density at the lung bases, usually horizontal, measure 1-3 mm in
thickness and are only a few cm long.

Atelectasis; Plate-like consolidations.

 lung field abnormalities -Atelectasis
Cicatrisation atelectasis:
§ Atelectasis can be the result of fibrosis of lung tissue.
§ This is seen after radiotherapy and in chronic infection, especially TB.

Contrast enhanced chest tomography (CECT) scan of

chest showing loss of lung volume on left side with
lower lobe cicatricial collapse and consolidation with
air-bronchogram
lung field abnormalities -Nodules and Masses
A solitary pulmonary nodule:
§ Defined as a discrete, well-marginated, rounded opacity less than or equal to 3 cm in
diameter that is completely surrounded by lung parenchyma, does not touch the
hilum or mediastinum, and is not associated with adenopathy, atelectasis, or pleural
effusion.
§ Lesions larger than 3 cm are considered masses and are treated as malignancies until
proven otherwise.

A 1.5-cmcoin lesion in the

left upper lobe in a patient
with prior colonic
carcinoma. Transthoracic
needle biopsy findings
confirmed this to be a
metastatic deposit
Nodules and Masses-solitary pulmonary nodule
Differential diagnosis:
Neoplastic Congenital
Malignant • Arteriovenous malformation
• Bronchogenic carcinoma • Lung cyst and Intrapulmonary Bronchogenic Cyst
• Solitary metastasis • Bronchial atresia with mucoid impaction
• Lymphoma
• Carcinoid tumours Miscellaneous
• Sarcoma • Hydatidcyst
Benign • Pulmonary infarct
•Pulmonary hamartoma • Intrapulmonary lymph node
•Pulmonary chondroma • Mucoidimpaction
Inflammatory • Pulmonary haematoma
• Granuloma (e.g. TB) • Pulmonary amyloidosis
• lung abscess • Fungal infection
• Rheumatoid nodule • Atelectasis
• Plasma cell granuloma • Wegener granulomatosis
• Round pneumonia
lung field abnormalities -Nodules and Masses
Solitary pulmonary nodule: benign versus malignant:
Feature Suggests Benign nodule Suggests Malignant nodule

Calcification

Size < 5 mm > 10 mm

Margin well-defined, Smooth Irregular, lobulated or spiculated

Cavitation thin, smooth wall thick, irregular walls

 Solitary pulmonary nodule: benign versus malignant
Feature Suggests Benign nodule Suggests Malignant nodule
Density Dense, Solid Nonsolid, ground-glass

Growth less than one month or more than Doubles in 1-18months (average 4-8
months, or remains the same size for months)
2 years
Contrast enhancement absence of significant lung nodule enhance more than 20 HU
enhancement (≤15 HU)

Positron emission low or no fluorine 18 (18F)–labeled fluorodeoxyglucose (FDG) uptake at PET/CT

tomography (PET) / CT suggest benignity
lung field abnormalities -Nodules and Masses

A. Uncomplicated cysts:
• well-circumscribed Hydatid Cyst:
• fluid attenuation lesions Large cyst with
thick wall is seen at
• homogenous content right upper lobe
• hypodense content and
smooth, hyperdense walls
• enhancement after
Hydatid Cysts:
contrast injection multiple hydatid cysts in
both lungs as well-
demarcated cystic masses
 Nodules and Masses –Hydatid Cyst

Air crescent sign

1. Meniscus sign or air crescent sign:
crescents of air between the pericyst
and the endocyst due to Bronchial
erosion
Inverse crescent
2. “Inverse crescent sign”: air sign
crescents along the posterior aspect
of lesion
3. Cumbosign or onion peel sign: air
Cumbo sign:
lining between the endocyst and Double air arc
pericyst has the appearance of an
onion peel
Nodules and Masses –Hydatid Cyst-Complicated cysts

4. “Whirl” or the “serpent sign”: Whirl sign: air and fluid

with multiple curvilinear
collapsed membranes After hyperattenuating
expectoration of cyst fluid membranes in dependant
part
5.“Air bubble sign”: Small intracystic air
foci can be seen at the periphery of
cyst
6.“Water lily sign”: With complete Air bubble sign

collapse, the crumpled endocyst

appears as a wavy membrane floating
on fluid
Water lily or Camelot sign
 Nodules and Masses –Hydatid Cyst-Complicated cysts

7. “Empty cyst sign”: cyst after complete Empty cyst sign

expectoration of fluid and membranes
8. “Ring enhancement sign”: Increases in
the cyst wall thickness with enhancement
due to infection
9. Consolidation adjacent to the cyst Ring enhancement sign
(ruptured cyst)
10. Other less common thoracic hydatid
manifestations include: invasion of the
mediastinum, pericardium, chest wall, An infected cavitary
cardiovascular system, or inferior vena cava lesion with adjacent
parenchymal
consolidation
lung field abnormalities -Nodules and Masses

A Pulmonary mass:
An area of pulmonary opacification that measures more
than 3 cm. The commonest cause for a pulmonary mass
is lung cancer.

Other causes :
• Hyperdense pulmonary mass: (a pulmonary mass
with internal calcification)
• Cavitating pulmonary mass (Pulmonary cavity) : (gas-
filled areas of the lung in the center of the mass. They
Two Lesions, the larger of the
are typically thick walled and their walls must be
two having a large central
greater than 2-5 mm. They may be filled with air as
cavity and air-fluid level
well as fluid and may also demonstrate air-fluid
levels).
lung field abnormalities -Nodules and Masses
Hyperdense pulmonary mass: They include:
• Granuloma: most common
• Pulmonary hamartoma
• Bronchogenic carcinoma
• Carcinoidtumours
• Pulmonary metastases
• Bronchogeniccyst
• Dystrophic calcification:
Papillary thyroid carcinoma
Giant cell tumourof bone
Synovial sarcoma Pulmonary hamartoma. A well defined
lobulated soft tissue mass occupying
Treated pulmonary metastases
the anterior basal segment of left lower
• Bone forming / cartilage mineralisation: lobe and shows popcorn calcification
Osteosarcoma and no significant enhancement. No fat
Chondrosarcoma could be identified within the lesion.
 lung field abnormalities -Cavities
Pulmonary cavities :
• Are gas-filled areas of the
lung in the center of a
nodule, mass or area of
consolidation.
• They are typically thick
walled and their walls must
be greater than 2-5 mm.
• They may be filled with air pulmonary tuberculosis. Cavitating
lesion with air-fluid level, in the left
as well as fluid and may also upper lobe with widespread patchy,
demonstrate air-fluid levels. linear and nodular opacities (tree in bud
appearance) along with consolidation.
 lung field abnormalities -Cavities
Pulmonary cavities : A helpful mnemonic is CAVITY:
C: cancer
• Bronchogenic carcinoma:
I: infection (bacterial/fungal)
(especially squamous cell
• Pulmonary abscess
carcinoma)
• Cavitating pneumonia
• Cavitatory metastasis (es):
• Pulmonary tuberculosis
• Squamous cell carcinoma
• Septic pulmonary emboli
• Adenocarcinoma, e.g.
T: trauma -pneumatocoeles
gastrointestinal tract, breast
Y: youth (not true "cavity")
• Sarcoma
• Congenital cystic adenomatoid
A: autoimmune; granulomas:
malformation (CCAM)
• Wegener's granulomatosis
• Pulmonary sequestration
• Rheumatoid nodules.
• Bronchogenic cyst
V: vascular (both bland and
septipulmonary embolus)
 lung field abnormalities -Cavities
Congenital pulmonary airway malformations (CPAM) or (CCAM):
• Classified by CT as:
Ø Type I(large (2-10 cm)variable cysts with at least
• one dominant cyst) and II(smaller(< 2 cm) uniform
cysts) CCAM demonstrate a multicystic (air-filled)
lesion. Type II CPAM: several
Ø Type III ( microcysts) CCAM: Least common types, small cysts (arrow) in
can appear as a consolidation. the right lower lobe.
• The cysts may be completely or partially fluid filled, in
which case the lesion may appear solidor with air
fluid levels.
• Large lesions may cause mass effect with resultant,
mediastinal shift, and depression and even inversion
of the diaphragm.

Type I CPAM: air-filled,

thin-walled spaces of
varying size.
 Pleural disease -Pneumothorax
Pneumothorax;
HRCT benefits:
1. CT is the most reliable imaging study for the diagnosis, but it is not
recommended for routine use
2. Confirm the diagnosis of pneumothorax in mechanically ventilated patients
3. Detect underlying emphysema, parenchymal and pleural diseases

Moderate left-sided pneumothorax. (A) Axial and ( B ) coronal CT demonstrating

subpleural blebs ( blue arrow ). Red arrows indicate pneumothorax
 Pleural disease –Pneumothorax -HRCT benefits
4. Determine the exact size of the pneumothorax
5. Detect occult(a pneumothorax that is seen only on CT and not
a conventional chest x-ray) pneumothoraces, blebs, bullae, cysts
and pneumomediastinum
Anteroposterior supine
radiograph shows no
abnormality.

CT scan shows the

existence of an occult
pneumothorax on the
Tension pneumothorax (green right side.
arrow) and subcutaneous
emphysema (red arrow). CT shows
increased volume of the right
hemithorax, reduction of ipsilateral
pulmonary volume and shifts the
mediastinum to the left
 Pleural disease – Pneumothorax - HRCT benefits
6. Distinguish between a large bulla and a pneumothorax
7. "Double wall" sign described in cases with ruptured
bulla causing pneumothorax (air outlining both sides of
the bulla wall parallel to the chest wall).

CT shows large asymmetric upper

lobe bullae. Chest tube is located
peripherally in right pleural space.
Chest radiograph shows unilateral Note presence of air in pleural
hyperlucency affecting the entire right lung space surrounding anterior bulla
(white arrows). (b) CT demonstrates a large on right (arrow) and parallel
bulla (star) on the right side causing configuration of bulla wall with
considerable compression of the mediastinum chest wall. This is double-wall
sign of pneumothorax.
 Pleural disease –Pneumothorax
Hydropneumothorax:
• The concurrent presence of both free fluid
and air within the pleural space
• It can occur secondary to various situations
such as thoracocentesis, thoracic trauma,
esophagopleural fistula, neoplastic processes,
post-traumatic, post-pneumonectomy,
infection, pulmonary infarction, cystic lung
disease, obstructive lung disease or
bronchopleural fistula. Axial contrast CT image
• CT depicts hydropneumothorax, with the demonstrates a right-sided
hydropneumothorax. Note the air
horizontal air fluid interface and fluid interface (arrow).
 Pleural disease -Pleural thickening
Pleural thickening; It is classified according to :
1.Aetiology:
Benign (greater than 5 cm in width, 8 cm in craniocaudal extent, and 3 mm in thickness):
>Recurrent inflammation
> Recurrent pneumothoraces
> Following a pleural empyema
> Complication of haemothorax
> Asbestosis & silicosis

Malignant (nodular (>1 cm),shows circumferential involvement, and involves the mediastinal pleura):
> Primary pleural malignancy
> Mesothelioma
> Primary pleural lymphoma
> Pleural metastases
> Secondary pleural lymphoma

2.Morphology:
> focal/pleural plaques(more than 5 mm)
> Diffuse (involvement more than 25% of chest wall if bilateral and 50% if unilateral)
 Pleural disease -Pleural thickening

Pleural metastases: Axial contrast- Tuberculous Pleural Effusion:

enhanced CT scan showing nodular CT scan with intravenous contrast
pleural thickening(arrows) involving enhancement shows loculated
the costal and mediastinal pleura with pleural fluid, thickening and
malignant pleural effusion in a case of enhancement of left pleura,
metastatic ovarian adenocarcinoma extrapleural fat proliferation.
 Pleural disease -Pleural thickening
Asbestos related pleural plaques:
§ Defined as variable-size localized
pleural thickenings of soft tissue, or
calcific densities attached along the
pleura of the chest wall, diaphragm,
and mediastinum on the CT scans.
§ Most pleural plaques are multiple,
bilateral, and often symmetrical
§ Located in the mid-portion of the
chest wall, adjacent to ribs, involving Non–contrast-enhanced computed
sixth to ninth ribs tomography (CT) of the chest shows
pleural thickening and extensively calcified
pleural plaques bilaterally (arrows).
 Pleural disease -Pleural thickening
Mesothelioma:
• The appearance is that of a soft tissue attenuation
nodular mass which spreads along pleural surfaces
including into pleural fissures and often creating a
pleural rind.
• Diffuse nodular pleural thickening, pleural plaques,
and pleural effusion
• Large pleural effusion without mediastinal shift may
also be seen
• Calcifications are seen involving the diaphragmatic
parietal pleura
• Unresectability includes encasement of diaphragm Malignant mesothelioma: Axial contrast-
enhanced CT scan showing enhancing nodular
and involvement of extrapleural fat, ribs, or other
pleural thickening(arrows) involving the costal
mediastinal structures and mediastinal pleura, extending into the
major fissure (arrowhead) with crowding of
ribs suggestive of volume loss changes in left
hemithorax
 Pleural disease -Pleural thickening
Apical pleural cap:
it is an irregular density, usually less than 5 mm thick, but the width is variable, located over the lung apex.
Compared with tumors, idiopathic caps are much smaller in craniocaudal than in axial dimensions

Causes:
Apical pleural scar. A,
• Pleural thickening/scarring
Chest radiograph
Ø Idiopathic: common feature of advancing age
shows asymmetric soft
Ø Tuberculosis, mycetoma
tissue thickening at
Ø Radiation fibrosis
the right apex.
• Pancoast tumour
• Haematoma
• Lymphoma
C, CT shows irregular
• Abscess
subpleural density,
• Metastases
with speculation
• Extrapleural fat.
mimicking lung cancer.
 Pleural disease -Pleural effusion
Pleural effusion is an abnormal collection of fluid in the pleural
space. Fluid may be (Transudate, Exudate, Pus, Blood, Chyle,
Cholesterol, Urine)
Indications of CT in effusions:
1. Assessment of pleural disease
2. Detect small effusions
3. Assesses mediastinum, lung parenchyma
4. Diagnose empyema
5. Distinguish lung abscess from empyema
6. Differentiate between benign and malignant pleural thickening
7. Size can be measured roughly as: < 20%, 20% to 40%, and >
40% of the hemithorax for small, moderate, and large effusions,
respectively
 Pleural disease -Pleural effusion
• Pleural effusion gives a homogeneous crescentic opacity in the most dependent part of the pleural cavity,
usually in the midthorax
• The lower CT attenuation of pleural fluid usually allows distinction from dependent atelectasis, pleural
thickening, and masses

Contrast-enhanced CT shows Aright- Contrast-enhanced CT shows a larger

sided effusion, associated with mild effusion causing marked compression
thickening and enhancement of the atelectasis of the right lower lobe
parietal pleura (arrow) and minimally (arrow). Note lack of enhancement of
enlarged mediastinal nodes. these the pleural surfaces, consistent with a
findings indicate an exudative effusion transudative effusion
 Pleural disease -Pleural effusion
Loculated pleural effusion:
• In the setting of pleuritis, loculation of fluid may occur within the fissures or
between the pleural layers (visceral and parietal).
• Loculation commonly occurs with exudative fluid, blood and pus.

Axial (left) and coronal (right) images demonstrate clearly the

loculated pleural effusion(arrows)
 Pleural disease -Pleural effusion –Loculated effusion
Encysted (encapsulated) pleural effusion in the
fissure:
• Loculated effusion in the fissures appears as
a well-defined elliptical opacity with pointed
margins.
• Pseudotumor/vanishing tumor (phantom
tumor): Loculated effusion in the fissures ,
secondary to congestive heart failure,
hypoalbuminemia, renal insufficiency or
pleuritis. Radiologically simulating a CT of the chest demonstrates cardiomegaly
neoplasm. It disappears rapidly in response and extensive smooth interlobular septal
thickening consistent with congestive cardiac
to the treatment of the underlying disorder. failure. There is focal fissural fluid collection
(arrow), so called pseudotumours.
 Pleural disease -Pleural effusion
Empyema: Features suggestive of an empyema include:
Empyema: Contrast-enhanced axial CT scan; loculated fluid in
the left major fissure, a pseudotumor (red arrow). Gas bubbles
are present (blue arrows).
• Typically appear lenticular with a smooth wall, conform to
the shape of the chest wall, and, if large, cause compression
of the lung
• Obvious septations
• Pleural thickening
• Gas bubbles in the pleura
• Loculations in fissures, septa
• Adjacent consolidation or abscess or lymphadenopathy
• Empyema necessitates: empyema extending into the chest
wall.
• Enhanced CT demonstrate the split-pleura sign; i.e. it is Empyema: Contrast-enhanced axial CT
contrast-enhanced thickened visceral and parietal pleura scan; loculated fluid in the left major
separated by fluid fissure, a pseudotumor (red arrow). Gas
bubbles are present (blue arrows).
 Pleural disease -Pleural effusion -Empyema
Empyema vs pulmonary abscess:

• Relationship to adjacent bronchi/vessels:

abscesses will abruptly interrupt the bronchovascular
structures
empyema will usually distort and compress adjacent lung
• Split pleura sign
• Wall: Split Pleura Sign-on CT, contrast-
abscesses have thick irregular walls enhanced visceral and parietal
empyema are usually smoother pleurae divide around a less-dense
• Angle with pleura: empyema
abscesses usually have an acute angle
empyema have obtuse angles
Coronal reformatted
chest CT show an
abscess (red arrow) and
an empyema(yellow
arrow)
 Pleural disease -Pleural effusion
How do you suggest the etiology of effusion from chest CT?
qBilateral: consider transudative effusions first. You will need clinical
information.
qBilateral effusions with cardiomegaly: Congestive heart failure
qBilateral pleural effusions associated with ascites in a alcoholic: Cirrhosis
qUnilateral: most of them are exudative
qLarge unilateral effusion: Malignancy
qPleural effusion with apical infiltrates: Tuberculosis
qPleural effusion with nodes or mass or lytic bone lesions: Malignancy
qLoculated effusions are empyemas
qPleural effusion with a missing breast suggesting resection for cancer:
Malignancy
qPleural effusion following chest trauma: Hemothorax
qIn patients with mediastinal lymphoma: Chylothorax
Rest of the topic will be covered in next class on
29th August 2020

Thank You