Brief discussion on ultrasonography of the chest: Benefits, Techniques and Instrumentation, Normal Anatomy, Diagnostic US of the chest, Limitations of Thoracic US, US based differential diagnosis, Take home points.

1. USG chest
Dr. Prashant
Gupta
NAMS, Bir

2. Contents
• Introduction
• Benefits of Thoracic US
• Technique and Instrumentation
• Normal Anatomy
• Diagnostic US of the Chest
• Limitations of Thoracic US
• US-based differential diagnosis
• Take home points

3. Introduction
• Examination of the chest is a rapidly developing
application of ultrasound (US) and may be used
to evaluate a wide range of peripheral
parenchymal, pleural and chest wall diseases.
• Particularly suited to bedside use in the intensive
care unit, where suboptimal radiography may
mask or mimic clinically significant abnormalities
and where differentiation of pleural from
parenchymal changes can be challenging

4. • Furthermore, US is increasingly used to guide
interventional procedures of the chest, such
as biopsy and placement of intercostal chest
drains.
• Thoracic US can also demonstrate various
acute pathologic conditions of the thoracic
wall, pleura, lung surface, cardiovascular
structures, and upper abdominal organs.

5. Benefits of Thoracic US
• Wide availability,
• Lower cost,
• Ability to perform the test at the patient’s
bedside,
• Real-time evaluation,
• Lack of radiation exposure.

6. Instrumentation
• Transthoracic chest US can be performed with
any modern US unit. A 2–5 MHz curvilinear
probe allows visualization of the deeper
structures, and the sector scan field allows a
wider field of view through a small acoustic
window.
• The chest wall, pleura, and lungs may be
quickly surveyed with the curvilinear probe.

7. • Once an abnormality has been identified, a
high-resolution 7.5–10 MHz linear probe can
be used to provide detailed depiction of any
chest wall, pleural, or peripheral lung
abnormality.
• Both gray-scale and color doppler imaging are
useful for the assessment of pleural and
parenchymal abnormalities.

8. Techniques
• Thoracic US has two main parts, which are
closely related: (a) lung and pleura US and (b)
focused cardiac US. In addition, US
interrogations may be performed of the
inferior vena cava for volume assessment and
of the groin areas for deep venous thrombosis.

9. Lung and Pleura
• Raising the arm above the patient's head
increases the rib space distance and facilitates
scanning with the patient in erect or
recumbent positions.

10. • The posterior chest is best imaged with the patient
sitting upright, while the anterior and lateral chest
may be assessed in the lateral decubitus position

11. • Before performing the US examination, it is
important to review the patient's chest
radiograph to localize the area of interest.
• Maximum visualization of the lung and pleural
space is achieved by scanning along the
intercostal spaces.

12. • Scanning should be performed during quiet
respiration, to allow for assessment of normal
lung movement, and in suspended respiration,
when a lesion can be examined in detail with
gray-scale or color Doppler US.
• On gray-scale images, the echogenicity of a
lesion can be compared with that of the liver
and characterized as hypoechoic, isoechoic, or
hyperechoic.

13. • Sonographic views of the upper anterior and
middle mediastinum can be obtained via a
suprasternal approach.
• The suprasternal approach allows adequate
assessment of the upper mediastinum in 90%-
95% of cases .
• The aorta and superior vena cava can be
recognized on the suprasternal view of the
mediastinum.

14. • Performed with the
patient in a supine
position, with
shoulders supported
with a pillow and head
extended backward.
Views of the upper
mediastinum should
be obtained in the
sagittal and axial
planes

15. • Color Doppler US is helpful in distinguishing
the great vessels from any mediastinal mass.
• Visualization of the mediastinum via a
parasternal or infrasternal approach is usually
less reliable.

16. Techniques
• Supine position, start at the anterior and
anterolateral chest wall (second intercostal
space at midclavicular line and at fourth or
fifth intercostal space at the midaxillary line),
posterior part of the lung and pleura may be
scanned with patient in upright position,
sagittal plane provides bat sign, longitudinal
scan is used for fracture detection

17. Normal US Appearance
• Bat sign (B-mode): a curvilinear hyperechoic
interface with posterior acoustic shadowing
from the two adjacent ribs; in the intercostal
space about 1–1.5 cm deep to the anterior rib
surface is a hyperechoic pleural interface, or
pleural line;

18. • Lung sliding (B-mode): normal gliding
movement between the parietal and visceral
pleurae synchronous with respiration;
• Seashore sign (M-mode): a combination of a
superficial layer of horizontal lines from the
static chest wall and a deep layer of granular
appearance from the lung movement

19. Normal lung and pleura US. Note the
pleural line (between arrows). (a)
Sagittal B-mode US image shows the
bat sign. a = subcutaneous fat, b =
muscles, c = ribs. (b) Sagittal M-mode
US image shows the seashore sign. d =
static thoracic wall, e = granular
pattern of the lung. (c) Sagittal power
Doppler US image shows the power
slide sign.

20. • It is important to note that many signs at
lung US represent artifacts occurring
naturally because of acoustic mismatch of
tissues reflecting sound waves.

21. Artifacts of lung and pleura US

22. Arrows indicate a transverse hyperechoic artifact just deep to the chest wall, a finding that
represents the pleural line. The pleural line is where lung sliding occurs at real-time imaging.
This line is an important landmark for identifying other artifacts because most artifacts arise
from or below this line.

23. US image shows multiple A-lines (arrowheads), which are horizontal parallel
hyperechoic linear artifacts depicted at regular intervals below the pleural line
(arrows).

24. US image shows A-lines (large arrowheads) and B-lines (small arrowheads). B-
lines are vertical hyperechoic artifacts originating from the pleural line (arrow)
that extend to the edge of the screen and erase the A-lines.

25. US image clearly shows multiple B-lines (arrowheads) and the pleural line
(arrows). At real-time imaging, B-lines move synchronously with lung sliding

26. US image shows E-lines (arrows), which are multiple comet-tail artifacts arising
superficial to and obscuring the pleural line. The E-lines represent faint
hyperechoic artifacts that extend to the edge of the screen.

27. US image depicts a combination of B-lines (arrowheads) and Z-lines (black
arrows). The Z-lines are short, ill-defined vertical hyperechoic lines arising from
the pleural line (white arrow). They do not reach the edge of the screen, erase
the A-lines, or follow the lung sliding.

28. Diagnostic US of the Chest

29. Diseases of the Pleural Space
• Pleural Effusions
 The classical appearance of a pleural effusion is
an echo-free layer between the visceral and
parietal portions of the pleura.
 The shape of the pleural effusion may vary with
respiration and posture.
 In inflammatory effusions, lung sliding may be
absent above the effusion as a result of lung
adhesion between the visceral and parietal
portions of the pleura

30. • The sonographic appearance of pleural effusion
depends on the cause, nature, and chronicity of
the collection
• Four different appearances are recognized at US:
Anechoic,
Complex but nonseptated,
Complex and septated,
Echogenic

31. • Transudates are almost invariably anechoic.
• Exudates may appear anechoic, complex, or
echogenic.
• Effusions that are complex, septated, or
echogenic are usually exudates.
• Mobile strands of echogenic tissue and
septations are frequently observed in
inflammatory effusions.
• Swirling hyperechoic debris secondary to cardiac
or respiratory motion may be seen (“plankton
sign”)

32. • Empyema can result in an echogenic collection
that mimics a solid lesion.
• In comparison, malignant effusions are more
frequently anechoic than echogenic .However,
a firm diagnosis of malignant effusion can be
made only if there is associated nodular
pleural thickening

33. • Small pleural effusions are readily detected and can be
distinguished from pleural thickening.
• The "fluid color" sign is demonstrable on color Doppler
scans in pleural effusions but is absent in pleural
thickening .
• The sign refers to the presence of color signal within
the fluid collection that is believed to arise from
transmitted respiratory and cardiac movements.
• The fluid color sign has a reported sensitivity of 89.2%
and specificity of 100% in identifying small effusions

34. • Supine chest radiography may reveal
abnormality when the amount of fluid reaches
175–525 mL, which is higher than that for
upright chest radiography
• US is far more sensitive for detection of
pleural effusion than chest radiography, being
able to depict as little as 5–20 mL of pleural
fluid with an overall sensitivity of 89%–100%
and specificity of 96%–100%

35. • The US appearance of hemothorax is highly
variable; it can be anechoic, hypoechoic, or
hyperechoic. Hemothorax tends to locate
along the dependent portion, mostly in the
posterior costophrenic sulcus in supine
patients

36. Pleural effusion, empyema, and hemothorax in
three different patients. (a) Coronal US image of a
77-year-old man with congestive heart failure
shows a large anechoic right pleural effusion (a).
(b) Transverse US image of a 48-year-old woman
with tuberculous pleural empyema shows a
complex-appearing left pleural effusion (b) with
multiple septa and hyperechoic contents. Note
the collapsed lung tissues (*). (c) Transverse US
image of a 20-year-old man who sustained blunt
thoracic trauma shows the heterogeneous
echogenicity of a large left pleural effusion (c)
secondary to hemothorax. Note the collapsed
lung tissues

37. Pleural Thickening
• Pleural thickening appears as hypoechoic
broadening of the pleura.
• Pleural thickening may occur in a variety of
conditions. It is most frequently related to
scarring, fibrosis, empyema, and pleuritis.
• Unlike pleural effusion, pleural thickening
does not exhibit the fluid color sign

38. • At US examination, pleuritis is seen as an
interruption of the pleural line and irregular
hypoechoeic thickening of the visceral pleura
• The chest radiograph is frequently
unremarkable when disease is readily
apparent at US. There may be an associated
pleural effusion with or without increased
vascularity at color Doppler US

39. • Previous asbestos exposure is a relatively
common cause of pleural thickening and may
be confirmed if calcified pleural plaques are
evident.
• These plaques cause focal areas of dense
reflectivity with dense posterior acoustic
shadowing, often with evidence of adjacent
noncalcified pleural thickening.

40. US demonstrates pleural thickening as a hypoechoic band, just
superficial to the echogenic pleural-lung interface.

41. Pleural Masses.
• Pleural masses may be benign or malignant.
• Benign pleural masses such as fibromas, lipomas,
and neuromas are uncommon.
• These appear as well-defined rounded masses of
variable echogenicity, depending on the fat
content of the cells.
• A biopsy is usually required to reach a definitive
diagnosis

42. • Malignant masses of the pleura include
mesothelioma, lymphoma, and metastases.
• Mesothelioma is seen as irregular thickening
of the pleura that may appear nodular and is
frequently associated with a large pleural
effusion
• However, CT remains the modality of choice in
the preoperative staging of malignant
mesothelioma

43. • Subpleural lymphomatous deposits appear as
wedge-shaped hypoechoeic infiltrates and
may resemble pulmonary infarcts .
• The most common pleural metastases are
from primary adenocarcinomas. Pleural
effusions almost invariably accompany pleural
metastases, but the volume of deposits on the
pleural surface may be small and beyond the
resolution of US.

44. • Pleural deposits more than 5 mm in diameter can
be identified as oval echogenic nodules,
frequently along the parietal or diaphragmatic
pleura.
• Metastases may also appear as diffuse thickening
of the parietal pleura and, to a lesser extent, the
visceral pleura. Malignant pleural disease may
invade the chest wall, with poor demarcation of
the pleural mass and infiltration into the chest
wall.

45. • Color Doppler US of a malignant pleural mass
may reveal neovascularity with irregular
tortuous vessels.
• At pulsed-wave US, the tumor vessels typically
exhibit a low-resistance flow pattern, in
keeping with neovascularization

46. Metastatic adenocarcinoma to the pleura in a 49-year-old
woman. CT scan demonstrates lobulated pleural masses
within the right hemithorax.

47. Pneumothorax
• Although a pneumothorax can usually be seen on
a chest radiograph, a small pneumothorax may
be overlooked on a radiograph of a supine
patient obtained in the intensive care unit.
• Radiographs obtained in the ICU are difficult to
interpret because suboptimal technical factors,
artifacts, and widespread lung changes can
obscure or simulate pneumothorax

48. • The key sonographic signs used to diagnose
pneumothorax include:
Absent lung sliding
Exaggerated horizontal artifacts
Loss of comet-tail artifacts
Broadening of the pleural line to a band

49. • Bedside sonography is useful for excluding
pneumothorax
• Use of a combination of absent lung sliding
and the loss of comet-tail artifact has a
reported sensitivity of 100%, specificity of
96.5%, and negative predictive value of 100%

50. • When real-time US is performed in the area of a
pneumothorax, static air in the pleural cavity
creates total reflection of the sound waves and
obscures the normally visible, movable pleural
line. This is called the “absence of lung sliding”
,which is a US sign suggestive of pneumothorax.
• The absence of lung sliding can also be
demonstrated as the lack of color signal
underneath the pleural line on a power Doppler
US image. The absence of lung sliding is sensitive
but not specific for pneumothorax.

51. • Lung sliding may be absent in patients with
previous pneumonectomy , one-lung
intubation, pleuroparenchymal adhesion, or
subpleural bullae
• So, absent lung sliding should not be used as
the sole criterion in the diagnosis of
pneumothorax.

52. • At M-mode US, the area underneath this soft
tissue–pneumothorax interface demonstrates
multiple horizontal bands of hyperechoic
artifacts caused by the lack of visible lung
motion. This M-mode appearance mimics a
traditional bar code (“bar code sign”) or the
stratosphere layer of Earth’s atmosphere
(“stratosphere sign”)

53. • The most specific finding of pneumothorax at US is the
lung point sign.
• The lung point represents the boundary between the
aerated lung and a pneumothorax.
• During US scanning at this boundary, the lung moves in
and out of the transducer field with the respiratory
cycle.
• During inspiration, the aerated lung displaces air in the
pleural space toward the transducer, hence creating an
appearance of normal lung sliding, or the seashore
sign, at US. During expiration, the lung becomes less
aerated and moves away from the transducer.

54. • The air in the pleural space returns to the
scanned area. This movement creates the
appearance of the loss of lung sliding, or a bar
code sign.
• The alternation of normal lung sliding and loss of
lung sliding in the same scanned area is the lung
point; this lung point sign has been shown to be
100% specific for pneumothorax and should
routinely be sought in patients with loss of lung
sliding

55. • Besides the high specificity of the lung point,
this sign is also helpful for estimation of the
size of a pneumothorax. In supine patients,
the more posterior the lung point is located,
the greater the pneumothorax .

56. • Although US is useful in the diagnosis of
pneumothorax, the technique is unable to
quantify the size of the pneumothorax.
• US may also be of limited use in patients with
subcutaneous emphysema or pleural
calcifications, because acoustic artifacts due to
these conditions may limit visualization of the
pleural interface

57. Loss of lung sliding secondary to pneumothorax in a 41-year-old man who presented with
acute chest pain. (a) B-mode US image shows multiple A-lines (arrowheads) and the
pleural line (arrows). (b) M-mode US image shows a bar code sign, or stratosphere sign, a
finding that indicates the absence of lung sliding.

58. Lung point. (a) M-mode US image of a 60-year-old man who sustained blunt thoracic
trauma shows an alternating presence and absence of lung sliding. The area between the
heads of the double-headed arrow represents a bar code sign, or stratosphere sign. (b)
Drawings explain the presence of lung sliding during inspiration (top) but absence of lung
sliding during expiration (bottom) because of the different degrees of expansion of the
pneumothorax (*).

59. Diagram of the suggested diagnostic algorithm for US diagnosis of pneumothorax.

60. Diseases of the Lung Parenchyma
• In healthy individuals, visualization of the lung
parenchyma is not possible because the large
difference in acoustic impedance between the
chest wall and the air within the lung results in
near total reflection of the ultrasound waves.
• However, in parenchymal diseases that extend
to the pleural surface, replacement of the air
within the lung creates an acoustic window,
allowing assessment of lung tissue

61. Pneumonia and Lung Abscesses.
• Lobar pneumonia, segmental pneumonia
affecting the pleura, and pleurally based
consolidation are detectable at US.
• In general, the size of the pneumonia appears
smaller at US than on radiographs.This is
because the periphery of the pneumonia is
more air-filled, which results in more artifacts,
thus limiting complete visualization of the
extent of consolidation.

62. • In the early phase of consolidation, the lung appears
diffusely echogenic, resembling the sonographic
texture of the liver .
• The shape of the pneumonia is rarely well defined,
often showing irregular or serrated outlines.
• Branching echogenic structures are often (87% of
patients) seen within the pneumonia and represent air
bronchograms .
• Multiple lenticular echoes, representing air inlets and
measuring a few millimeters in diameter and extending
to the pleural surface, are also frequently observed.
These lenticular echoes vary with respiration.

63. • The dendritic-like air bronchogram may be
seen as hyperechoic foci moving through the
bronchi (dynamic air bronchogram) within the
consolidation. This sign may be used to
differentiate pneumonia from resorptive
atelectasis, in which the air bronchogram is
usually static

64. • The branching pattern of vascular flow within
the consolidated lung segment can be
observed by using color Doppler US.
Relaxation atelectasis is usually depicted as a
mobile hypoechoic lesion along with reduced
lung volume next to a large pleural effusion.

65. • Fluid bronchograms may also be observed in
pneumonia .
• These are identified as anechoic tubular
structures, representing fluid-filled airways.
• The fluid bronchogram is seen in bronchial
obstruction, which can result from either
impacted secretions or a proximal tumor .

66. • Although the fluid bronchogram may be seen
in isolated pneumonia, the presence of this
sign in the appropriate clinical context should
raise the suspicion of postobstructive
pneumonitis.
• Indeed, US may be able to help in
distinguishing the central obstructing tumor as
a hypoechoic mass from the distal more
echogenic consolidation.

67. • As the disease progresses, the echogenicity of
the pneumonia increases and becomes more
heterogeneous.
• With successful treatment, reestablished
ventilation within the consolidation gives rise
to more air-inlet artifacts, and the area of
pneumonia diminishes in size.

68. • Although pneumonia is the most common cause of
lung consolidation, its appearance is nonspecific.
• Infarction, hemorrhage, vasculitis, lymphoma, and
brochoalveolar carcinoma can result in consolidation
that appears similar to that of pneumonia at US.
• When the diagnosis is uncertain, US may be used to
guide lung biopsy .This is especially useful in
immunocompromised patients in whom pulmonary
consolidation may pose a diagnostic problem.

69. • Pneumonia resulting from pyogenic organisms
can undergo necrosis leading to lung abscess
formation.
• A lung abscess can be identified at US as a
hypoechoic lesion with a well-defined or
irregular wall.
• The center of the abscess is usually anechoic
but may contain internal echoes and
septations.

70. US demonstrates an area of consolidation within the right lower lobe. The texture
of the consolidated lung appears isoechoic to the liver. Multiple echogenic foci are
seen within the consolidated lung and correspond to air-filled airways.

71. On the color Doppler scan, a pulmonary artery branch
supplying the segment is clearly seen.

72. Community-acquired pneumonia in a 13-year-old girl. Coronal US image shows
consolidation (*) with internal hyperechoic tubular air in the left lower lobe, as
well as a minimal left pleural effusion (arrow). Spl = spleen.

73. Relaxation atelectasis next to a large pleural effusion in a 40-year-old man with
congestive heart failure. US image shows homogeneous hypoechoic areas (*) of the
lung without internal hyperechoic air, which are surrounded by a large pleural
effusion (e). Movement of atelectasis is seen during respiration. Note the
hyperechoic interface (arrows) between atelectasis and normal lung tissue.

74. Neoplasms.
Primary Lung Neoplasms :
 Appears as a homogeneous, well-defined mass that is
usually hypoechoic but may be slightly echogenic.
 There is usually posterior acoustic enhancement.
 Consolidation and fluid bronchograms may been seen
adjacent to the mass.

75. • US is useful for assessing invasion of the chest wall by
tumor. High-resolution linear US probes are best suited
for this purpose. US (sensitivity, 76.9%; specificity,
68.8%) is more sensitive than CT (sensitivity, 69.2%;
specificity, 72.4%) in the evaluation of chest wall
invasion.
• Extension of the tumor beyond the parietal pleura into
the chest wall can be confidently determined if the
mass is seen to breach the pleura, with loss of
movement of the mass with respiration.

76. • Color Doppler US has been shown to be useful
in distinguishing malignant from benign
pulmonary masses
• Color Doppler signal may be obtained in
peripheral malignant masses in a substantial
proportion (64%) of cases
• Malignant masses are associated with
neovascularity, which demonstrates low-
impedance flow

77. • A constant flow pattern has a high correlation with
malignancy, whereas a pulsatile or triphasic flow
pattern may be seen in both benign and malignant
neoplasms
• It has been shown that malignant tumors have a lower
pulsatility index, resistive index, and peak systolic
velocity but a higher end diastolic velocity compared
with benign tumors. A resistive index of 0.52 ± 0.13
(sensitivity, 100%; specificity, 95%) and pulsatility index
of 1.43 ± 0.13 (sensitivity, 97%; specificity, 95%) is
reportedly useful in differentiating malignant from
benign masses

78. • US is a valuable tool in the assessment of
Pancoast or superior sulcus tumors.
Visualization of the extent of the tumor can be
limited at CT because of the orientation of the
scan plane. US is able to depict the tumor
mass, help assess any associated pleural or
chest wall extension, and guide percutaneous
biopsy

79. Figure 10b. Middle-aged man with Pancoast tumor. The mass is
clearly visible on the US scan, appearing as a hypoechoeic mass that
contains foci of strong reflectivity and acoustic shadowing and
corresponding air-filled bronchioles. The mass can be easily biopsied
under US guidance.

80. • Metastasis: Peripheral pulmonary metastasis
may be detected at sonography, apppearing as
multiple subpleural echogenic nodules measuring
about 1–2 cm in diameter.
• Color Doppler imaging demonstrates the high
vascularity of these lesions and their low-
resistance flow pattern. After successful
chemotherapy, residual nodules showed
diminished vascularity at color doppler imaging

81. Pulmonary Embolism and Infarction
• Pulmonary embolism most commonly originates from
deep venous thrombosis of the legs.
• The clinical manifestation ranges from asymptomatic
chronic thrombotic pulmonary hypertension to
massive embolism causing immediate cardiopulmonary
collapse and death.
• About 79% of patients with pulmonary embolism have
evidence of deep venous thrombosis in the legs.
• On the other hand, pulmonary embolism occurs in as
many as 50% of patients with proximal deep venous
thrombosis.

82. • The combination of thoracic, focused cardiac,
and groin US is a promising technique to
evaluate patients with suspected pulmonary
embolism.
• The diagnosis of acute pulmonary embolism
may be suggested if a patient with dyspnea
has deep venous thrombosis of the lower
extremity, a right ventricular strain pattern,
and subpleural lung consolidations.

83. • Subpleural consolidations in this setting may represent
pulmonary infarction.
• The subpleural consolidations manifest as multifocal
wedge- or triangle-shaped heterogeneous hypoechoic
lesions, located predominantly in the lower lobes
• The presence of subpleural consolidations, along with
other signs, has a sensitivity of 87% and specificity of
81.8% in the diagnosis of pulmonary embolism
• Small basal or localized pleural effusions may also be
seen in about half of the patients.

84. Acute Alveolar-Interstitial Syndrome
• Acute alveolar-interstitial syndrome is a
heterogeneous group of conditions with
pathologic involvement of the pulmonary
interstitium, resulting in impaired gas
exchange.
• Abnormally increased lung water content and
reduced air in the alveoli result in fluid leakage
into the pulmonary interstitium and alveolar
spaces.

85. • At US, these abnormalities are demonstrated
as multiple vertical hyperechoic artifacts
called “B-lines.”
• The B-lines are a type of reverberation artifact
secondary to reflection of sound waves at the
interlobular septa. The B-lines have distinct
characteristics of being vertical, strongly
hyperechoic, and laserlike, with sharp
margins.

86. • The B-lines originate at the pleural line and extend to
the edge of the US screen (in contradistinction to the
shorter comet tail artifacts, or Z-lines, usually seen at
the pleural interface).
• The term lung rocket has been coined for B-lines
because of their appearance mimicking the appearance
of the exhaust gas created when a rocket is launched
• When A-lines are present, the B-lines obscure the A-
lines. At real-time scanning, B-lines also move with
respiration.

87. Pulmonary Edema
• Pulmonary edema is a classic cause and the most
common cause of acute alveolar-interstitial
syndrome in the emergency department
• Pulmonary edema can be secondary to (a)
increased hydrostatic pressure, (b) abnormal
capillary permeability with or without diffuse
alveolar damage, or (c) simultaneously increased
hydrostatic pressure and abnormal
permeability—as a result of either cardiogenic or
noncardiogenic causes.

88. • Although chest radiography remains the imaging
modality most frequently used to detect and quantify the
degree of pulmonary edema, it is not without limitations.
• A lag time exists between the onset of a patient’s
symptoms and the appearance of radiographic
abnormalities. In addition, mild or subtle changes may be
overlooked and can be subjective, especially with
suboptimal portable radiography. US abnormalities may
precede those of radiography and can be diagnostic of
pulmonary edema, with a sensitivity and specificity of
97% and 95%, respectively

89. • In pulmonary edema, multiple B-lines are seen
on each image obtained in different zones of
both lungs. Generally, at least three B-lines
with a convex transducer or at least six with a
linear transducer are considered “multiple”
and consistent with pathologic B-lines.

90. • Other US findings supportive of the diagnosis of
cardiogenic pulmonary edema include pleural
effusion, distention of the inferior vena cava with
loss of respiratory collapse, and impaired cardiac
contractility.
• The number of B-lines may correspond to the
severity of pulmonary edema.
• At follow-up US, resolution of B-lines also
correlates with improvement of a patient’s
symptoms and radiographic findings

91. ARDS
• ARDS is another example of acute alveolar-
interstitial syndrome that can be diagnosed at
US.

92. • In patients with ARDS, multiple B-lines with an
inhomogeneous distribution, small subpleural
consolidations with posterior and basal lung
predominance, and punctate hyperechoic foci
of air bronchograms within the consolidations
have been described and may help distinguish
ARDS from acute cardiogenic pulmonary
edema.

93. Asthma and COPD
• Multiple B-lines at US are suggestive of
alveolar-interstitial syndrome, which can be
used to rule out acute COPD exacerbation
with 100% sensitivity and 92% specificity
• In general, the US appearance of the lungs
and pleura in asthmatic patients and patients
with an acute COPD exacerbation
demonstrates multiple A-lines with normal
lung sliding.

94. Diseases of the Chest Wall
Soft-Tissue Disease.
• US is sensitive for the detection of soft-tissue
masses arising within the chest wall. Most of
these lesions are benign, such as lipomas
sebaceous cysts, hematomas, and abscesses.
• Unfortunately, sonography of chest wall
masses is frequently nonspecific, showing a
mass of variable echogenicity

95. Lymph Nodes.
• Lymph nodes, particularly within the axilla and
supraclavicular fossa, are easily examined with
US.
• Sonography can be helpful in distinguishing
reactive (inflammatory) lymph nodes from
those infiltrated by a malignant process.

96. • Reactive lymph nodes are oval or triangular in
shape, demonstrating an echogenic fatty
hilum that may become even more prominent
with inflammation.
• Malignant lymph nodes usually appear plump,
rounded, hypoechoic, with loss of the fatty
hilum
• Irregularity in the borders of these lymph
nodes suggests extracapsular spread

97. • At color Doppler US, increased vascularity may
be demonstrable within these infiltrated
lymph nodes
• Enlarged nodes in lymphoma also appear
rounded and hypoechoic but are usually well
defined.

98. Rib Abnormalities.
• After chest trauma, US may be used in the
diagnosis of rib fracture. Sonography is best
performed along the line of the rib and over
the site of maximum tenderness.

99. • US is more sensitive than radiography in the
detection of rib fractures.
• Fracture appears as a gap, step, or displacement
of the cortex of the rib
• The fracture may be associated with a localized
hematoma, effusion, or soft-tissue swelling.
Subtle crack fractures may exhibit a small
reverberation artifact known as the “light-house
phenomenon” or “chimney phenomenon”

100. • During the acute healing phase, increased
echogenicity is seen filling in the space of the
rib fracture, representing callus formation.
With time, calcification of the callus may cast
a small acoustic shadow.
• When union and remodeling are completed, a
slight contour abnormality of the cortex may
be all that is discernible.

101. • Bony metastases to the ribs can sometimes be
visualized at US.
• Infiltration of the bone appears as a
hypoechoic mass, replacing the normal
echogenicity of the rib. There is disruption of
the echogenic cortical line, which may be
associated with abnormal acoustic
transmission

102. Rib fractures in a 61-year-old man who sustained blunt thoracic trauma. Longitudinal
US images of two adjacent ribs show a curved hyperechoic interface underneath the
thoracic wall muscles with posterior acoustic shadowing, a finding that represents the
anterior cortex of the ribs. (a) US image shows a minimally displaced rib fracture
(arrow). (b) US image shows a displaced rib fracture (arrows) and an adjacent
hematoma (*).

103. Sternal fractures in two different patients who sustained blunt thoracic trauma. (a)
Longitudinal US image of a 25-year-old woman shows a buckle fracture (arrows) of the
sternum. (b) Sagittal US image of a 26-year-old man shows a nondisplaced fracture
(arrow) of the sternum.

104. Clavicle fracture in a 48-year-old man who sustained blunt thoracic trauma. Longitudinal
US images show a cortical discontinuity (arrow) of the left clavicle. Note the focal
reverberation artifact (arrowhead) deep to the site of the fracture. The right clavicle is
normal.

105. Subcutaneous emphysema in a 43-year-old man who sustained blunt thoracic trauma. B-
mode US image shows multiple “fuzzy” hyperechoic artifacts, or “E-lines” (arrows),
within the subcutaneous tissue, which are casting dirty shadows across the depth of the
image. The pleural line and the ribs are not depicted.

106. Pulmonary contusion in a 16-year-old male patient who sustained blunt thoracic
trauma. US image shows subpleural consolidation (*) next to a small hemothorax
(e).

107. • Diaphragmatic Abnormalities
There is wide variability in the normal
movement of the diaphragm during
respiration. There is normally asymmetry in
the movement of the two leaves of the
diaphragm.

108. Diaphragmatic Paralysis
• Diaphragmatic paralysis may be identified as
paradoxical movement of the diaphragm with
respiration.
• A paralyzed diaphragm may appear atrophic,
with less contraction and shortening on
inspiration than occurs in the normal
diaphragm

109. Limitations
• Although the role of US of the thorax has been
well recognized in areas of cardiac imaging,
evaluation of pleural effusion, and guidance
for thoracentesis, the value of US in evaluation
of the lungs remains limited.
• Several lung signs at US are artifacts, which
may prove themselves obsolete and
unpredictable as US technology advances.

110. • Artifacts are affected by machine factors such as focal
zone, frequency, and gain settings.
• Similar to US of other body parts, patient and operator
factors play Patients with a large body habitus, no
accessible areas for scanning, an inability to cooperate,
air in the subcutaneous tissue, or skin infection are
generally not candidates for thoracic US.
• Image quality at US is heavily dependent on
sonographer skill and patient cooperation
• Time constraints are another limiting factor in
performing US in the emergency department.

112. Take home points

115. References
• Transthoracic US of the Chest: Clinical Uses
and Applications, RadioGraphics 2002
• Emergency Thoracic US: The Essentials,
RadioGraphics 2016

116. Thank
You