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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5769_Библиотеки_им_академика_М_И_Перельмана
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90 oracic ultrasound
Figure 23 – To the left , in the CT image the variation of density between parenchyma and emphysema
bubbles is evident. Echographic scans focused on the areas defined by the arrows, show signs of
interstitial disease at parenchymal level and an appearance of “hypermirror” at bubbles level. In this
case, the image is characterized by evident A Lines and Z Lines, which are the expression of massive
reflection on the pleural plane.
Figure 24 – Another case of massively reflective pleural plane. The patient is very thin and has thin
chest walls. His lungs are relatively expanded. The ultrasound scans show a linear pleura, strong Lines A,
and some Z Lines consisting of densely overlapping horizontal lines. We have defined this “hypermirror”,
which indicates a subpleural lung with very low density.
Semiotics of chest ultrasound 91
In normal subjects, rare vertical artifacts of pleural origin may appear, they move in synchrony
with the pleural line’s movements and they cover the A Lines. ese vertical artifacts were
initially defined “comet tail artifacts”, now they are called B Lines
34,35
. B Lines, unless they
are few (less than 8, both sides), are symptoms of interstitial disease, or of loss of aeration
(Figs. 25-26).
ISOLATED B LINE
Figure 25 – Isolated B Line, no pathological meaning.
ISOLATED B LINES
Figure 26 – Rare B Lines, no pathological meaning.
92 oracic ultrasound
Interstitial syndrome
26,34
“Interstitial syndrome” is an anatomical and radiological term. From the anatomical point
of view it identifies a group of diseases whose target is the interstitium of the lung. In interstitial disease of the lung, the interstitium expands because of the infiltration of fluids, cells,
tissues, collagen or mixed. e obvious radiological consequence is opacity or hyperdensity,
that in X-ray or in computed tomography scan (CT) identifies an altered interstitial tissue.
In conventional radiology, this is expressed with a septal, reticular or nodular hypodiaphaneity, different from alveolar consolidation for a certain degree of residual ventilation. In CT,
details are naturally enhanced, especially in high resolution scans, which currently represent
the gold standard for the diagnosis of interstitial diseases.
e terminology of CT will be summarized in the specific chapter of interstitial lung disease.
It allows a fine exploration of intralobular or interlobular septa, and of centrilobular structures,
with septal, peribronchial, perivascular, lymphatic and nodular components.
In CT, unlike alveolar consolidation, residual ventilation allows to visualize the bronchovascular markers. Beyond the evidence of interstitial and nodular morphologies, hyperdensity
called “ground glass”, is a characteristic sign of interstitial disease36.
e lung interstitial disease modifies the organ density primarily because of a pathological
gravimetric and volumetric increase in parenchyma, and secondarily (in certain cases) because
of the associated decrease in air content or because of an extraneous content on the alveolar
walls (e.g. hyaline membranes). e interstitial disease also modifies topology and geometry,
that is the layout and dimensions of subpleural air spaces27.
In lung echography, ultrasound “finds” the pleura and interacts with acoustic mechanisms on
the ventilated subpleural layer. In this process the production of traditional images (images
of parenchyma) is prevented. In the specific case of interstitial disease, residual parenchimal
air prevents the production of anatomical images.
Artifacts are the only phenomena with diagnostic value, at least up to a critical level of density that replaces those artifactual images with images of parenchyma. e latter constitute
the densimetric limits of consolidation (or alveolar syndrome), that will be discussed later.
Since its discovery in 1997, the interstitial syndrome was characterized by the presence of
many B Lines in the lung fields. e number of B Lines was greater than what is supposedly
normal (6-8 overall B Lines both sides). In its mildest phase, the interstitial syndrome shows
thinned B Lines, separated by reasonable distances according to the spaces between subpleural
interlobular septa (1-3 cm). In more severe cases, B Lines tend to merge with each other,
covering A Lines and generating a strong echogenicity of the fields explored (Figs. 27-28)
(Clips 14-16).
Clips 14, 15 – Many B Lines in patient with severe pulmonary edema.
Clip 16 – Patient in the early stage of ARDS after fat embolism: the
echographic result is indistinguishable from that of severe pulmonary edema.
Semiotics of chest ultrasound 93
Figure 27 – Interstitial syndrome located at the
right base in a case of pulmonary contusion.
Figure 28 – Interstitial syndrome in interstitial
pneumonia. Small subpleural consolidation.
ere is a correlation between the presence of thinned artifacts of type B and the expansion
of subpleural interlobular septa (Kerley B Lines of conventional radiology)34, and between
merged B Lines and ground glass findings36 (Figs. 29-34).
Figure 29 – In interstitial syndrom B Lines may appear with different density. a: B Lines easily countable
and spaced 1-3 cm identifying the so-called “septal syndrome”. In b and c B Lines increasingly tend to
coalesce. In d they are very close (white lung).
94 oracic ultrasound
Figure 30 – B Lines in case of cardiogenic pulmonary edema, explored with convex probe (3,5 MHz)
(above), and with linear probe (10 MHz) (below).
Figure 31 – Interstitial syndrome in a patient with severe cardiogenic pulmonary edema.
Semiotics of chest ultrasound 95
Figure 32 – Chest X-ray in the case of Figure 31.
NUMEROUS B LINES
Figure 33 – Interstitial syndrome in a patient with lobite for amiodarone.
96 oracic ultrasound
Figure 34 – CT of the case of Figure 33, highlighting areas of ground-glass.
is is not surprising when considering the anatomy of the interstitial syndrome and its
pathogenetic hypotheses, that have been discussed in the chapter on the physics of lung
ultrasound. Subpleural lung density (not consolidating) is an important element for the
echographic interpretation of interstitial syndrome. e severity of this change in density (or
porosity) of the lung is expressed by the number or concentration of B Lines (number of B
Lines/linear cm, but even better categorized with semiquantitative evaluation).
a
Figure 35 – When B Lines take on a relatively regular arrangement and can actually be counted
in a scan, subpleural interlobular septa may constitute reverberation focal points. But this is a special
case, in the context of mechanisms of acoustic interaction on a porous pattern. To the left, a coronal
reconstruction of lung CT, illustrating the interlobular septa thickened by edema (septal syndrome).
b
e considerations made so far, include the possibility or not to count B Lines. In our opinion, B Lines should not be counted27. Aside from the obvious difficulty of counting B Lines
when they are very numerous, they vary in number along the same line of view, depending
Semiotics of chest ultrasound 97
on the angle chosen for the insonation. On a phantom, the numerical variation of vertical
artifacts is clearly different, depending on the impact of the ultrasound beam on its surface.
For these reasons, we support a semi-quantitative estimate of the concentration of B lines in
interstitial lung disease.
Identifiable B Lines, 0.7 to 3 cm away from each other, indicate interstitial syndrome with
separated B Lines (or septal, because they may actually report the interlobular septa) (Fig. 35).
Closer B Lines, but still not confluent (i.e. merge into each other at certain points but still
remain identifiable as B Lines) are called dense B Lines.
Dense B Lines, that tend to merge partially into each other, but maintain a clear artifactual
nature, are called confluent B Lines.
White lung is a widespread subpleural echogenicity not generated by a confluence of B Lines.
is classification is characterized by a certain degree of subjectivity, especially in the definition
of confluence. On the contrary, there are no doubts on the description of septal lines and white
lung, as long as the transducer used, the deep set and the angle of insonation are specified.
Linear scan
Pleural line Pleural line
B lines
Figure 36 – 4 x 4 rule. To the left, a schematic representation of a linear scan of 4 cm with dense B
Lines. There are more than 9 B Lines. Less than 90% of the reciprocal intervals (double arrow), measured
5 mm below the pleura, measures less than 4 mm. To the right, pattern with confluent B Lines. Intervals
between B Lines measure less than 4 mm in 100% of the cases (Soldati G
Morphological-Ultrasound relationship. JUMB 2012;38:1169-79).
B lines
Linear scan
et al.
Ex vivo Lung Sonography:
In our opiniwon, an objective categorization of interstitial diseases can be possible only if, as
already mentioned, reference is made to a specific transducer, to an angle of insonation, and
to an estimate of the artifacts (i.e. if density/cm of artifacts is measured).
In an experimental setting (animal) we have adopted such a method (explained in Figure 36,
4 x 4 rule) in which, with respect to a pleural linear scan of 4 cm:
• pattern with rare B Lines: refers to a number of B Lines between 3 and 9;
• pattern with dense B Lines: more than 9 B Lines, less than 90% of the spaces interposed
less than 4 mm;
• pattern with confluent B Lines: more than 9 B Lines, 90% or more than 90% of the spaces
interposed less than 4 mm.
98 oracic ultrasound
is shows that it is very difficult to give objectivity to artifactual findings that are highly
variable by location and definition. We are not aware that similar methods have so far had
human or clinical applications.
Pure white lung (WL) (as seen for example in cases of ARDS, acute interstitial pneumonia
or hyaline membrane disease of the newborn) does not have a known genetic and biophysical explanation. From a clinical point of view, however, WL is a sign of interstitial disease
and deflation of the lung in a pre-consolidating phase, so it is a marker of lung hyperdensity.
As such, it also correlates with ground glass, evident in CT. e relationship between WL
and strongly confluent comets is also unknown. However, there is some evidence that both
findings are equivalent to ground glass, and that they have the same meaning in a certain
pathological context.
According to some preliminary personal observations, WL is indicative of a symmetrical coarctation of the air spaces or of an interstitial disease, which increases the organ density, but
does not modify deeply the geometry/symmetry of pleural and subpleural spaces.
e presence of multiple, heterogeneous reverberation artifacts originating from subcutaneous
emphysema, covering the pleural line and the ribs, should not be confused with an interstitial
syndrome. ese artifacts are defined E Lines (E from emphysema) (Fig. 37) (Clips 17-18).
PLEURAL LINE
E LINES
Figure 37 – Evidence of E Lines originating above the pleural line, caused by subcutaneous emphysema.
Clips 17, 18 – The presence of subcutaneous emphysema generates
vertical artifacts, covering the pleural line and the ribs (E Lines).
Alveolar syndrome
e term “alveolar syndrome” identifies the group of diseases in which there is submassive or
complete filling of the alveoli. It also has anatomical and radiological significance. e alveolar syndrome produces a marked increase in lung density. In echography it is evident when
Semiotics of chest ultrasound 99
the lung density is close to 0.8-0.9 g/ml. is is equivalent to stating that a good acoustic
window on the pleural plane (macrohole) has been formed, and it is constituted by a tissue
whose porosity (content of air) is around 10% or less.
e typical alveolar syndrome is a lung consolidation, where most of the subpleural spaces
are clogged by non-physiological tissue or material. For this reason, even if overlapping is
possible in echographic images, the origin of consolidation is different from obstructive atelectasis. In atelectasis the compaction and the critical reduction of lung porosity occur for
volume contraction (loss of air). In the image the effect is partially overlapping, as the acoustic
permeability of the lungs is greatly increased in both cases
37,38,39
.
Lung consolidation is considered as alveolar filling (hepatization) by exudate, transudate,
blood, fibrin or whatever replaces the air. If it reaches the pleural surface (as it usually happens), it appears as a structured area of the lung. is means that its shape, size, echogenicity
and echostructure are recognizable.
e extension (and size) may be lobar, segmental or random. e overall appearance may
be bulging, normal or retractable. It takes origin in an artifactual background, where the
consolidation is hypoechoic and homogeneous, except for the presence of residual air that
is bright. Typically, the pleural line that dominates the consolidated area, is interrupted or
much less echogenic (superficial alveologram). Within the consolidated area bronchi and vessels can be demonstrated with echography. is finding normally isn’t possible (Figs. 38-39).
PNEUMONIA
Figure 38 – Evidence of tree-shaped air bronchograms, in a case of inflammatory lung consolidation.
AIR BRONCHOGRAMS
e interruption of the echogenic pleural line confirms that it is an artifact, which disappears
whenever the pleura is massively permeabilized.
e alveolar syndrome is observed in pneumonia and bronchopneumonia
40,41
, in embolization42 with parenchymal alteration (atelectasis or infarction) and in parenchymal contusions43
with massive extravasation of blood and alveolar collapse. Even tumors to the pleura may be
of a similar appearance. Atelectasis (which are retractable and often completely lack of air),
even if of different pathogenesis, also appear very similar. In obstructive atelectasis that last
from a few hours, the absence of air bronchograms is observed (Fig. 40).
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