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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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110 oracic ultrasound
e vast majority (90%) of pleural effusions result from heart failure, cirrhosis, ascites, infection, tumors or pulmonary embolism. Heart failure is the most common cause of pleural
effusion, while neoplasm are associated to most of the exudates. Pulmonary embolism is a
cause for pleural effusion, often not properly considered8.
At least 30% of patients with pulmonary embolism show a pleural effusion, which is typically
small. Other causes for pleural effusion are intra-abdominal diseases, such as subphrenic, hepatic, splenic and pancreatic abscesses and acute and chronic pancreatitis (with pseudocyst).
Table 1 illustrates an etiological classification of pleural effusions.
Table 1 – Etiological classification of pleural effusions
Transudates
Exudates
Increased hydrostatic pressure
• Congestive Heart Failure
• Constrictive pericarditis
• Obstruction of the superior vena cava
Neoplasms
• Bronchogenic carcinoma
• Mesothelioma
• Metastasis
• Leukemias and lymphomas
Pulmonary embolism
Connective or allergic diseases
• Rheumatoid Arthritis
• Systemic lupus erythematosus
• Dressler’s syndrome
• Hypersensitivity to medecines
Miscellany
• Boerhaave Syndrome
• Myxedema
• Atelectasis
• Uremia
• Lymphedema
• Familial Mediterranean fever
• From Asbestos
Idiopathic
Decreased colloidal osmotic
pressure of plasma
• Nephrosis
• Cirrhosis
• Hypoalbuminemia
Infections
• Parapneumonic effusions and
empyema
• Viral infections
• Fungal infections
• Tuberculosis
• Mycoplasma
• Parasites
Intra-abdominal pathology
• Meigs’ syndrome
• Acute Pancreatitis
• Subdiaphragmatic abscess
Hemothorax
Lipidic
• Chylothorax
• Cholesterinic or pseudochylous
Pathology of the pleura 111
A pleural effusion may be identified in the context of a causal pathology, an inflammatory
state, during the staging of a neoplasm or associated to heart failure. In other cases, it produces
symptoms such as chest pain, fever, cough or dyspnea.
Here it is useful to remind the effusions that occur for the first time, that show symptoms
leading the patient to the emergency department or that complicate the intensive care management. ese effusions have a rapid growth and can also occur simultaneously to another
disease already causing dyspnea (e.g. congestive heart failure, anemic state or obstructive
pulmonary disease).
e radiological investigation is reliable when it is performed under optimal conditions. e
better position is when the patient lies on his affected side. In this position 5 ml of liquid
are enough to be seen.
In the more common PA scan, when the patient is standing, at least 200 ml are required to
obscure lateral costophrenic angles, but sometimes 500 ml of liquid do not cause any change
in these regions
When the patient is supine, radiography is less accurate in detecting pleural effusions
9,10
.
11,12
especially when they are bilateral and mask any difference in transparency between the two
hemithoraces. Moreover in the upright position any subpulmonary effusion can be confused
with a rise of the hemidiaphragm13.
Finally, the loculation or the intrascissural position of an effusion14 may appear as a circumscribed opacity of dubious interpretation, quite different from the expected sign of occlusion
of the pleural recesses15.
CT is very accurate and specific for the diagnosis of pleural effusion16. CT allows to define
the presence of pleural fluid and to estimate its radiological density. It also allows to detect
the solid pathology of the pleura, the lung parenchymal abnormalities and the presence of
pulmonary embolism (CCTA). CT finally completes diagnostic data showing a pericardial
effusion, or a subdiaphragmatic disease.
e disadvantage of CT is the use of ionizing radiation, its cost and the possibility to be used
only in appropriate clinical condition.
Due to these considerations, we believe that ultrasonography has a very important role in the
primary identification and quantification of pleural effusions.
Normally the pleural space is virtual, so it cannot be investigated by ultrasound. e pleura
appears as a hyperechoic line, immediately behind the parietal plane formed by the ribs and
the intercostal muscles. Its “thickness”, largely virtual, is 1-2 mm and its surface is flat17.
Paying attention to the images, it is possible to highlight the sliding of the deep portion of the
pleural line (visceral pleura) against the internal surface of the chest. erefore, the ultrasound
images deviate from the real anatomy, in which the two pleurae separated by a virtual space
not exceed the size of 0.3-0.4 mm19.
Recently it has been noted that even normal subjects may present minimum amounts of
liquid, in the form of millimetric liquid films18. ese details are visible through the use of
small parts probes with relatively high frequencies.
e sliding of the visceral pleura is a fundamental sign in chest ultrasound and it expresses
the physiological dynamics of the lung in the absence of pathology (sliding sign)20.
is sign must be constantly researched in every area of the lung surface. is observation
is facilitated because the sliding part of the pleura is often not perfectly uniform, but it has
112 oracic ultrasound
minimal surface irregularities, which sometimes emit small comet tail artifacts, typically short
and irregularly spaced.
Even if the patient does not breathe deeply or is in apnea, the visceral pleura can be seen
moving close to the heart, as it takes part in the systolic activity with characteristic end-shake
movements. ese aspects are amplified using a linear probe, operating at the fundamental
frequency as low as possible (6-7 MHz) and lowering the machine gain to darken the background (sensitized exploration of the pleura).
➣ Ultrasonography of pleural effusions
Similarly to effusions in other cavities, a pleural effusion appears as a fluid collection with
variable echogenicity. Perfect transonicity is observable only in non-corpuscular transudates21.
e presence of fibrin, cells or debris in suspension produces echoes that are mobile in the
liquid synchronously with the acts of breathing. Otherwise, sedimentations and appositions
with structured appearance can be observed, particularly in empyemas (effusions rich in
22,23
fibrin)
(Figs. 1-6) (Clips 1-3).
SMALL PLEURAL EFFUSION
Figure 1 – Small pleural effusion in left costophrenic angle.
Figure 2 – Massive pleural effusion in right hemithorax.
Diaphragm
Pathology of the pleura 113
CORPUSCULAR EFFUSION
Figure 3 – Corpuscular effusion in right base.
PLEURAL EFFUSION
Figure 4 – Small pleural effusion in right costophrenic angle.
Spleen
Diaphragm
Pleural eusion
Left subdiaghramatic liquid
Figure 5 – The evidence of the diaphragm allows the distinction between pleural (A) and intraperitoneal
effusion (B).
114 oracic ultrasound
PLEURAL
EFFUSION
DIAPHRAGM
Figure 6 – Simultaneous presence of intraperitoneal fluid and pleural effusion separated by the
diaphragm.
Clip 1 – Longitudinal scan on the costophrenic sinus: evidence of pleural
effusion.
Clip 2 – Longitudinal scan on the right costophrenic sinus: abundant pleural
effusion with atelectatic lung (compressive atelectasis) immersed in the
effusion.
ASCITES
Clip 3 – Corpuscular pleural effusion: echoes floating in the pleural fluid and
moving synchronously with the acts of breathing.
Fibrin can produce real branches that connect wall, diaphragm and parenchyma, pleural
thickening or septations, up to real capsules that surround the effusion (circumscribed effusions)24. If the effusion is particularly rich in cells and debris, it sometimes has a pseudosolid
aspect and poses problems for the differential diagnosis25 (Figs. 7-10) (Clips 4-5).
Clip 4 – Fibrinous effusion with full compression of the lung.
Clip 5 – Pleural empyema with fibrin strands.
Pathology of the pleura 115
Diaphragm
Fibrin
Figure 7 – Pleural effusion with fibrin strands.
FIBRIN BRANCHES
Figure 8 – Pleural effusion with initial alveolar conformation.
EMPYEMA
Figure 9 – Pleural empyema with alveolar appearance.
116 oracic ultrasound
Subdiaphragmatic liquid
Non-set complex pleural liquid
Diaphragm
Figure 10 – Pleural empyema with pseudosolid aspect of the liquid.
Transudate is transonic and free to vary its morphology with changes of patient’s position.
A pleural effusion is also an excellent acoustic window, that enhances any parietal or visceral
pleural irregularity or lung lesions26 (Fig. 11). For this characteristic, the pleural effusion
shows the diaphragm line with thoracic coronal scans. is is not possible without effusion,
because the lung curtain hides the costophrenic recesses.
Figure 11 – Small pleural effusion, that allows the best visualization of the pleural irregularities in a
case of pulmonary fibrosis.
e respiratory activity appears with the synchronous movement of the pulmonary lobes in
the effusion. When the effusion is large, the compressed lung floats in the liquid with very
characteristic movements (Clips 6-7). In occasional situations, the pleural fluid is not transonic,
but shows air bubbles. In this case, after excluding the possibility of anaerobic empyema, the
most likely diagnosis is hydropneumothorax (Fig. 12).
Clip 6 – Movement of the lower lobe of the right lung in the pleural fluid,
synchronous with the acts of breathing.
Pathology of the pleura 117
Figure 12 – Exudative pleural effusion with air (hydro pyothorax). The air has a horizontal retroparietal
disposition and is contiguous to fibrinous septa (arrows). It appears as bright reverberant echoes.
Clip 7 – In more abundant pleural effusions, the compressed lung “floats”
in the liquid.
In large hydro or hemopneumothorax, air can be much more abundant, appearing as an
echogenic layer over the fluid without sliding. Of course, below the air, the liquid is covered
by fixed reverberation artifacts (Clip 8).
Clip 8 – Hydro pneumothorax in an infant with hyaline membrane disease.
A small pleural effusion is evident on the right. Artifacts due to the presence
of air that floats in the horizontal portions of the effusion are shown.
Sometimes pleural scars or thickening can have a hypoechoic aspect that is easily confusable
with a pleural effusion. ese alterations have a fixed morphology and contrast with the typical
mobility of free effusions. In other words, the thickness of a fibrous pleural plaque does not
vary with the acts of breathing, while an effusion generally does, unless it is characterized by
extremely dense liquid. Slight movements of individual particles in suspension can be useful
for the correct diagnosis.
Sometimes small circumscribed effusions are problematic for the differential diagnosis. e
uncertainty regards the solid or liquid nature of the image. In case of low viscosity liquid,
M-Mode scan can highlight a sinusoidal movement of the visceral pleura (sinusoid sign)
27
(Fig. 13). However, when the effusion is longstanding and particularly structured, the sinusoid
sign may be absent (Fig. 14).
When necessary, the use of a contrast media bolus is definitive. Pleural effusions do not
enhance after Contrast Enhanced Ultrasound (CEUS).
In the case of pleural effusion, the compressed or atelectatic lung can be seen as a tissue immersed in the fluid with a typical echogenicity (and in some cases with a typical echostructure),
very different from that of the uncompressed lung27 (Fig. 15) (Clip 9).
118 oracic ultrasound
CIRCUMSCRIBED
EFFUSION
Figure 13 – Sinusoid sign: the sinusoidal movement of the visceral pleura confirms the liquid nature of
this small pleural effusion.
NO “SINUSOID SIGN”
Figure 14 – No sinusoid sign is observed in the case of a circumscribed longstanding and very dense
effusion.
Figure 15 – Compressive atelectasis with different degrees of lung aeration.
NO
Pathology of the pleura 119
Clip 9 – Compressive atelectasis.
is evaluation is extremely important because it allows to determine the degree of deflation
of the pulmonary distal airways. In practical way, it represents the pathophysiological weight
(in terms of altered ventilation) of an effusion.
e pressure of a pleural effusion on a normally aerated lung is variable. It ranges from a
slight decrease in collapsible “air spaces” (i.e. decrease in cortical porosity) to the complete
occlusion of easily collapsible airspaces. In a fully compressed lung, the cortical tissue is solid
and only the largest airways are accessible and more resistant to pressure.
Sonographic data related to part of a lung immersed in the pleural fluid bring different
clinical information. A purely artifactual subpleural acoustic pattern is the confirmation of
lobular aeration. White lung and B Lines signal a greater compression with a cortical density
up to about 0.8 g/ml. Finally, a pattern of collapsed cortical lung indicates a non-breathing
organ, and air bronchograms only represent death spaces. According with this approach, the
clinical situation of the patient is the best indication for thoracentesis, but also the pattern
of compressed lung can be a useful indication.
Ultrasound determines the presence of a pleural effusion with almost 100% of sensitivity
and specificity, but it is also used to define the characteristics of the liquid and to assume its
inflammatory genesis or not.
Depending on echogenicity, the collection can be classified into anechoic, complex or homogeneously echogenic. e term “complex” is used whenever echogenic material is visible
in the effusion. A complex effusion can be non areolar or areolar. An effusion is areolar when
there are fibrin branches that divide the collection through septa28 (Figs. 16-19). Otherwise,
the complex effusion shows randomly dispersed strands.
If it is true that transudates are transonic collections, exudates can show all aspects, although
they frequently appear as complex or areolar effusions.
Figure 16 – Anechoic effusion.
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