Hypoechoic Masses

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16.2 Compression Atelectasis

Partial atelectasis

Atelectasis shown in chest radiograph,

B-mode ultrasound, and CEUS

c A 73-year-old man with squamous cell carcinoma and a radiograph showing a white hemithorax on the right side.

Ultrasound demonstrates e usion and upper lobe atelectasis (UL). The central hypoechoic masses are consistent with lymph node metastasis (L).

d–f A 35-year-old man with bronchial carcinoma.

d Chest radiograph shows complete opacification of the left hemithorax.

e and f Longitudinal and transverse scans show pronounced e usion with atelectasis of upper (UL) and lower (LL) lobes. COR = heart; PE = pleural e usion.

Autopsy studies show that pulmonary embolism is among the leading causes of death (10–30%). An intravital diagnosis is made in just 20–30% of cases. An acute pulmonary embolism is accompanied by hemorrhagic lung infarction in approximately 45–60% of cases.

Diagnosis. Pulmonary embolism is diagnosed with the aid of available methods and includes an overall assessment of clinical findings, chest radiography, pulmonary scintigraphy, CT, echocardiography, and MRI.

Role of ultrasound. Although lung tissue that has undergone hemorrhagic infarction or consolidation can in principle be visualized on the basis of abnormal pulmonary sound transmis-

sion, the role of thoracic ultrasound in the diagnosis of pulmonary infarction cannot be adequately evaluated at present.6,7 For a pulmonary embolism to be detectable with ultrasound, there must be a significant perfusion defect causing compromise of alveolar ventilation. But in many cases a large pulmonary embolism involving pulmonary, lobar and segmental arteries will not produce an infarction because there is an adequate collateral supply, usually via branches of the bronchial rami (Fig.16.5). This type of embolism cannot be visualized with thoracic ultrasound ( 16.4a–c). Embolisms at the subsegmental level are more apt to cause hemorrhage into the alveolar airspace, making them accessible to ultrasound imaging.

Thus, thoracic ultrasound has a special role in the diagnosis of small, scintigraphically negative embolisms and infarctions that are 2 cm or less in diameter.

Although the hemorrhage associated with pulmonary embolism may resolve completely within a matter of days, a pulmonary infarction will show delayed regression in serial ultrasound examinations. Generally these lesions heal by scarring.

Sonographic features. Pulmonary embolism can have various ultrasound appearances ( 16.5). All possible patterns of involvement may be associated with varying degrees of pleural effusion.

16.3 Obstructive Atelectasis

Middle lobe atelectasis

a and b Bronchial carcinoma.

a Chest radiograph shows signs of middle lobe atelectasis.

Atelectasis caused by lung cancer

d and e Bronchial carcinoma.

d Chest radiograph shows almost complete opacification of the left hemithorax.

g–i Bronchial carcinoma in a 74-year-old woman.

g Chest radiograph shows opacification of the left lower lung field.

Flow profile in atelectasis

b Right anterior intercostal scan shows hypoechoic transformation of the lung with an echo-free “fluid bronchogram” caused by central obstruction. AT = atelectasis; LU = lung; COR = heart.

e Transverse scan shows upper lobe atelectasis (AT) with delineation of a central tumor (TU). The arrows point to the severely narrowed upper lobar bronchus. COR = heart; UL = upper lobe; LU = lung.

h Ultrasound shows homogeneous hypoechoic transformation of the left lower lobe consistent with atelectasis (AT). D = diaphragm; M = spleen.

c Bronchial carcinoma in a 67-year-old man, atelectasis of middle lobe seen on radiograph. Right anterior ultrasound scan shows hypoechoic transformation of the lung consistent with atelectasis (AT). A central tumor mass (TU) is identified. LU = lung; COR = heart.

f Patient with bronchial carcinoma. Right lateral intercostal scan shows “hepatization” of the lung characteristic of atelectasis (AT). Color Doppler shows increased flow signals in the atelectatic lung tissue. L = liver; LU = lung.

i The central portions of the upper lobe (UL) are still aerated. Together with scant pleural e usion (PE), this suggests obstructive atelectasis of the lower lobe.

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j–l Suspected bronchial carcinoma in a 74- year-old woman.

j Color Doppler mode: in the paravertebral scan direction on the right side, tumor formation of the lung like an atelectasis.

k–l In the color Doppler scanning of atelectasis, characteristic waveforms can usually be sampled from the pulmonary arteries (“extremity” pattern) and pulmonary veins. AT = atelectasis; LU = lung.

Localized irregular entry echo. Irregular entry echoes are a common finding even in patients with deep lower-extremity venous thrombosis who are clinically asymptomatic for pulmonary embolism (“sentinel emboli”). Irregular entry echo refers to a localized disruption in the sharp pleural line measuring less than 2 cm. The foci may be in the millimeter size range.

They may have a wedge or square shape with homogeneous low echogenicity. They may represent hemorrhages and may resolve within a few days. Frequently, no clinical or scintigraphic correlate is found to explain the sonographic change ( 16.4 d–i).

Band-like disruption of the entry echo. This feature is characterized by a lengthy disruption in the normal pleural entry echo. It is less common than a localized disruption and frequently has a scintigraphic correlate (“tip of the iceberg”; 16.4 g–i).

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16.3 Obstructive Atelectasis (Continued)

Focal lesion in atelectasis: gray-scale image, power-mode, CEUS

m–o A 73-year-old man with a cytologically malignant pleural e usion.

m Chest radiograph shows a right-sided pleural e usion.

p–r Bronchial carcinoma in a 65-year-old man.

p Chest radiograph shows a white hemithorax on the left side.

Atelectasis shown in contrast-enhanced ultrasound (CEUS)

n Upper lobe atelectasis with a central hypoechoic focus. LE = liver; PE = pleural e usion.

q Ultrasound scan shows homogeneous, hypoechoic transformation of the left lower lobe consistent with obstructive atelectasis. AT = atelectasis; D = diaphragm.

o The absence of intralesional flow signals on color Doppler is consistent with incipient liquefaction, but a metastasis cannot be excluded. AT = atelectasis; PE = pleural e usion.

r Scan shows a rounded, hypoechoic, partially air-filled mass within the atelectasis in the upper lobe, consistent with obstructive pneumonitis.

16.4 Entry Echo in Pulmonary Embolism

Normal entry echo vs. localized irregularity

a–c Suspected pulmonary embolism in a 64-year-old man.

a and b Lung scintiscans. The findings in segments 2 and 3 of the right upper lobe are consistent with pulmonary embolism.

Pulmonary infarction, progress

c Ultrasound shows a completely normal, sharp pleural entry echo along segments 2/3 of the right lung (LU).

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g–i Scintigraphically confirmed pulmonary embolism in a 46-year-old woman.

g Chest radiograph shows no lung abnormalities.

h Extended irregular entry echo, consistent with pulmonary embolism. LU = lung.

i Normal pleural entry echo for comparison. LU = lung.

j–l Pulmonary embolism in an 80-year-old woman.

j CT shows thrombotic material in the right pulmonary artery.

k and l Ultrasound scans through di erent intercostal spaces show variable pleural structural defects in the posterior part of the right lower lung field. LU = lung; S = spleen.

Fig. 16.6 Role of ultrasound in the diagnosis of pulmonary embolism.9 UCG = echocardiography.

In rare cases an afferent vessel may be demonstrated.

CEUS. Peripheral lung embolisms are marked in CEUS by missing or inhomogenous vascularization. This differentiates them from lesions caused by inflammation, which have increased vascularization ( 16.5r–u).

The definitive role of thoracic ultrasound in the diagnosis of pulmonary embolism remains to be determined. However, it is superior to all other modalities for selected applications, particularly the detection of smaller pulmonary embolisms (Fig.16.6).6

a and b Scintigraphically confirmed pulmonary embolism in a 71-year-old woman.

a Chest radiograph shows opacity in the left lower lung field.

b Left lateral intercostal scan shows a wedge-shaped hypoechoic lesion. Color Doppler shows a erent flow signals but none within the lesion. The finding is suspicious for pulmonary infarction.

c–h Scintigraphically confirmed pulmonary embolism in a 34-year-old man. c–e Chest radiographs show the progres-

sion of a pulmonary embolism in the right lower lobe.

c Initial radiograph shows no abnormalities.

d and e Radiographs at 4 and 8 weeks document regression of findings in the right lower field.

16.5 Wedge-Shaped Lesions and More Diffuse Areas of Structural Transformation due to Pulmonary Embolism (Continued)

f–h Right lateral intercostal scans in postinfarction pneumonia show the progression of sonographic findings over a 4-week period.

Hypoechoic transformation

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i–k Pulmonary embolism in a 56-year-old man.

i CT shows thrombotic material in the right pulmonary artery.

j Hypoechoic transformation of lung parenchyma.

k Color Doppler does not record flow signals consistent with pulmonary infarction.

o Chest radiograph. The costophrenic angle is not defined at the edge of the lower left field.

p Follow-up radiograph shows consolidation in that region.

q Left-sided pulmonary embolism on scintigraphy.

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16.6 Pulmonary Tumors and Metastases (Continued)

Adhesion to the chest wall

Infiltration of the chest wall

Necrosis

Bronchoalveolar carcinoma

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m–o Bronchoalveolar carcinoma in an 83- year-old man.

m Chest radiograph shows di use opacity in the right middle and upper zones.

n Right lateral intercostal scan shows a nonhomogeneous hypoechoic lung region with irregular margins. The tumor shows a positive air bronchogram.

o CT: lung consolidation with a positive air bronchogram.