Emerging roles for transthoracic ultrasonography in pulmonary diseases

Abstract

As a result of many advantages such as the absence of radiation exposure, non-invasiveness, low cost, safety, and ready availability, transthoracic ultrasonography (TUS) represents an emerging and useful technique in the management of pleural and pulmonary diseases. In this second part of a comprehensive review that deals with the role of TUS in pleuropulmonary pathology, the normal findings, sonographic artifacts and morphology of the most important and frequent pulmonary diseases are described. In particular, the usefulness of TUS in diagnosing or raising suspicion of pneumonia, pulmonary embolism, atelectasis, diffuse parenchymal diseases, adult and newborn respiratory distress syndrome, lung cancer and lung metastases are discussed, as well as its role in guidance for diagnostic and therapeutic interventional procedures. Moreover, the preliminary data about the role of contrast enhanced ultrasonography in the study of pulmonary pleural-based lesions are also reported. Finally, the limits of TUS when compared with chest computed tomography are described, highlighting the inability of TUS to depict lesions that are not in contact with the pleura or are located under bony structures, poor visualization of the mediastinum, and the need for very experienced examiners to obtain reliable results.

Keywords: Lung diseases; Pleural diseases; Ultrasonography.

Figure 1

Ring-down artifacts, characterized by a series of hyperechoic, narrow-based bands spreading from the pleural line into the lung.

Figure 2

Pulmonary fibrosis. Multiple comet-tail artifacts departing from a thickened and irregular pleural line.

Figure 3

Pneumonia. Posterior intercostal scan shows a hypoechoic consolidated area that contains multiple echogenic lines that represent an air bronchogram (arrows).

Figure 4

Post-stenotic pneumonia. Posterior intercostal scan shows a hypoechoic consolidated area that contains anechoic, branched tubular structures in the bronchial tree (fluid bronchogram) (arrows).

Figure 5

Contrast-enhanced ultrasonography of pneumonia. A: Baseline scan shows a hypoechoic consolidated area; B: Seven seconds after iv bolus of contrast agent, the lesion shows marked and homogeneous enhancement; C: The lesion remains substantially unmodified after 90 s.

Figure 6

Contrast-enhanced ultrasonography evaluation of pneumonia with pleural effusion. Baseline scan shows parenchymal consolidation with air bronchogram (arrows) and subtle surrounding effusion (arrowheads) (left side of the split-screen). After iv bolus of contrast agent, the consolidation is enhanced and better demarcated from the effusion (right side of the split-screen).

Figure 7

Pneumonia complicated by abscesses. Multiple small collections of fluid are irregularly settled in a consolidated liver-like infiltrate. Loc: Loculation; Microloc: Microloculation.

Figure 8

Lung abscess. A: An anechoic oval lesion is surrounded by an echodense capsule; B: After iv bolus of contrast agent, the lesion shows no contrast agent uptake, whereas the capsule is strongly enhanced.

Figure 9

Lung abscess with air inside the lesion. A: High amplitude echoes are clearly visible (arrow), as well as multiple echogenic small air inclusions (arrowheads); B: Corresponding computed tomography scan shows the same findings.

Figure 10

Pulmonary infarction. Posterior intercostal scan shows a triangular-shaped hypoechoic lesion with central hyperechoic structures that indicate the presence of air occupying the affected bronchiole (arrows).

Figure 11

Dynamic course of pulmonary infarction. A: Lateral intercostal scan of the right lung shows a typical triangular-shaped peripheral lesion; B: Likewise, computed tomography scan of the lateral segment of the lower right lobe shows a triangular pleural-based lesion with the vertex towards the hilum; C: After 40 d, the lesion is no longer visible by computed tomography scan; D: The lesion appears reduced in size at transthoracic ultrasonography examination.

Figure 12

Contrast-enhanced ultrasonography of pulmonary infarction. After iv bolus of contrast agent, the lesion (the same one as in Figure 11A) shows no contrast agent uptake in the arterial phase, which suggests the absence of blood supply.

Figure 13

Compression atelectasis. Posterior intercostal scan shows a liver-like consolidation with the typical shape of a jelly bag cap surrounded by pleural effusion.

Figure 14

Contrast-enhanced ultrasonography evaluation of compression atelectasis. Baseline scan shows a liver-like consolidation surrounded by multiloculated pleural effusion (left side of the split-screen). Twelve seconds after iv bolus of contrast agent, the consolidation shows marked and homogeneous enhancement, whereas pleural effusion shows no enhancement.

Figure 15

Adult respiratory distress syndrome. Oblique subcostal scan through the right lobe of the liver shows the typical transthoracic ultrasonography pattern of intense retro-phrenic hyperechogenicity due to complete reverberation of the US beam (arrows).

Figure 16

Peripheral bronchial carcinoma. Posterior intercostal scan shows a hypoechoic consolidation with relatively well-delineated borders. The air bronchogram is absent.

Figure 17

Contrast-enhanced ultrasonography evaluation of bronchial carcinoma. Baseline scan shows consolidation with inhomogeneous echotexture (left side of the split-screen). Twenty seconds after iv bolus of contrast agent, necrotic areas can be depicted as anechoic regions inside the enhanced viable tumor (right side of the split-screen).

Figure 18

Bronchial carcinoma infiltrating the pleural wall. A: Posterior intercostal scan shows a hypoechoic lesion accompanied by rib destruction (arrows); B: Twenty-four seconds after iv bolus of contrast agent, the lesion appears inhomogeneously enhanced; the disrupted rib appears more echogenic than the tumor (arrowheads), as a consequence of the incomplete tissue suppression due to the strong echogenicity of bone tissue.

Figure 19

Contrast-enhanced ultrasonography of bronchial carcinoma. A: Baseline scan shows a hypoechoic lesion with irregular borders (left side of the split-screen). Ten seconds after iv bolus of contrast agent, the pulmonary parenchyma near the lesion is already enhanced (arrows), whereas the lesions is still unenhanced (right side of the split-screen); B: Twenty seconds later, the lesion shows delayed inhomogeneous enhancement, which indicates a preferential bronchial arterial supply (right side of the split-screen).

Figure 20

Pulmonary metastasis. Posterior intercostal scan shows a round-shaped, clear-bordered lesion.

Figure 21

Contrast-enhanced ultrasonography of pulmonary metastasis. A: Baseline scan shows a small hypoechoic lesion (left side of the split-screen). Ten seconds after iv bolus of contrast agent, the lesion appears unenhanced with respect to the early enhancement of the pulmonary parenchyma (arrows) (right side of the split-screen); B: Fifty seconds later, the lesion shows inhomogeneous enhancement with reduced contrast agent extent (arrowhead) with respect to the pulmonary parenchyma (right side of the split-screen).