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EFSUMB European Course Book Student Edition Editors: Jan Tuma, Radu Badea, Christoph F. Dietrich

Chest Gebhard Mathis

Internistische Praxis, Rankweil, Austria Corresponding author: Prof. Dr. Gebhard Mathis Internistische Praxis Bahnhofstrasse 16/2 6830 Rankweil Austria Email: gebhard.mathis@cable.vol.at

Acknowledgment: None.

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Content Content ....................................................................................................................... 2 Introduction ................................................................................................................. 2 Technical Requirements ............................................................................................. 2 Examination Technique .............................................................................................. 2 Chest wall ................................................................................................................... 5 Soft tissue lesions ................................................................................................... 5 Bony lesions............................................................................................................ 5 Normal sonographic appearance................................................................................ 7 Patient preparation .............................................................................................. 7 Pneumothorax......................................................................................................... 9 Pleuritis ................................................................................................................. 10 Lung consolidations .................................................................................................. 10 Pulmonary embolism ............................................................................................ 11 Lung cancer .......................................................................................................... 12 Atelectasis............................................................................................................. 12 Interstitial syndrome .......................................................................................... 13 Recommended reading ............................................................................................ 13

Introduction The majority of physicians believe that ultrasonography has limited use in lung diseases. Bone and air are physical enemies to this imaging procedure because of absorption of ultrasound energy by bony structures and total reflection of the air-filled lung. However, lung sonography represents an emerging and useful technique in the management of many pulmonary diseases.

Technical Requirements Sonographic examination of the chest wall and the axillar/supraclavicular region generally requires a linear array probe using frequencies of 5.0 to 10 MHz. For pleural and peripheral pulmonary lesions, sector scanners are more suitable for intercostals access to the pleura and lung through the narrow intercostal space. For daily clinical use in chest sonography, the best combination is a 3.5-5 MHz sector or curved array probe and a small-parts linear scanner. This combination is used in many other applications, e.g., abdominal, vascular and small parts US.

Examination Technique Emergency, bedridden and intensive care patients are examined in supine and oblique positions by turning them to the oblique position in the bed. Usually the dorsal and lateral images are obtained with the patient sitting, whereas the supine position is used for visualizing the ventral side. Raising the arms and crossing them behind the head causes intercostal spaces to be extended and facilitates access.

Tilting and angulation of the probe provide a good view of most parts of the pleura

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and underlying pulmonary consolidations. To visualize the region covered by the scapula the patient puts his/her hands behind the head or on the contralateral shoulder. The transducer is moved along the intercostal space from dorsal to ventral in longitudinal and transversal positions. Turning the probe in different positions provides the examiner with a three-dimensional image. During every stage of examination, the user should determine the breath-related moving of the lung, the socalled sliding sign [Figures 1-4, Video 1 and 2].

Figure 1

A: Linear probe placed intercostally in an oblique view. The right arm is elevated behind the head or positioned on the contralateral shoulder. The intercostals spaces are extended and the scapula is turned. B: Corresponding sonographic view. – see Video 1 and 2

Figure 2

A: Linear probe in an anterior longitudinal scan. B: The pleura line dorsal to the rib cartilage (c) is shifted ventrally towards the transducer as a result of various ultrasound beam rates in cartilage an soft tissue of the chest wall: C: R = bony rib with sound shadow

From the abdomen, in subcostal section by the transhepatic route on the right side and to a lesser extent through the spleen on the left side, the diaphragm is examined [Figure 3]. The axilla should be examined in the supine position with the arm

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abducted over the head. The supraclavicular access allows the investigator to view the region of the brachial plexus, the subvclavian vessels and the lung tip [Figure 4].

Suprasternally, the anterior upper mediastinum can be viewed.

Figure 3

Transhepatic examination. A: Convex probe placed subcostally from the right. B: Corresponding sonographic image, Lung is indicated as a mirror artefact above the diaphragm. D = diaphragm

Figure 4

Examination of the supraclavicular region. A: Linear probe placed longitudinally on the lateral base of the neck B: Corresponding sonographic image. N Plexus brachialis M Scalenus muscles

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Chest wall Soft tissue lesions Any suspicious findings on palpation of the chest may be an indication for chest sonography: lipomas [Figure 5], invisible hematomas, and lymph nodes can be detected (see Chap Lymph nodes).

Figure 5

Palpable mass at back. Oval capsulated lesion – typical lipoma

Bony lesions Typical sonographic findings of rib fractures are gap, step, dislocation, hematoma and minimal concomitant pleural effusion, pneumothorax and lung contusion [Figure 6]. Minute dislocations and fissures are visible by a reverberation artifact at the traumatised point, also known as the so-called chimney phenomenon. On US examination, the patient indicates the site of pain and the examiner obtains a crosssectional image of the region in two planes, with the image closely following the course of the ribs. In chest x-ray non dislocated rib fractures are frequently not seen.

At the first sight, it is surprising to note that the diagnosis of rib fractures is made twice as frequently by ultrasound compared to chest radiography.

Figure 6

Rib fracture. One mm step in the corticalis reflexion

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Osteolytic metastases in the bony thorax cause disruption of the corticalis reflex with pathologic US transmission. Osteolyses are usually seen as well-demarcated round or oval space-occupying lesions with a partly hypoechoic and partly rough structure.

Color-coded duplex sonography reveals corkscrew-like neovascularisation or a vascular inferno, especially in patients suffering from multiple myeloma [Figure 7].

Figure 7

Mulitple myeloma in a palpable thickened rib. Enhanced irregular vascularisation. The diagnosis was established by ultrasound guided biopsy

Ultrasound is significantly superior to CT in detecting chest wall infiltration by lung cancer. Direct evidence of infiltration of wall structures and rib destruction are reliable criteria. An interruption of the pleural reflex and/or limited respiratory motion of the space-occupying lesion provides an indication but not proof of infiltration of the chest wall. Accompanying inflammatory accompanying reactions may mimic tumour infiltration of the chest wall.

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Pleura Normal sonographic appearance The normal pleura is only 0.2-0.4 mm thick and hence at the resolution limit of ultrasound. The parietal pleura shows a fine echogenic line, the pleural space as an echo-free band. The visceral pleura is submerged in the thick “sliding sign� of the total reflection of the ultrasound at the air of the lung [Figure 8, Video 2]. As soon as the peripheral lung is consolidated and free of air, the visceral pleura can be marked off as a fine echogenic line.

Figure 8

Pleura. Normal sonographic appearance.

Patient preparation Small amounts of pleural fluid (5-10 ml) are detectable with ultrasound as an echofree zone in the pleural space. Pleural fluid minimally exceeding the physiological amount is best recorded in the diaphragmatic sinus in the dorsal axillary line [Figure 9]. Pleural effusions change their shape during respiration.

Figure 9

Pleural effusion, nearly echo-free in heart failure. Estimated volume = 400 ml.

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Transudates are almost always echo-free, whereas some 50% of exudates are reflective. Swirling or floating echoes indicate particles in the pleural fluid, such as cells, protein, fibrin or blood. Movable strands, fibrinous strings and septations are typical of inflammatory effusions [Figure 10]. Metastatic pleural effusions are more often echo-free than echogenic, nodules on the diaphragm may indicate malignancy [Figure 11].

Figure 10

Mixed echogenic pleural effusion with septations in a patient with pleura empyema

Figure 11

Nodules on the diaphragm are suspicious for malignacy

Due to the anatomical differences and various shapes of the thorax, an exact measurement of volume of the effusion is not possible with any imaging modality.

There are several modalities to estimate the volume of pleural effusion by means of sonography. For sitting patients a good method is to calculate the sum of the basal lung to diaphragm distance and the lateral height of the effusion and to multiply the sum by 70. In supine patients a distance of more than 5 cm between the basal lung and the chest wall in the posterior axillary line correlates well with an effusion volume of more than 500-800 ml. In routine clinical follow up, it is sufficient to measure the

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subpulmonary and lateral fluid level in the case of medium size effusions and to perform planimetry in the case of small angular effusions.

Sonography offers the best facilities for determining the location for puncture during examination and for a subsequent diagnostic chest tap. The drainage liquid can then be macroscopically examined for cloudiness, pus or blood. Further information is supplied by assay of LDH, total protein, pH, leukocytes, bacteriology and cytology.

Pneumothorax The examination is conducted with the patient supine. The starting point is the 3 rd or 4th intercostal space between the parasternal and the mid-clavicular line. With the patient supine, this is usually the highest point. Air rises up to this point if it is not trapped elsewhere. First the longitudinal axis is investigated to locate the rib shadows and the respiration dependent pleural reflex in the intercostal space. This approach also enables the less experienced operator to be sure that they have located two rib shadows, the intercostal musculature and the deeper seated pleural line. The focus is placed on the pleural line, and the respiration synchronous sliding sign is observed [Video 1, 2]. If lung sliding can be demonstrated, then pneumothorax is not present.

In case of no sliding, the probe is fanned anticlockwise onto the intercostal space to enable further signs to be better assessed. These are B-lines and the lung pulse.

Absence of these indicates the presence of pneumothorax. The lung pulse and lung sliding can be documented with M-mode or colour. The most definite evidence of pneumothorax is the lung point. This is the transition point between the inflated lung and the pneumothorax. The lung point is respiration synchronous [Figure 12, Video 3]. If the criteria for a pneumothorax are present with the probe in the starting position, it is moved laterocaudally to look for the lung point, which permits a careful estimate of the extent of the pneumothorax.

Lung sliding may be absent if pleural adhesions are present. Respiratory excursions are limited in the presence of severe chronic pulmonary obstructive disease, and lung sliding may not always be demonstrable. To exclude pneumothorax, therefore, all four criteria must be fully investigated and the two sides of the chest must always be compared (see Chapter on E-FAST).

Figure 12

Lung point with pneumothorax (anterior intercostal). 1, Normal lung; 2, Lung point; 3, Pneumothorax

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Pleuritis Pleuritis is usually diagnosed clinically by inspiratory chest pain, being rarely accompanied by laboratory or imaging findings. At the point of pain US reveals the following findings: - thickening of pleura often with rough appearance and interruption of the normally, smooth pleura - small subpleural consolidations between 2- 10 mm in size - localised pleural effusions - fibrinous echogenic bands at the lung surface, towards the parietal pleura or dividing an accompanying pleural effusions [Figure 13].

Figure 13

Pleuritis: small subpleural consolidations inspiratory pain. Focal interstitial syndrome

at

the

point

of

Lung consolidations Pulmonary processes can be visualised when they come up to the pleura; are accessible via a sound window, and no subcutaneous emphysema or pneumothorax is present. Purely central processes cannot be sonographically visualised and therefore cannot be ruled out with this technique.

In the early congestive stages of pneumonia, the echo texture of the consolidated lung is similar to the liver. However, a marked tree-shaped bronchoaerogram, and a large number of lens shaped echo reflections measuring a few millimetres in size are frequently observed up to the pleura [Figure 14]. Viral or fungal pneumonias are quite often more poorly ventilated and reveal less marked air bronchograms. Pneumonia is characterized by an irregular, serrated and somewhat blurred margin. The fluid bronchogram is characterized by anechoic/hypoechoic branched tubular structures in the course of the bronchial tree. It does not have a perfusion signal. A persistent fluid bronchogram arouses suspicion of poststenotic pneumonitis and requires suitable bronchoscopic investigation.

On colour-coded duplex sonography, pneumonia has a typical appearance: circulation is uniformly increased and branched, vessels have a normal course.

When pneumonia is in the healing phase, the infiltrated lung tissue is increasingly ventilated. Such air gives rise to reflection and reverberation artefacts [Figure 15].

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The pneumonia recedes on the ultrasound image and appears smaller than on chest radiograph, reflecting better the clinical course.

Figure 14

Pneumonia: tissue or liver like lung bronchoaerogram. Reventilated after 5 days

consolidation

with

Pulmonary embolism Several minutes after occlusion of a pulmonary subartery, the surfactant collapses.

Interstitial fluid and erythrocytes flow into the alveolar space. This hemorrhagic congestion offers ideal conditions for ultrasound imaging. These consolidations are open at the periphery along with their base, which creates good conditions for transthoracic sonography. The frequency of hemorrhagic reperfusionable pulmonary infarction is much higher than reported, proven by new imaging procedures [Figure 15].

Figure 15

Pulmonary embolism: wedge-shaped pleural based consolidations

The sonographic signs of pulmonary embolism include the following:  Echo poor  Well demarcated  1-3 (0.5-7) cm in size

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Pleural based Triangular > rounded Vascularisation stop 2.5 consolidations/patient on average 2/3 dorso-basally located Small pleural effusion

In the dynamic process of thromboembolism, chest sonography should be performed in association with echocardiography and leg vein sonography. With one system, using US, one can “kill three birds with one stone”, source, way and outcome of pulmonary embolism with an accuracy of more than 90%.

Lung cancer Lung carcinomas and metastases are sonographically visualised as hypoechoic or moderately echogenic inhomogeneous structures. Mostly they are round, oval or polycyclic. Pulmonary malignancies may have a variable echo texture sometimes with echo poor necrotic areas. They frequently have sharp margins and fringed or finger-shaped ramifications into the ventilated lung [Figure 16].

In dynamic US examination, malignant invasion of the chest wall or subclavian vessels can better be depicted by US than by CT. The following are reliable criteria for infiltration of the chest wall: direct evidence of infiltration of the wall structures and rib destruction. An interruption of the pleural reflex and/or limited respiratory motion of the subpleural consolidation provides an indication but not proof of infiltration of the chest wall. Inflammatory accompanying reactions can also cause these signs.

Malignant invasion of the chest wall frequently causes local pain. Targeted USinvestigation of the region will help to diagnose the condition immediately.

Figure 16

Peripheral lung cancer: rounded consolidation, sharp margins, fringed ramifications and irregular vascularisation

US of the supraclavicular and lower cervical lymph nodes has a special role in the staging of bronchial carcinoma. Routine ultrasound evaluation of supraclavicular lymph nodes reveals suspicious lymph nodes three times more than by palpation, and more than using CT. Atelectasis

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Lung atelectases are characterised by partial or complete absence of ventilation.

Compression atelectasis is caused by voluminous pleural effusion. It is largely airless and liver like. The patient may develop triangular, hypoechoic consolidations shaped like a wedge or a pointed cap and show blurred margins to ventilated lung parenchyma. The compression atelectasis is floating in the effusion like a waving hand. These are partially reventilated during inspiration and after puncture of effusion. In color- Doppler sonography atelectasis shows increased branch like vessel visualisation.

The sonographic image of obstructive atelectasis is marked by a largely homogeneous, hypoechoic presentation of lung tissue in terms of hepatisation.

Effusion is absent or small. Depending on the duration of atelectasis, intraparenchymatous structures may also be seen: hypoechoic vascular lines and echogenic bronchial reflexes. Secretory congestion of bronchi presents a fluid bronchogram. The image is similar to that of pneumonia but with significantly less air bronchograms. In the case of lobar atelectasis, the border to the ventilated lung is clear and smooth. Sometimes it is also possible to detect an underlying central tumor. On color Doppler sonography, regular vessels along the bronchi are seen.

In cases of blunt chest trauma, especially serial rib fractures, pulmonary contusions are better seen on sonography than on radiographs. Alveolar oedema and alveolar hemorrhage caused by trauma are visualized as hypoechoic, plate-like lesions bordered partially clearly and partially unclearly with respect to the ventilated lung.

Interstitial syndrome The interstitial lung involvement in heart failure, ARDS, pulmonary fibrosis and interstitial lung infections share a similar sonographic pattern. Although poorly specific, the sonographic diagnosis of interstitial syndrome is useful in many clinical scenarios, such as in the differentiation between pulmonary oedema and exacerbation of chronic obstructive pulmonary disease (COPD) during acute respiratory failure. The technique is based on the recognition of lung sliding and some vertical artifacts, the B lines. B-lines are defined as discrete laser-like vertical hyperechoic reverberation artifacts that arise from the pleural line (previously described as „„comet tails‟‟), extend to the bottom of the screen without fading, and move synchronously with lung sliding. Multiple B-lines are the sonographic sign of lung interstitial syndrome. The patient is examined in the supine or near-to-supine position. In the evaluation of interstitial syndrome, the sonographic technique ideally consists of scanning eight regions. A more rapid anterior two-region scan may be sufficient in some cases. A positive region is defined by the presence of three or more B-lines in a longitudinal plane between two ribs.

Causes of interstitial syndrome include the following conditions: – Pulmonary oedema of various causes – Interstitial pneumonia or pneumonitis – Diffuse parenchymal lung disease (pulmonary fibrosis) A positive examination for sonographic diffuse interstitial syndrome allows bedside distinction between a cardiogenic versus a respiratory cause of acute dyspnoea.

Recommended reading 

Mathis G (Ed) Chest Ultrasound Sonography. 3rd Edition Springer Berlin Heidelberg New York 201.

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Bandi V, Lunn W, Ernst A et al. Ultrasound vs CT in detecting chest wall invasion by tumor. A prospective study. Chest 2008; 133: 881-886.

Lichtenstein D, Meziere G, Lascols N et al. Ultrasound diagnosis of occult pneumothorax. Crit Care Med 2005; 33:1231-1238.

Mathis G, Blank W, Reißig A et al. Thoracic ultrasound for diagnosing pulmonary embolism. A prospective multicenter study of 352 patients. Chest 2005; 128:1531-1538.

Prosch H, Mathis G, Mostbeck G. Percutaneous ultrasound in diagnosis and staging of lung cancer. Ultraschall in Med 2008; 29: 466-484.

Reißig A, Copetti R, Mathis G et al. Lung ultrasound in the diagnosis and followup of community-acquired pneumonia. Chest 2012; 142: 965–972.

Reuss J. Sonography of the Pleura. Ultraschall in Med 2010; 31: 8–25.

Squizzato A, Rancan E, Dentali F et al. Diagnostic accuracy of lung ultrasound for pulmonary embolism: a systematic review and meta-analysis. J Thrombosis and Haemostasis 2013 E-Pub. Soldati G, Testa A, Sher S, et al. Occult traumatic pneumothorax: diagnostic accuracy of lung ultrasonography in the emergency department. Chest 2008;133: 204-211.

Volpicelli G, Elbarbary M, Blaivas M et al International evidence-based recommendations for point-of-care lung ultrasound. Intensive Care Med 2012; 38: 577-591