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Original Research: CHEST ULTRASONOGRAPHY |

Ultrasound in Peripheral Pulmonary Air-Fluid Lesions: Color Doppler Imaging as an Aid in Differentiating Empyema and Abscess FREE TO VIEW

Hung-Jen Chen, MD; Yang-Hao Yu, MD; Chih-Yen Tu, MD; Chia-Hung Chen, MD; Te-Chun Hsia, MD; Kuen-Daw Tsai, MD; Chuen-Ming Shih, MD, PhD; Wu-Huei Hsu, MD, FCCP
Author and Funding Information

*From the Division of Pulmonary and Critical Care Medicine (Drs. H.-J. Chen, Yu, Tu, C.-H. Chen, Hsia, Shih, and Hsu), Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan; and the Department of Internal Medicine (Dr. Tsai), China Medical University Beigang Hospital, Yunlin, Taiwan.

Correspondence to: Wu-Huei Hsu, MD, FCCP, Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, China Medical University Hospital, 11F-5, No. 497, Jiansing Rd, North District, Taichung City 404, Taiwan; e-mail: hsuwh@mail.cmuh.org


This work was supported in part by China Medical University Hospital grant DMR-97-033.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).


© 2009 American College of Chest Physicians


Chest. 2009;135(6):1426-1432. doi:10.1378/chest.08-2188
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Background:  The aim of this study was to reevaluate the clinical significance of sonographic appearances, in particular the application of color Doppler ultrasound imaging, in discriminating peripheral air-fluid lung abscess from empyema.

Methods:  We retrospectively studied patients who had had peripheral air-fluid lesions due to empyema or lung abscess and who had undergone color Doppler ultrasound and grayscale ultrasound examinations between January 2003 and October 2007. A total of 34 patients with confirmed lung abscess and 30 patients with empyema were identified. The four sonographic characteristics observed and analyzed were the wall characteristics of the lesions (wall width, luminal margin, outer margin, and chest wall angle), split pleura sign, internal echogenicity (suspended microbubble sign, complex-septated effusions, and passive atelectasis), and identification of color Doppler ultrasound vessel signals in pericavitary lesions (consolidation or atelectasis).

Results:  Among the sonographic characteristics, complex-septated effusions and passive atelectasis were specific for empyema, but the sensitivity was only 40% (n = 12 of 30) and 47% (n = 14 of 30), respectively. The identification of color Doppler ultrasound vessel signals in pericavitary consolidation was the most useful and specific for identifying lung abscesses. In our series, if we define the identification of color Doppler ultrasound vessel signals in a pericavitary consolidation as a predictor for peripheral lung abscess, we can achieve sensitivity, specificity, positive predictive value, and negative predictive value of 94%, 100%, 100%, and 94%, respectively.

Conclusions:  Color Doppler ultrasound is a powerful tool for differentiating the peripheral air-fluid abscess from empyema, with high specificity and without any risk.

Figures in this Article

The differentiation between lung abscess and empyema is important. Prolonged antibiotic therapy and postural drainage are appropriate for lung abscess, but early external drainage is essential therapy for empyema. Nevertheless, the differentiation by chest radiograph alone is difficult when the empyema presents with an air-fluid level.1,2 Friedman and Hellekant3 found that the most helpful features for distinguishing lung abscess from empyema are the shape and the relationships of the air-fluid level to the chest wall, in that empyema is fusiform and over the posterior costophrenic angle location, and an abscess tends to be spherical and farther from the ribs. However, the method does not work when the air-fluid lung abscess is attached to the chest wall.4 In selected cases, lung abscess and empyema may coexist, further complicating the clinical interpretation.

Thoracic CT scanning can prove valuable in differentiating lung abscess from empyema5,6; however, the problems of radiation exposure and contrast-induced renal failure sometimes limit its application. Furthermore, CT scanning is still a relatively expensive imaging examination. With advances in imaging technology and computerized functions, chest ultrasound examination has been widely used in the diagnosis and management of lung cancer, uncommon pulmonary consolidations, mediastinal tumors, and pleural diseases.7,8 As reported, the sonographic features of the wall characteristics, shape, chest wall angle, and split pleura sign (thickened visceral and parietal pleural layers separated by empyema)6 are helpful in the differentiation of lung abscess and empyema.4,9 Lin et al9 also showed that the curtain sign (the movement of air-fluid level synchronized with respiration in ultrasonography) is valuable in distinguishing pyopneumothorax from lung abscess.

In our daily practice, the split pleura sign hardly was observed with sonography. The sensitivity of the curtain sign in air-fluid empyema may be lower due to lesion-pleura adhesion resulting from strong inflammation. Furthermore, lung abscess has not revealed specific imaging signs in previous reports, whether with CT scanning or with ultrasound. The role of color Doppler ultrasound in this situation remains undetermined. Herein, we collected and analyzed the sonographic appearances of peripheral air-fluid lesions in empyema or lung abscess in our hospital. The aim was to reevaluate their clinical significance in the hope that the sonographic images, in particular the application of color Doppler ultrasound imaging, may be helpful in the differential diagnosis between lung abscess and empyema.

Identified Patients

We retrospectively collected and carefully reviewed the medical records of patients who had had peripheral air-fluid lesions due to empyema or lung abscess and had undergone color Doppler ultrasound and grayscale ultrasound examinations between January 2003 and October 2007 (a 58-month period) in our hospital. A mixed diagnosis of empyema and lung abscess was excluded (n = 2). A total of 34 patients with confirmed lung abscess and 30 patients with empyema were identified. All had demonstrated peripheral air-fluid lesions on a chest radiograph or CT scan. A physician diagnosis of lung abscess or empyema was accepted based on an appropriate clinical course, thoracic CT scan images,6 serial follow-up of chest radiographs performed, and response to standard therapy. The study was approved by the Institutional Review Board in our hospital.

Of the 34 patients with lung abscess, 29 were men, with ages ranging from 33 to 79 years (mean age, 58 years). The lesion was on the right in 25 patients and on the left in 9 patients. All 30 patients with empyema were men, with ages ranging from 26 to 86 years (mean age, 50 years). The lesion was on the right in 20 patients and on the left in 10 patients.

Chest Ultrasound Examination

All patients underwent chest sonographic examinations with an ultrasound machine (Aplio-80; Toshiba Medical Systems Co, Ltd; Tokyo, Japan) equipped with a 3.75-MHz convex transducer under fixed parameter settings, such as power, gain setting of 80 decibels, and transmitted focus at a depth of 6 cm in routine practice. Without prior knowledge of the definite diagnosis, chest ultrasound was performed by three well-trained pulmonologists with > 5 years of experience under the following standard procedures.

The patients were examined in the supine or sitting position, as clinically appropriate. Grayscale ultrasound was used first to localize the whole lesion, and then a color Doppler ultrasound examination was added. Before the start of the color Doppler ultrasound examination, the Doppler filter usually was set at 100 Hz to eliminate low-frequency signals from vessel wall motion and to avoid interference from respiratory and cardiac movement.10 The color Doppler window was focused on the whole wall of the air-fluid lesion to detect flow signals; if no signals were detected, the steering angle of the color Doppler window was adjusted to −45° or + 45° in order to avoid false-negative results. The blood flow in a vessel was seen as a persistent area of color signal with a tubular, curvilinear, or branching distribution on real-time images; color signals that persisted in the same location during the respiratory cycle were considered to be blood-flow signals and not due to interference.11 The sonographic appearances regularly were recorded on the hard disk of the ultrasound machine.

Interpretation of Sonographic Appearances

The recorded sonographic appearances were analyzed carefully, and the following four characteristics were observed: the wall characteristics of the lesion (wall width, luminal margin, outer margin, and chest wall angle); split pleura sign; internal echogenicity (suspended microbubble sign, complex-septated effusions, and passive atelectasis); and identification of color Doppler ultrasound vessel signals in pericavitary lesions (consolidation or atelectasis). The suspended microbubble sign was defined as the image scattered with numerous hyperechoic pinpoints that moved synchronously with respiration in various directions.12 Complex-septated effusions were defined as the presence of strands (hyperechoic lines within the effusion) floating inside the pleural space, web-like or branching.13 Passive atelectasis was defined as homogeneously echoic transformations with band-like shape on the extent of intrapleural fluid.14,15

To obtain interpretations of the sonographic appearances of the lesion and interobserver agreement, three of the authors, who are chest physicians, independently interpreted all the static images from the recorded hard disks of the ultrasound machines, without knowledge of clinical data, laboratory test results, or pathologic findings. The final interpretations had the concordant agreement of at least two of the physician-authors. When there was not unanimity on a case, that case was labeled as one with interobserver variability.

Statistical Analysis of the Sonographic Appearances in Differentiating Air-Fluid Lung Abscess and Empyema

The characteristics of sonographic appearances in air-fluid lung abscess and empyema were compared by χ2 test with the use of statistical software (SPSS, version 12.0; SPSS Inc; Chicago, IL). Statistically, a p value < 0.05 was considered to be significant.

The sonographic features of lung abscess and empyema are summarized in Table 1. The differences in wall characteristics (width uniformity, luminal margin, and outer margin), complex-septated effusions, passive atelectasis, and the identification of color Doppler ultrasound vessel signals in pericavitary consolidation were significant in the differential diagnosis made between the two diseases. The chest wall angle, split pleura sign, and suspended microbubble sign had limited value in making a differential diagnosis.

Table Graphic Jump Location
Table 1 Sonographic Features for the Differential Diagnosis of Air-Fluid Lung Abscess and Empyema*

*Values are given as No. of patients in category/total No. of patients (%), unless otherwise indicated. Not all features could be assessed in every patient.

†Significant (analyzed by χ2 test).

In further analyses of wall characteristics, the air-fluid lesions with width uniformity (48%; n = 14 of 29), and smooth luminal (52%; n = 15 of 29) and outer (50%; n = 15 of 30) margins were highly suggestive of empyema (Fig 1, top, a). A lung abscess typically had an irregular wall width (91%; n = 20 of 22), irregular luminal margin (91%; n = 21 of 23), and blurred outer margin (91%; n = 30 of 33) [Fig 1, bottom, b]. However, some wall characteristics could not be evaluated in 20% of all the patients (n = 13) because of a poor acoustic window. The interobserver variabilities were also higher in the interpretation of the wall characteristics (51% of width uniformity, 40% of luminal margin, and 32% of outer margin), leading to unreliable conclusions.

Figure Jump LinkFigure 1 Top, a: empyema. A 32-year-old man had an empyema in the right upper lobe. Ultrasound examination of the chest revealed a hypoechoic lesion with complex-septated effusions (arrow), passive atelectasis (arrowhead), width uniformity, and smooth luminal and outer margins. Color Doppler ultrasound could not identify vessel signals in pericavitary atelectasis. Bottom, b: abscess. A 64-year-old man had an abscess in the right lower lobe. Ultrasound examination of the chest revealed a hypoechoic lesion with typical pulmonary consolidation (characterized by tree-shaped air bronchogram with ramifications) [arrowhead], irregular wall width, and irregular luminal and outer margins. Color Doppler ultrasound could identify vessel signals in pericavitary consolidation (arrow).Grahic Jump Location

On the other hand, the identification of internal echogenicity (suspended microbubble sign, complex-septated effusions, and passive atelectasis) and color Doppler ultrasound vessel signals in pericavitary consolidation had good interobserver agreement (92 to approximately 100%). Suspended microbubble sign could be found in 15% of lung abscesses (n = 5) and 23% of empyema patients (n = 7), but without statistical significance. By contrast, complex-septated effusions and passive atelectasis (Fig 1, top, a) were specific for empyema, but the sensitivity was only 40% (n = 12) and 47% (n = 14), respectively. Among the analyzed sonographic characteristics, identification of color Doppler ultrasound vessel signals in pericavitary consolidation was the most useful and specific for lung abscess (Fig 1, bottom, b). In our series, if we defined the identification of color Doppler ultrasound vessel signals in a pericavitary consolidation as a predictor for peripheral lung abscess, then we could achieve the sensitivity, specificity, positive predictive value, and negative predictive value of 94%, 100%, 100%, and 94%, respectively.

Lung abscess is defined as a localized area of suppuration with destruction of the lung parenchyma. Empyema is a pleural-based lesion. Distinguishing between empyema and lung abscess on the basis of conventional radiologic findings often is difficult (Fig 2, top left, a, and top right, d, and Fig 3, top left, a, and top right, e) because of the inability to adequately resolve the pleural-parenchymal interface; thus, the actual site of the air-fluid level cannot be determined.3

Figure Jump LinkFigure 2 Top left, a, to bottom left, c: empyema. Top left, a: radiograph of the chest of a 43-year-old man shows an air-fluid level (arrow) in the left lower lobe. Middle left, b: grayscale ultrasound examination reveals a hypoechoic lesion with suspended microbubble sign (arrowhead), irregular wall width, and irregular luminal and outer margins (arrow). The sonographic characteristics favored lung abscess. Bottom left, c: color Doppler ultrasound, however, could not identify vessel signals in pericavitary lesion (arrow), which is the typical finding of empyema. Top right, d, to bottom right, f: abscess. Top right, d: radiograph of the chest of a 37-year-old man shows an air-fluid level (arrow) in the right lower lobe. Middle right, e: grayscale ultrasound examination reveals a hypoechoic lesion with suspended microbubble signs (arrowhead), irregular wall width, and irregular luminal and outer margins (arrow). The sonographic characteristics favored lung abscess. Bottom right, f: color Doppler ultrasound also could identify vessel signals in pericavitary consolidation (arrow).Grahic Jump Location
Figure Jump LinkFigure 3 Top left, a, to bottom left, d: empyema. Top left, a: chest radiograph of a 39-year-old man shows an air-fluid level (arrow) in the right lower lobe. Top center left, b: CT scan image shows a cavitary lesion with an air-fluid level (arrowhead) and split pleura sign (arrow). Bottom center left, c: grayscale ultrasound examination reveals a band-like shape with smooth margin and straight air-bronchograms (arrowhead) [not like typical pulmonary consolidation characterized by irregular, serrated, and somewhat blurred margin and a marked tree-shaped air bronchogram with ramifications]. The band-like shape does not surround the air-fluid lesion continuously (arrow), which is a typical presentation of passive atelectasis. Bottom left, d: the vessels in passive atelectasis, like the air bronchogram, are relatively straight. Top right, e, to bottom right, h: abscess. Top right, e: radiograph of the chest of a 47-year-old man shows an air-fluid level (arrow) in the left lower lobe. Top center right, f: CT scan image shows a cavitary lesion with an air-fluid level (arrowhead), mimicking split pleura sign (arrow). Bottom center right, g: grayscale ultrasound examination of the chest reveals a hypoechoic lesion with suspended microbubble sign (arrowhead), which is surrounded by whole-lung parenchyma (arrow). Bottom right, h: color Doppler ultrasound can identify vessel signals in pericavitary consolidation in a lung abscess. The vessels in pulmonary consolidation are abundant, branching, and twisted.Grahic Jump Location

Plain film and CT scan findings emphasizing the shape and wall characteristics have been reported6 as being useful for differentiating lung abscess from empyema as follows: an abscess tends to be round and usually appears with an irregular wall width (irregular luminal and outer margins); empyema tends to be lenticular and shows width uniformity. Our sonographic study had the same findings; however, exceptions often occurred (Fig 2, middle left, b). By changing the sonographic plane, the shape may shift from lenticular to oval or round and vice versa.4 In our series, the interobserver variabilities were around 32 to 51% in the interpretation of the wall characteristics. How smooth should be considered “smooth?” How uniform should be considered “uniform?” Apparently, this differential method is too subjective to be reliable.

Lung compression and split pleura sign were specific features for empyema seen on CT scans.6 Compression of the adjacent lung was identified by noting distorted and bowed bronchi and pulmonary vessels around the periphery of the lesion.6 As empyema progresses, a fibrin peel coats the surfaces of the visceral and parietal pleural layers, with ingrowth of capillaries and fibroblasts and subsequent thickening; this forms the basis of the split pleura sign. The split pleura sign usually is seen on contrast material-enhanced chest CT scan images.6 In the sonographic examination, it is difficult to differentiate the visceral-parietal pleural layers from lung parenchyma without contrast material enhancement. We could identify only one split pleura sign in 30 empyemas. The sonographic appearance of passive atelectasis develops homogeneously echoic transformations with band-like shape on the extent of intrapleural fluid15 (Fig 1, top, a, and 3, bottom center left, c, and bottom left, d). Passive atelectasis is specific for empyema in sonography, like lung compression in CT scanning, but was seen in 47% of all empyemas in our series.

Suspended microbubble sign and complex-septated effusions are specific sonographic characteristics. Lin et al9 found that the suspended microbubble sign might be of value in differentiating empyemic and nonempyemic hydropneumothorax. However, the suspended microbubble sign was not specific for empyema. As reported9,12 and from our experience, both empyema and lung abscess could have the suspended microbubble sign in which the pus was expected to be aspirated (Fig 2, middle left, b, and middle right, e). On the other hand, the complex-septated appearance was specific for pleural diseases, such as complicated parapneumonic effusions, empyema, or tuberculous pleural effusions.8 Visualization of complex-septated effusions was noted in only 40% of all air-fluid empyemas (Fig 1, top, a).

Of the imaging examinations used in chest medicine (ie, chest radiography, CT scanning, ultrasound, MRI, angiography, and fluoroscopy), color Doppler ultrasound is the only imaging modality capable of assessing the vessel signals in peripheral pulmonary lesions.10 In pulmonary consolidation, Yang et al16 found that Doppler ultrasound was excellent in demonstrating blood flow present in the pulmonary vasculature. The vascular linear echoes could be traced to the hilar region, which may join the pulmonary artery.16 Lung abscess is surrounded by the consolidated lung parenchyma, so we assume that the air-fluid abscess may be encircled by pulmonary vasculature. Thoracic empyema, by comparison, is defined as pus in the pleural cavity. Compression of the adjacent lung by empyema6 may cause a local reduction of blood flow.17 In Figure 2 (panels top left, a, to bottom left, c, compared to panels top right, d, to bottom right, f), both serial pictures had almost the same grayscale sonographic appearance, and we could not distinguish between lung abscess and empyema confidently until the application of color Doppler ultrasound. If we define the identification of color Doppler ultrasound vessel signals in pericavitary consolidation as a predictor for lung abscess, we can achieve sensitivity, specificity, positive predictive value, and negative predictive value of 94%, 100%, 100%, and 94%, respectively. There were no interobserver variabilities in our series because color Doppler ultrasound vessel signals were easy to recognize.

Although thoracic CT scanning can prove to be valuable in differentiating lung abscess from empyema,5,6 it has some limitations. In Figure 3 (panels top left, a, to bottom left, d compared to panels top right, e, to bottom right, h), almost the same air-fluid characteristics and split pleura sign are seen in the CT scan. However, we could identify the difference with ultrasound. Additionally, there are some advantages to sonography that make ultrasound cooperate with CT scanning in differentiating lung abscess from empyema. First, ultrasound is performed in real time. Second, the device is portable and it's use convenient; diagnostic and therapeutic procedures can be performed at bedside for patients who are critically ill.18 Third, color Doppler ultrasound is the only imaging modality capable of assessing the vessel signals in peripheral lung abscess.

This clinical study had some weak points, however. First, the retrospective reading of static images could not reach 100% correctness. Second, we might have misjudged the vessels in passive atelectasis as the vessels in pericavitary consolidation, although the rate of identification of color Doppler ultrasound vessel signals was 14% (n = 2 of 14) in patients with passive atelectasis and only 6% (n = 2 of 30) in patients with empyema in our series. In our experience, there were three key points in the avoidance of mistakes. First, the passive atelectasis in empyema (Fig 3, bottom center left, c) is band-like in shape with smooth margins and straight air bronchograms (not like a typical pulmonary consolidation [Fig 1, bottom, b], which is characterized by irregular, serrated, and somewhat blurred margins and a marked tree-shaped air bronchogram with ramifications19). Second, the vessels in patients with lung atelectasis, like those in patients with air bronchograms, are relatively straight14,15 (Fig 3, bottom left, d). Third, the passive atelectasis does not surround the air-fluid lesion continuously (Fig 3, bottom center left, c). On the contrary, the lung abscess is surrounded by lung parenchyma with prominent consolidation (Figs 1, bottom, b, and 3, bottom center right, g); the vessels in patients with pulmonary consolidation are abundant, branching, and twisted (Figs 1, bottom, b, and 3, bottom right, h).

In conclusion, color Doppler ultrasound is a powerful tool for differentiating the air-fluid abscess from empyema, with high specificity and without any risk. It is worthy of being widely used in chest medicine.

Landay MJ, Conrad MR. Lung abscess mimicking empyema on ultrasonography. AJR Am J Roentgenol. 1979;133:731-734. [PubMed]
 
Zinn WL, Naidich DP, Whelan CA, et al. Fluid within preexisting pulmonary air-spaces: a potential pitfall in the CT differentiation of pleural from parenchymal disease. J Comput Assist Tomogr. 1987;11:441-448. [PubMed] [CrossRef]
 
Friedman PJ, Hellekant CA. Radiologic recognition of bronchopleural fistula. Radiology. 1977;124:289-295. [PubMed]
 
Wu HD, Yang PC, Lee LN. Differentiation of lung abscess and empyema by ultrasonography. J Formos Med Assoc. 1991;90:749-754. [PubMed]
 
Baber CE, Hedlund LW, Oddson TA, et al. Differentiating empyemas and peripheral pulmonary abscesses: the value of computed tomography. Radiology. 1980;135:755-758. [PubMed]
 
Stark DD, Federle MP, Goodman PC, et al. Differentiating lung abscess and empyema: radiography and computed tomography. AJR Am J Roentgenol. 1983;141:163-167. [PubMed]
 
Beckh S, Bolcskei PL, Lessnau KD. Real-time chest ultrasonography: a comprehensive review for the pulmonologist. Chest. 2002;122:1759-1773. [PubMed]
 
Chen HJ, Hsu WH, Tu CY, et al. Sonographic septation in lymphocyte-rich exudative pleural effusions: a useful diagnostic predictor for tuberculosis. J Ultrasound Med. 2006;25:857-863. [PubMed]
 
Lin FC, Chou CW, Chang SC. Differentiating pyopneumothorax and peripheral lung abscess: chest ultrasonography. Am J Med Sci. 2004;327:330-335. [PubMed]
 
Hsu WH, Yu YH, Tu CY, et al. Color Doppler US pulmonary artery vessel signal: a sign for predicting the benign lesions. Ultrasound Med Biol. 2007;33:379-388. [PubMed]
 
Yuan A, Yang PC, Lee L, et al. Reactive pulmonary artery vasoconstriction in pulmonary consolidation evaluated by color Doppler ultrasonography. Ultrasound Med Biol. 2000;26:49-56. [PubMed]
 
Lin FC, Chou CW, Chang SC. Usefulness of the suspended microbubble sign in differentiating empyemic and nonempyemic hydropneumothorax. J Ultrasound Med. 2001;20:1341-1345. [PubMed]
 
Yang PC, Luh KT, Chang DB, et al. Value of sonography in determining the nature of pleural effusion: analysis of 320 cases. AJR Am J Roentgenol. 1992;159:29-33. [PubMed]
 
Kim OH, Kim WS, Kim MJ, et al. US in the diagnosis of pediatric chest diseases. Radiographics. 2000;20:653-671. [PubMed]
 
Gorg C.Mathis G, Lessnau KD. Mechanical Lung Consolidations: atelectasis. Atlas of chest sonography. 2003;1st ed. New York, NY Springer:72-89
 
Yang PC, Luh KT, Chang DB, et al. Ultrasonographic evaluation of pulmonary consolidation. Am Rev Respir Dis. 1992;146:757-762. [PubMed]
 
West JB, Wagner PD.Murray JF, Nadel JA. Respiratory physiology: ventilation, blood flow, and gas exchange. Textbook of respiratory medicine. 2000;3rd ed. Philadelphia, PA Saunders:55-89
 
McGahan JP, Anderson MW, Walter JP. Portable real-time sonographic and needle guidance systems for aspiration and drainage. AJR Am J Roentgenol. 1986;147:1241-1246. [PubMed]
 
Mathis G. Thoraxsonography: part II. Peripheral pulmonary consolidation. Ultrasound Med Biol. 1997;23:1141-1153. [PubMed]
 

Figures

Figure Jump LinkFigure 1 Top, a: empyema. A 32-year-old man had an empyema in the right upper lobe. Ultrasound examination of the chest revealed a hypoechoic lesion with complex-septated effusions (arrow), passive atelectasis (arrowhead), width uniformity, and smooth luminal and outer margins. Color Doppler ultrasound could not identify vessel signals in pericavitary atelectasis. Bottom, b: abscess. A 64-year-old man had an abscess in the right lower lobe. Ultrasound examination of the chest revealed a hypoechoic lesion with typical pulmonary consolidation (characterized by tree-shaped air bronchogram with ramifications) [arrowhead], irregular wall width, and irregular luminal and outer margins. Color Doppler ultrasound could identify vessel signals in pericavitary consolidation (arrow).Grahic Jump Location
Figure Jump LinkFigure 2 Top left, a, to bottom left, c: empyema. Top left, a: radiograph of the chest of a 43-year-old man shows an air-fluid level (arrow) in the left lower lobe. Middle left, b: grayscale ultrasound examination reveals a hypoechoic lesion with suspended microbubble sign (arrowhead), irregular wall width, and irregular luminal and outer margins (arrow). The sonographic characteristics favored lung abscess. Bottom left, c: color Doppler ultrasound, however, could not identify vessel signals in pericavitary lesion (arrow), which is the typical finding of empyema. Top right, d, to bottom right, f: abscess. Top right, d: radiograph of the chest of a 37-year-old man shows an air-fluid level (arrow) in the right lower lobe. Middle right, e: grayscale ultrasound examination reveals a hypoechoic lesion with suspended microbubble signs (arrowhead), irregular wall width, and irregular luminal and outer margins (arrow). The sonographic characteristics favored lung abscess. Bottom right, f: color Doppler ultrasound also could identify vessel signals in pericavitary consolidation (arrow).Grahic Jump Location
Figure Jump LinkFigure 3 Top left, a, to bottom left, d: empyema. Top left, a: chest radiograph of a 39-year-old man shows an air-fluid level (arrow) in the right lower lobe. Top center left, b: CT scan image shows a cavitary lesion with an air-fluid level (arrowhead) and split pleura sign (arrow). Bottom center left, c: grayscale ultrasound examination reveals a band-like shape with smooth margin and straight air-bronchograms (arrowhead) [not like typical pulmonary consolidation characterized by irregular, serrated, and somewhat blurred margin and a marked tree-shaped air bronchogram with ramifications]. The band-like shape does not surround the air-fluid lesion continuously (arrow), which is a typical presentation of passive atelectasis. Bottom left, d: the vessels in passive atelectasis, like the air bronchogram, are relatively straight. Top right, e, to bottom right, h: abscess. Top right, e: radiograph of the chest of a 47-year-old man shows an air-fluid level (arrow) in the left lower lobe. Top center right, f: CT scan image shows a cavitary lesion with an air-fluid level (arrowhead), mimicking split pleura sign (arrow). Bottom center right, g: grayscale ultrasound examination of the chest reveals a hypoechoic lesion with suspended microbubble sign (arrowhead), which is surrounded by whole-lung parenchyma (arrow). Bottom right, h: color Doppler ultrasound can identify vessel signals in pericavitary consolidation in a lung abscess. The vessels in pulmonary consolidation are abundant, branching, and twisted.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 Sonographic Features for the Differential Diagnosis of Air-Fluid Lung Abscess and Empyema*

*Values are given as No. of patients in category/total No. of patients (%), unless otherwise indicated. Not all features could be assessed in every patient.

†Significant (analyzed by χ2 test).

References

Landay MJ, Conrad MR. Lung abscess mimicking empyema on ultrasonography. AJR Am J Roentgenol. 1979;133:731-734. [PubMed]
 
Zinn WL, Naidich DP, Whelan CA, et al. Fluid within preexisting pulmonary air-spaces: a potential pitfall in the CT differentiation of pleural from parenchymal disease. J Comput Assist Tomogr. 1987;11:441-448. [PubMed] [CrossRef]
 
Friedman PJ, Hellekant CA. Radiologic recognition of bronchopleural fistula. Radiology. 1977;124:289-295. [PubMed]
 
Wu HD, Yang PC, Lee LN. Differentiation of lung abscess and empyema by ultrasonography. J Formos Med Assoc. 1991;90:749-754. [PubMed]
 
Baber CE, Hedlund LW, Oddson TA, et al. Differentiating empyemas and peripheral pulmonary abscesses: the value of computed tomography. Radiology. 1980;135:755-758. [PubMed]
 
Stark DD, Federle MP, Goodman PC, et al. Differentiating lung abscess and empyema: radiography and computed tomography. AJR Am J Roentgenol. 1983;141:163-167. [PubMed]
 
Beckh S, Bolcskei PL, Lessnau KD. Real-time chest ultrasonography: a comprehensive review for the pulmonologist. Chest. 2002;122:1759-1773. [PubMed]
 
Chen HJ, Hsu WH, Tu CY, et al. Sonographic septation in lymphocyte-rich exudative pleural effusions: a useful diagnostic predictor for tuberculosis. J Ultrasound Med. 2006;25:857-863. [PubMed]
 
Lin FC, Chou CW, Chang SC. Differentiating pyopneumothorax and peripheral lung abscess: chest ultrasonography. Am J Med Sci. 2004;327:330-335. [PubMed]
 
Hsu WH, Yu YH, Tu CY, et al. Color Doppler US pulmonary artery vessel signal: a sign for predicting the benign lesions. Ultrasound Med Biol. 2007;33:379-388. [PubMed]
 
Yuan A, Yang PC, Lee L, et al. Reactive pulmonary artery vasoconstriction in pulmonary consolidation evaluated by color Doppler ultrasonography. Ultrasound Med Biol. 2000;26:49-56. [PubMed]
 
Lin FC, Chou CW, Chang SC. Usefulness of the suspended microbubble sign in differentiating empyemic and nonempyemic hydropneumothorax. J Ultrasound Med. 2001;20:1341-1345. [PubMed]
 
Yang PC, Luh KT, Chang DB, et al. Value of sonography in determining the nature of pleural effusion: analysis of 320 cases. AJR Am J Roentgenol. 1992;159:29-33. [PubMed]
 
Kim OH, Kim WS, Kim MJ, et al. US in the diagnosis of pediatric chest diseases. Radiographics. 2000;20:653-671. [PubMed]
 
Gorg C.Mathis G, Lessnau KD. Mechanical Lung Consolidations: atelectasis. Atlas of chest sonography. 2003;1st ed. New York, NY Springer:72-89
 
Yang PC, Luh KT, Chang DB, et al. Ultrasonographic evaluation of pulmonary consolidation. Am Rev Respir Dis. 1992;146:757-762. [PubMed]
 
West JB, Wagner PD.Murray JF, Nadel JA. Respiratory physiology: ventilation, blood flow, and gas exchange. Textbook of respiratory medicine. 2000;3rd ed. Philadelphia, PA Saunders:55-89
 
McGahan JP, Anderson MW, Walter JP. Portable real-time sonographic and needle guidance systems for aspiration and drainage. AJR Am J Roentgenol. 1986;147:1241-1246. [PubMed]
 
Mathis G. Thoraxsonography: part II. Peripheral pulmonary consolidation. Ultrasound Med Biol. 1997;23:1141-1153. [PubMed]
 
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