Menu
doi: 10.1590/S1806-37132014000100001
PMID: 24626263
This article has been cited by other articles in PMC.
In recent years, there has been an increasing interest in the use of ultrasound for theevaluation of chest diseases, especially for the study of bedridden, critically illpatients. In fact, the ultrasound method presents various advantages: it uses no radiation;it is inexpensive; it can be used at the bedside; it is noninvasive; and it can be repeatedas necessary. In addition, ultrasound is starting to be a method used by professionals,other than radiologists, who have specific clinical questions,(,) having become an importanttool for the pulmonary physician. In this context, the utility of ultrasound for thediagnosis and management of pleural effusion is well documented.
On 'Pardon My Take,' Big Cat & PFT Commenter deliver the loudest and most correct sports takes in the history of the spoken word. Daily topics, guests, and an inability to tell what the hosts might be doing will make this your new favorite sports talk show. This is a podcast that will without a doubt change your life for the better- guaranteed, or your money back.
In the present issue of the Brazilian Journal of Pulmonology, Perazzo etal.(,) present a randomized controlled trial aimed at assessing whetherultrasound-assisted thoracentesis, in contrast with a blinded method, would reduce the rateof pneumothorax. The authors also aimed to assess whether ultrasound improves the efficacyof the procedure (in terms of the number of successful fluid removal procedures and theamount of fluid removed). It is of note that, in that study, experienced operatorsperformed both methods, following a standardized protocol, in order to focus attention onthe influence of using ultrasound or not, and removed other factors that could beresponsible for complications. For these purposes, 160 inpatients and outpatients withpleural effusion requiring pleural puncture were randomized into two groups. In the studygroup (comprising 80 patients), thoracentesis was performed with the use of ultrasound,whereas it was performed without ultrasound in the control group (also comprising 80patients). In comparing the study and control groups, the authors observed that the formerhad a significantly lower pneumothorax rate (1.25% vs. 12.5%; p = 0.009; OR = 0.09), ahigher number of patients with successful drainage (79/80 vs. 72/80), and a higher amountof fluid drained (mean ± SD: 960 ± 500 mL vs. 770 ± 480 mL). They concluded that the use ofultrasound during thoracentesis reduced the number of cases of pneumothorax and increasedthe efficiency of the procedure.
The findings of Perazzo et al.(2) corroborate data already described in theliterature-thoracentesis involving the use of ultrasound is safer than is the blindedapproach. Nevertheless, the study is interesting because it confirms the idea thatultrasound can provide advantages even to more experienced operators. In addition, thestudy is a randomized controlled trial, which increases the power of their findings.
Despite its utility, ultrasound presents some limitations. Soft tissue edema, subcutaneousemphysema, or obesity can reduce the quality of the images. We also think that physiciansneed adequate training in order to avoid misreading ultrasound images and, consequently, toavoid mistakes.
Ultrasound and diagnosis of pleural effusion
The first step in the evaluation of patients with suspected pleural effusion is toconfirm the diagnosis, especially in the case of a white hemithorax on chest X-rays.Ultrasound is a useful method for these purposes because it allows the distinctionbetween effusion and lung consolidations(,) and has a higher accuracy in detecting pleuraleffusion in comparison with bedside chest X-rays (93% vs. 47%).(,) In fact, chest X-rays can detect the presence of pleural effusion inpatients in the orthostatic position only if the volume of the effusion is at least 200mL,(,) andthe sensitivity of this method decreases in the supine position, whereas ultrasound candetect effusions as small as 20 mL.(,)
The ultrasound evaluation of a patient in a sitting position is better because it allowsa more precise quantification of pleural effusion. In this position, the free fluid willcollect in the dependent space, whereas it will be found in a posterior location withthe patient in the supine position. In addition, ultrasound allows the identification ofadjacent structures: chest wall, hemidiaphragm (over the liver or spleen), and visceralpleural surface. This is important, especially in the case of an invasive procedure, inorder to avoid organ injury (Figure 1).
Ultrasound identification of pleural effusion at a specific site (lowerimage). pe: pleural effusion; d: diaphragm; and c: chest wall.
A second step is the distinction between transudative and exudative pleural effusions.The aspect of pleural effusion on ultrasound can suggest the nature of the fluid,although a definitive diagnosis requires a thoracentesis in order to allow physical,chemical, and microbiological studies. According to the characteristics of the pleuraleffusion on ultrasound, it can appear as anechoic (black), complex nonseptated (blackwith white strands), complex septated (black with white septa), or homogeneouslyechogenic (white).(,) In general, the presence of complex pleural effusionsuggests exudative effusion, whereas an anechogenic effusion might be transudative.However, in contrast to what we expect, transudative effusion can also appear as complexnonseptated effusion(,); this is due to the fact that transudates are notpure water, having various components (i.e., cells, proteins, and lipids), and exudativeeffusions can also appear as anechogenic effusion. Homogeneous echogenic effusions arethe result of hemorrhagic effusions or empyema (Table1).
Table 1
Ultrasound patterns and the nature of pleural effusion.
In some cases, ultrasound images other than those of the effusion can help assess thenature of the pleural effusion. For example, the presence of thickened pleura or of apulmonary consolidation with dynamic air bronchogram (suggestive of an infectiousorigin) is usually indicative of an exudate. The presence of a diffuse sign of lungcongestion (B lines) suggests transudative effusion during heart failure.
Laing & Filly(,) reported that nearly 20% of the anechogenic imagesof the pleura revealed a solid lesion, not the presence of fluid. Therefore, especiallyin cases of small or loculated pleural effusion (Figure2), or when thoracentesis is requested, it is important to focus on thedifferential diagnosis. One aspect that can facilitate the diagnosis is that pleuraleffusions are associated with a typical movement of the adjacent structure thatdetermines a change in the shape of the effusion-the movement of the collapsed lung intothe effusion or that of particles inside the fluid. The use of the M mode can help inthe visualization of the sinusoidal movement of the collapsed lung in the fluid(sinusoid sign).(,) However, very dense or loculated pleural effusionsmight present no variation in the shape.
![Nao Obstante Podcast Nao Obstante Podcast](http://www.naoobstante.com/naobslogo.jpg)
CT (in A) and ultrasound (in B) revealing loculated pleural effusion. pe:pleural effusion; L:lung; and r: rib. The thin arrow indicates the parietalpleural line.
Although various ultrasound methods have been described for the quantification of thevolume of pleural effusions,(,) they all require several measurements. We believethat knowledge of the exact amount of fluid has limited usefulness in clinical practice.Therefore, we prefer a qualitative approach, which is summarized in Table 2. In addition, ultrasound can help estimatethe effect of pleural effusion on the lung parenchyma by enabling the visualization ofdifferent degrees of collapse. This information, combined with clinical judgment, canhelp physicians in the decision-making process regarding thoracentesis (Figure 3).
Table 2
X-ray (in A) and ultrasound (in B) revealing pleural effusion and lungcollapse. pe: pleural effusion.
Ultrasound and thoracentesis
The use of ultrasound in thoracentesis reduces the rate of complications (i.e.,pneumothorax) and increases the successfulness of fluid removal when compared withtraditional methods.(,) Ultrasound is especially useful when the pleuraleffusion is small or loculated.
Ultrasound allows the identification of the best site to perform the puncture and themeasurement of the depth of the adjacent organs in order to avoid organ injury. Forexperts, ultrasound allows the study of the intercostal spaces prior to needleinsertion, in order to identify aberrantly positioned intercostal vessels, thus avoidingvascular injury.
On ultrasound images, the appearance of pleural effusion can also provide clues to thenecessary intervention: for example, a complex septated effusion could require the useof a larger catheter. There are two different techniques employed in thoracentesis withthe use of ultrasound: the landmark-based method, in which ultrasound is used in orderto identify the best site of the puncture; and the ultrasound-guided method, in whichthe procedure is closely monitored in real time by continuous visualization of theneedle. This second method requires the involvement of a professional who is moreexperienced in the use of ultrasound.
Ultrasound and pneumothorax
The use of ultrasound reduces the risk of pneumothorax following thoracocentesis from18% to 3%.(,).As shown in one retrospective study,(,) that is especially true when theultrasound-guided method is used, the rates of pneumothorax being significantly lowerthan when the landmark-based method is used (4% vs. 10%). In addition, Weingardt etal.(,)demonstrated that ultrasound can be an effective rescue method in 88% of cases in whichblind thoracocentesis is unsuccessful. The authors noted that, in 69% of those cases,the site of puncture chosen in the blind approach was below the diaphragm.Interestingly, ultrasound-guided thoracentesis resulted safe for use in mechanicallyventilated patients as well.(,)
Ultrasound is also a more useful method to detect pneumothorax after thoracentesis thanare chest X-rays using a supine anterior approach. The sensitivity of these two methodsis 78.6% and 39.8%, respectively, whereas their specificity is 98.4% and 99.3%,respectively.(,)
As shown in Figure 4, the major ultrasonographicsigns for the diagnosis of pneumothorax are the absence of lung sliding-movement of thepleura during respiratory excursion-which is more evident using the M mode with thestratosphere sign; the absence of B lines (negative predictive value: 100%); and thepresence of the lung point (positive predictive value: 100%) in the absence of massivepneumothorax.
![Podcast Podcast](/uploads/1/2/5/8/125838265/878785210.jpg)
Ultrasound signs of pneumothorax. In A, normal lung, showing the seashoresign in M mode. In B, pneumothorax, showing the stratosphere sign in M mode. InC, subcutaneous emphysema. Arrowheads indicate the pneumothorax.
In summary, ultrasound represents a highly useful tool for the evaluation of patientswith pleural effusion during the diagnostic phase and in combination with invasiveprocedures.
Footnotes
* Dr. Prina is a research fellow supported by the long-term research fellowshipprogram of the European Respiratory Society.
Contributor Information
Elena Prina, Department of Pulmonology, Heart Institute, University of São Paulo School of Medicine Hospital das Clínicas, São Paulo, Brazil, Institut Clínic del Tórax (ICT), Servei de Pneumologia, Hospital Clínic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Ciber de Enfermedades Respiratorias, Barcelona, Spain.
Antoni Torres, Institut Clínic del Tórax (ICT), Servei de Pneumologia, Hospital Clínic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Ciber de Enfermedades Respiratorias, Barcelona, Spain.
Carlos Roberto Ribeiro Carvalho, Heart Institute (InCor), Hospital das Clínicas, University of São Paulo School of Medicine, São Paulo, Brazil.
References
1. Koenig SJ, Narasimhan M, Mayo PH. Thoracic ultrasonography for the pulmonaryspecialist. Chest. 2011;140(5):1332–1341. http://dx.doi.org/10.1378/chest.11-0348 [PubMed] [Google Scholar]
2. Perazzo A, Gatto P, Barlascini C, Ferrari-Bravo M, Nicolini A. Can ultrasound guidance reduce the risk of pneumothoraxfollowing thoracentesis? J Bras Pneumol. 2014;40(1):6–12.[PMC free article] [PubMed] [Google Scholar]
3. Yu CJ, Yang PC, Wu HD, Chang DB, Kuo SH, Luh KT. Ultrasound study in unilateral hemithorax opacification.Image comparison with computed tomography. Am Rev Respir Dis. 1993;147(2):430–434. http://dx.doi.org/10.1164/ajrccm/147.2.430 [PubMed] [Google Scholar]
4. Lichtenstein D, Goldstein I, Mourgeon E, Cluzel P, Grenier P, Rouby JJ. Comparative diagnostic performances of auscultation,chest radiography, and lung ultrasonography in acute respiratory distresssyndrome. Anesthesiology. 2004;100(1):9–15. http://dx.doi.org/10.1097/00000542-200401000-00006 [PubMed] [Google Scholar]
5. Blackmore CC, Black WC, Dallas RV, Crow HC. Pleural fluid volume estimation: a chest radiographprediction rule. Acad Radiol. 1996;3(2):103–109. http://dx.doi.org/10.1016/S1076-6332(05)80373-3 [PubMed] [Google Scholar]
6. Rahman NM, Singanayagam A, Davies HE, Wrightson JM, Mishra EK, Lee YC, et al. Diagnostic accuracy, safety and utilisation ofrespiratory physician-delivered thoracic ultrasound. Thorax. 2010;65(5):449–453. http://dx.doi.org/10.1136/thx.2009.128496 [PubMed] [Google Scholar]
7. Lomas DJ, Padley SG, Flower CD. The sonographic appearances of pleuralfluid. Br J Radiol. 1993;66(787):619–624. http://dx.doi.org/10.1259/0007-1285-66-787-619 [PubMed] [Google Scholar]
8. Chen HJ, Tu CY, Ling SJ, Chen W, Chiu KL, Hsia TC, et al. Sonographic appearances in transudative pleuraleffusions: not always an anechoic pattern. Ultrasound Med Biol. 2008;34(3):362–369. http://dx.doi.org/10.1016/j.ultrasmedbio.2007.09.009 [PubMed] [Google Scholar]
9. Laing FC, Filly RA. Problems in the application of ultrasonography for theevaluation of pleural opacities. Radiology. 1978;126(1):211–214. [PubMed] [Google Scholar]
11. Remérand F, Dellamonica J, Mao Z, Ferrari F, Bouhemad B, Jianxin Y, et al. Multiplane ultrasound approach to quantify pleuraleffusion at the bedside. Intensive Care Med. 2010;36(4):656–664. http://dx.doi.org/10.1007/s00134-010-1769-9 [PubMed] [Google Scholar]
12. Diacon AH, Brutsche MH, Solèr M. Accuracy of pleural puncture sites: a prospectivecomparison of clinical examination with ultrasound. Chest. 2003;123(2):436–441. http://dx.doi.org/10.1378/chest.123.2.436 [PubMed] [Google Scholar]
13. Barnes TW, Morgenthaler TI, Olson EJ, Hesley GK, Decker PA, Ryu JH. Sonographically guided thoracentesis and rate ofpneumothorax. J Clin Ultrasound. 2005;33(9):442–446. http://dx.doi.org/10.1002/jcu.20163 [PubMed] [Google Scholar]
14. Weingardt JP, Guico RR, Nemcek AA Jr, Li YP, Chiu ST. Ultrasound findings following failed, clinicallydirected thoracenteses. J Clin Ultrasound. 1994;22(7):419–426. http://dx.doi.org/10.1002/jcu.1870220702 [PubMed] [Google Scholar]
15. Lichtenstein D, Hulot JS, Rabiller A, Tostivint I, Mezière G. Feasibility and safety of ultrasound-aided thoracentesisin mechanically ventilated patients. Intensive Care Med. 1999;25(9):955–958. http://dx.doi.org/10.1007/s001340050988 [PubMed] [Google Scholar]
16. Alrajab S, Youssef AM, Akkus NI, Caldito G. Pleural ultrasonography versus chest radiography for thediagnosis of pneumothorax: review of the literature andmeta-analysis. Crit Care. 2013;17(5):R208–R208. http://dx.doi.org/10.1186/cc13016[PMC free article] [PubMed] [Google Scholar]