A pictorial review of thoracic imaging of intensive care patients

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1 A pictorial review of thoracic imaging of intensive care patients Poster No.: C-1003 Congress: ECR 2010 Type: Educational Exhibit Topic: Chest Authors: E. Y. P. Lee, H. C. Mathias; Cardiff/UK Keywords: Intensive care unit, Portable chest radiograph, Thorax pathologies DOI: /ecr2010/C-1003 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 24

2 Learning objectives Demonstrate various thoracic imaging findings in ICU patients Highlighting imaging pitfalls Background Intensive care units (ICU) were introduced after the World War II and since, they have continued to expand. The complexity of ICU patients has also increased due to advance in technologies in sustaining lives. In some hospitals, up to a third of inpatient chest radiographs (CXR) was performed on ICU. Beside portable chest radiograph remains an important thoracic imaging for ICU patients, though with limitations which are well documented. Quality of portable chest radiograph is often compromised by inadequate exposure, anteroposterior projection, rotation and positioning of ICU patients (1,2). Further factors like instrumentation, ventilation equipment, various lines and tubes can also distract the viewer from the underlying pathology (3,4). Therefore it is not surprising that interpretation of ICU CXR is not straightforward and easy. Cross sectional imaging like computed tomography (CT) is gaining its popularity among ICU patients and often provides more information which is not suspected on CXR (5). Miller at all showed that 52% of the thoracic findings were only visible on CT but not CXR, however only 22% was clinically significant and altered clinical management (6). Imaging findings OR Procedure details Page 2 of 24

3 ICU patients can present with a variety of thoracic abnormalities due to their underlying complex medical conditions. These can be broadly categorised into: Pulmonary Pulmonary consolidation is due to accumulation of fluid, pus or blood in the alveoli. Hospital acquired pneumonia is common in ICU patients and is the leading cause of death. Pneumonia can be difficult to be differentiated from other causes of air space shadowing but tends to be patchy initially and becomes more confluent consolidation with presence of air-bronchogram. Fig.: Portable CXR shows consolidation with collapse of the right upper lobe. Noticed that the trachea is being pulled to the ipsilateral right side. Page 3 of 24

4 Fig.: A young immunocompromised patient with H1N1 swine flu infection. Portable CXR showed extensive air-space shadowing at both lower lobes with presence of airbronchogram. Pulmonary oedema causes accumulation of fluid in the interstitium and alveolar space. This can be cardiac in origin due to pump failure, or non-cardiac for example fluid overload or endothelial damage. Manifestations of pulmonary oedema include: -interlobular septal thickening, sometimes reticular pattern mimicking fibrotic disease -loss of definition of the pulmonary vessels Page 4 of 24

5 -upper lobe blood diversion, maybe difficult to appreciate on a background of air-space opacification and supine positioning -peribronchial thickening -perihilar air space shadowing when the alveoli are filled with fluid, fanning out from both hila producing "batwing" appearance -pleural effusion. Fig.: Portable CXR showed extensive air-space shadowing, in almost "batwing" distribution. There is more confluent consolidation at the right lower zone which could represent superimposed infection. This patient had previous history of myocardial infarction. Page 5 of 24

6 Fig.: Coronal reformat from CT thorax in the same patient illustrating the distribution of the air-space shadowing which showed sparing of the lung peripheries. Page 6 of 24

7 Fig.: Portable CXR after treatment of pulmonary oedema. There remained atelectasis at the right base. Adult respiratory distress syndrome (ARDS) is associated with high mortality and is not uncommon in ICU patients. To differentiate ARDS from cardiac pulmonary oedema can be tricky and the two entities can co-exist. In ARDS, the pulmonary venous pressure is normal, normally with no evidence of cardiac enlargement (3,8). Page 7 of 24

8 Fig.: Portable CXR showed extensive air-space shadowing. Adult respiratory distress syndrome can mimic extensive consolidation or acute pulmonary oedema. History, clinical presentation and echocardiography may help to distinguish the aetiology. Collapse and atelectasis are due to failure of the lung to expand causing alveolar hypoventilation and intrapulmonary shunt. The radiographic appearances range from linear atelectasis to total lobar collapse. Signs of volume loss are the consequences we observe with elevation of the hemidiaphragm, displacement of the fissures, crowding of the pulmonary vessels and mediastinal shift (8). They could also present as patchy opacification which simulate pneumonia. Collapsed segments or lobes followed well-recognised anatomical pathways, therefore producing well-described radiological appearances. ICU patients have high risk of developing pulmonary embolism due to immobility and underlying medical conditions. Symptoms and signs are non-specific; CXR has very low sensitivity for pulmonary embolism but remains a good first-line imaging to rule out other pulmonary pathology which could account for the hypoxaemia. The gold standard is Page 8 of 24

9 performing CT pulmonary angiogram (CTPA) to look for filling defect in the pulmonary arteries and its sequelae. Fig.: Contrasted CT pulmonary angiography showed multiple filling defects at the main pulmonary arteries consistent with pulmonary embolisms. Pleural Space Pleural effusion is very common in ICU patient. As most portable ICU CXRs are taken in supine or semi-erect positions, fluid accumulates in the most dependent area. Therefore the classical "meniscus sign" maybe absent and appears haziness in the chest. Page 9 of 24

10 Fig.: Generalised haziness over the left hemithorax on a supine portable CXR. The left hemidiaphragm is obliterated. Appearances are of a large left pleural effusion. There is also right upper lobe consolidation and collapse. Empyema is collection of pus in the pleural space. On CXR, this can be difficult to differentiate from simple pleural fluid; sometimes this pus collection can be loculated. CT thorax showed avid pleural enhancement in keeping with hyperaemia and inflammation. US chest is useful, particularly in guiding the insertion of chest drain. Pneumothorax Most of the ICU patients are intubated and ventilated or have had tracheostomy. Barotrauma could occur secondary to ventilation. As air rises to the non-dependent area, this will accumulate anteriorly and medially within the pleural space in a supine ICU patient. Therefore pneumothorax can mimic pneumomediastinum or pneumopericardium. When air accumulates in the basal region, then it produces Page 10 of 24

11 increased translucency at the sulcus, giving rise to the "deep sulcus sign" of pneumothorax. Fig.: Portable CXR demonstrated bilateral pneumothoraces with bilateral intercostal chest drains in situ. There was clear demarcation of the mediastinal structures and diaphragm due to the presence of air in the pleural spaces. Page 11 of 24

12 Fig.: Left pneumothorax with intercostal chest drain on this portable CXR. In addition, there is extensive consolidation in the right lung secondary to infection. Page 12 of 24

13 Fig.: Axial CT thorax of the same patient on lung window setting demonstrating the left pneumothorax and right consolidation with air-bronchogram. The tip of the left intercostal chest drain was seen. Page 13 of 24

14 Fig.: Demonstration of the "deep sulcus" sign on the left on this portable CXR. The loculated left basal pneumothorax was better delineated with subsequent CT. Page 14 of 24

15 Fig.: Sagittal reformat of CT thorax illustrating the loculated left basal pneumothorax in the same patient. Page 15 of 24

16 Fig.: Right tension pneumothorax following attempted insertion of central venous catheter. There was marked mediastinal shift to the contralateral side. Mediastinum Pneumomediastinum can be associated with pneumothorax, surgical emphysema, recent surgery, trauma or alveolar rupture with centripetal dissection of interstitial air towards the mediastinum. It is seen as lucent line, outlining the mediastinal structures. This finding could be difficult to appreciate on a portable CXR but CT thorax delineates the pathology very well. Page 16 of 24

17 Fig.: Portable CXR showed extensive surgical emphysema. It was difficult to exclude underlying pneumothorax on plain film. There was a rim of lucency surrounding the aortic knuckle suggestive of pneumomediastinum. This was later confirmed by CT. Page 17 of 24

18 Fig.: Axial CT in lung window setting of the same patient. This confirmed the presence of a left pneumothorax and also pneumomediastinum. Mediastinal collection can be either due to pus or blood. This is seen as mediastinal widening on CXR but is rather insensitive due to the projection used in ICU patients. Other signs present include obscuration of the aortic knuckle and aortic contour, displacement of the trachea and left main bronchus. Mediastinal widening post-thoracotomy rarely needs re-exploration unless this is significant, usually more than 60% Page 18 of 24

19 Fig.: CXR showed marked mediastinal widening in a patient following recent aortic valve and aortic root replacement. Page 19 of 24

20 Fig.: Axial CT thorax confirmed presence of a large perigraft collection surrounding the aortic root replacement. Page 20 of 24

21 Fig.: Sagittal reformat of CT thorax showing the mediastinal drain positioned into the perigraft collection. Iatrogenic Complication Numerous interventional procedures are performed in ICU as part of monitoring and treating these patients. Accurate positioning of these devices is vital and CXR remains a good examination in assessing the correct positioning and any complication associated with the procedure. Page 21 of 24

22 Fig.: The nasogastric tube was in the left main bronchus. This was subsequently repositioned. Page 22 of 24

23 Fig.: Nasogastric tube was misplaced into the right lower lobe bronchus. Page 23 of 24

24 Conclusion In the form of pictorial review, we hope to demonstrate a variety of common thoracic pathologies encounter in ICU and improve the understanding of their limitations. Hence enhancing interpretation and selection of ICU patients for thoracic CT. Personal Information References Roddy LH, Unger KM, Miller WC. Thoracic computed tomography in the critically ill patient. Crit Care Med 1981;9: Ovenfors C, Hedgecock MW. Intensive care unit radiography: problems of interpretation. Radiol Clin North Am 1978;16: Henschke CI, Yankelevitz DF, Wand A, Davis SD, Shiau M. Chest Radiography in the ICU. Clin Imag 1997; 21: Savoca CJ, Gamsu G, Rohlfing BM. Chest Radiography in Intensive Care Units. West J Med 1978; 129: Khan AN, Al-Jahdali H, Al-Ghanem S, Gouda A. Reading Chest Radiographs in the Critically Ill (Part I): Normal Chest Radiographic Appearance, Instrumentation and Complications from Instrumentation. Annals of Thoracic Medicine 2009; 4(2): Mirvis SE, Tobin KD, Kostrubiak I, Belzberg H. Thoracic CT in detecting occult disease in critically ill patients. AJR 1987;148: Miller WT, Tino G, Friedburg JS. Thoracic CT in the Intensive Care Unit: Assessment of Clinical Usefulness. Radiology 1998; 209: Khan AN, Al-Jahdali H, Al-Ghanem S, Gouda A. Reading Chest Radiographs in the Critically Ill (Part II): Normal Chest Radiographic Appearance, Instrumentation and Complications from Instrumentation. Annals of Thoracic Medicine 2009; 4(3): Katzberg R, Whitehouse G, de Weese J. The Early Radiologic Findings in the Adult Chest after Cardiopulmonary Bypass. Cardiovasc Radiol 1978; 1: Page 24 of 24