imaging of thoracic trauma
TRANSCRIPT
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Imaging of Thoracic Trauma
Rathachai Kaewlai, MD Ramathibodi Hospital, Mahidol University, Bangkok Emergency Radiology Minicourse 2013 Slides available at RiTradiology.com or Slideshare.net/rathachai
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Introduction • Trauma leading cause of death in
developing countries | 4th in first-world countries
• Loss of productive years of life – because most occur in young individuals
• Traffic accidents, falls, recreational, violence
• Rapid diagnosis important to avoid morbidity and mortality
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Introduction • Thoracic injuries
– 10-15% of all trauma – 25% of trauma fatalities
• Blunt (70-80%) > penetrating – Compression thoracic wall injuries – High velocity injury visceral injuries
• Rx mostly conservative. Thoracotomy rate... – <10% in blunt thoracic trauma – 15-30% in penetrating thoracic trauma
Image from http://www.veomed.com/va041842172010
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Initial Assessment
• Primary survey – Airway (prevent hypoxia, stridor = UAO) – Breathing (tension ptx, open ptx, flail chest) – Circulation (BP, pulse monitor, arrhythmia,
massive hemothorax, cardiac tamponade) • Secondary survey
– Others
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Imaging Survey
• Portable CXR – Tube/line malposition – Large pneumothorax, hemothorax – Flail chest – Mediastinal widening (suspected aortic injury)
• Ultrasound (as a part of extended FAST) – Pericardial effusion (presumed
hemopericardium) – Pneumothorax / hemothorax
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Portable Trauma CXR
• Tube and line malposition – most critical • Large pneumothorax • Large hemothorax • Flail chest • Mediastinal widening • Other important things:
pneumomediastinum, diaphragm injury, unstable spine fractures
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Tube/line Malposition
Right mainstem bronchial intubation
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Tube/line Malposition
Left chest tube – chest wall placement
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Pneumothorax on Supine CXR
• Deep sulcus • Hyperexpanded
hemithorax • Increased lucency • Increased
sharpness of heart border
• Subcutaneous emphysema
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Pneumothorax on Supine CXR
12 hours later
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Tension Pneumothorax
• One-way valve • Mediastinum displaced to other side
– Decreasing venous return – Compressing opposite lung
• Clinical diagnosis! (air hunger, respiratory distress, tachycardia, hypotension, tracheal deviation, JVD, etc)
• Immediate decompression needed
Image from freedictionary.com
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Tension Pneumothorax
• Hyperexpanded chest • Shift of mediastinum • Depression of
hemidiaphragm • Sometimes we can
see it on imaging – Can be insidious, esp
in mechanical ventilation
Postmortem CXR. Image from trauma.org
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Flail Chest
• Most significant chest wall injuries • Paradoxical movement of a segment
of chest wall • Problems of underlying lung contusion
and pain leading to hypoxia • 3 or more contiguous segmental rib
fractures • Variations include anterior flail,
posterior flail and flail including sternum
• CXR may not show all fractures, esp anterior and lateral fractures
Images from wikipedia
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Flail Chest
Anterior rib fractures difficult to see on CXR Pneumothorax doesn’t clear even after chest tube placement.
3D CT shows displaced right rib fractures (note absent rib attachment to the sternum (green arrows).
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Hemothorax
• Blood in pleural space • Source: chest wall, lung
parenchyma, heart or great vessels • Chest wall injuries can cause
bleeding from intercostal and IMA • As much as 1,000 mL of blood may
be missed when viewing portable supine CXR (400-500 mL required for blunt CP angle on upright CXR)
• Massive hemothorax – >1,500 mL of blood or – > 1/3 of blood volume
Supine CXR: apical capping, lateral extrapleural density
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Trauma Ultrasound: FAST
• FAST includes pericardial and pleural spaces evaluation
• Fluid in acute trauma = blood until proven otherwise
• Straightforward, “Yes/No” answer • Pericardial evaluation is very important
and should be the first part of all FAST scans, esp. penetrating trauma
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Pericardial Evaluation
• Presence of pericardial fluid • Source of blood
– Great vessels – Heart – Pericardial vessels
• Tamponade physiology? – Collapsed right heart chambers: right atrium – sensitive,
right ventricle - specific – Distended IVC (caval index = 1)
• Key elements of tamponade – Rate of fluid accumulation – Effectiveness of compensatory mechanisms
Nypemergency.org
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Pleural Evaluation
• Perihepatic and perisplenic views of FAST must include “pleural cavity”
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Pleural Evaluation Extended FAST (EFAST) • Best resolution of pleural interface with high-
resolution probe and small footprint • But most practical using same probe as FAST
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Detection of Pneumothorax • Pneumothorax occult on CXR in 29-72% • EFAST can identify pneumothorax before CXR • Identify contiguity of visceral and parietal pleura
using simple US signs – To exclude pneumothorax – Extended FAST (EFAST) – Normal = lung sliding (B), seashore sign (M mode) – Abnormal = loss of lung sliding (B), stratosphere (M),
lung point (B & M)
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Detection of Pneumothorax: Principles • “Air rises, water descends”
– Dependent disorders: effusion, consolidation – Nondependent disorders: pneumothorax,
interstitial process
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Normal Appearance: Evaluate for Pneumothorax - EFAST
• Sagittal view at mid-clavicular line “bat-sign” – Lung sliding? – A-line sign? – Lung point?
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Detection of Pneumothorax
• Normal lung sliding – Twinkling at level of
pleural line in real time – Sliding of visceral
against parietal pleura – Relative motionless of
chest wall to lungs – Seashore appearance
on M-mode
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Pneumothorax: Loss of Lung Sliding • Sensitivity 80-100%
(lower in trauma) • Specificity 83-100%
• Real-time US • M mode = Barcode or
stratosphere sign
Barcode sign
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Pneumothorax:
A line sign • Seeing A-line with loss of
lung sliding suspect pneumothorax
• One B-line can R/O pneumothorax where probe is applied
Lung point • Most specific sign • At border between
aerated lung and ptx, there is intermittent appearance of lung sliding during inspiration/expiration
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Looking for Pneumothorax on US
Lung sliding?
Yes Pneumothorax ruled out
No B-lines?
Yes
No Lung Point? No Use other
tools
Yes
Pneumothorax
Adapted from Lichtenstein D.
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Detection of Pneumothorax
• Absent lung sliding – Sensitivity 100%, specificity 78%
• Absent lung sliding + A line sign – Sensitivity 95%, specificity 94%
• Lung point – Specificity 100%
• EFAST more sensitive than portable CXR trauma
Lichtenstein DA et al. Crit Care Med 2005
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Pitfalls of US on Pneumothorax
• “Loss of lung sliding” alone is not specific for pneumothorax – Pleural adhesion/thickening – Atelectasis – Lobec/pneumonectomy – One-lung intubation
• Look for “Lung Point” • Comparison with contralateral lung
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CT in Thoracic Trauma
• Role of CT used to be for R/O thoracic aortic injury
• Now CT believed to be most accurate for diagnosis several thoracic trauma
• Yield of CT is higher when done after an abnormal initial CXR or performed selectively based on clinical criteria
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Patient Preparation for CT
• Hemodynamic – must be stable • NPO – should not wait • IV contrast – a must (if conditions allow) • Renal function test – risk/benefit ratio • Pregnancy test - yes
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CT Technique • Helical mode • Thinnest collimation possible and reformatted
to 2-2.5 mm for viewing • 120 kV • Automatic tube current modulation • No plain scan • Late arterial phase + delays at site of
vascular injuries • Routine coronal and sagittal reformations
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What Else We Are Looking For?
• ABC’s of Jud W. Gurney (chestx-ray.com) – Systematic evaluation of blunt thoracic trauma – A, B, C, D, E, F, G, H, I
• Missed diagnosis – 4% died within 24 hours – 30% missed interpreted
• Aortic injury • Diaphragmatic trauma • Flail chest
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ABC’s Approach* Aortic injury
Bronchial injury Cord injury
Diaphragm injury Esophageal tear
Flail chest Gas (pneumothorax) Heart (cardiac injury)
Iatrogenic tube/line malposition
*Borrowed from Jud W. Gurney MD FACR
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Cautions
• Satisfaction of search • Subtle signs
• CXR is a “screening” exam. Rarely it is diagnostic of an injury
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Aortic Injury (TAI)
• 16% MVA fatalities • 85-90% mortality prior to reaching hospital
– Survivors • 30% died within 6 hours • 50% died within 24 hours • 72% died within 8 days • 90% died within 4 months
uvahealth.com
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Azizzadeh A et al. J Vasc Surg 2009
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Aortic Injury (TAI)
CXR Signs of TAI Mediastinal widening (>8 cm at aortic arch level, or by visual assessment) Loss of AP window, descending T-aorta Tracheal shift to the right of T4 SP NG tube displacement to the right Widened paraspinal or right paratracheal stripes Left apical pleural cap sign Normal (10-15%)
For CXR: PPV 10%, NPV 98% but TAI is life-threatening, keep low threshold for CT
X-ray signs are related to mediastinal hematoma
>8 cm
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Most common location = aortic isthmus (90%)
Pseudoaneurysm and periaortic hematoma
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Aortic Injury (TAI)
• Indirect CT signs – Periaortic hematoma
• Direct CT signs – Pseudoaneurysm – Intimal flap – Intimal irregularity – Pseudocoarctation – Extravasation
• Term “traumatic dissection” is discouraged (confusing with aortic dissection related to hypertension)
Pseudoaneurysm and periaortic hematoma
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Aortic Injury (TAI)
• Periaortic mediastinal hematoma – Small veins in area of injury or vasa vasorum – Does not arise directly from aorta tear – Usually adjacent to aoric arch and prox descending
aorta, but may tracts down descending aorta to diaphragm (retrocrural)
Retrocrural hematoma seen on abdominal CT without clear etiology (ie, spine fracture)
should raise a concern for TAI
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Aortic Injury (TAI) • Transesophageal echocardiography (TEE)
– Heart (for contusion) and t-aorta – More invasive than CT and usu requires sedation – Blind spots: arch, arch vessels, distal ascending aorta – May be used intraoperatively
• Catheter aortography – Prior gold standard, now reserved for selected cases
and for endovascular Rx
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(Tracheo)Bronchial Injury
• 1.5% of major thoracic trauma • 30% missed • 80% within 2.5 cm of carina
J R Coll Surg Edin 1999
Persistent or Progressive Pneumothorax or Pneumomediastinum
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(Tracheo)Bronchial Injury
• Traumatic pneumomediastinum: must exclude – Airways injuries (larynx, tracheobronchus) – Esophageal injuries
• Bronchoscopy gold standard
• However, most are benign – Extension of pneumothorax
through pleural tear – Pulmonary alveolar rupture
“Macklin effect”
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Cord Injury
• 25% spine fractures • 90% neurologic injury • Most common site = T9-11
– Critical zone – Transition of facet joint orientation: T facets face
inward, L facets face outward • Difficult assessment on trauma CXR
– Portable technique – Rule of 2’s
Thoracic spine fractures often causes spinal cord injury because cord is large in
relation to the canal
Image from superhuman.net.au
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• On AP view, look at pedicles and spinous processes
• Everything no more than 2 mm from one level to the next – Interspinous space – Interpedicular distance
• Elevated paravertebral stripes – Also sign of TAI
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Injuries with paraspinal hematoma in upper T can simulate mediastinal widening (findings of TAI)
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Diaphragmatic Trauma
• 5% blunt thoracic trauma • Left > right • 70% initially missed
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Diaphragmatic Trauma
CXR Signs Diaphragmatic elevation Abdominal organ in thorax NG tube in thorax Basilar lung opacities/hemothorax Mediastinal shift Distorted diaphragm contour Lower rib fracures
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Diaphragmatic Trauma CT Signs Direct discontinuity (“tear”) of diaphragm Herniation of abdominal contents above diaphragm Collar sign Dependent viscera sign
Collar sign
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Esophageal Perforation
• Very rare injury • Upper esophagus most common location
Suspect this injury when pneumomediastinum is present in a
trauma patient ---
Next step is CT or water-soluble contrast esophagogram
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Flail Chest
Rib fractures • Most common findings after blunt
chest trauma • CXR sensitivity 18-50% • Most common = rib 4-9
– Rib 1-3 neurovascular injury – Rib 9-12 liver, spleen, kidney
• Absence of fracture lines: – In adults >65 years may warrant rib series. – In children, it does not mean mild injuries because of
pliable ribs
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Flail Chest
• > 3 consecutive segmental rib fractures
• Anterior, posterior or costosternal segments
• Paradoxical motion of chest wall respiratory compromise
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Gas (Pneumothorax) • 15-40% of cases
CXR Signs on Supine View Deep sulcus Sharp cardiac borders Basilar hyperlucency Visualized pericardial fat tags
Deep sulcus sign
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Heart Injury
• Mostly myocardial contusion • Less common
– Pericardial laceration – Rupture of myocardium – Rupture of valve – Laceration of coronary artery
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Heart Injury
• Hemopericardium • Pneumopericardium • Pericardial laceration
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Conclusions
• Portable CXR: Tube/line position, hemo-pneumothorax, flail chest, mediastinal widening
• US: hemothorax, pneumothorax • CT: aortic injury, diaprhagm and
tracheobronmchial injury • Use CT with a lower threshold especially if initial
CXR is abnormal – IV contrast needed – Coronal and sagittal reformats needed