imaging of thoracic trauma

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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


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


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


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


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


Tube/line Malposition

Right mainstem bronchial intubation


Tube/line Malposition

Left chest tube – chest wall placement


Pneumothorax on Supine CXR

•  Deep sulcus •  Hyperexpanded

hemithorax •  Increased lucency •  Increased

sharpness of heart border

•  Subcutaneous emphysema


Pneumothorax on Supine CXR

12 hours later


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


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


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


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).


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


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


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


Pleural Evaluation

•  Perihepatic and perisplenic views of FAST must include “pleural cavity”


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


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)


Detection of Pneumothorax: Principles •  “Air rises, water descends”

– Dependent disorders: effusion, consolidation – Nondependent disorders: pneumothorax,

interstitial process


Normal Appearance: Evaluate for Pneumothorax - EFAST

•  Sagittal view at mid-clavicular line “bat-sign” – Lung sliding? – A-line sign? – Lung point?


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


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


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


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.


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


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


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


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


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


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


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


Cautions

•  Satisfaction of search •  Subtle signs

•  CXR is a “screening” exam. Rarely it is diagnostic of an injury


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


Azizzadeh A et al. J Vasc Surg 2009


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


Most common location = aortic isthmus (90%)

Pseudoaneurysm and periaortic hematoma


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


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


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


(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


(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”


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


•  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


Injuries with paraspinal hematoma in upper T can simulate mediastinal widening (findings of TAI)


Diaphragmatic Trauma

•  5% blunt thoracic trauma •  Left > right •  70% initially missed


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


Diaphragmatic Trauma CT Signs Direct discontinuity (“tear”) of diaphragm Herniation of abdominal contents above diaphragm Collar sign Dependent viscera sign

Collar sign


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


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


Flail Chest

•  > 3 consecutive segmental rib fractures

•  Anterior, posterior or costosternal segments

•  Paradoxical motion of chest wall respiratory compromise


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


Heart Injury

•  Mostly myocardial contusion •  Less common

– Pericardial laceration – Rupture of myocardium – Rupture of valve – Laceration of coronary artery


Heart Injury

•  Hemopericardium •  Pneumopericardium •  Pericardial laceration


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

imaging of thoracic trauma

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