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
Mainlyfromphysicalexam



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?



•  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.



•  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



CXR Signs
Diaphragmatic elevation
Abdominal organ in thorax
NG tube in thorax
Basilar lung opacities/
hemothorax
Mediastinal shift
Distorted diaphragm contour
Lower rib fracures



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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