RSNA 2002 Refresher Course "Imaging of Chest trauma"

Course #408

Imaging in the Assessment of Blunt Chest Trauma-Notes

Eric J. Stern, M.D.

Harborview Medical Center

University of Washington

CXR-Initial Assessment

Part of the "HMC trauma series"-c/spine, CXR, AP pelvis

In conjunction with the ATLS ABC¹s o Helps guide resuscitation efforts

1) Detect potential life threatening injuries/problems

2) Monitor intervention/support devices

3) Detect other--non-life threatening abnormalities

Accept the Limitations of the Test

Supine CXR can miss life-threatening abnormalities

Some abnormalities can mask others Potential Life-Threatening Injuries Detectable by CXR

Pneumothorax

Hemothorax

Aortic injury

Cardiac injury/Tamponade

Pulmonary contusion

Tracheobronchial disruption

Other Severe Injuries Detectable by CXR

Sternoclavicular dislocation

Scapulothoracic dissociation

Diaphragm rupture

Pneumoperitoneum

Iatrogenic misadventures

Diffuse lung injury

Other Important, Detectable Non-Life Threatening Injuries

Rib fractures/flail chest

Extremity fractures

Thoracic spine fractures

Pulmonary lacerations

Aspirations

The Really, Really, Important Don¹t miss findings

Typically easily corrected

1) Iatrogenic misadventures

2) Pneumothorax Iatrogenesis Imperfecta

ETT malposition/Esophageal intubation

Thoracostomy tube malposition

Venous access line malposition

Other

Pneumothorax

Up to 40% of blunt chest injuries

Supine position makes detection difficult

Direct signs ­ Pleural line: lucent pleural separation o Indirect signs ­ Deep sulcus ­ +/- associated rib fx Hemothorax

Pleural fluid assumed to be blood

Small ­ difficult to detect in supine position

Large ­ Opaque pleural separation (apex more sensitive?) ­ Diffuse opacity of hemithorax ­ +/- associated rib fx Aortic Injury

Mediastinal hemorrhage :

­ A marker of energy absorption

Absence excludes aortic injury with about 99% certainty

Detection ­ Sometimes easy/sometimes hard

"Well-recognized" Signs of Mediastinal Hemorrhage

widened mediastinum (>8 cm)

aortic "knob" obliteration

AP window opacification

left apical pleural cap

trachea to the right

ET tube or NG tube to the right o depression of left mainstem bronchus

widened paraspinous "stripe"

left hemothorax

Mediastinal "Widening"

Mediastinal hemorrhage

Position- Supine

Obesity

Fluid status-resuscitation

Projection

Can we rely on mediastinal widening on CXR to identify subjects with aortic injury?

1) CXR normal or not normal? A Gestalt Read

2) is mediastinum widened?

CXR: 30 with ATAI/47 controls o 6 radiologists blinded to diagnosis

Agreement, sensitivity, and specificity Results

Agreement for overall assessment was substantial (kappa=0.64)

Individual sensitivity from 0.77 to 0.97

Individual specificity from 0.62 to 0.89

"Widening" agreement was moderate (kappa=0.49)

"Widening" was less sensitive than the radiologists¹ overall impression (p=0.01)

sensitivity from 0.50 to 0.83

no difference in specificity (p=0.36), from 0.81 to 0.94

Conclusions

"Mediastinal width" has unacceptable sensitivity for predicting aortic injury (0.50-0.83)

Substantial inter-reader variability

Ingrained and widely promoted concept of mediastinal widening may be misleading

Ho RT, Blackmore CC, Bloch RD, Hoffer EK, Mann FA, Stern EJ, Wilson AJ.

Can we rely on mediastinal widening on chest radiography to identify subjects with aortic injury?

Emergency Radiology (in press)

CT Signs of ATAI

hemorrhage contiguous with the aorta

aortic pseudoaneurysm just beyond the left subclavian artery

aortic intimal flap or divided lumen

irregular aortic contour o pseudocoarctation (sudden decreased caliber of descending thoracic aorta)

Case Study AJR Trauma Case from Harborview Medical Center

38-year-old woman o restrained (lap-belted) driver in a rollover MVC

c/o mild abdominal and back pain

CXR showed right PTX and left pleural effusion

CT scan at level of diaphragmatic crura ­ descending thoracic aortic pseudoaneurysm ­ intimal flap ­ periaortic hematoma

Aortogram confirmed aortic injury 1 cm proximal to the celiac axis

most common location of ATAI (survivors) is the aortic isthmus (80-90%)

5-9% ascending aorta

1-3% distal tears at the diaphragmatic hiatus

high association with nearby spinal fractures

flexion and extension forces cause fracture?

direct laceration by fracture fragments?

Pitfalls in DX of Aortic Injury

AJR Trauma Case from Harborview Medical Center

30-year-old woman in motorcycle crash

Abnormal CXR

CT scan chest showed ­ normal aorta ­ multilevel T-spine fx Spine Fracture and Mediastinum

100 patients with mediastinal hemorrhage

Spine fractures/dislocations caused mediastinal hemorrhage in 9 patients

J Trauma 1988 Jun;28(6):789-93

Spinal fractures in blunt chest trauma.

Woodring JH, Lee C, Jenkins K

Pulmonary Contusion

Marker of high energy absorption

Can be extensive: ­ dyspnea ­ tachycardia ­ hypoxemia--potentially lethal Pulmonary Contusion

Common in MVC (up to 25%)

Usually develops within 6 hours of injury--can be insidious o Risk factor for acute lung injury

Mask underlying injury

Masked by other injuries

Independent injury

Resolve to normal

Basilar contusions/lower rib fx: marker of intra-abdominal injury

Diaphragm Rupture

1-6% of severe blunt trauma

Rarely isolated injury

Prevalence R v. L?

Dx can be delayed for several reasons

Associated HTX, hemoperitoneum, ATX, other compelling abdominal injuries

Imaging diagnosis can be difficult (accuracy 20-50%)

Sine qua non: GI viscera within thorax

Apparently elevated but distorted hemidiaphragm

Dx aided by passage of a nasogastric tube or barium

CT scan most helpful? ­ need strong clinical suspicion ­ appropriate mechanism of injury

"Bergqvist Triad"

6 diaphragmatic ruptures, 435 consecutive cases of BAT (1946-1976) -all MVC

3 patients "a rather specific injury combination occurred--diaphragmatic rupture, multiple costal fractures, and pelvic or vertebral fracture"

Multiple injuries above and below the diaphragm should raise suspicion for diaphragm injury

J Trauma 1978;18:781-783

Rupture of the diaphragm in patients wearing seatbelts.

Bergqvist D, Dahlgren S, Hedelin H.

Why does the GI viscera herniate into the thorax?

Confounding Variable: Intubation and positive pressure ventilation

May prevent herniation of abdominal organs until weaning is achieved

So-Called "Delayed Rupture"

Retrospective review of 166 patients (ADI ) over 8 years

6 patients: herniation of stomach above the diaphragm when high levels of ventilator support were decreased

Diaphragmatic injuries cannot be excluded if patients are intubated

Chest radiographs should be reviewed in sequence as ventilator support is decreased

Am Surg 2002 Feb;68(2):167-72

The impact of positive pressure ventilation on the diagnosis of traumatic diaphragmatic injury.

Karmy-Jones R, Carter Y, Stern EJ

CT Findings of Diaphragmatic Rupture

The more traditional thinkingŠŠ...

Constriction of herniated viscera

"Collar" sign o Suggestive signs: ­ co-existing hemothorax + hemo/pneumoperitoneum

Diaphragmatic defect (about 75% of cases)

Herniation of omental fat is common

Visceral herniation ­ stomach and left colon most frequent (about 60%) ­ Any abdominal organ may herniate

Helical CT Findings of Diaphragmatic Rupture

84% sensitive, 77% specific

Coronal and sagittal reconstructions of limited use

Crus measurements not helpful

Recommend familiarity with all signs

Most sensitive sign--dependent viscera

CT: Dependent Viscera Sign

upper one third of the liver abuts the posterior right ribs

bowel or stomach lay in contact with the posterior left ribs

83% sensitive R-sided rupture

100% sensitive L-sided rupture

Bergin D, Ennis R, Keogh C, Fenlon HM, Murray JG.

The "dependent viscera" sign in CT diagnosis of blunt traumatic diaphragmatic rupture.

AJR 2001;177:1137-40

Beyond the Initial Assessment

Pulmonary Lacerations:

frank disruption of lung tissue

localized internal leak of ­ air (pneumatocele) ­ blood (hematoma) variable quantities

spherical or elliptical due to inherent lung elasticity

variable appearance over time

CT can define mechanism of injury

Compression Rupture

Shear

Puncture

Adhesion tear

Radiology 1988;167:77-82

Classification of parenchymal injuries of the lung.

Wagner RB, Crawford WO Jr, Schimpf PP

AJR Trauma Case from Harborview Medical Center

19-year-old in high speed MVC

mild respiratory distress

SQ emphysema

decreased R-sided breath sounds

supine CXR large R- PTX, R- 1st rib and clavicle fractures

pneumomediastinum

Tube thoracostomy, large air leak, persistent PTX

CT scan, persistent large R- PTX, pneumomediastinum, and tracheal rupture

Operative bronchoscopy confirmed the injury, primarily repaired

Tracheobronchial Rupture

classic radiographic triad

1) SQ emphysema

2) persistent or progressive PTX

3) pneumomediastinum

85% within 2.5 cm of carina

Equal involvement, R=L

Chest Wall Injuries

The Significance of Scapular Fractures

rib fractures, 53.6%

pulmonary contusions, 53.6%

clavicular fracture, 26.8%

brachial plexus injury, 12.5%

subclavian, brachial, or axillary artery injury, 10.7%

J Trauma 1985 Oct;25(10):974-7

The significance of scapular fractures.

Thompson DA, Flynn TC, Miller PW, Fischer RP

Scapulothoracic Dissociation

Closed forequarter amputation ­ Disruption of muscular attachments ­ Brachial plexus ­ Vascular supply

Sternoclavicular dislocation

Diastatic clavicle, scapula fracture

Extrapleural hematoma

CTA, angio Post.

Sternoclavicular Dislocation

Rare (<1% of all dislocations)

Proximity to critical thoracic outlet structures

Impingement/possible injury to trachea, esophagus, underlying great vessels, and brachial plexus

Anterior and posterior‹similar radiographic findings

Often subtle‹look for apparent asymmetry in clavicular head height

CT scanning useful in quickly and accurately diagnosing

Injuries of the Sternum

direct kinetic energy absorption

indirect forces generated by flexion of the cervical and upper dorsal spine

40% of fxs associated with wedge compression fractures of the upper dorsal spine

important to exclude associated fractures of the spine

AJR Trauma Case from Harborview Medical Center

71-year-old, high-speed, MVC

left-sided hemidiaphragm rupture, left seventh rib fracture, lung contusion and splenic laceration

CXR, 4 days after injury showed a new lucency in the left lateral chest wall

CT scan showed lung herniating through the 9-10 intercostal space

Lung Hernia

Occur through ­ lung apices ­ Diaphragm ­ chest wall

Congenital

Acquired ­ trauma (typically penetrating) ­ chest wall neoplasms ­ infection

AJR Trauma Case from Harborview Medical Center

72-year-old woman

restrained driver in a high-speed, head-on, rollover MVC

CXR showed asymmetrically enlarged left breast

CT showed a large breast hematoma with active arterial contrast extravasation

HCT dropped from 32 to 18

4 units of blood raised the hematocrit to 34, which then dropped to 20 in three hours

Repeat CT 16 hours later showed an enlarging breast hematoma

angiography, a branch of the left IMA actively bleeding

successful flow directed gel foam and coil embolization