Radiological Category: Trauma
Principal Modality (1): General Radiography
Principal Modality (2): CT
Case Report
Author:
Jeff Rhodes, MSIV
Date:
24 August, 2010
Case History
JB is a 30 year old male who presented to Hermann Emergency Department after
moderate speed motor vehicle collision in which he was an unrestrained
passenger vs. an 18 wheeler truck . He had multiple injuries involving the face,
extremities, and pelvis. He did have loss of consciousness at the scene, but
was conscious on arrival. No known past medical history.
Radiological Presentations
Radiological Presentations
Abnormal contour of left paraspinal line
Widened right paratracheal stripe
Loss of contour of descending aorta
Differential Diagnosis
Most common causes of a widened mediastinum:
•MOST COMMON: False positive, especially on portable AP films
•Associated with trauma:
•Vascular insult/hematoma
•Esophageal rupture
•Non-traumatic:
•Aortic aneurysm
•Anterior masses: thyroid CA/goiter, thymus/thymoma,
lymphadenopathy, germ cell tumor
• Posterior masses: neurogenic tumors, lymphadenopathy
Signs of mediastinal hematoma on chest radiograph
1. widened mediastinum (>8cm at aortic arch, or subjective)
2. irregularity or obstruction of aortic arch margin
3. deviation of trachea to the right of the T4 spinous process
4. deviation of an NG tube to the right of the T4 spinous process
5. left apical cap
6. depression of left main stem bronchus (>40o below the horizontal )
7. widening of left paraspinal interface (>5mm)
8. widening of right paraspinal interface (subjective)
9. loss of contour of descending aorta
10. thickening of right paratracheal stripe (>4mm)
***Negative predictive value of normal chest radiograph is 96% for supine views and
98% for erect views.
Next Step
What radiographic study do you want to order next??
Chest CT with contrast
Radiological Presentations
Radiological Presentations
Radiological Presentations
Radiological Presentations
Radiological Presentations
Radiological Presentations
Radiological Presentations
CT Findings
There is an outpouching of the descending aorta distal to the left subclavian artery
measuring 4.6 cm in the craniocaudal dimension consistent with a traumatic
pseudoaneurysm. Mediastinal hematoma is also noted surrounding the aortic arch and
descending aorta.
There are bilateral pleural fluid collections, left greater than right, consistent with
hemothoraces
Other findings that are not shown and will not be discussed: pericardial fluid which
may represent hemopericardium; hypodense area near porta hepatis consistent with
grade 3 liver laceration; right lateral nondisplaced sixth rib fracture; mildly displaced
left anterior seventh rib fracture
Diagnosis
Traumatic aortic pseudoaneurysm with mediastinal hematoma
Definition: a pseudoaneurysm forms when the intima and media are ruptured, but the
adventitia remains intact, resulting in an outpouching of the aorta.
Discussion
Trauma commonly resulting in thoracic aortic injury: rapid deceleration injury and
crushing chest injury
Several forces may contribute to aortic injury:
- shearing stress: aortic arch is relatively mobile and the
descending
aorta is fixed, so they decelerate at different rates
- bending stress: occurs with flexion of the aorta over the left
pulmonary artery and left main-stem bronchus
- osseous pinch theory: aorta is squeezed between anterior bony
structures (manubrium, clavicle, first rib) and the spine
posteriorly
- water-hammer effect: sudden increase in intra-aortic pressure
which may cause rupture into the pericardium
Discussion
Relationship between mediastinal hematoma and aortic injury
- Aortic injury is the cause of mediastinal hematoma in only 12.5% of cases.
- Usually, mediastinal hematoma is not directly caused by aortic injury
- In these cases, hematoma is formed due to rupture of smaller vessels in the
mediastinum.
Lines and Stripes
Interrelationships of various structures in the lung, mediastinum, and pleura form
several recognizable “lines and stripes” that may appear on a normal chest
radiograph. Abnormal appearance of any of these warrants further investigation.
They include:
-Anterior and posterior junction lines
-Right and left paratracheal stripes
-Aortic-pulmonary stripe
-Aortopulmonary window
-Right and left paraspinal lines
-Posterior tracheal stripe
-Azygoesophageal recess
-Posterior wall of the bronchos intermedius
Lines and Stripes
Right paratracheal stripe – formed by lateral border of trachea, adjacent
mediastinal fat, and pleura of right upper lobe outlined by air in the trachea and in
the right lung. Normally no more than 4mm. Present in most normal radiographs.
Most common causes of abnormal right
paratracheal stripe:
-pleural disease
-lymphadenopathy
-thyroid or parathyroid neoplasms
-tracheal carcinoma or stenosis
-hematoma
Lines and Stripes
Radiological Presentations
Widened right paratracheal stripe
Lines and Stripes
Left paraspinal line – formed by contact of the left lung and pleura with posterior
mediastinal fat, left paraspinal muscles, and adjacent soft tissues. It extends from
aortic arch to the diaphragm.
Most common causes of abnormal
left paraspinal line:
- osteophytes
- prominent mediastinal fat
- tortuous descending aorta
- mediastinal hematoma
- mass
- esophageal varices
Lines and Stripes
Radiological Presentations
Abnormal contour of left paraspinal line
9 days s/p stent placement
References
Gibbs JM, Chandrasekhar CA, Ferguson EC, Oldham SA. Lines and Stripes: Where Did
They Go? – From Conventional Radiography to CT. Radiographics January-February
2007; 27:33-48.
Creasy JD, Chiles C, Routh WD, Dyer RB. Overview of traumatic injury of the thoracic
aorta. Radiographics January 1997; 17:27-45.
Herring, William. Learning radiology. Philadelphia, PA: Mosby, 2007. 112-120. Print