Traumatic Diaphragmatic Rupture

Published on 19/07/2015 by admin

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Last modified 19/07/2015

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 Discontinuity of hemidiaphragm with focal defect (segmental diaphragmatic defect)

image Dangling diaphragm sign: Free edge of torn diaphragm curls inward on axial images rather than continuing its normal course parallel to chest wall
image Absent diaphragm sign: Absence of diaphragm in expected location without visualization of discrete tear
image Herniation of abdominal contents through a discrete diaphragmatic defect
image Collar sign: Waist-like narrowing of herniated structure as it extends through diaphragmatic tear
image Fallen or dependent viscus sign: Herniated viscus abuts posterior ribs and thoracic wall without intervening lung
image Secondary signs of injury include simultaneous presence of pneumothorax and pneumoperitoneum or hemothorax and hemoperitoneum, active extravasation of contrast in or near diaphragm, or injuries to organs lying near diaphragm

PATHOLOGY

• 75% of cases caused by blunt trauma, and 25% caused by penetrating trauma
• Strong association with polytrauma and other major traumatic injuries

CLINICAL ISSUES

• 1-5% of all patients with substantial blunt abdominal or thoracic trauma
• True incidence is likely underestimated, as these injuries may be frequently missed on imaging
• Surgical repair of diaphragm indicated for all diaphragmatic injuries, even when small
image
(Left) Chest x-ray in a young man following a motor vehicle crash shows a pneumothorax, chest tube, and an NG tube image that is curved up toward the chest.

image
(Right) Axial CT in the same patient shows the typical signs of diaphragmatic injury, including the fallen viscus sign. The stomach image lies in the chest. Note that it has “fallen” medially and posteriorly to lie against the posteromedial chest wall. The stomach appears pinched image as it traverses the defect in the diaphragm (collar sign).
image
(Left) Axial CECT shows the stomach in the thorax, and it has “fallen” through the diaphragmatic defect to lie against the posteromedial chest wall. The anterior wall of the stomach image directly abuts the lung, and is not confined by the diaphragm.

image
(Right) Coronal CECT in the same patient demonstrates the stomach image extending upward through a diaphragmatic defect.

TERMINOLOGY

Synonyms

• Traumatic diaphragmatic hernia

Definitions

• Diaphragmatic rupture ± herniation of abdominal contents into thorax

IMAGING

General Features

• Best diagnostic clue

image Discontinuity of hemidiaphragm with fallen or dependent viscus sign
• Location

image 90-98% occur on left side (usually posterolateral part of diaphragm, medial to spleen)

– Left hemidiaphragm has weaker pleuroperitoneal membrane, while right hemidiaphragm is protected by liver
• Size

image Blunt trauma

– Most tears are large (> 10 cm in length)
image Penetrating trauma

– Gunshot wounds (blast injuries) → large defects in diaphragm
– Stab wounds → shorter lacerations (usually 1-2 cm)

image More likely to have delayed diagnosis
image Initial short laceration may be overlooked, but will often enlarge over time
• Morphology

image Curvilinear lacerations
• Key concepts

image Due to blunt and penetrating trauma
image Occur in 1-5% of all blunt trauma victims
image Accounts for 5% of all diaphragmatic hernias

– Hiatal, Bochdalek, and Morgagni hernias are much more common
image 90% of all strangulated diaphragmatic hernias are due to trauma

CT Findings

• Multiple different direct and indirect signs of diaphragmatic injury, each with variable sensitivity and specificity 

image Discontinuity of hemidiaphragm with focal defect (segmental diaphragmatic defect)

– Free edge of diaphragm may appear thickened and hypoenhancing due to muscle retraction or hemorrhage
– Should be carefully differentiated from a chronic diaphragmatic defect unrelated to trauma
– Diaphragm may appear abnormally hypoenhancing
image Dangling diaphragm sign: Free edge of torn diaphragm curls inward on axial images rather than continuing its normal course parallel to chest wall
image Absent diaphragm sign: Absence of diaphragm in expected location (without visualization of discrete tear)
image Herniation of abdominal contents through discrete diaphragmatic defect

– Herniated organs: Stomach > omentum, colon, small bowel, spleen, liver
image Collar sign: Waist-like narrowing of herniated structure as it extends through diaphragmatic tear

– Often easier to appreciate on coronal multiplanar reformats
– May be associated with hump sign: Unusual contour of liver as it extends through diaphragmatic defect, often with a band-like region of hypoperfusion of liver at base of hernia
image Fallen or dependent viscus sign: Herniated viscus abuts posterior ribs and thoracic wall without intervening lung
image Abdominal contents lateral to diaphragm on axial images
image Active extravasation of contrast in or near diaphragm
image Secondary signs of injury include simultaneous presence of pneumothorax and pneumoperitoneum or hemothorax and hemoperitoneum, active extravasation of contrast in or near diaphragm, or injuries to organs lying near diaphragm

– Trajectory of penetrating injury can often be surmised from other injuries and ectopic gas, and can increase suspicion for diaphragmatic injury
• Diaphragmatic rupture remains difficult diagnosis on CT, with reported sensitivities as low as 73% and specificities as low as 50%

image Multiplanar reformations are critical to diagnosis, and partially explain superior performance of modern MDCT compared to pre-MDCT technology

MR Findings

• Normal diaphragm on T1- and T2WI appears as a continuous hypointense band

image Diaphragm is generally easier to visualize on MR than on CT, but MR is usually more appropriate for evaluation of stable patient, not in acute trauma setting
• Imaging findings parallel those on CT
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