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Traumatic Diaphragmatic Rupture

Published on 19/07/2015 by admin

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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

Radiographic Findings

• Radiography

image Radiographs are significantly less sensitive than CT for diaphragmatic injury, but may often be initial study performed

– Nonvisualized or abnormal diaphragmatic contour with abnormally elevated hemidiaphragm contour

image Upper diaphragmatic contour may be elevated > 6 cm above contralateral hemidiaphragm
– Presence of lower thoracic soft tissue density mass or gas density suggesting herniated abdominal viscera

image Herniation of hollow viscus (stomach, colon, small bowel with air-fluid levels) should not be confused with loculated hydropneumothorax or vice-versa
image Focal constricted gas-filled bowel loop (collar sign) may be visualized at site of diaphragmatic tear (similar to CT)
– Visualization of nasogastric (NG) tube above left hemidiaphragm with abnormal U-shaped course and tip directed back toward left shoulder
– Secondary findings include contralateral shift of mediastinum and presence of ipsilateral thoracic injuries (pneumothorax, rib fractures, pulmonary contusion, etc.)
image Pleural effusion, contusion, atelectasis, and phrenic nerve palsy can mask diaphragmatic injury

Fluoroscopic Findings

• Fluoroscopic-guided contrast studies

image Collar sign: Focally constricted (site of tear) contrast-filled bowel loop partly in thorax and abdomen

– On upper GI series or barium enema

image Rarely indicated in acute setting
image Can be useful in diagnosis of “delayed” diaphragmatic hernia
image Mostly obviated by CT

Imaging Recommendations

• Best imaging tool

image CECT with multiplanar reformations

DIFFERENTIAL DIAGNOSIS

Congenital Diaphragmatic Hernias (Bochdalek or Morgagni Hernias)

• Bochdalek hernia is a congenital defect in posteromedial diaphragm, while Morgagni hernia is a parasternal defect of anteromedial diaphragm
• Key distinction is lack of trauma history or other secondary signs of trauma adjacent to diaphragm

Eventration of Diaphragm

• Thinning of diaphragmatic muscle, which still retains its continuity and attachments to costal margin

image Usually anteromedial aspect of right hemidiaphragm
• No evidence of a discrete diaphragmatic defect, collar sign, or fallen viscus sign

Paralyzed Diaphragm

• Properly formed diaphragm that fails to contract, resulting in asymmetric elevation of involved hemidiaphragm
• Can occur due to abnormalities of brain, spinal cord, neuromuscular junction, phrenic nerve, or muscle
• No evidence of a discrete diaphragmatic defect, collar sign, or fallen viscus sign

Pleural Effusion or Pulmonary/Extrapleural Mass

• Can mimic traumatic diaphragmatic hernia on radiographs, but not on CT

PATHOLOGY

General Features

• Etiology

image 75% of cases caused by blunt trauma

– Most common cause of blunt diaphragmatic injury is motor vehicle collision (MVC)
– Other causes include fall from height or crushing blow
– Lateral impact more likely to injure diaphragm through shear injury, while frontal impact increases intraabdominal pressures which cause diaphragmatic rupture
image 25% of cases caused by penetrating trauma

– Most often due to gunshot and stab wounds
image Iatrogenic (surgery near diaphragm)
• Associated abnormalities

image Strong association with polytrauma and other major traumatic injuries (52-100% of cases)

– Left-sided blunt diaphragmatic injuries most associated with injuries to spleen
– Right-sided blunt diaphragmatic injuries associated with injuries to liver, right kidney, aorta, heart, and bones (pelvis, ribs, spine)
image Frequently associated thoracic injuries (pneumothorax, rib fractures, pleural effusion)

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Most commonly dyspnea, upper abdominal pain, and chest pain
image Physical exam may reveal bowel sounds auscultated in chest, decreased breath sounds on affected side, asymmetry of chest wall, and dullness on percussion
image Hypotension, tachycardia, and other symptoms of severe polytrauma

Demographics

• Age

image More common in young adults (more often injured in MVC and penetrating injuries)
• Gender

image M > F (due to greater incidence of trauma in males)
• Epidemiology

image 1-5% of all patients with substantial blunt abdominal or thoracic trauma
image True incidence is likely underestimated, as these injuries may be frequently missed on imaging

– Diaphragmatic injuries missed in 7-66% of cases
– Right-sided diaphragmatic injuries more likely to be missed

Natural History & Prognosis

• Complications

image Obstruction and ischemia of bowel herniated into chest
image Torsion, devascularization, and ischemia of herniated solid organs
image Lung injuries: Laceration with hemopneumothorax, pneumonia, respiratory failure
image Central venous obstruction due to mass effect from herniated structures
image Accounts for 5% of all diaphragmatic hernias

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

image Patients with diaphragmatic injury have high mortality from other severe injuries (12-42%)
image Early diagnosis and repair: Good prognosis
image Delayed diagnosis and repair: Poor prognosis

– Diagnosis delayed in a large proportion of cases
– Initial diaphragmatic injury may be missed, even at surgery, due to attention to life-threatening injuries
– In pre-CT era, many or most cases were diagnosed months after initial trauma
– Diaphragmatic injuries will not heal spontaneously without treatment
– Even if abdominal contents do not herniate into chest immediately, will eventually herniate in most patients due to negative intrapleural pressure (80% within 3 years)

image Positive pressure ventilation in acute setting may prevent herniation into chest and cause injury to be missed
– Morbidity and mortality rate: Up to 50% in visceral herniation and strangulation

Treatment

• Surgical repair of diaphragm indicated for all diaphragmatic injuries, even when small

DIAGNOSTIC CHECKLIST

Image Interpretation Pearls

• Multiplanar reformations are critical for identification of subtle diaphragmatic injuries
• Intrathoracic herniation of abdominal contents
• Fallen viscus sign: Herniated viscus is no longer supported posteriorly by injured diaphragm and falls to dependent position against posterior ribs
• Lung contusion, pneumothorax, effusion, atelectasis, and phrenic nerve palsy can mask a diaphragmatic injury

Reporting Tips

• Remember to look for subtle diaphragmatic injury in addition to more apparent visceral injuries

image
(Left) Axial CECT in a patient following MVC shows the stomach image lying too far medial, posterior, and superior, indicating herniation through the diaphragm. This is the fallen viscus sign.
image
(Right) Axial CECT in a patient after a stab wound demonstrates a splenic laceration image with hematoma, left hemothorax image, and subcutaneous emphysema image. The presence of hematoma above and below the left diaphragm was concerning for diaphragmatic injury, subsequently confirmed at surgery.
image
(Left) Coronal CECT in a trauma patient demonstrates a gap in the left hemidiaphragm with the colon image protruding into the thorax. Note the extensive enteric contrast material image throughout the left thorax due to colonic perforation.

image
(Right) Coronal T2 MR demonstrates diaphragmatic injury due to surgical error. A tear is seen in the left hemidiaphragm with the stomach image herniating into the chest. The diaphragm is identified as a low-signal curvilinear structure image with a central gap.
image
(Left) Axial CECT in a trauma patient demonstrates that the stomach is “pinched” image as it traverses a defect in the left diaphragm. Another sign of diaphragmatic rupture is the presence of abdominal fat image outside the confines of the diaphragm image (therefore, in the thorax).

image
(Right) Coronal CECT in the same patient demonstrates how coronal reformations help to visualize the diaphragmatic defect image.
image
Axial CECT at lung windows shows splenic flexure of the colon image abutting the lung and pneumothorax.

image
Axial CECT shows the spleen in a dependent position, and abdominal fat lateral to the diaphragm image.
image
Axial CECT shows the “dependent” viscus, with colon and abdominal fat lying lateral to the diaphragm image, indicating thoracic position.
image
Chest radiograph shows an “elevated,” distorted diaphragm, and high position of the NG tube image.
image
Axial CECT shows the “dependent viscus” sign as the stomach abuts the posterior ribs.
image
Coronal reformation from an axial CECT shows herniation of the abdominal contents into the left thorax. Note the constriction of the stomach image at the site of the tear.
image
Axial CECT shows the “dependent” viscus sign with the spleen and bowel abutting the posterior ribs.
image
Chest radiograph shows an “elevated” and indistinct left hemidiaphragm. The tip of the NG tube is pointed up image.
image
Chest radiograph in a 66-year-old man following a MVC shows a high and distorted left hemidiaphragm, or abnormal intrathoracic contents, with the NG tube image curled back up, indicating a high position of the stomach.
image
Axial CT in the same patient shows the “fallen” viscus sign with the stomach image lying adjacent to the spine and posterior chest wall, instead of being suspended by the left hemidiaphragm. Note the NG tube image.

SELECTED REFERENCES

1. Dreizin, D, et al. Evolving concepts in MDCT diagnosis of penetrating diaphragmatic injury. Emerg Radiol. 2014. [ePub].

 

Panda, A, et al. Traumatic diaphragmatic injury: a review of CT signs and the difference between blunt and penetrating injury. Diagn Interv Radiol. 2014; 20(2):121–128.

Patlas, MN, et al. Diaphragmatic injuries: why do we struggle to detect them? Radiol Med. 2014. [ePub].

Sprunt, JM, et al. Computed tomography to diagnose blunt diaphragm injuries: not ready for prime time. Am Surg. 2014; 80(11):1124–1127.

Dreizin, D, et al. Penetrating diaphragmatic injury: accuracy of 64-section multidetector CT with trajectography. Radiology. 2013; 268(3):729–737.

Desir, A, et al. CT of blunt diaphragmatic rupture. Radiographics. 2012; 32(2):477–498.

Kuo, IM, et al. Blunt diaphragmatic rupture—a rare but challenging entity in thoracoabdominal trauma. Am J Emerg Med. 2012; 30(6):919–924.

Dirican, A, et al. Acute traumatic diaphragmatic ruptures: A retrospective study of 48 cases. Surg Today. 2011; 41(10):1352–1356.

Atri, M, et al. Surgically important bowel and/or mesenteric injury in blunt trauma: accuracy of multidetector CT for evaluation. Radiology. 2008; 249(2):524–533.

Stein, DM, et al. Accuracy of computed tomography (CT) scan in the detection of penetrating diaphragm injury. J Trauma. 2007; 63(3):538–543.

Rees, O, et al. Multidetector-row CT of right hemidiaphragmatic rupture caused by blunt trauma: a review of 12 cases. Clin Radiol. 2005; 60(12):1280–1289.

Iochum, S, et al, Imaging of diaphragmatic injury: a diagnostic challenge? Radiographics. 2002;(22 Spec No):S103–S116. [discussion S116-8].

Larici, AR, et al. Helical CT with sagittal and coronal reconstructions: accuracy for detection of diaphragmatic injury. AJR Am J Roentgenol. 2002; 179(2):451–457.

Yao, DC, et al. Using contrast-enhanced helical CT to visualize arterial extravasation after blunt abdominal trauma: incidence and organ distribution. AJR Am J Roentgenol. 2002; 178(1):17–20.

Bergin, D, et al. The “dependent viscera” sign in CT diagnosis of blunt traumatic diaphragmatic rupture. AJR Am J Roentgenol. 2001; 177(5):1137–1140.

Killeen, KL, et al. Helical CT of diaphragmatic rupture caused by blunt trauma. AJR Am J Roentgenol. 1999; 173(6):1611–1616.

Shackleton, KL, et al. Traumatic diaphragmatic injuries: spectrum of radiographic findings. Radiographics. 1998; 18(1):49–59.

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