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CT in blunt chest trauma: Pulmonary, tracheobronchial, and diaphragmatic injuries
CT in Blunt Chest Trauma: Pulmonary, Tracheobronchial, and Diaphragmatic Injuries Eun-Young Kang and Nestor L, MOiler Routine use of CT in the initial evaluation of blunt chest trauma is controversial. CT, however, has been shown to be useful in the diagnosis of unsuspected chest injuries and in directing therapeutic interventions. This review discusses the CT findings in patients with pulmonary, tracheobronchial, and diaphragmatic injuries after blunt chest trauma. Copyright © 1996 by W.B. Saunders Company
HEST TRAUMA accounts for approximately 20% of deaths resulting from trauma. ~Chest trauma is described traditionally as either blunt or penetrating. This distinction is based primarily on whether the chest wall remains intact or whether its integrity is breached. 2 Blunt chest trauma is much more common than penetrating trauma 1-3 and usually results from a motor vehicle accident. 1,3-6 The chest radiograph serves as the principal screening test for the immediate assessment of the thorax after blunt chest trauma. The radiograph, however, often is limited by poor or absent patient cooperation, suboptimal patient positioning, and magnification and distortion of the mediastinum on the supine view. 7 CT is helpful as a complementary imaging modality in selected cases to clarify abnormalities suspected on the chest radiograph. 7-1° CT is particularly useful in the detection of pulmonary lacerations and diaphragmatic tears. 8,11-13
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PULMONARY INJURY
Pulmonary Contusion Pulmonary contusion is present in 30% to 70% of patients with blunt chest trauma. 4,7,1°,11 Pulmonary contusion, defined as injury to lung parenchyma resulting in edema and interstitial and intraalveolar hemorrhage, usually is the result of acceleration-deceleration forces. It often occurs without gross lung laceration or a break in the pleural integument and tends to occur in the lung adjacent to solid structures,
From the Department of Radiology, University of British Columbia and Vancouver Hospital and Health Sciences Centre, Vancouver, BC, Canada. Address correspondence to Nestor L. Miiller, Department of Radiology, Vancouver Hospital and Health Sciences Centre, 855 W12th Ave, Vancouver, BC, Canada V5Z 1M9. Copyright © 1996 by W.B. Saunders Company 0887-2171 / 96 / 1702-000455. O0/ 0 114
such as ribs, vertebrae, heart, and liver. Adjacent rib fractures are seen often,3,9 more commonly in adults. 9 An estimation of the severity of the contusion is significant clinically because it correlates with the degree of post-traumatic respiratory insufficiency.4,9,1°,14In a study by Kollmorgen et al, TM 10 of 100 patients with pulmonary contusion died, 7 of whom died as a consequence of extensive pulmonary injury. Radiologically, pulmonary contusions present as areas of consolidation that tend to be peripheral, nonsegmental, and geographic in distribution. Contusions are usually evident radiographically at presentation or within 6 hours. The short time interval is helpful in differentiating contusions from a fat embolism, which may appear similar but which usually is not apparent radiographically until 1 or more days after the injury. Initial clearing of lung contusions usually is apparent radiographically 48 to 72 hours after the injury. CT is superior to chest radiography in detecting pulmonary contusions5,6,830,15,16,17 and estimating their extent. 16 In a study performed in experimental animals, 16CT detected 27 (100%) of 27 pulmonary contusions, confirmed pathologically immediately after the trauma. Therefore, pulmonary contusion is highly unlikely in patients with a normal CT appearance. Pulmonary contusion is characterized on CT by the presence of localized, scattered, ill-defined areas of consolidation adjacent to the area of trauma 8-1°(Fig 1).
Pulmonary Laceration Lung laceration in blunt trauma results from shearing forces associated with trauma leading to disruption of alveolar spaces and formation of a cavitating space, usually filled with blood or air, and with consequent production of hema-
Seminarsin Ultrasound, CT, andMRI, Vo117, No 2 (April), 1996: pp 114-118
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Fig 1. Pulmonary contusion in a 42-year-old patient who had a CT scan 12 hours after a motor vehicle accident. (A) CT scan shows a localized, ill-defined area of consolidation consistent with pulmonary contusion. Characteristic peripheral location and adjacent chest wall injury (arrow} are noted. (B) Additional small pulmonary lacerations (arrows} are seen as air-containing cavities within focal areas of lung contusion.
toma or pneumatocele. ~s Children seem to be affected more commonly than adults. ~8 Immediately after the trauma, the radiographic evidence of pulmonary laceration often is obscured by associated contusion. With clearing of the contusion, single or multiple lesions become visible, most often in the periphery of the lung. On the chest radiograph, the appearance of a round or oval radiolucency, several hours or a few days after the trauma, represents the area of ruptured alveolar walls forming an empty space. This lesion also is called a traumatic lung cyst or pseudocyst. When this ruptured air space is filled partially with blood, an air-fluid level may be seen within the cavity. The space may be completely filled with blood, resulting in a well-circumscribed round opaque density of a pulmonary hematoma. 7 Clearing usually is slow with radiographic findings persisting for months or years. 7,18 Early detection of pulmonary laceration can prevent it from later being confused with the delayed cavitation of a lung abscess caused by infected contusion, atelectasis, or aspiration pneumonitis. 9 The CT diagnosis of lung laceration is based on the presence of a localized air collection within an area of consolidation after trauma 1° (Figs 1 and 2). CT has been shown to be superior to the chest radiograph in the diagnosis of pulmonary injury resulting from blunt chest trauma. 11 In a study of 85 patients with blunt trauma, Wagner et aP 1 detected 99 lacerations on CT scans, compared with only 5 on chest radiographs. CT's major contribution
in lung parenchymal disease after trauma is its ability to diagnose thoracic infections, such as lung abscess and empyema, leading to appropriate therapy. 19 TRACHEOBRONCHIAL INJURY
Fracture (eg, rupture, tear) of the tracheobronchial tree is an uncommon but serious complication of blunt chest trauma and is associated with other thoracic emergencies, such as pneumothorax or vascular trauma, that often obscure the diagnosis of a ruptured airway. Multiple proposed mechanisms include anteroposterior chest compression forcing bronchi outward, increased intraluminal pressure against a closed glottis, and traction shearing forces. 7,2°,2I The usual site of injury is within 2.5 cm of the carina, the area of junction between the fixed segment of trachea and the freely mobile seg-
Fig 2. Pulmonary laceration caused by a motor vehicle accident in a 30-year-old patient. CT scan shows two localized air-containing cavities with thin walls and air-fluid levels (arrows), signs that are consistent with traumatic lung cysts in the right lower lung.
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ments of the distal trachea and the b r o n c h i . 7,2°-23 Fracture of the bronchi is more common than that of the trachea, and the right side is affected more often than the left. 7,21,24 The most common radiographic manifestation of tracheobronchial rupture is pneumothorax, often associated with pneumomediastinum and subcutaneous emphysema, which may be massive, and fractured ribs, particularly one or more of the first three ribs. 18,21,22,25,26Failure of reexpansion of the lung after tube thoracostomy for pneumothorax is suggestive of a bronchial tear. 18 More specific radiographic findings for tracheobronchial rupture include falling of the collapsed lung away from the hilum, overdistension of the tracheal intubation balloon, and abnormalities in the position of the endotracheal tube. ayaS,26 Approximately 10% of patients have no radiographic or physical evidence of tracheobronchial tear. a8 The value of CT in the diagnosis of tracheobronchial tear has not been assessed. Findings at CT suggestive of tracheobronchial rupture include a markedly distended balloon cuff, a herniated balloon, or a malpositioned endotracheal tube.l°,27 DIAPHRAGMATIC INJURY
Diaphragmatic rupture (eg, tear, laceration) can result from blunt and penetrating thoracoabdominal injuries. 28-3°Mechanisms of diaphragmatic rupture after blunt trauma probably are multiple and include a sudden increase in intrathoracic or intraabdominal pressure while the diaphragm is fixed by a crushing force. 3° Leftsided rupture is more common, presumably because the liver protects the right hemidiaphragm. 12,15,18,31-36Most diaphragmatic ruptures originate in the posterolateral portion of the diaphragm at the junction of its tendon and posterior leaves. 3,1° Frequently, diaphragmatic rupture is not recognized in the immediate posttraumatic period because overlying pulmonary and pleural abnormalities often obscure the diaphragm and associated clinical and radiographic findings often are nonspecific. 2'10'13'28'29'34'35 In a study by Wiencek et al, 28 a prospective preoperative diagnosis of diaphragmatic injury for chest radiographic findings was possible in only 24 (15%)
Fig 3, Diaphragmatic tear in a 24-year-old patient who had a CT scan 10 days after a motor vehicle accident. CT image shows a sharp discontinuity of the left hemidiaphragm (arrow).
of 165 patients. Recognition of traumatic diaphragmatic rupture is important because of the frequency and severity of associated injuries 28,29 and its potential as a source of strangulation of herniated abdominal viscera. 18,36 Findings suggestive of diaphragmatic tear on the radiograph include abnormal course of the nasogastric tube, elevated hemidiaphragm, high or intrathoracic location of abdominal organs, and loss of diaphragm contour. 1°,36,37 On CT, the intact left hemidiaphragm usually appears as a continuous curvilinear structure of soft tissue attenuation outlined by lung superiorly and subdiaphragmatic fat inferiorly. The posterolateral portion of both hemidiaphragms usually are shown best, and thus the tears at these sites are detected readily. ~2,13 Recently, Worthy et a112 reported the CT findings in 11 patients with diaphragmatic tears. All three right-sided tears and seven (88%) of eight left-sided tears had been identified correctly preoperatively. The most common CT findings included sharp discontinuity of the diaphragm (Fig 3), a finding that was present in 9 (82%) of 11 patients in this study. Other CT findings of diaphragmatic rupture included lack of visualization of the hemidiaphragm, the so-called absent diaphragm sign (Fig 4); herniation of intraabdominal fat, solid organs, or bowel (Fig 5); and constriction of the bowel or stomach at the site of herniation. Although local discontinuity of the diaphragm was the most common finding in patients with a diaphragmatic tear, it should be
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Fig 4. Diaphragmatic tear in a 60-year-old patient who had a CT scan 5 years after a motor vehicle accident. The left hemidiaphragm is not visualized, the so-called absent diaphragm sign.
Fig 5. Diaphragmatic tear in a 28-year-old patient who had a CT scan 1 year after trauma. This study shows intrathoracic herniation of bowel and fat. The torn end of the left hemidiaphragm (arrow) is identified.
noted that there is a normal increase in diaphragmatic defects with age. In a review of CT scans in !20 patients, Caskey et aP 8 found these localized defects in 13 patients (11%). All of the 13 patients were at least 39 years old. Defects were seen in only 1 (5%) of 20 patients aged 40 to 49 years, but defects were seen in 7 (35%) of
20 patients age 70 years or more. The majority of traumatic diaphragmatic ruptures occur in young adults, 31,39 in whom discontinuity of the diaphragm is not seen normally. It is possible, however, that diaphragmatic defects normally seen in the elderly may be confused with diaphragmatic tears.
REFERENCES 1. LoCicero J I I I , Mattox KL: Epidemiology of chest trauma. Surg Clin North Am 69:15-19, 1989 2. Groskin SA: Selected topics in chest trauma. Radiology 183:605-617, 1992 3. Shorr RM, Crittenden M, Indeck M, et al: Blunt chest trauma, analysis of 515 patients. Ann Surg 206:200-205, 1987 4. Dougall AM, Paul ME, Finley R J, et al: Chest trauma-current morbidity and mortality. J Trauma 17:547-553, 1977 5. Poole GV, Morgan DB, Cranstom PE, et al: Computed tomography in the management of blunt thoracic trauma. J Trauma 35:296-302, 1993 6. Marts B, Durham R, Shapiro M, et al: Computed tomography in the diagnosis of blunt thoracic injury. Am J Surg 168:688-692, 1994 7. Mirvis SE, Templeton P: Imaging in acute thoracic trauma. Semin Roentgeno127:184-210, 1992 8. Toombs BD, Sandler CM, Lester RG: Computed tomography of chest trauma. Radiology 140:733-738, 1981 9. Kerns SR, Gay SB: CT of blunt chest trauma. AJR Am J Roentgeno1154:55-60, 1990 10. Tocino I, Miller MH: Computed tomography in blunt chest trauma. J Thorac lmag 2:45-59, 1987 11. Wagner RB, Crawford WO Jr, Schimpf PP: Classifi-
cation of parenchymal injuries of the lung. Radiology 167:77-82, 1988 12. Worthy SA, Kang EY, Hartman TE, et al: Diaphragmatic rupture: CT findings in 11 patients. Radiology 194:885888, 1995 13. Heiberg E, Wolveson MK, Hurd RN, et al: CT recognition of traumatic rupture of the diaphragm. AJR Am J Roentgenol 135:369-372, 1980 14. Kollmorgen DR, Murray KA, Sullivan JJ, et al: Predictors of mortality in pulmonary contusion. Am J Surg 168:659-664, 1994 15. Reginald R: Lung alterations in thoracic trauma. J Thorac lmag 2:1-11, 1987 16. Schild HH, Strunk H, Weber W, et al: Pulmonary contusion: CT vs plain radiograms. J Comput Assist Tomogr 13:417-420, 1989 17. Smejkal R, O'Malley KF, David E, et al: Routine initial computed tomography of the chest in blunt torso trauma. Chest 100:667-669, 1991 18. Wiot JF: The radiologic manifestation of blunt chest trauma. JAMA 231:500-503, 1975 19. Mirvis SE, Rodrigues A, Whitley NO, et al: CT evaluation of thoracic infections after major trauma. AJR Am J Roentgenol 144:1183-1187, 1985
118
20. Roxburgh JC: Rupture of tracheobronchial tree. Thorax 42:681-688, 1987 21. Harvey-Smith W, Buch W, Northrop C: Traumatic bronchial rupture. AJR Am J Roentgenol 134:1189-1193, 1980 22. Wiot JF: Tracheobronchial trauma. Semin Roentgenol 18:15-22, 1983 23. Pratt LW, Smith RJ, Guite LA, et al: Blunt chest trauma with tracheobronchial rupture. Ann Otol Rhinol Laryngol 93:357-363, 1984 24. Fraser RG, Pare JAP, Pare PD, et al (eds): Diagnosis of Diseases of the chest, (ed 3). Philadelphia, Saunders, 1991:4, pp 2480-2571 25. Woodring JH, Fried AM, Hatfield DR, et al: Fractures of first and second ribs: Predictive value for arterial and bronchial injury. AJR Am J Roentgenol 138:211-215, 1982 26. Unger JM, Schuchmann GG, Grossmann JE, et al: Tears of the trachea and main bronchi caused by blunt trauma: Radiologic findings. AJR Am J Roentgenol 153: 1175-1180, 1989 27. Rollins RJ, Tocino I: Early radiographic signs of tracheal rupture. AIR Am J Roentgenol 148:695-698, 1987 28. Wiencek RG, Wilson RF, Steiger Z: Acute injuries of the diaphragm: An analysis of 165 cases. J Thorac Cardiovasc Surg 92:989-993, 1986 29. Meyers BF, McCabe CJ: Traumatic diaphragmatic hernia. Occult marker of serious injury. Ann Surg 218:783790, 1993
KANG AND MULLER
30. Wilson RF, Murray C, Antonenko DR: Nonpenetrating thoracic injuries. Surg Clin North Am 57:17-36, 1977 31. Voeller GR, Reisser JR, Fubian TC, et al: Blunt diaphragmatic injuriesl A five-year experience. Am Surg 56:28-31, 1990 32. Sukul DMKSK, Kats E, Johannes EJ: Sixty-three cases of traumatic injury of the diaphragm. Injury 22:303306, 1991 33. Morgan AS, Flanchaum L, Esposito T, et al: Blunt injury to the diaphragm: An analysis of 44 patients. J Trauma 26:565-568, 1986 34. Fataar S, Rad FF, Schulman A: Diagnosis of diaphragmatic tears. Br J Radio152:375-381, 1979 35. Ball T, McCroy R, Smith JO, et al: Traumatic diaphragmatic hernia: Errors in diagnosis. AIR Am J Roentgenol 138:633-637, 1982 36. Paredes S, Hipona FA: The radiologic evaluation of patients with chest trauma. Med Clin North Am 59:37-63, 1975 37. Perlman SJ, Rogers LF, Mintzer RA, et al: Abnormal course of nasogastric tube in traumatic rupture of left hemidiaphragm. AJR Am J Roentgenol 142:85-88, 1984 38. Caskey CI, Zerhouni EA, Fishman EK, et al: Aging of the diaphragm: A C T study. Radiology 171:385-389, 1989 39. Gelman R, Mirvis SE, Gens D: Diaphragmatic rupture due to blunt trauma: Sensitivity of plain chest radiographs. AJR Am J Roentgenol 156:51-57, 1991
HEST TRAUMA accounts for approximately 20% of deaths resulting from trauma. ~Chest trauma is described traditionally as either blunt or penetrating. This distinction is based primarily on whether the chest wall remains intact or whether its integrity is breached. 2 Blunt chest trauma is much more common than penetrating trauma 1-3 and usually results from a motor vehicle accident. 1,3-6 The chest radiograph serves as the principal screening test for the immediate assessment of the thorax after blunt chest trauma. The radiograph, however, often is limited by poor or absent patient cooperation, suboptimal patient positioning, and magnification and distortion of the mediastinum on the supine view. 7 CT is helpful as a complementary imaging modality in selected cases to clarify abnormalities suspected on the chest radiograph. 7-1° CT is particularly useful in the detection of pulmonary lacerations and diaphragmatic tears. 8,11-13
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PULMONARY INJURY
Pulmonary Contusion Pulmonary contusion is present in 30% to 70% of patients with blunt chest trauma. 4,7,1°,11 Pulmonary contusion, defined as injury to lung parenchyma resulting in edema and interstitial and intraalveolar hemorrhage, usually is the result of acceleration-deceleration forces. It often occurs without gross lung laceration or a break in the pleural integument and tends to occur in the lung adjacent to solid structures,
From the Department of Radiology, University of British Columbia and Vancouver Hospital and Health Sciences Centre, Vancouver, BC, Canada. Address correspondence to Nestor L. Miiller, Department of Radiology, Vancouver Hospital and Health Sciences Centre, 855 W12th Ave, Vancouver, BC, Canada V5Z 1M9. Copyright © 1996 by W.B. Saunders Company 0887-2171 / 96 / 1702-000455. O0/ 0 114
such as ribs, vertebrae, heart, and liver. Adjacent rib fractures are seen often,3,9 more commonly in adults. 9 An estimation of the severity of the contusion is significant clinically because it correlates with the degree of post-traumatic respiratory insufficiency.4,9,1°,14In a study by Kollmorgen et al, TM 10 of 100 patients with pulmonary contusion died, 7 of whom died as a consequence of extensive pulmonary injury. Radiologically, pulmonary contusions present as areas of consolidation that tend to be peripheral, nonsegmental, and geographic in distribution. Contusions are usually evident radiographically at presentation or within 6 hours. The short time interval is helpful in differentiating contusions from a fat embolism, which may appear similar but which usually is not apparent radiographically until 1 or more days after the injury. Initial clearing of lung contusions usually is apparent radiographically 48 to 72 hours after the injury. CT is superior to chest radiography in detecting pulmonary contusions5,6,830,15,16,17 and estimating their extent. 16 In a study performed in experimental animals, 16CT detected 27 (100%) of 27 pulmonary contusions, confirmed pathologically immediately after the trauma. Therefore, pulmonary contusion is highly unlikely in patients with a normal CT appearance. Pulmonary contusion is characterized on CT by the presence of localized, scattered, ill-defined areas of consolidation adjacent to the area of trauma 8-1°(Fig 1).
Pulmonary Laceration Lung laceration in blunt trauma results from shearing forces associated with trauma leading to disruption of alveolar spaces and formation of a cavitating space, usually filled with blood or air, and with consequent production of hema-
Seminarsin Ultrasound, CT, andMRI, Vo117, No 2 (April), 1996: pp 114-118
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Fig 1. Pulmonary contusion in a 42-year-old patient who had a CT scan 12 hours after a motor vehicle accident. (A) CT scan shows a localized, ill-defined area of consolidation consistent with pulmonary contusion. Characteristic peripheral location and adjacent chest wall injury (arrow} are noted. (B) Additional small pulmonary lacerations (arrows} are seen as air-containing cavities within focal areas of lung contusion.
toma or pneumatocele. ~s Children seem to be affected more commonly than adults. ~8 Immediately after the trauma, the radiographic evidence of pulmonary laceration often is obscured by associated contusion. With clearing of the contusion, single or multiple lesions become visible, most often in the periphery of the lung. On the chest radiograph, the appearance of a round or oval radiolucency, several hours or a few days after the trauma, represents the area of ruptured alveolar walls forming an empty space. This lesion also is called a traumatic lung cyst or pseudocyst. When this ruptured air space is filled partially with blood, an air-fluid level may be seen within the cavity. The space may be completely filled with blood, resulting in a well-circumscribed round opaque density of a pulmonary hematoma. 7 Clearing usually is slow with radiographic findings persisting for months or years. 7,18 Early detection of pulmonary laceration can prevent it from later being confused with the delayed cavitation of a lung abscess caused by infected contusion, atelectasis, or aspiration pneumonitis. 9 The CT diagnosis of lung laceration is based on the presence of a localized air collection within an area of consolidation after trauma 1° (Figs 1 and 2). CT has been shown to be superior to the chest radiograph in the diagnosis of pulmonary injury resulting from blunt chest trauma. 11 In a study of 85 patients with blunt trauma, Wagner et aP 1 detected 99 lacerations on CT scans, compared with only 5 on chest radiographs. CT's major contribution
in lung parenchymal disease after trauma is its ability to diagnose thoracic infections, such as lung abscess and empyema, leading to appropriate therapy. 19 TRACHEOBRONCHIAL INJURY
Fracture (eg, rupture, tear) of the tracheobronchial tree is an uncommon but serious complication of blunt chest trauma and is associated with other thoracic emergencies, such as pneumothorax or vascular trauma, that often obscure the diagnosis of a ruptured airway. Multiple proposed mechanisms include anteroposterior chest compression forcing bronchi outward, increased intraluminal pressure against a closed glottis, and traction shearing forces. 7,2°,2I The usual site of injury is within 2.5 cm of the carina, the area of junction between the fixed segment of trachea and the freely mobile seg-
Fig 2. Pulmonary laceration caused by a motor vehicle accident in a 30-year-old patient. CT scan shows two localized air-containing cavities with thin walls and air-fluid levels (arrows), signs that are consistent with traumatic lung cysts in the right lower lung.
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ments of the distal trachea and the b r o n c h i . 7,2°-23 Fracture of the bronchi is more common than that of the trachea, and the right side is affected more often than the left. 7,21,24 The most common radiographic manifestation of tracheobronchial rupture is pneumothorax, often associated with pneumomediastinum and subcutaneous emphysema, which may be massive, and fractured ribs, particularly one or more of the first three ribs. 18,21,22,25,26Failure of reexpansion of the lung after tube thoracostomy for pneumothorax is suggestive of a bronchial tear. 18 More specific radiographic findings for tracheobronchial rupture include falling of the collapsed lung away from the hilum, overdistension of the tracheal intubation balloon, and abnormalities in the position of the endotracheal tube. ayaS,26 Approximately 10% of patients have no radiographic or physical evidence of tracheobronchial tear. a8 The value of CT in the diagnosis of tracheobronchial tear has not been assessed. Findings at CT suggestive of tracheobronchial rupture include a markedly distended balloon cuff, a herniated balloon, or a malpositioned endotracheal tube.l°,27 DIAPHRAGMATIC INJURY
Diaphragmatic rupture (eg, tear, laceration) can result from blunt and penetrating thoracoabdominal injuries. 28-3°Mechanisms of diaphragmatic rupture after blunt trauma probably are multiple and include a sudden increase in intrathoracic or intraabdominal pressure while the diaphragm is fixed by a crushing force. 3° Leftsided rupture is more common, presumably because the liver protects the right hemidiaphragm. 12,15,18,31-36Most diaphragmatic ruptures originate in the posterolateral portion of the diaphragm at the junction of its tendon and posterior leaves. 3,1° Frequently, diaphragmatic rupture is not recognized in the immediate posttraumatic period because overlying pulmonary and pleural abnormalities often obscure the diaphragm and associated clinical and radiographic findings often are nonspecific. 2'10'13'28'29'34'35 In a study by Wiencek et al, 28 a prospective preoperative diagnosis of diaphragmatic injury for chest radiographic findings was possible in only 24 (15%)
Fig 3, Diaphragmatic tear in a 24-year-old patient who had a CT scan 10 days after a motor vehicle accident. CT image shows a sharp discontinuity of the left hemidiaphragm (arrow).
of 165 patients. Recognition of traumatic diaphragmatic rupture is important because of the frequency and severity of associated injuries 28,29 and its potential as a source of strangulation of herniated abdominal viscera. 18,36 Findings suggestive of diaphragmatic tear on the radiograph include abnormal course of the nasogastric tube, elevated hemidiaphragm, high or intrathoracic location of abdominal organs, and loss of diaphragm contour. 1°,36,37 On CT, the intact left hemidiaphragm usually appears as a continuous curvilinear structure of soft tissue attenuation outlined by lung superiorly and subdiaphragmatic fat inferiorly. The posterolateral portion of both hemidiaphragms usually are shown best, and thus the tears at these sites are detected readily. ~2,13 Recently, Worthy et a112 reported the CT findings in 11 patients with diaphragmatic tears. All three right-sided tears and seven (88%) of eight left-sided tears had been identified correctly preoperatively. The most common CT findings included sharp discontinuity of the diaphragm (Fig 3), a finding that was present in 9 (82%) of 11 patients in this study. Other CT findings of diaphragmatic rupture included lack of visualization of the hemidiaphragm, the so-called absent diaphragm sign (Fig 4); herniation of intraabdominal fat, solid organs, or bowel (Fig 5); and constriction of the bowel or stomach at the site of herniation. Although local discontinuity of the diaphragm was the most common finding in patients with a diaphragmatic tear, it should be
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Fig 4. Diaphragmatic tear in a 60-year-old patient who had a CT scan 5 years after a motor vehicle accident. The left hemidiaphragm is not visualized, the so-called absent diaphragm sign.
Fig 5. Diaphragmatic tear in a 28-year-old patient who had a CT scan 1 year after trauma. This study shows intrathoracic herniation of bowel and fat. The torn end of the left hemidiaphragm (arrow) is identified.
noted that there is a normal increase in diaphragmatic defects with age. In a review of CT scans in !20 patients, Caskey et aP 8 found these localized defects in 13 patients (11%). All of the 13 patients were at least 39 years old. Defects were seen in only 1 (5%) of 20 patients aged 40 to 49 years, but defects were seen in 7 (35%) of
20 patients age 70 years or more. The majority of traumatic diaphragmatic ruptures occur in young adults, 31,39 in whom discontinuity of the diaphragm is not seen normally. It is possible, however, that diaphragmatic defects normally seen in the elderly may be confused with diaphragmatic tears.
REFERENCES 1. LoCicero J I I I , Mattox KL: Epidemiology of chest trauma. Surg Clin North Am 69:15-19, 1989 2. Groskin SA: Selected topics in chest trauma. Radiology 183:605-617, 1992 3. Shorr RM, Crittenden M, Indeck M, et al: Blunt chest trauma, analysis of 515 patients. Ann Surg 206:200-205, 1987 4. Dougall AM, Paul ME, Finley R J, et al: Chest trauma-current morbidity and mortality. J Trauma 17:547-553, 1977 5. Poole GV, Morgan DB, Cranstom PE, et al: Computed tomography in the management of blunt thoracic trauma. J Trauma 35:296-302, 1993 6. Marts B, Durham R, Shapiro M, et al: Computed tomography in the diagnosis of blunt thoracic injury. Am J Surg 168:688-692, 1994 7. Mirvis SE, Templeton P: Imaging in acute thoracic trauma. Semin Roentgeno127:184-210, 1992 8. Toombs BD, Sandler CM, Lester RG: Computed tomography of chest trauma. Radiology 140:733-738, 1981 9. Kerns SR, Gay SB: CT of blunt chest trauma. AJR Am J Roentgeno1154:55-60, 1990 10. Tocino I, Miller MH: Computed tomography in blunt chest trauma. J Thorac lmag 2:45-59, 1987 11. Wagner RB, Crawford WO Jr, Schimpf PP: Classifi-
cation of parenchymal injuries of the lung. Radiology 167:77-82, 1988 12. Worthy SA, Kang EY, Hartman TE, et al: Diaphragmatic rupture: CT findings in 11 patients. Radiology 194:885888, 1995 13. Heiberg E, Wolveson MK, Hurd RN, et al: CT recognition of traumatic rupture of the diaphragm. AJR Am J Roentgenol 135:369-372, 1980 14. Kollmorgen DR, Murray KA, Sullivan JJ, et al: Predictors of mortality in pulmonary contusion. Am J Surg 168:659-664, 1994 15. Reginald R: Lung alterations in thoracic trauma. J Thorac lmag 2:1-11, 1987 16. Schild HH, Strunk H, Weber W, et al: Pulmonary contusion: CT vs plain radiograms. J Comput Assist Tomogr 13:417-420, 1989 17. Smejkal R, O'Malley KF, David E, et al: Routine initial computed tomography of the chest in blunt torso trauma. Chest 100:667-669, 1991 18. Wiot JF: The radiologic manifestation of blunt chest trauma. JAMA 231:500-503, 1975 19. Mirvis SE, Rodrigues A, Whitley NO, et al: CT evaluation of thoracic infections after major trauma. AJR Am J Roentgenol 144:1183-1187, 1985
118
20. Roxburgh JC: Rupture of tracheobronchial tree. Thorax 42:681-688, 1987 21. Harvey-Smith W, Buch W, Northrop C: Traumatic bronchial rupture. AJR Am J Roentgenol 134:1189-1193, 1980 22. Wiot JF: Tracheobronchial trauma. Semin Roentgenol 18:15-22, 1983 23. Pratt LW, Smith RJ, Guite LA, et al: Blunt chest trauma with tracheobronchial rupture. Ann Otol Rhinol Laryngol 93:357-363, 1984 24. Fraser RG, Pare JAP, Pare PD, et al (eds): Diagnosis of Diseases of the chest, (ed 3). Philadelphia, Saunders, 1991:4, pp 2480-2571 25. Woodring JH, Fried AM, Hatfield DR, et al: Fractures of first and second ribs: Predictive value for arterial and bronchial injury. AJR Am J Roentgenol 138:211-215, 1982 26. Unger JM, Schuchmann GG, Grossmann JE, et al: Tears of the trachea and main bronchi caused by blunt trauma: Radiologic findings. AJR Am J Roentgenol 153: 1175-1180, 1989 27. Rollins RJ, Tocino I: Early radiographic signs of tracheal rupture. AIR Am J Roentgenol 148:695-698, 1987 28. Wiencek RG, Wilson RF, Steiger Z: Acute injuries of the diaphragm: An analysis of 165 cases. J Thorac Cardiovasc Surg 92:989-993, 1986 29. Meyers BF, McCabe CJ: Traumatic diaphragmatic hernia. Occult marker of serious injury. Ann Surg 218:783790, 1993
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