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251 RADIOLOGIC CLINICS OF NORTH AMERICA Radiol Clin N Am 44 (2006) 251–258 Nonvascular Mediastinal Trauma Juntima Euathrongchit, MD, Nisa Thoongsuwan, MD, Eric J. Stern, MD* & Tracheobronchial injury & Thoracic duct injury Clinical findings Clinical and radiologic findings of thoracic Radiologic findings of tracheobronchial duct injury injury & Miscellaneous & Esophageal injury & Summary Clinical findings & References Radiologic findings of esophageal trauma & Tracheoesophageal fistula Clinical and radiologic findings of tracheoesophageal fistula This article discusses the radiologic and clinical the intrathoracic trachea. The intrathoracic trachea features of nonvascular mediastinal trauma, and courses in the midline with a slight deviation to the focuses on the tracheobronchial tree, the esopha- right, which is caused by the aortic arch. It bifur- gus, and the thoracic duct. Blunt chest and pene- cates into the left and right main bronchi at the trating trauma account for most of the causes of tracheal carina at approximately the T4 vertebral such nonvascular injuries, but iatrogenic and inha- body level [Fig. 1]. Both main bronchi are consid- lation injuries are other well-known causes. The ered mediastinal structures before exiting by way of injury distribution and clinical manifestations are each hilum to divide into the major lobar bronchi. different for each structure. In our combined expe- Tracheobronchial injury (TBI) is reported to occur rience at a level 1 trauma center, the overall preva- in only 1% to 3% of patients who have blunt chest lence of injury in each organ is low compared with trauma, and in 2% to 9% of those who suffer pene- vascular injuries. As such, and given the frequent trating chest injuries [2,3]. The tracheobronchial nonspecific nature of clinical signs and symptoms tree is protected from injury to some extent by sur- of nonvascular mediastinal injuries, the diagnosis rounding structures, including the sternum, both often is delayed and results in poor treatment out- lungs, and the great vessels anterolaterally, and the come . thoracic vertebrae and esophagus, posteriorly. As such, injuries to these surrounding structures are seen in association with TBI. Similarly, given poten- Tracheobronchial injury tially violent injury mechanisms, TBI is associated The trachea can be divided arbitrarily at the tho- with closed head injury, spinal cord injury, facial racic inlet into two parts: the cervical trachea and fractures, lung injury, aortic traumatic injury, chest Harborview Medical Center, Department of Radiology, University of Washington School of Medicine, Seattle, WA, USA * Corresponding author. Harborview Medical Center, Department of Radiology, University of Washington School of Medicine, Box 359728, Seattle, WA 98104-2499. E-mail address: email@example.com (E.J. Stern). 0033-8389/06/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2005.10.001 radiologic.theclinics.com 252 Euathrongchit et al rina, resulting in rupture of the trachea and bronchi, especially near the lower tracheal– carinal junction. A single, transverse rupture of the tracheobron- chial tree is seen much more commonly than a longitudinal or complex tear. Iatrogenic tracheal rupture from intubation commonly occurs at the pos- terior membranous wall. Inhalation injury, such as inspired hot gases, steam, or toxic fumes (eg, chlorine gas), can result in severe damage to the tracheal mucosa, starting with edema and followed by necro- sis, ulceration, scar formation, and finally, tracheal stenosis . Fig. 1. Coronal reconstruction of the chest CT scan shows normal course of the trachea deviation to the Clinical findings right from the aortic arch (*) and division into the left Diagnosis of TBI is delayed in up to two thirds of and right main bronchus at the T4 vertebral level. patients because the airway column is maintained by intact peritracheobronchial tissue [7,8]. Com- wall injury, and abdominal injuries in from 40% to mon symptoms of TBI are nonspecific and in- 100% of cases. Combined esophageal and tracheal clude dyspnea, cough, hoarseness, and hemoptysis. rupture is seen in approximately 20% of cases of Clinical signs also are nonspecific and include sub- TBI . cutaneous emphysema, hemoptysis, respiratory dis- The two primary causes of trauma to the tracheo- tress, and hypoxia. Persistent pneumomediastinum; bronchial tree are penetrating injuries (in ~70% of pneumothorax; subcutaneous emphysema, despite cases) and blunt trauma (in the remainder) . The treatment; fractures of the first three ribs; or pos- other causes of injury, such as foreign body aspira- terior dislocation of sternoclavicular joint are tion, inhalation, and iatrogenic injuries from intu- suggestive of, or associated with, TBI . Endo/ bation or tracheostomy, are uncommon. bronchoscopy can confirm the diagnosis when the Penetrating trauma is seen more commonly in clinical and radiologic features are suspected. Late the cervical, rather than the intrathoracic, trachea effects of undiagnosed TBI may be tracheobron- [2,6,7], and usually involves the anterior portion of chial stenosis from granulation tissue and fibrosis tracheal cartilage and intercartilaginous ligament. that leads to chronic airway obstruction. For the intrathoracic airway, the distal trachea, just above the carina, and the right lower bronchus Radiologic findings of tracheobronchial injury are the regions that are involved most com- The most direct radiologic sign of tracheal rupture monly . is demonstration of a tracheal wall defect or tra- In contrast to penetrating injuries, 80% of cases cheal deformity. These findings are seen far more of blunt TBI occur within 2.5 cm of the carina readily using CT than conventional radiography. In- [7,8]. The right main stem bronchus tends to be direct signs of injury include an airway leak into the injured more commonly than the left because there surrounding mediastinal tissue, an abnormal con- is less protection from surrounding structures [7,8]. figuration of the endotracheal tube balloon cuff, Mechanisms of blunt tracheal injury include the and distal lung parenchymal abnormalities (eg, per- following [7,9,10]: sistent atelectasis). The most common radiologic • Rapid increased intraluminal tracheal pressure from sudden chest compression against a closed features of TBI are pneumomediastinum (60%) and pneumothorax (≤70%) that result from air glottis, typically during high-speed crashes. In escaping through a tracheal tear into the mediasti- these cases, rupture usually occurs in the mem- num and pleural space . Persistent subcuta- branous portion. neous emphysema, pneumothorax, or atelectasis, • Separation and stretching of the tracheobron- chial tree due to anteroposterior chest compres- despite appropriate therapy, should be considered suspicious for TBI in the proper clinical setting. sion and hyperextension of the neck or direct Deviation of an endotracheal tube from its ex- crushing of the trachea between the sternum pected course, and focal overdistension of the en- and thoracic vertebrae, causing tracheobron- dotracheal tube balloon cuff or protrusion of the chial disruption. balloon through a tracheal laceration are highly • Rapid deceleration with shearing forces passed to the relative fixed cricoid cartilage and ca- suggestive radiologic findings for tracheal injury [Figs. 2 and 3] . The lung distal to the injury Nonvascular Mediastinal Trauma 253 Fig. 2. Tracheal rupture from a high-speed vehicle accident. (A) The axial CT scan of the cervical spine shows the focal left posterolateral protrusion of the endotrachial tube balloon cuff (arrow). (B) The sagittal CT scan of the cervical spine again shows the focal protrusion of the balloon cuff (arrow). (C ). With the three-dimensional reconstruction, the abnormal figure of the balloon cuff is demonstrated well (arrow). can be atelectatic, especially with complete disrup- number of patients who have TBI who are diag- tion of the airway. The distal collapsed lung will nosed in the acute trauma setting. ‘‘fall’’ to the most dependent portion of the pleural space, which produces the so-called ‘‘fallen lung Esophageal injury sign.’’ Although essentially pathognomonic for the diagnosis of TBI, it is a rare finding [10,11]. The esophagus can be divided into three portions: Whereas conventional chest radiograph is the cervical, thoracic, and intra-abdominal. The intra- initial imaging study for the evaluation of blunt thoracic esophagus is located along the right lateral chest trauma, and typically establishes the diag- descending aorta in the middle mediastinum, be- noses of pneumothorax and pneumomediastinum, hind the trachea and in front of the thoracic spine. the direct diagnosis of TBI is made more much Protected by the thoracic cage, the incidence of confidently and commonly with CT . Multi- esophageal injury from external chest trauma is detector CT (MDCT) has improved markedly our rare, typically less than 1% [4,12,13]. The most ability to make this diagnosis, particularly when common cause of esophageal perforation is medi- supplemented by the use of thin-slice collimation, cal procedures [14,15], such as endoscopy and multiplanar reformation, mini–maximum intensity dilation procedures. Typically, these procedures projection rendering, and virtual CT bronchoscopy. are performed for esophageal pathology that results The increasing use of screening chest CT in patients in a weaker wall that is more prone to perforation. who have blunt chest trauma should increase the The remaining causes of esophageal injury include 254 Euathrongchit et al Fig. 3. Tracheal rupture after blunt trauma. (A) Admission chest radiograph of elderly woman shows diffuse soft tissue air and huge hiatal hernia. (B) CT shows air surrounding thoracic trachea with apparent bulging of endotracheal balloon posteriorly. (C and D). Coronal and sagittal volume rendered images confirm endotracheal balloon bulging through membranous tracheal tear (arrow in C). certain toxic ingestions, emetic injury (Boerhaave’s subcutaneous emphysema, pneumomediastinum, syndrome), and external penetrating trauma. pneumothorax, and demonstration of gastric con- Penetrating esophageal injuries result mainly from tents in pleural fluid. Most cases of blunt or pene- gun shot, shotgun, and stab wounds . Penetrat- trating esophageal injury are delayed in diagnosis, ing and blunt esophageal ruptures often are asso- which leads to a poor outcome [4,16]. ciated with injury to the surrounding organs, such as heart, great vessels, trachea, and spine . Radiologic findings of esophageal trauma Patients who have a penetrating injury track Clinical findings through the mediastinum should be evaluated by Esophageal injuries have a high morbidity and mor- esophagography, starting with water-soluble con- tality, and early diagnosis and treatment improve trast media, and if negative, followed by barium outcome. Symptoms and signs of esophageal in- swallow; the higher density contrast allows detec- jury are dependent on the depth of esophageal tion of smaller lesions or contrast leaks. Flexible wall involvement. The most common symptom of fiber optic or rigid esophagoscopy also can be per- esophageal injury is retrosternal chest pain. Other formed with a diagnostic sensitivity that ranges nonspecific symptoms include dysphagia, odyno- from 50% to 90% . phagia, pleuritic chest pain, and dyspnea. Signs of The depth of esophageal penetration directly full-thickness tear without tracheal trauma include affects radiologic findings. In superficial penetrat- Nonvascular Mediastinal Trauma 255 ing injury, esophagography will not demonstrate right pleural effusion, whereas injury of the lower a tear easily; however, if the injury extends to one third results in a left pleural effusion . the lumen, a full-thickness perforation potentially The chest radiograph, as the usual initial imaging produces pneumomediastinum, pneumothorax, examination to evaluate suspected esophageal per- pleural effusion, and leakage of contrast medium foration, is used to demonstrate air collections in during a swallowing study. Malposition of a surgi- the mediastinum and subcutaneous soft tissues cal appliance (eg, stent) or demonstration of a [Fig. 4]. For confirmation and localization of foreign body in or near the course of the esopha- the site of rupture, contrast study of the esophagus gus on radiography indicates a potential esopha- can be performed under fluoroscopy with compli- geal perforation. Progressive leakage of esophageal mentary conventional radiographs. CT can readily fluid content with superimposed inflammation show a small leak of contrast material from the and infection gradually alters the mediastinal con- esophagus that may be difficult to visualize on tour and produces widening and indistinct bor- conventional radiography, and can detect a small ders. The anatomic position of the esophagus in metallic foreign body from accidental ingestion the thorax results in preferential injury patterns; . Other CT abnormalities include extraluminal injury to the superior two thirds usually results in air, periesophageal fluid, and esophageal thicken- Fig. 4. Esophageal rupture from an all-terrain vehicle accident. (A) Chest radiograph shows the right pneumo- thorax (arrowheads) with the chest tube. The lung contusion at the right lung apex also is noted. (B) CT scan of the chest shows air leakage around the esophagus (arrows). The right pneumothorax (*) and the right rib frac- ture (arrowhead) also are demonstrated. (C ) The esophagography confirms the leakage at the esophagogastric junction (arrow). 256 Euathrongchit et al chemia producing focal necrosis of the esophageal and tracheal walls and subsequent formation of a fistula [21,23]. Clinical and radiologic findings of tracheoesophageal fistula The most common site of a tracheoesophageal fis- tula is at or just above the carina. Classic symptoms and signs are evidence of pneumonia or coughing after swallowing that occur in the 3 to 10 days after chest trauma [23,24]. Esophagography and CT can diagnose and demonstrate the fistula location directly. Otherwise, radiologic findings are indi- rect, and include pneumonia, gaseous dilatation of the esophagus, pneumomediastinum, and sub- cutaneous emphysema. Fig. 5. Esophageal contrast leak. CT was performed after esophagram for penetrating mediastinal injury Thoracic duct injury and shows leak of contrast from the esophagus (ar- The thoracic duct is a lymphatic drainage system row). Pneumomediastinum is observed and the tra- that arises from the cisterna chyli, passes into the chea had a full-thickness injury at surgery. (From thoracic cavity by way of the aortic hiatus, and Mirvis SE. Diagnostic imaging of thoracic trauma. In: Mirvis SE, Shanmuganathan K, editors. Imaging in courses to the right side of the spine between the trauma and critical care. 2nd edition. Philadelphia: azygos vein and the aorta. At the carinal level, the WB Saunders; 2003. p. 297–367). course of the thoracic duct changes to the left— just lateral to the left side of the trachea—and is ing that can be clues to esophageal perforation [see directed between the esophagus and the left sub- Figs. 4 and 5]. Recently, CT has played an increas- clavian artery, where it drains into the venous sys- ing role in evaluating esophageal injury because it tem at the junction of the left brachiocephalic and has come into general use as a common method to internal jugular veins. Understanding this course evaluate patients who have acute chest pain. CT helps to locate the points of potential injury, techniques include imaging with and without intra- because the lower third of the duct lies mainly to venous contrast medium injection and, when pos- the right of midline and leads to right-sided chylo- sible, distending the esophagus with water and thorax, as opposed to injury to the upper tho- ingestion of effervescent granules [19,20]. racic portion, which causes a left-sided chylothorax [25,26]. Bilateral chylothoraces may be seen when injury occurs near the carina. Isolated external pene- trating and nonpenetrating thoracic duct injuries are Tracheoesophageal fistula rare and usually occur in association with the vas- Acquired tracheoesophageal fistula after chest cular or tracheoesophageal injury . trauma is rare, and occurs in just 0.2% of patients Proposed mechanisms of blunt thoracic duct rup- who have blunt chest injury [7,21]. Most cases ture include shearing of lymphatic channels from involve young adult patients. In cases of penetrat- hyperflexion and extension of the vertebral col- ing trauma, injury usually involves the trachea and umn, and disruption of the chyle-containing lym- esophagus . phatic system from stretching and tearing motion Typically, the mechanism of the blunt traumatic during acute compression . tracheoesophageal fistula is a compression of the trachea and esophagus between the sternum and Clinical and radiologic findings of thoracic duct the vertebrae, which results in injury to the mem- injury branous portion of the trachea and the anterior Thoracic duct injury results in a chylothorax or esophageal wall. Because most young patients chylopericardium. Prolonged leakage of lymph may have a highly elastic chest wall, concurrent fracture lead to nutritional deficiencies, respiratory dysfunc- of the thoracic cage is infrequent. The most com- tion, and immunosuppression with a mortality of mon traumatic cause of tracheoesophageal fistula up to 50% . Chylous effusions contain a high is long-term use of an endotracheal tube and naso- triglyceride content—greater than 110 mg/dL—that gastric tube, with esophageal and tracheal wall is- produces a milky appearance . Demonstration Nonvascular Mediastinal Trauma 257 of a chylothorax or chylous fluid from a surgical cheobronchial injuries: treatment and outcomes. wound is most likely due to thoracic duct perfora- Ann Thorac Surg 2001;71:2059–65. tion . If chylothorax is noted after blunt chest  Chen JD, Shanmuganathan K, Mirvis SE, et al. trauma, esophageal injury should be sought care- Using CT to diagnose tracheal rupture. AJR Am fully . J Roentgenol 2001;176:1273–80.  Stern EJ. Airway rupture/laceration. In: Stern EJ, Lymphangiography is the imaging procedure of Hunter JC, Mann FA, et al, editors. Trauma ra- choice to diagnose and localize a laceration point. diology companion, methods, guidelines, and Abnormal lymphangiography shows leakage of con- imaging fundamentals. 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