Unenhanced dynamic mediastinal computed tomography in the selection of patients requiring thoracic aortography for the detection of acute traumatic aortic injury

In our institution, the selection of patients who require thoracic aortography to evaluate for acute traumatic aortic injury (ATAI) is based upon an appropriate mechanism of injury and radiologic demonstration of a mediastinal hematoma. When plain chest or chest and/or mediastinal radiographs demonstrate a mediastinal hematoma, the patient undergoes thoracic aortography as promptly as is clinically feasible. If the plain film studies are negative for mediastinal hematoma, thoracic aortography is not performed because the patient is presumed not to have an ATAI. When the plain film studies are equivocal and the patient is stable, unenhanced computed tomography (CT) of the mediastinum is used to evaluate for a mediastinal hematoma. CT signs of a mediastinal hematoma include a soft tissue density, representing the hematoma admixed with mediastinal fat, which obscures or obliterates the normal aortic-mediastinal fat interface; hematoma admixed with fat of the right paratracheal stripe causing increased width and density of the stripe; and hematoma surrounding, and frequently displacing, the esophagus to the right of its normal position. Six of 36 patients (17%) with mediastinal hematoma demonstrated by unenhanced mediastinal CT had ATAI by thoracic aortography and confirmed surgically. The thoracic aortograms of the remaining 30 of 36 patients (83%) were negative. Sixty-three of 100 patients (63%) with equivocal plain chest or mediastinal radiographs had negative mediastinum by unenhanced CT. All 63 patients (100%) with normal mediastinal CT and who did not have thoracic aortography were discharged from the hospital 1–42 days (mean, 9.3 days) post-injury without clinical or radiographic signs of aortic rupture. Supported in part by the John S. Dunn Research Foundation.     

Spiral CT aortography: an efficient technique for the diagnosis of traumatic aortic injury

The objective of this study was to assess the efficiency of spiral CT (SCT) aortography for diagnosing acute aortic lesions in blunt thoracic trauma patients. Between October 1992 and June 1997, 487 SCT scans of the chest were performed on blunt thoracic trauma patients. To assess aortic injury, the following SCT criteria were considered: hemomediastinum, peri-aortic hematoma, irregular aspect of the aortic wall, aortic pseudodiverticulum, intimal flap and traumatic dissection. Aortic injury was diagnosed on 14 SCT examinations (2.9 %), five of the patients having had an additional digital aortography that confirmed the aortic trauma. Twelve subjects underwent surgical repair of the thoracic aorta, which in all but one case confirmed the aortic injury. Two patients died before surgery from severe brain lesions. The aortic blunt lesions were confirmed at autopsy. According to the follow-up of the other 473 patients, we are aware of no false-negative SCT examination. Our limited series shows a sensitivity of 100 % and specificity of 99.8 % of SCT aortography in the diagnosis of aortic injury. It is concluded that SCT aortagraphy is an accurate diagnostic method for the assessment of aortic injury in blunt thoracic trauma patients. Received 18 July 1997; Revision received 11 September 1997; Accepted 23 October 1997     

Role of contrast-enhanced helical CT in the evaluation of acute thoracic aortic injuries after blunt chest trauma

The purpose of this retrospective study was to determine the value of contrast-enhanced helical CT for detecting and managing acute thoracic aortic injury (ATAI). Between June 1995 and February 2000, 1419 consecutive chest CT examinations were performed in the setting of major blunt trauma. The following CT findings were considered indicative of ATAI: intimal flap; pseudoaneurysm; contour irregularity; lumen abnormality; and extravasation of contrast material. On the basis of these direct findings no further diagnostic investigations were performed. Isolated mediastinal hematoma on CT scans was considered an indirect sign of ATAI: In these cases, thoracic aortography was performed even if CT indicated normal aorta. Seventy-seven patients had abnormal CT scans: Among the 23 patients with direct CT signs, acute thoracic aortic injuries was confirmed at thoracotomy in 21. Two false-positive cases were observed. The 54 remaining patients had isolated mediastinal hematoma without aortic injuries at CT and corresponding negative angiograms. The 1342 patients with negative CT scans were included in the 8-month follow-up program and did not show any adverse sequela based on clinical and radiographic criteria. Contrast-enhanced helical CT has a critical role in the exclusion of thoracic aortic injuries in patient with major blunt chest trauma and prevents unnecessary thoracic aortography. Direct CT signs of ATAI do not require further diagnostic investigations to confirm the diagnosis: Isolated aortic bands or contour vessel abnormalities should be first considered as possible artifacts or related to non-traumatic etiologies especially when mediastinal hematoma is absent. In cases of isolated mediastinal hematoma other possible sources of bleeding should be considered before directing patients to thoracic aortography.     

Acute posttraumatic rupture of the thoracic aorta: The role of angiography in a 7-year review

Between 1983 and 1989, 15 patients with acute rupture of the thoracic aorta by blunt trauma were seen. Superior mediastinal widening and obscuration of the aortic arch were the most important findings on chest radiograph. Computed tomography examinations in 7 patients showed mediastinal hematomas but did not reveal aortic lesions. Definitive diagnosis of traumatic aortic rupture was established by aortography in all 15 patients. Intraarterial digital substraction angiography proved to be as accurate as conventional film aortography and saved time.     

Diagnostic problems in traumatic rupture of the thoracic aorta. Observations on 8 surgically treated cases

The authors report their experience concerning the diagnosis of traumatic rupture of the thoracic aorta, based on a review of eight surgically treated cases. They emphasize the importance of the immediate performance of an aortography which, providing highly specific findings, permits the diagnosis of this serious lesion, which is often misrecognized. The diagnostic value of the standard chest roentgenogram is discussed, with special attention to mediastinal enlargement which (especially if associated with a CT finding of a periaortic haematoma) must lead to the performance of an aortography, even in those cases with atypical or absent symptoms. Following this diagnostic approach, an early surgical treatment of the aortic lesions, with favorable results in five out of eight cases was obtained.     

Evaluation of the role of chest computed tomography in the management of trauma patients

The role of chest computed tomography (CT) in the management of trauma patients is evolving. The present study reviews the chest radiographic and chest CT findings in a group of trauma patients to determine the clinical impact of findings noted exclusively on chest CT.Fifty-five trauma patients examined with chest radiography and chest CT and whose clinical charts were available for review were retrospectively identified. There were 46 men and 9 women, with a mean age of 39 years. The presence (and size) of pneumothorax, hemothorax, pulmonary contusion, and fractures was tabulated for the chest radiographs and CT scans. The presence of mediastinal widening on chest radiographs and all mediastinal findings on CT were noted. The results of aortography, when applicable, were correlated. The clinical charts were reviewed to assess the impact of CT findings on patient management.Pneumothorax (P<0.05), hemothorax (P<0.05), pulmonary contusions, and fractures were noted more frequently on chest CT than on chest radiography. However, clinical management was affected in only three (5%) of these patients. Chest CT findings related to the mediastinum affected patient management in 13 (24%) patients. CT obviated the need for aortography in 7 of 10 patients with mediastinal widening on chest radiographs. Six other patients had aortography, four for mediastinal hematoma with a normal-appearing aorta on contrast medium-enhanced CT, and two for mediastinal hematoma and aortic injury on CT.Despite detection of significantly more pneumothoraces and hemothoraces on chest CT, clinical management was affected in only a small minority (5%) of cases. CT did prove useful in evaluating the mediastinum, obviating the need for aortography in 7 of 10 patients with a widened mediastinum on chest radiography and accurately diagnosing the presence and site of aortic injury in the two patients with that diagnosis.     

Making the transition: the role of helical CT in the evaluation of potentially acute thoracic aortic injuries

OBJECTIVE: The purpose of this study was to show that helical CT could be used at our center in lieu of routine aortography to examine patients who have had serious blunt chest trauma. We also wanted to assess the potential savings of using CT to avoid unnecessary aortography. MATERIALS AND METHODS: The institutional review board approved the parallel imaging-CT immediately followed by aortography-of patients presenting with blunt chest trauma between August 1997 and August 1998. To screen patients for potential aortic injuries, we performed parallel imaging on 142 patients, and these patients comprised our patient population. CT examinations of the patients were reviewed for signs of injury by radiologists who were unaware of each other's interpretations and the aortographic results. Findings of CT examinations were classified as negative, positive, or inconclusive for injury. Aortography was performed immediately after CT. The technical and professional fees for both transcatheter aortography and helical CT were also compared. RESULTS: Our combined kappa value for all CT interpretations was 0.714. The aortographic sensitivity and negative predictive value were both 100%. Likewise, the sensitivity and negative predictive value of CT were 100%. The total costs of performing aortography were estimated at approximately $402,900, whereas those for performing helical CT were estimated at $202,800. CONCLUSION: Helical CT has a sensitivity and negative predictive value equivalent to that of aortography. Using CT to eliminate the possibility of mediastinal hematoma and to evaluate the cause of an abnormal aortic contour in a trauma patient allows us to use aortography more selectively. Avoiding the performance of unnecessary aortography will expedite patient care and reduce costs. We report the results of our experience with CT and how our center successfully made this transition in the initial examination of patients with serious thoracic trauma.     

Can chest CT be used to exclude aortic injury?

PURPOSE: To determine whether chest computed tomography (CT) can be used to exclude aortic injury. MATERIALS AND METHODS: Patients in whom there was very high suspicion of traumatic aortic injury were examined with aortography only. Other patients were examined with contrast material-enhanced CT. Follow-up aortography was performed in all patients with moderate to high suspicion of traumatic aortic injury and in all patients with CT scans that were positive for traumatic aortic injury. CT scans were regarded as positive when they showed mediastinal hematoma or direct findings of aortic injury. During a 4 1/2-year period, 1,009 patients (263 female, 746 male; age range, 3-90 years) were evaluated for possible traumatic aortic injury. RESULTS: Of the 207 patients who underwent aortography directly without CT, 10 had traumatic aortic injury. Of the 802 patients who were examined with CT, 382 underwent follow-up aortography. In this group, there were 10 true-positive and no false-negative CT scans. CT had 100% sensitivity and a 100% negative predictive value for the detection of traumatic aortic injury.     

Computed tomography in the diagnosis of traumatic rupture of the thoracic aorta

Over a 26-month period, 25 patients admitted to the Trauma Unit at UCSD Medical Center following blunt trauma were investigated for suspected traumatic rupture of the thoracic aorta by computed tomography (CT) of the chest. A retrospective review of these patients was performed. Twenty-one (84%) also had CT of other body areas, most commonly the head or abdomen. Nine of the 25 patients subsequently had aortography; in 15 patients the CT findings were felt at the time to exclude rupture, and one patient was not investigated further because of severe head injuries. In general, if CT failed to show a mediastinal haematoma, aortography was not performed. However, five patients with CT evidence of a haematoma, including two with vertebral fractures, were not investigated by aortography. Two of the 25 patients (8%) had angiographically proven aortic ruptures; in both CT had shown not only a haematoma but also an abnormal outline of the aorta on contrast-enhanced scans. The haematoma was large in one patient and small in the other. Although 10 of the 25 patients had unenhanced scans, no case of aortic rupture is known to have been missed. During the same study period, 47 patients were investigated for suspected aortic rupture solely by aortography. Four patients (8% of this group) had aortic rupture, and two had subclavian or innominate artery ruptures. Only a minority (approximately one-quarter) also had CT of the head or abdomen. The role of CT in the diagnosis of traumatic rupture of the aorta is critically assessed in the light of our experience and a review of the literature.     

Value of plain chest film in predicting traumatic aortic rupture

Plain chest film performed after blunt chest trauma showed blurring of the left pulmonary hilum in 53% of cases of traumatic aortic rupture (Group A, n = 15), and in no cases with negative aortography (Group B, n = 10). This sign can be explained by diffusion of mediastinal hemorrhage through the peri-bronchovascular connective tissue; the close relationship between aortic isthmus, the side of most frequent rupture, and the left pulmonary hilum is the anatomical basis for this asymmetrical finding. Review of all radiological alterations of the plain chest film shows a statistically significant difference between groups A and B only for mediastinal widening and aortic knob alterations (p less than 0.05). A combination of some findings due to aortic injury (mediastinal widening, aortic knob alterations, shift of trachea and left main bronchus, left apical cap, left hilar blurring, obscuring of descending aorta) was typical of aortic rupture when four or more signs were found (33%); these findings were absent only in patients with negative aortogram (8%). In the remaining cases (60%), the plain chest film showed two or three of these signs in both groups, making it impossible to differentiate between patients with and without aortic injury.     

Direct versus indirect signs of traumatic aortic injury revealed by helical CT: performance characteristics and interobserver agreement

OBJECTIVE: The purpose of this study was to evaluate the relative value of and interobserver agreement on direct versus indirect (hematoma) signs of traumatic aortic injury using helical CT. MATERIALS AND METHODS: From April 1994 through January 1997, 40 patients who were suspected to have traumatic aortic injury and who underwent contrast-enhanced helical CT had subsequent proof or exclusion of aortic injury. All available CT scans of these patients were combined with CT scans of 13 randomly chosen patients that had been initially interpreted as negative, and clinical follow-up showed no evidence of aortic injury. Two emergency radiologists and a nonemergency radiologist who were unaware of clinical outcome performed independent review of these cases to evaluate for mediastinal hematoma, periaortic hematoma, and direct signs of aortic injury. RESULTS: Direct signs of injury were seen on helical CT by both emergency radiologists in all 17 cases of aortic injury with no false-positive interpretations. The nonemergency radiologist failed to observe subtle direct signs in two cases of aortic injury, but patient management would not have been adversely affected. All observers had more false-negative interpretations for both mediastinal hematoma and periaortic hematoma than for direct signs. Interobserver agreement was higher for direct signs (kappa = .93) than for either mediastinal hematoma (kappa = .65) or periaortic hematoma (kappa = .71). CONCLUSION: In this study, helical CT revealed direct signs of traumatic aortic injury that were more accurate and more often observed than were indirect signs. Emphasis on direct signs should improve confidence in using helical CT to evaluate traumatic aortic injury.     

Periaortic hematoma at diaphragmatic crura at helical CT: sign of blunt aortic injury in patients with mediastinal hematoma

PURPOSE: To evaluate periaortic hematoma (PH) near the level of the diaphragm at abdominal computed tomography (CT) as an indirect sign of acute traumatic aortic injury after blunt trauma in patients with mediastinal hematoma. MATERIALS AND METHODS: From 1998 to 2001, 97 patients with CT evidence of mediastinal hematoma after blunt thoracic trauma were retrospectively identified at two level 1 trauma centers. The presence or absence of PH near the level of the diaphragmatic crura was retrospectively established by a blinded reviewer at each institution. Aortic injury status was determined by reviewing angiographic, surgical, and clinical records. Sensitivity, specificity, positive and negative productive values, and positive and negative likelihood ratios were calculated. RESULTS: Among the 97 patients with mediastinal hematoma, 14 had both PH near the level of the diaphragm and aortic injury; six had aortic injuries without PH, five had PH near the level of the diaphragm without aortic injury, and 72 had no evidence of PH near the diaphragm and no aortic injury. Sensitivity for PH near the level of the diaphragm as a sign of aortic injury was 70%; specificity, 94%; positive predictive value, 74%; and negative predictive value, 92%. The positive likelihood ratio for the presence of aortic injury was 10.8, and the negative likelihood ratio was 0.3. CONCLUSION: PH near the level of the diaphragmatic crura is an insensitive but relatively specific sign for aortic injury after blunt trauma. The presence of this sign at abdominal CT should prompt imaging of the thoracic aorta to evaluate potential thoracic aortic injury.     

Imaging of acute traumatic injuries of the thoracic aorta

Blunt traumatic aortic injuries are a major concern in the settings of high-speed deceleration accidents, since they are associated with a very high mortality rate; however, with prompt diagnosis and surgery, 70% of the patients with a blunt aortic lesion who reach the hospital alive will survive. This statement challenges the emergency radiologist in charge to evaluate the admission radiological survey in a severe chest trauma patient. With a 95% negative predictive value for the identification of blunt traumatic aortic lesions, plain chest film represents an adequate screening test. If aortography remains the gold standard, it tends, at least in hemodynamically stable trauma patients, to be replaced by spiral-CT angiography (SCTA), which demonstrates a 96.2% sensitivity, a 99.8% specificity, and a 99.7% accuracy. In unstable patients, trans-esophageal echography (TEE) plays a major diagnostic role. Knowledge of advantages and pitfalls of these imaging techniques, as reviewed in this article, will help the emergency radiologist to choose the appropriate algorithm in the diagnosis of traumatic aortic injury, for each trauma patient.     

Direct findings of aortic injury on contrast-enhanced CT in surgically proven traumatic aortic injury: a multi-centre review

OBJECTIVE: To review the contrast-enhanced CT findings in surgically proven traumatic aortic injury (TAI). MATERIALS AND METHODS: We searched the trauma registries of three academic medical centres from 1994 to 2000 and found 34 patients with surgically proven TAI that received pre-operative contrast-enhanced chest CT. Two chest radiologists recorded by consensus the size and location of direct (pseudoaneurysm, intimal flap) and indirect (mediastinal haematoma) findings of TAI. The imaging findings were correlated with surgical reports. RESULTS: Direct findings of aortic injury (pseudoaneurysm or intimal flap) were seen on contrast enhanced CT in all patients and confirmed at surgery. Specifically, a pseudoaneurysm was seen in 33 (97%), presenting either as a focal bulge in 22 (65%) or as more diffuse aneurysmal enlargement in 11 (32%). An intimal flap was identified in 31 cases (91%). A periaortic haematoma was seen in 31 cases (91%). In the three patients without periaortic haematoma, the only indications of aortic injury were a focal pseudoaneurysm in two (6%) and an intimal flap in one (3%). CONCLUSION: In this series of surgically proven TAI, direct findings of aortic injury were seen in all cases. Aortic tear occurred without mediastinal haematoma in 9% (3/34) of patients.     

Value of chest radiography in excluding traumatic aortic rupture

A retrospective review of chest radiographs from 205 patients with blunt chest trauma who also underwent aortography was performed. Forty-one of the 205 had aortographically proved aortic rupture. Discriminant analysis of 16 radiographic signs indicated that the most discriminating signs were loss of the aorticopulmonary window, abnormality of the aortic arch, rightward tracheal shift, and widening of the left paraspinal line without associated fracture. No single or combination of radiographic signs demonstrated sufficient sensitivity to indicate all cases of traumatic aortic rupture on plain chest radiographs without the performance of a large number of aortographically negative studies. The bedside anteroposterior "erect" view of the chest proved far more valuable than the supine view in detecting true-negative studies. Despite significant reader variability in the interpretation of the various radiographic signs, in general the analysis confirmed the role of chest radiography in this clinical situation, but suggests that its most beneficial use is in excluding the diagnosis and eliminating unwarranted aortography rather than in predicting aortic rupture.     

The value of the chest radiograph in thoracic aortic dissection and traumatic rupture (author's transl)]

The plain chest radiographs of 40 patients with angiographically proven thoracic aortic dissection or traumatic rupture are analyzed retrospectively with regard to their value. Only in two cases completely normal findings were observed. In all other cases characteristic changes could be observed leading to an immediate aortography. The plain chest radiograph is very important in the decision whether and when an aortography has to be performed on clinical suspected patients.     

Evaluation of traumatic aortic injury: does dynamic contrast-enhanced CT play a role?

To investigate the value of 5-mm contrast material-enhanced computed tomography (CT) in patients with moderate to low probability of aortic laceration after a substantial deceleration injury, scans were obtained through the upper mediastinum in 160 consecutive patients. Thoracic angiography and aortography were performed in patients with evidence of mediastinal hemorrhage at CT. There was no evidence of mediastinal hemorrhage in 132 patients with normal admission chest radiographs. In the 28 patients with abnormal admission chest radiographs, CT helped exclude mediastinal hemorrhage in 22 patients (78%), and 19 patients (68%) were treated without undergoing angiography. Six patients had mediastinal hematoma at CT. Only one had an aortic laceration at angiography. The authors conclude that 5-mm contrast-enhanced CT can help exclude mediastinal hemorrhage and reduce the angiography rate in low-to-moderate-risk patients with a widened or indeterminate mediastinum. There were no unsuspected cases of mediastinal hemorrhage in patients with normal chest radiographs. Angiography is recommended for patients considered to be at high risk for aortic laceration.     

Computed tomographic characteristics of the normal thymus gland: Relationship to mediastinal hematoma

Computed tomography (CT) is frequently used in the screening process to determine the need for angiography in patients with possible blunt thoracic aortic injury. Misinterpretation of normal mediastinal structures (particularly the thymus in patients under age 40 years) as mediastinal hematoma may result in a significant number of false-positive scans. During a 20-month period, we reviewed the chest CT examinations of 1247 patients to select two groups of patients: group I, in whom the mediastinum was normal by CT, and group II, in whom the CT identification of a mediastinal hematoma had been proven surgically. Two major mediastinal CT differences were noted between the groups. The first was a normal cleavage plane between the lateral aspect of the aortic arch and the soft tissue density of the thymus seen in 100% of patients with normal mediastinum (group I) and 0% of patients with known mediastinal hematoma (group II). The second difference relates to the anatomic fact that the thymus is normally present only in the anterior mediastinum. Thus, the presence of a soft tissue density throughout the right paratracheal region of the middle mediastinum, which was seen in 100% of group II (mediastinal hematoma) patients and in 0% of group I (normal) patients, represented blood and not thymus tissue. These results demonstrate fundamental differences in appearance between thymic tissue, regardless of its state of involution, and a mediastinal hematoma on unenhanced mediastinal CT (UMCT). It is important that these differences be recognized so that thymic tissue is not confused with a mediastinal hematoma resulting in unnecessary thoracic aortography. Supported in part by the John S. Dunn Research Foundation.     

Blunt thoracic aortic injury in children

Thoracic aortic injury (TAI) in children secondary to blunt chest trauma is rare and less well documented than TAI in adults. To further establishe the incidence and radiographic manifestations of this severe injury, we reviewed our experimence with TAI in children over an 8-year period. We performed a computer search from the Trauma Registry at our level I trauma center for all cases of TAI among patients 16 years of age or younger who were admitted after sustaining blunt chest trauma between August 1984 and September 1992. We reviewed our records of all thoracic aortograms performed on children for blunt trauma during this same time period. Indication for angiography was determined by review of chest radiographs and medical records of all patients who underwent thoracic aortography. We reviewed medical records and all available chest radiographs, computed tomography (CT) examinations, and thoracic aortograms of children diagnosed with TAI. Of 308 children admitted with blunt chest trauma, 26 (8.4%) underwent angiography to exclude aortic or great vessel injury. Of these 26 patients, three (11.5%) were diagnosed with TAI, and one patient demonstrated a traumatic pseudoaneurysm of the proximal left subclavian artery. The incidence of TAI among children who sustained blunt chest trauma was 1.0% in our series. All three patients with TAI in our series were male, ages 10–12 (mean: 11 years). Chest radiographs on two of the patients with TAI revealed mediastinal widening, ill-defined aortic outline, shift of the trachea and nasogastric tube, and depression of the left main stem bronchus. The chest radiograph in one patient with TAI was technically inadequate. CT demonstrated abnormalities in two patients. Angiographic findings were similar to those seen in adults. TAI in children is rare, occurring in 1% of children sustaining blunt chest trauma in our series. Our findings support previous reports that the plain film, CT, and angiographic findings with this injury resemble those found in adults.     

Traumatic injuries: imaging of thoracic injuries

Chest trauma is one of the most important causes of death, in particular in individuals under the age of 40 years. The mortality rate for chest trauma, often related to motor vehicle accidents, is approximately 15.5%; it increases dramatically to 77% with associated shock and head injury (Glasgow scores of 3-4). The accurate diagnosis of pathologies consequent to blunt chest trauma depends on a complete knowledge of the different clinical and radiological manifestations. The first diagnostic approach is classically based on chest X-ray often carried out on supine position at the hospital admission. A CT study must then be performed in all chest trauma patients in whom there is even the smallest diagnostic doubt on plain film. In particular, spiral CT (SCT) assumes a fundamental role in the demonstration of mediastinal hemorrhage and direct signs of aortic lesions. At present, SCT is routinely part of a diagnostic evaluation which also includes scans of the brain and the abdomen in polytraumatized patients. Magnetic resonance is the ideal method for visualizing diaphragmatic lesions. Furthermore, recent reports have demonstrated the high diagnostic value of MR in evaluating aortic injuries. The purpose of this article is to review the most common radiological patterns related to chest trauma.