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© Turkish Society of Radiology 2007

Lung parenchymal injury and its frequency inblunt thoracic trauma: the diagnostic value ofchest radiography and thoracic CT

Muzaffer Elmalı, Ahmet Baydın, Mehmet Selim Nural, Bora Arslan, Meltem Ceyhan,Nevzat Gürmen

Thoracic traumas are becoming more frequent every day, especiallyas a consequence of motor vehicle accidents. Trauma is the mostcommon cause of death during the first 3 decades of life and deaths

due to thoracic trauma account for 25% of all trauma deaths (1–3).The first-line radiological examination in patients with thoracic trau-

ma is chest X-ray. The assessment of X-rays obtained in emergency con-ditions may be limited by some negative factors due to the patient’s con-dition. In particular, X-rays taken just a few hours after the occurrenceof blunt trauma may not demonstrate the injury. In cases of lung pa-renchymal contusion, hematoma, or laceration, morbidity and mortal-ity increase significantly in those with thoracic trauma. For this reason,early detection of lung parenchymal injuries is critically important forrevealing the dispersion and accompanying pathologies, and for treat-ment planning. Mortality rates can be reduced by emergency radiolo-gists experienced in chest radiography, and the fast and effective use ofother radiologic modalities, with good cooperation between radiologistsand emergency physicians.

The aims of this study were to evaluate the diagnostic value of chest X-rays in detecting lung parenchymal injuries after blunt thoracic trauma,and to reveal the frequency of parenchymal injuries using thoracic com-puted tomography (CT).

Materials and methods

Anteroposterior chest radiographs and axial CT images of 65 patientsthat presented to the emergency room and were subsequently hospi-talized for multiple trauma between January 2005 and June 2006 wereevaluated retrospectively. Five patients that had CT imaging performed>1 h after chest X-ray, had penetrating traumas, or had chest X-raysthat did not qualify for parenchymal assessment were excluded fromthe study. Injuries in the study population were caused by motor ve-hicle accidents, falling from a height, direct trauma, and occupationalaccidents. Mean age of the patients was 43 years (range, 16–85 years),48 were male, and 12 were female. Chest radiographs were obtainedimmediately after presentation to the emergency room and thoracicCTs were taken within 1 h of chest X-rays, based on patient respira-tory system findings. Chest radiographs of the trauma patients wereroutinely obtained in the supine anteroposterior position. Thoracic CTimages were taken using a spiral CT (Xpres/GX, Toshiba, Japan) andwith intravenous administration of 100 ml of iodine-containing non-ionic contrast medium, without using an automatic injector. Technicalparameters were as follows: section thickness, 7 mm; table speed, 7 mm(pitch, 1); kVp, 120; mAs, 150.

Assessments were made by 2 radiologists experienced in chest radiol-ogy, and final decisions were made by consensus. An abnormal increase

ORIGINAL ARTICLE

Diagn Interv Radiol 2007; 13:179–182 CHEST IMAGING

From the Departments of Radiology (M.E. muzafel@yahoo.

com.tr , M.S.N., M.C., N.G.), and Emergency Medicine (A.B.,

B.A.), 19 Mayıs University School of Medicine, Samsun, Turkey.

Received 12 December 2006; revision requested 14 May 2007; revisionreceived 28 May 2007; accepted 1 August 2007.

PURPOSEThe aims of this study were to determine the value ofchest radiography in diagnosing lung parenchymalinjury in patients with thoracic trauma, and to evalu-ate the frequency of lung parenchymal injury by us-ing thoracic computed tomography (CT).

MATERIALS AND METHODSBetween January 2005 and June 2006, we retrospec-tively evaluated the anteroposterior chest radiographsand thoracic CTs of 60 patients that presented to ouremergency department and were hospitalized due tomulti-organ trauma.

RESULTSChest radiography revealed parenchymal injury in 32of the patients, while thoracic CT confirmed paren-chymal injury in only 27 of these 32 patients. Chestradiographs did not reveal any parenchymal injuryin 28 of the patients, whereas thoracic CT detectedparenchymal injury in 12 of these 28 patients. Tho-racic CT results were accepted as the gold standardin the evaluation of patients with chest trauma andshowed that the sensitivity, specificity, positive pre-dictive value, and negative predictive value of chestradiography in determining parenchymal injury were69%, 76%, 84%, and 57%, respectively. In addition,thoracic CT revealed that 65% of the patients withblunt thoracic trauma suffered parenchymal injury.

CONCLUSIONThe sensitivity of anteroposterior chest radiography inidentifying lung parenchymal injury was low, with ahigh false negative rate; therefore, we think that earlyevaluation with thoracic CT is extremely helpful inthe diagnosis and treatment of patients with thoracictrauma, adding to the cooperative work that existsbetween radiologists and emergency physicians.

Key words: • blunt thorax trauma • chest radiography• computed tomography, thoracic • lung contusion• lung injury

 

Elmalı et al.180 • December 2007 • Diagnostic and Interventional Radiology

in parenchymal intensity was consid-ered parenchymal injury. In thoracicCT, parenchymal injuries were clas-sified as follows: Contusion: alveolaror ground-glass parenchymal densityincreases, which were tending to coa-lesce; laceration: ripped or cavity-shaped air spaces that were separatedfrom or located within the lung pa-renchymal contusion area; hematoma:homogenous hyperdense areas close toblood density that were smooth bor-dered and tended to be spherical. Inaddition to parenchymal injury find-ings in thoracic CT, accompanyingextra-parenchymal observations, suchas rib fracture and pneumothorax werealso noted. The sensitivity, specificity,and positive and negative predictivevalues of chest radiographs were calcu-lated by accepting thoracic CT as thegold standard.

Results

Among the 60 chest radiographs,32 revealed a pathological densityincrease related to parenchymal in-jury, whereas 28 did not reveal find-ings indicative of parenchymal injury(Table). In 27 of the 32 patients inwhich parenchymal injury was detect-ed with chest radiographs, parenchy-mal injury was confirmed by thoracicCT. The remaining 5 patients did notshow any signs of parenchymal injurywith thoracic CT, and 3 of them hadhemothorax and 2 had chest wall he-matomas. Among the 28 patients withnegative findings of parenchymal in-jury according to chest radiographs,12 were found to have parenchymalcontusions based on thoracic CT, andone had accompanying laceration.

Considering thoracic CT findings thegold standard, the sensitivity of chestradiography in detecting parenchymalinjury in patients with blunt traumawas 69%, the specificity was 76%, thepositive predictive value was 84%, andthe negative predictive value was 57%.

Of the 60 patients, 39 (65%) hadlung parenchymal injuries (Figs. 1–3).

Among them, 37 had contusion (62%),4 had laceration (7%), and 2 had he-matoma (3%). The most commonpathologies that accompanied the pa-renchymal injuries were rib fractures(84%), hemothorax (82%), and pneu-mothorax (73%), and 5 patients (8%)presented with pneumomediastinum.Mediastinal major vascular injuries,tracheobronchial injury, and diaphrag-matic, esophageal, and other injurieswere not observed. In 2 patients, sole-ly lung parenchymal injury (isolatedcontusion) was detected without anyaccompanying thoracic wall or bonepathologies.

Discussion

In multi-trauma patients, when in-juries of the head and neck, spine, ab-domen, or extremities are prominent,pathologies concerning the thoraxmay be overlooked, or if the initialchest radiograph is considered to besufficient, parenchymal injuries mayremain undetected. Mortality ratesranged from 14% to 40% in multi-trauma patients with lung contusionwhen accompanied by other organinjuries (4). In a study by Dee, themortality rate of patients with isolat-ed parenchymal injuries and no otherchest injuries was 11%, whereas therate increased to 22% in the presenceof any other injury (5). Therefore, pa-tients with contusion detected withchest radiography need to be fol-lowed up closely. Any change in thefindings should be evaluated and aCT scan should be scheduled. In ourstudy, we achieved full remission inthe 2 patients with isolated paren-chymal injury. Our mortality rate inpatients with multiple organ injuriesaccompanying lung parenchymal in-jury (n = 39) was 21%.

Thoracic traumas can be classified asparenchymal and extra-parenchymal.Parenchymal traumas include contu-sion, laceration, hematoma, and tor-sion of pulmonary tissue. With theprogression of those findings or as a

complication, respiratory distress syn-drome, aspiration pneumonia, and at-electasis may occur. Contusion occursas a result of the effect of direct pressureafter a blunt trauma and is usually seenadjacent to solid structures like verte-brae, ribs, the liver, and the heart (6).In chest radiographs, lung contusionappears within the first 6–8 h follow-ing trauma as a non-homogenous den-sity increase (4, 7). Radiographic find-ings may not be visible within the firstfew days. The contusion area becomesmore difficult to visualize in cases ofaccompanying hemothorax, aspira-tion pneumonia, or atelectasis. Contu-sions are often seen as non-segmental,non-lobar, peripheral, and in the formof increased density on thoracic CT.It is more likely to detect contusionswith thoracic CT than with chest radi-ography (8). In blunt traumas, contu-sions are reported in 17%–70% of cases(9–13). In our study, the rate of lungcontusions in blunt thoracic traumaswas 62%, and contusion was the majorcomponent (95%) of lung parenchy-mal injuries.

Lung laceration occurs more fre-quently with penetrating traumas,whereas it may occur in blunt traumasdue to the direct effects of pressure onthe thorax, the effects of rib fracture,sudden collapse of pulmonary tissue,or corresponding strokes in differentpositions. It is difficult to detect lacera-tions with chest radiography as theyusually overlap accompanying contu-sion areas. Following trauma, the de-tection of a non-homogenous densityincrease, in addition to radiolucentair spaces, can be indicative of lacera-tion. When lung contusion begins toresolve within 2–4 days of the trauma,lacerations become more visible inthoracic CT than in chest radiograph(13). A Swiss cheese appearance occursif there are numerous small lacera-tion areas inside the contusion region(14) (Fig. 2c). Hematomas are seen aswell-defined, spherical or oval, homog-enous increased densities, both withthoracic CT and chest radiography. Inour study, the laceration rate was 7%and the hematoma rate was 3% due toblunt thoracic injury.

While evaluating the patient, onemust keep in mind that there may beinjuries of the lungs and mediastinumwithout any accompanying thoraxwall damage. Additionally, as childrenand young patients have more flex-

Parenchymal injury in patients according to chest radiography and thoracic CT

Patients withparenchymal injury

Patients withoutparenchymal injury

Total

Chest radiography 32 28 60

Thoracic CT 39 21 60

 

Lung parenchymal injury in blunt thoracic trauma  • 181Volume 13 • Issue 4

Figure 1. a, b. On chest radiograph (a) there is no sign of parenchymal injury,whereas on axial thoracic CT image (b) atthe parenchymal window, obtained followinghemoptysis, non-homogenous increaseddensities, consistent with contusion, in themiddle lobe of the right lung and bilateralposterior paraspinal regions are evident.

ba

ible chest walls, there may not be a ribfracture even if there is a lung injury(15). In our study, 2 patients who hadisolated lung contusion without extra-parenchymal findings were 18 and 24years of ages.

Fractures in the first 3 ribs portray aserious amount of energy transfer dur-ing the trauma and in this case there isa high risk of tracheobronchial, vascu-lar, cardiac, and pulmonary parenchy-mal injury (4). Chest radiography can

be ineffective in evaluating such con-ditions. For that reason, use of thoracicCT when a rib fracture is detected inthat region can prevent serious prob-lems from being overlooked. As a mat-ter of fact, among the 5 patients withfractures of the first 3 ribs in our study,4 had lung contusion and 1 had ac-companying laceration.

Some research has indicated a lowsensitivity of chest radiography, com-pared to thoracic CT, in the detectionof lung injuries in thoracic traumas (8,16). In the present study, the sensitiv-ity of chest radiography in detectingparenchymal injury was 69%, and thespecificity was 76%. While chest radio-graphs of 28 patients were negative forlung parenchymal damage, we detect-ed contusion in 12 of them using tho-racic CT; thus, the false negativity rateof chest radiography was 43%. For thatreason, we think that the indication forthoracic CT must be determined imme-diately for patients with severe thoracictrauma. It is not possible to determineearly parenchymal injury signs us-ing chest radiography and, moreover,

Figure 2. a–c. On chest radiograph (a) density increase consistent with contusion at the right lung’s superior and middle zones is evident. Axialthoracic CT images (b, c) of the same patient at the parenchymal window, which were obtained following the chest radiograph, indicate abroad contusion area with laceration (arrow , b) and an additional Swiss cheese appearance (arrow , c) in the right lung.

ba   c

Figure 3. a, b. On chest radiograph (a), air-fluid level (hemopneumothorax) and atelectasis isvisible at the right side. Non-homogenous density increase within the atelectatic parenchymaat the right paracardiac region is also seen. On axial thoracic CT image (b) at the parenchymalwindow, a spherical hematoma (arrow) with homogenous density is seen at the posterior rightlung.

ba

 

Elmalı et al.182 • December 2007 • Diagnostic and Interventional Radiology

pathologies can be overlooked becauseof blind spots, like areas neighboringthe diaphragm, or retrocardiac and par-aspinal regions. Motion artifacts usu-ally occur in traumatic patients, thusincreasing the difficulty of evaluatingthe images and offering an explanationfor the low specificity and high falsenegativity in detecting parenchymalinjuries with chest radiography. Initialchest radiography obtained in chesttrauma patients is also insufficient inthe differential diagnosis of contusion,hemorrhage, laceration, hematoma, at-electasis, and hemothorax. In our study,among the 5 patients that we consid-ered to have had lung parenchymal in-jury, according to their anteroposteriorchest X-rays, 3 of them had rib fractureand hemothorax, and 2 had rib fractureand thoracic soft tissue hematomas ontheir thoracic CTs. These false positiveswere due to superimpositions on chestradiographs. Lateral images may reducethese superimpositions to a certain de-gree. As superimpositions on chest ra-diographs are avoided in thoracic CT,all thoracic structures can be evaluatedin detail. Detection of these findings in

the early stage promotes effective treat-ment planning and positively affectsthe prognosis.

In conclusion, the sensitivity of an-teroposterior chest radiography in de-tecting lung parenchymal injuries islow, with a high rate of false negativ-ity. Therefore, we think that thoracicCT evaluation of patients with severethoracic trauma, in the early stage,with the cooperation of emergencyphysicians and radiologists will bebeneficial for diagnosis and treatmentplanning.

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