Review
DOI: 10.11152/mu.2013.2066.174.evpAbstract
The use of ultrasound in the evaluation of blunt thoraco-abdominal trauma is well described. Evidence for the use of ul- trasound in the evaluation of penetrating cardio-thoracic and abdominal trauma, however, is more limited and varied. Current literature demonstrates that ultrasound is an excellent screening tool for penetrating thoracic and cardiac injuries with a high sensitivity for detecting injury requiring acute intervention. For abdominal injuries, however, the sensitivity for detection of injury is low and thus the utility of ultrasound as a screening tool is limited. This review summarizes the existing literature addressing the clinical utility of ultrasound for penetrating trauma to the pericardium, thorax and abdomen.
Keywords: ultrasound, echocardiography, hemopericardium, hemothorax, hemoperitoneum,
Ultrasound in the evaluation of penetrating thoraco-abdominal trauma: a review of the literature.
Nicholas J. Governatori
1, Turandot Saul
2, Sebastian D. Siadecki
2, Resa E. Lewiss
31Thomas Jefferson University Hospital, Philadelphia PA, 2Department of Emergency Medicine, Division of Emergen- cy Ultrasound, Mount Sinai St. Luke’s Mount Sinai Roosevelt Hospital Center, New York, 3University of Colorado Hospital, Aurora CO USA
Received 15.09.2015 Accepted 08.10.2015 Med Ultrason
2015, Vol. 17, No 4, 528-534
Corresponding author: Turandot Saul, MD
Mount Sinai St. Luke’s Hospital Mount Sinai Roosevelt Hospital Department of Emergency Medicine Division of Emergency Ultrasound 1000 Tenth Avenue, Room GE-01 New York, New York 10019
Phone: 212-523-3981, Fax: 212-523-2186 E-mail: [email protected]
Ultrasound for the evaluation of blunt abdominal trau- ma was first described by Scandinavian interventional ra- diologist Kristensen et al in the early 1970s [1]. Twenty years later, in the 1990s, trauma surgeon Grace Rocyzki et al were using ultrasound as the primary modality for injured patient assessment [2]. Initially, called the FAST (focused abdominal sonography for trauma) examina- tion, as the application expanded and it was incorporated into the Advanced Trauma Life Support Course, the ac- ronym’s meaning changed to the Focused Assessment for the Sonographic examination of the Trauma patient [3]. During this period, surgeons and emergency physi- cians rapidly adopted this noninvasive imaging method of evaluating trauma patients at the bedside [2,4]. Since then, the role of ultrasound in blunt trauma has been well studied. Level 1 evidence exists for the FAST examina-
tion to be considered the initial diagnostic modality to exclude hemoperitoneum in these patients [5-9]. Current- ly, practitioners accept the accuracy rate for ultrasound as nearly equivalent to that of diagnostic peritoneal lavage (DPL) and computed tomography (CT) [10-12]. How- ever, the evidence is less clear for the use of ultrasound in the setting of penetrating thoraco-abdominal trauma.
This review presents the current literature on the role of ultrasound in the evaluation of a patient presenting with penetrating cardiac, pleural and peritoneal injury.
Ultrasound for penetrating cardiac injury
A 1980 study by DeGennero et al advocated imme- diate surgical intervention in all patients with “potential penetrating thoracic injuries in or near the cardiac sil- houette”. The authors based their recommendations upon a comparison of the clinical course of 10 trauma patients treated with observation and conservative management with 33 trauma patients who went immediately for op- erative intervention. Survival rates increased from 20%
to 67% after the direct to the operating room policy was instituted [13]. Consequently, through the late 1980s, di- agnostic sub-xiphoid pericardiotomy was performed to evaluate for a pericardial effusion following a penetrat- ing injury to the thorax[14]. This approach was very reli-
able but resulted in many negative procedures, one study reporting a rate of 76%, and potential complications as high as 54% in another study[15,16].
Ultrasound is very sensitive for the detection of fluid in the pericardial space. With optimal images and correct interpretation, as little as 20 cc of fluid can be visualized [17]. A 1984 case report was one of the earliest publica- tions to advocate for the use of ultrasound in penetrating trauma. A patient with a stab wound to the chest present- ed with a left hemothorax diagnosed on chest radiograph and was treated with tube thoracostomy. After discharge, the patient returned with repeated syncopal episodes and negative chest radiographs until a sonographic cardiac examination demonstrated hemopericardium[18]. The actual number of patients that develop late pericardial ef- fusions is unknown [19].
A 1988 case report provided another example of the utility of cardiac ultrasound in penetrating trauma. A pa- tient with a stab wound to the right upper chest was found to have right-sided pleural fluid on chest radiograph. Af- ter tube thoracostomy did not improve his clinical status, a cardiac ultrasound revealed a pericardial effusion and the patient was taken to the operating room[20]. The au- thors concluded that with a penetrating thoracic injury, ultrasound examination was able to provide a fast and efficient way to demonstrate pericardial fluid. Similar re- sults were reported in a case of a ventral septal defect di- agnosed after detection of hemopericardium on bedside ultrasound [21]. Ultrasound evaluation offered an alter- native to observation versus the aggressive straight to the operating room approach.
Further research was needed to determine a clear role for ultrasound in penetrating thoracic trauma. In 1990 the first prospective study demonstrating the accuracy, sen- sitivity and specificity of ultrasound was published. In this study, 73 patients with penetrating thoracic trauma and stable vital signs received an ultrasound followed by a sub-xiphoid pericardial window in the operating room. Overall, ultrasound was found to have an accuracy of 96%, specificity of 97%, and sensitivity of 90% for predicting cardiac injury [14]. Importantly, the authors concluded that the selective use of sub-xiphoid pericar- diotomy only in patients with a positive ultrasound could eliminate unnecessary surgical procedures.
A 1991 study from the University of California, Davis et al, yielded similar results. Thirty six hemodynamically stable patients with penetrating precordial trauma re- ceived a cardiology department ultrasound examination to determine their disposition: directly to the operating room (large effusion), Intensive Care Unit for 48 hours (small effusion) or ward bed (no effusion). There was no evidence of missed cardiac injury during hospitalization
or after hospital discharge [22]. Ultimately, the authors concluded that the high negative predicative value made from ultrasound an excellent screening tool allowing prompt detection of cardiac injury in the stable patient.
In 1992, the first article was published involving a large group of emergency medicine physicians trained to perform this procedure [23]. This 10-year retrospec- tive review of 49 patients found that point of care (POC) cardiac ultrasound not only decreased time to diagnosis and disposition to the operating room (15.5 minutes in the ultrasound group versus 42.4 minutes in the non- ultrasound group), but also improved both the survival rate (100% in the ultrasound group compared to 57% in the non-ultrasound group)and neurological outcomes.
This was thought to be due to more rapid diagnosis and prompt surgical intervention. There were no false nega- tive examinations on chart review of patient outcomes.
In 1995, a second retrospective chart review from Cook County Hospital examined 121 clinically stable patients with penetrating wounds in the proximity of the heart following an institutional policy change[24].
Patients with evidence of sonographic pericardial effu- sion by the cardiology fellow immediately underwent a sub-xiphoid pericardial window, while those without were admitted and observed for 24-48 hours. The over- all sensitivity, specificity and accuracy of ultrasound was determined to be 96.8%, 100%, and 99.2% respectively with a positive predictive value of 100% and a negative predictive value of 98.9%. The number of sub-xiphoid windows was reduced from 105 to 15 during this period and no clinically significant injuries were missed.
Despite the overwhelmingly positive literature during this period, two articles were also published warning of concerning false negative cases. A 1993 case series em- phasizes that a cardiac ultrasound without significant peri- cardial fluid did not necessarily rule out major injury [25].
The article presented five cases of hemodynamically sta- ble patients with penetrating pericardial trauma, all who had major intra-pericardial injuries. The missed diagnoses were thought to be due to the operator dependent nature of ultrasound and the difficulty in obtaining cardiac views in patients with chest wounds and/or bandages.
Similarly, in a 1995 prospective study of 105 hemo- dynamically stable patients with penetrating thoracic trauma, Meyer et al reported that ultrasound performed by the attending surgeon had significant limitations in identifying serious cardiac injuries in patients with an as- sociated hemothorax (initial chest radiographic evidence of fluid within the pleural cavity) [26]. When compared to sub-xiphoid exploration as the gold standard, POC ultrasound missed four significant cardiac injuries mak- ing it only 56% sensitive in these patients. Two poten-
tial reasons were cited by the authors as explanations;
first, an injury that lacerates the pericardium may allow decompression of intra-pericardial fluid into the pleural cavity, decreasing the accumulation of fluid collection at the pericardial-myocardial interface. Second, the com- plex echoes of adjacent pleural fluid/blood may alter the interpretability of the cardiac ultrasound.
Further research in the late 1990s seemed to reaffirm the utility of POC ultrasound. A 1996 study from Emory University achieved 100% sensitivity and specificity. In this study, surgeons performed pericardial ultrasound ex- aminations in 247 hemodynamically stable patients with penetrating truncal wounds but no immediate indication for operative intervention[27]. Patients were followed during their admission, through discharge and as outpa- tients in clinic, and there here were no false negative or false positive studies. Unlike Meyer’s findings, which suggested that ultrasound had limited sensitivity in pa- tients with an associated hemothorax [26], four of the ten patients in this study with cardiac tamponade also had hemothoraces, and hemopericardium was easily identi- fied on the initial pericardial ultrasound examination.
A larger multi-center study, which included prospec- tively collected data from cardiac ultrasound performed by surgeons or the cardiology department of five Level 1 trauma centers, was published in 1999[28]. Patients with positive examinations underwent surgical explora- tion and those with negative examinations were admitted for observation and followed for a minimum of 23 hours.
Of the pooled 261 patients, there were no false negative studies and seven false positive studies, all of which ex- amined only a single subcostal view. Six of these patients had an associated hemothorax. Overall the sensitivity of ultrasound was 100%, the specificity was 96.9% and the accuracy was 97.3% for detecting hemopericardium.
Furthermore, the mean time from ultrasound to operat- ing room was 12.1 minutes. The authors concluded the study stating they “routinely use ultrasound initially and almost exclusively for the evaluation of patients with penetrating injuries to the precordial or transthoracic region” and that the “indications for a sub-xiphoid peri- cardial window had narrowed substantially.”
As outlined by a 2015 study, the high sensitivities achieved in prior studies may be related to the small numbers of patients with actual cardiac injuries. One hundred seventy two patients presenting with penetrat- ing chest wounds were examined by ultrasound followed by a subxiphoid pericardial window. There were a total of eighteen false negatives: eleven had an associated hemothorax, six had pneumopericardium, while one of the patients returned with a delayed cardiac tamponade after two negative studies (overall sensitivity of 86.7%).
The authors found that, if there is presence or suggestion of either hemothorax or pneumopericardium, then fur- ther diagnostic testing is required [29]. Similarly, a 2009 study, found that the numbers of false negatives were in- creased with concurrent lacerations of the pericardial sac secondary to sequestration of the blood into the thoracic cavity therefore preventing accumulation of a hemoperi- cardium [30].
Both authors conclude that if none of these condi- tions are suspected, the patient may be safely discharged home. A 2013 report from Cook County warns against this policy, citing that it is challenging if not impossible to determine the true incidence of missed cardiac injuries through retrospective studies [31]. Without a doubt fur- ther studies are required to determine whether ultrasound is a safe and effective screen tool for penetrating cardiac injury.
Ultrasound for penetrating pleural injury Hemothorax
Ultrasound can serve as a diagnostic tool for the de- tection of hemothorax in penetrating thoracic injury. It is estimated that 50-100 cc of pleural fluid can be detected on upright chest radiograph [32], while 175 cc is usually necessary for detection when the radiograph is taken with the patient supine[33]. Even smaller quantities of fluid can be detected with ultrasound, with one study estimat- ing that as little as 20 cc of pleural fluid can be visualized [34].
In 1995, Ma et al compared emergency medicine physician-performed thoracic ultrasound for free pleural fluid in 240 trauma patients to a gold standard of chest radiograph or tube thoracostomy drainage. In the 25 pa- tients with hemothorax (from both blunt and penetrating injuries) all were detected by ultrasound and there were no false negative examinations in the patients with pen- etrating trauma [10].
Several of the same authors conducted a further study in 1997 comparing emergency medicine physician-per- formed ultrasound to the gold standard of computed to- mography, tube thoracostomy or both[35]. Ultrasound accurately detected all 18 cases of hemothorax from penetrating thoracic injury. There were no false positive findings resulting in a sensitivity and specificity of 100%.
Pneumothorax
Multiple studies have evaluated the test character- istics of ultrasound for the detection of pneumothorax in blunt thoracic trauma with sensitivities ranging from 92-100% and specificities ranging from 94-99% when compared to a gold standard of computed tomography [36-38]. Several studies have also evaluated the test char-
acteristics of ultrasound for pneumothorax in the setting of penetrating trauma. In 2001, Dulchavsky et al com- pared surgeon-performed thoracic ultrasound to chest radiograph findings as a gold standard. In the 83 cases of penetrating thoracic trauma, 15 patients had a radio- graphic pneumothorax, all of which were detected by ul- trasound, for a sensitivity and specificity of 100%. It was noted that in two cases the pleural interface could not be visualized due to the presence of subcutaneous air [39].
A 2004 study by Knudtson et al also compared surgeon- performed ultrasound to findings on chest radiograph in 21 patients and reported the sensitivity, specificity, posi- tive predictive value, negative predictive value, and ac- curacy for pneumothorax to all be 100% [40]. The au- thors concluded from their findings that ultrasound could be used as an adjunct or precursor to chest radiography in the evaluation of the trauma patient.
A 2012 study by Ku et al compared thoracic ultra- sound for pneumothorax by both surgeons and emergen- cy medicine physicians to a more robust gold standard of computed tomography, tube thoracostomy output or supine chest radiograph followed by clinical observation.
In 47 patients with pneumothorax (blunt and penetrat- ing), ultrasound had a sensitivity of 57% and a specific- ity of 99%. The authors contributed the poor sensitivity to the diverse and varied prior ultrasound experience of their sonographer group, recognizing that most other previous studies were performed by a small number of highly trained sonographers [41].
Evaluating thoracic ultrasound for pneumothorax due to all causes, a 2012 meta-analysis by Alrajhi et al pooled data from 8 studies (6 trauma studies [both blunt and penetrating] and 2 iatrogenic) that all used computed tomography or tube thoracostomy drainage as the gold standard. Overall, the authors reported a sensitivity of 90.9%, a specificity of 98.2%, a positive predictive val- ue of 94.4%, and a negative predictive value of 97.0%
[42]. Ultrasound had excellent test characteristics for the detection of pneumothoraces in this large population of mixed etiology.
Ultrasound for penetrating thoraco-abdominal injury
Initially, most studies in penetrating trauma focused on pericardial fluid, but later, several studies evaluated its utility in abdominal trauma as well. A study by Ma et al in 1995 prospectively evaluated the use of a rapid trauma ultrasound examination in blunt and penetrating torso trauma patients. After emergency medicine resi- dents, fellows and faculty underwent 10 hours of didactic instruction, case review and hands-on sessions, they were
able to detect pericardial fluid with a sensitivity of 100%
and a specificity of 99% and detected intra-peritoneal fluid with a sensitivity of 86% and a specificity of 99%
when compared to the gold standards of CT, diagnostic peritoneal lavage, radiograph, operative findings, or car- diology department echocardiography. They concluded that regardless of the performing physician’s specialty, the more important details were immediate availability and a desire to learn how to perform a trauma ultrasound examination [10].
A 2001 study from the University of Maryland ex- amined 75 consecutive stable patients with penetrating injuries to the abdomen, back and flank. Twenty two of 54 patients with a surgeon-performed negative FAST had intra-abdominal injury at laparotomy yielding an over- all sensitivity of 46%. There were two false positives (a hepatic vein thought to be free fluid and pleural fluid thought to be peritoneal fluid) yielding a specificity of 94%. When compared to other modalities, the FAST ex- amination had the highest specificity and positive predic- tive value whereas computerized tomography (CT) had the highest accuracy [43]. The authors concluded that a positive FAST warranted immediate surgical interven- tion, whereas a negative study required further diagnostic imaging.
A similarly designed prospective observational study, also in 2001, demonstrated a slightly increased sensi- tivity of 67% with a specificity of 98% for the use of technician-performed sonography in penetrating torso injury. Despite the high specificity for detecting pericar- dial or peritoneal fluid, 6 of the 53 initially negative ex- aminations had a significant abdominal injury detected by further diagnostic testing, 5 of which required surgi- cal repair. The authors concluded that ultrasound should be used as one component of a diagnostic algorithm and should not be the definitive test in all cases[44].
A 2004 prospective observational study from Caroli- nas Medical Center reported a 100% sensitivity and spec- ificity for evaluation of traumatic pericardial effusion and intra-peritoneal fluid. Thirty-two hemodynamically sta- ble patients with penetrating trauma were evaluated by emergency medicine physicians and trauma surgeons. Of the 16 patients whose ultrasound was initially negative, no other diagnostic imaging revealed any further injury nor did any return to the hospital within six months with a missed injury. Although the high sensitivity in detect- ing hemopericardium had been reproduced in prior stud- ies, this study was the first to show 100% sensitivity and 100% specificity for detecting intra-peritoneal injury [45].
Ultrasound does not usually detect the actual solid or visceral organ injury but rather relies on the evaluation of
potential spaces as a marker of injury, not necessarily identification of the injury itself, leading to sensitivi- ties ranging from 46-100%, specificities from 48-100%, and negative predictive values from 60-98%. The data is further complicated by the lack of standardization of anatomical landmarks between ultrasound scan protocols across studies.
Conclusion
This article summarizes the existing literature ad- dressing the clinical utility of ultrasound for penetrating trauma. Current literature demonstrates that ultrasound is an excellent screening tool for penetrating thoracic and cardiac injuries with a high sensitivity for detecting in- jury requiring acute intervention. For abdominal injuries, however, the sensitivity for detection of injury is low and thus the utility of ultrasound as a screening tool is limited.
Conflict of interest: none
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