DOI: 10.1148/radiol.2462070082
(Radiology 2008;246:410-419.)
© RSNA, 2008
Blunt Trauma: Feasibility and Clinical Utility of Pelvic CT Angiography Performed with 64–Detector Row CT1
Stephan W. Anderson, MD,
Jorge A. Soto, MD,
Brian C. Lucey, MD,
Peter A. Burke, MD,
Erwin F. Hirsch, MD, and
James T. Rhea, MD
1 From the Departments of Radiology (S.W.A., J.A.S., B.C.L., J.T.R.) and Surgery (P.A.B., E.F.H.), Boston University Medical Center, 88 E Newton St, 2nd Floor, Boston, MA 02215. Received January 12, 2007; revision requested March 15; revision received May 10; accepted June 12; final version accepted August 1.
Address correspondence to S.W.A. (e-mail: Stephan.anderson{at}bmc.org).
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ABSTRACT
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Purpose: To retrospectively evaluate the integration of pelvic computed tomographic (CT) angiography into the thoracoabdominal CT examination of blunt trauma by using 64–detector row CT to differentiate active arterial from active venous hemorrhage.
Materials and Methods: This study was institutional review board approved and HIPAA compliant; the requirement for informed patient consent was waived. Fifty-three patients (30 male, 23 female; mean age, 42 years) with multiple blunt trauma underwent pelvic CT angiography with 64–detector row CT at admission. Arterial phase and portal venous phase pelvic CT angiograms were evaluated for evidence of vascular injury. In patients with active extravasation, the size of the hemorrhaging area was measured on arterial, portal venous, and delayed phase images. The Fisher exact test was used to correlate presence of vascular injury with subsequent clinical management. The Wilcoxon rank sum test was used to test the association between size of active hemorrhage during the vascular enhancement phases and subsequent clinical outcome. Finally, the Fisher exact test was used to correlate presence of vascular injury with severity of osseous injury.
Results: At pelvic CT angiography, 21 of the 53 patients had evidence of vascular injury: 10 isolated active arterial extravasations, three isolated arterial occlusions, three cases of both arterial extravasation and occlusion, two cases of arterial and venous extravasations, and three isolated venous extravasations. Eleven of the 21 patients also underwent conventional angiography, with subsequent embolization performed in seven of these 11 patients. The remaining 10 patients were successfully treated conservatively. When the foci of active arterial extravasation were compared on arterial, portal venous, and delayed phase images, the mean areas of hemorrhage across all three phases were larger in patients who required conventional angiography than in those successfully treated with conservative management.
Conclusion: With use of 64–detector row scanning, pelvic CT angiography was successfully integrated into the authors' CT protocols and enabled differentiation between active arterial and active venous hemorrhage, which may influence clinical management.
© RSNA, 2008
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INTRODUCTION
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Computed tomography (CT) has been shown to be valuable for evaluating vascular injury in patients who have blunt trauma with pelvic injury (1–9). Given the morbidity and mortality associated with vascular injuries of the pelvis, prompt assessment and diagnosis are crucial (1–3,5,10–15). Traditionally, digital subtraction angiography has been the preferred test for detecting injuries to large pelvic arteries and treating the foci of active extravasation. Improvements in CT technology have led to the implementation of CT angiography for the examination of patients with acute trauma (16–19).
Multidetector CT represents further evolution in the application of CT for trauma imaging (7–9,20). The increasing acquisition speeds and decreasing section thicknesses afforded by advances in multidetector CT technology have yielded improved image quality and multiplanar capabilities (10,21,22). Sixty-four–detector row CT, with unprecedented short acquisition times, affords the ability to tailor complex multiphasic tests in which pelvic CT angiography and extremity CT angiography are combined into a single comprehensive examination (19). The main resultant benefit is that CT angiography then enables rapid assessment of arterial injuries, and when integrated into the remaining part of the trauma CT examination, it may be performed by using a single bolus of intravenous contrast material (19). Thus, the purpose of this study was to retrospectively evaluate the integration of pelvic CT angiography into the thoracoabdominal CT examination of patients with blunt trauma by using 64–detector row CT to differentiate active arterial from active venous hemorrhage.
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MATERIALS AND METHODS
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Patients
Approval to perform this retrospective study was obtained from our institutional review board. The study was conducted in compliance with the Health Insurance Portability and Accountability Act, and the requirement for informed patient consent was waived. We reviewed our hospital's trauma registry and electronic medical records to identify all patients aged 16 years or older who had undergone pelvic CT angiography as part of a CT evaluation of blunt trauma during a 19-month period (April 2005 through October 2006). The decision to perform CT angiography of the pelvis was made by the attending trauma surgeon at the time of admission and was based on the results of both initial clinical assessment, including hemodynamic status and blood gas determinations, and pelvic radiography performed in the trauma unit.
Fifty-three patients (30 male, 23 female; age range, 17–86 years; mean age, 42 years) fulfilled the criteria for inclusion in this study. The male patients had a mean age of 43 years (range, 20–84 years), and the female patients had a mean age of 39 years (range, 17–86 years). Mechanisms of blunt trauma were as follows: 32 patients were passengers involved in a motor vehicle collision, 11 fell from a heightened platform, and 10 were struck by a motor vehicle. Forty-six patients underwent pelvic CT angiography combined with CT of the chest, abdomen, and pelvis, and seven underwent pelvic CT angiography combined with CT of the abdomen and pelvis.
CT Protocol
All CT examinations were performed with a 64–detector row scanner (LightSpeed Pro; GE Medical Systems, Milwaukee, Wis). Pelvic CT angiography, defined as CT scanning of the pelvis during the arterial phase of vascular enhancement, included the acquisition of images from the iliac crests to the greater trochanters with use of the following parameters: a section thickness of 0.625 mm, a pitch of 1:0.987, a noise factor of 29, and a gantry rotation time of 0.5 second. The pelvic CT angiogram was acquired immediately before the remaining part of the intravenous contrast material–enhanced CT examination of the abdomen and pelvis and, when necessary, the chest. CT scans of the chest, abdomen, and pelvis were acquired in the craniocaudal direction from the lung apices to the lowest part of the diaphragm—constituting the chest—and from the highest part of the diaphragm to the pubic symphysis—constituting the abdomen—by using the following parameters: a section thickness of 1.25 mm, a pitch of 1:0.987, a noise factor of 19, and a gantry rotation time of 0.5 second.
In addition, given the severity of the injuries detected on the portal venous phase images, 5-minute delayed phase images of the abdomen and pelvis were acquired in all patients by using parameters identical to those used for portal venous phase scanning, with the exception that the noise factor was increased from 19 to 29. This change in noise factor led to a 50%–60% reduction in radiation dose. Multiplanar reformations in orthogonal planes (ie, direct multiplanar images) were also obtained in all patients and for each portion of the multiphasic examinations.
All patients received a single intravenous bolus of 100 mL of iohexol (350 mg of iodine per milliliter, Optiray; Mallinckrodt Imaging, Hazelwood, Mo), which was injected through an 18- or 20-gauge cannula in an antecubital vein at a rate of 5 mL/sec by using a dual-syringe power injector. We administered 30 mL of saline solution as a chasing bolus after the intravenous contrast material injection. Acquisition of the pelvic CT angiograms began 23 seconds after the start of the contrast material injection. CT scanning of the chest, abdomen, and pelvis was completed after the pelvic CT angiogram acquisition. Scanning delays from the time of injection were 30 seconds for chest CT, 70 seconds for abdominopelvic CT, and 5 minutes for delayed phase CT. In keeping with our departmental blunt trauma CT protocol, no oral contrast material was administered.
Image Analysis
Two radiologists (S.W.A., J.A.S.) retrospectively reviewed all of the CT images in consensus at a picture archiving and communication system workstation. The radiologists were presented with the arterial, portal venous, and delayed phase images obtained in all the patients. They were asked to evaluate the images for evidence of arterial injury, including areas of active extravasation, dissection, occlusion, pseudoaneurysm formation, and arteriovenous fistula formation. The radiologists were also asked to evaluate the images for evidence of venous injury, including active hemorrhage and occlusion. Active arterial hemorrhage was defined as extravascular high-attenuating regions with attenuation similar to or greater than that of the aorta on arterial phase images. In addition, areas of active arterial hemorrhage were expected to increase in size and remain of higher attenuation than the aorta on both portal venous phase and delayed phase images.
Extravascular high-attenuating foci that were identified on the portal venous phase images only, without corresponding abnormality on the earlier acquired arterial phase images, were considered to be of venous origin. Patients who demonstrated both areas of active arterial hemorrhage and areas of active venous hemorrhage that were distinct in location were considered to have active arterial and active venous hemorrhage. Before areas of active arterial and active venous extravasation could be described as distinct in location, multiple planes had to be reviewed to ensure that there was no continuity between the high-attenuating areas on the portal venous or delayed phase images. The radiologists were instructed to use transverse as well as the routinely generated coronal and sagittal images when necessary. They were also free to use further postprocessing options such as curved planar reformations and maximum intensity projections as needed.
One of the two radiologists (S.W.A.) measured the area of the largest focus of active extravasation seen on the arterial phase images. These measurements were performed by using the area measurement tools provided on the picture archiving and communication system workstation. The same radiologist then identified and measured the same extravascular focus on the portal venous and delayed phase images by using the anatomic landmarks depicted on the transverse CT images. This radiologist then measured the attenuation of the following pelvic arteries on the arterial phase images: common iliac, external iliac, internal iliac, superior gluteal, superficial femoral, and profunda femoris arteries. Measurements were obtained on both sides of the pelvis, and the mean value was recorded for each vessel. Finally, the two interpreting radiologists were asked to classify the identified associated pelvic fractures by using Kane's modification of the Key-Conwell fracture classification system (Table 1) (23).
One of the two radiologists (S.W.A.) conducted an electronic chart review to evaluate the clinical management and outcomes of the patients. Clinical management and outcomes were grouped into one of four categories: successful conservative management, recovery after conventional angiography with or without embolization, recovery after surgical intervention, or death. In the patients who underwent conventional angiography, the angiographic results and the need for coil embolization were also recorded.
Statistical Analyses
The Fisher exact test (R Statistical System, version 2.0.1, language and environment for statistical computing and graphics) was used to correlate the presence of vascular injury with the subsequent clinical management, and patients were accordingly assigned to one of two groups: The first group comprised patients who were treated with conservative management or underwent conventional angiography without subsequent embolization. The second group comprised patients who underwent conventional angiography with subsequent embolization, underwent surgical repair, or died. By using the Wilcoxon rank sum test to analyze results in specifically those patients with active arterial extravasation, associations between the size of the area of arterial extravasation on the arterial, portal venous, and delayed phase images and the subsequent clinical management were tested, and patients were accordingly assigned to one of two groups: a group comprising patients successfully treated with conservative management and a group comprising patients who underwent conventional angiography, underwent surgical repair, or died.
In addition, with use of the Wilcoxon rank sum test, the size of the extravasation during the three phases was correlated with the clinical outcome by using a second, different grouping of subsequent clinical management: Among the patients who underwent conventional angiography, those who underwent coil embolization were compared with those who demonstrated no further evidence of active hemorrhage at conventional angiography. The Fisher exact test was used to correlate the osseous pelvic injury classification with both the presence or absence of arterial injuries and the need for conventional angiography and subsequent embolization. P < .05 was considered to indicate significance.
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RESULTS
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Vascular Injury
Twenty-one (40%) of the 53 patients had findings of vascular injury on the pelvic CT angiograms, whereas the remaining 32 (60%) patients did not. The specific lesions found in the 21 patients were isolated arterial extravasation (n = 10), isolated arterial occlusion (n = 3), both arterial extravasation and arterial occlusion (n = 3), isolated venous extravasation (n = 3), and both arterial and venous extravasation (n = 2).
At Fisher exact testing, we found significant differences in subsequent clinical management based on the presence or absence of vascular injury (P < .001): Eight (38%) of the 21 patients with vascular injury required coil embolization, required surgical repair, or died, and all 32 (100%) patients without vascular injury were treated conservatively (P < .001).
Active Arterial Extravasation
Fifteen patients had active arterial extravasation at CT angiography (Table 2, Fig 1). Two of these patients had associated venous extravasation, and 13 did not. Three of these 15 patients also had arterial occlusion. Ten of the 15 patients underwent conventional angiography, which revealed arterial extravasation in seven of them. All seven of these patients required coil embolization of the injury. The remaining three patients who underwent conventional angiography had no evidence of ongoing hemorrhage and recovered without the need for further intervention. Four of the 15 patients with active extravasation were successfully treated with conservative management. The decision to treat these patients conservatively was made by the attending trauma surgeon and was based on clinical factors, such as hemodynamic stability, and the extent of active arterial hemorrhage identified at CT angiography. The remaining patient with active extravasation at CT angiography died shortly after CT as a result of extensive pelvic and solid visceral organ injuries.
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Figure 1a: Transverse CT angiograms obtained in 86-year-old woman after motor vehicle collision. (a) Arterial phase image shows small focus of active arterial extravasation (arrow). Corresponding (b) portal venous phase and (c) delayed phase images show enlargement of the focus (arrow). This patient underwent conventional angiography with successful coil embolization. A right obturator hematoma also is noted.
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Figure 1b: Transverse CT angiograms obtained in 86-year-old woman after motor vehicle collision. (a) Arterial phase image shows small focus of active arterial extravasation (arrow). Corresponding (b) portal venous phase and (c) delayed phase images show enlargement of the focus (arrow). This patient underwent conventional angiography with successful coil embolization. A right obturator hematoma also is noted.
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Figure 1c: Transverse CT angiograms obtained in 86-year-old woman after motor vehicle collision. (a) Arterial phase image shows small focus of active arterial extravasation (arrow). Corresponding (b) portal venous phase and (c) delayed phase images show enlargement of the focus (arrow). This patient underwent conventional angiography with successful coil embolization. A right obturator hematoma also is noted.
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Active Venous Extravasation
Five patients had pelvic CT angiographic findings of active venous hemorrhage (Table 2, Fig 2). Three of these patients had isolated venous hemorrhage, and two also had evidence of active arterial extravasation at pelvic CT angiography. Two of the five patients with active venous extravasation underwent conventional angiography. One of these two patients had CT angiographic findings of both active arterial and active venous extravasation, and the other had findings of isolated venous extravasation. The patient with both active arterial and active venous hemorrhage was found to have ongoing arterial hemorrhage at conventional angiography and was treated with coil embolization (Fig 3). However, no active hemorrhage in the region of venous extravasation was seen at conventional angiography in this patient. The patient with isolated venous hemorrhage underwent conventional angiography of the pelvic arteries in conjunction with therapeutic coil embolization of hepatic vascular injuries. No evidence of active arterial extravasation was seen in the pelvis at the time of conventional angiography. A single patient with isolated venous hemorrhage underwent exploratory laparotomy secondary to bowel injuries that were identified at admission CT. This patient did not require surgical repair of pelvic vascular injuries. The remaining two of the five patients with active venous extravasation—one with isolated venous hemorrhage and one with active arterial and active venous extravasation at pelvic CT angiography—were successfully treated with conservative management.
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Figure 2a: Transverse oblique CT angiograms obtained in 23-year-old woman struck by a motor vehicle. (a) Arterial phase image shows no evidence of vascular injury. Corresponding (b) portal venous phase and (c) delayed phase images show an enlarging focus of active venous hemorrhage (arrow). The absence of corresponding extraluminal contrast agent in a confirms this injury to be of venous origin. This patient was successfully treated with conservative management.
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Figure 2b: Transverse oblique CT angiograms obtained in 23-year-old woman struck by a motor vehicle. (a) Arterial phase image shows no evidence of vascular injury. Corresponding (b) portal venous phase and (c) delayed phase images show an enlarging focus of active venous hemorrhage (arrow). The absence of corresponding extraluminal contrast agent in a confirms this injury to be of venous origin. This patient was successfully treated with conservative management.
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Figure 2c: Transverse oblique CT angiograms obtained in 23-year-old woman struck by a motor vehicle. (a) Arterial phase image shows no evidence of vascular injury. Corresponding (b) portal venous phase and (c) delayed phase images show an enlarging focus of active venous hemorrhage (arrow). The absence of corresponding extraluminal contrast agent in a confirms this injury to be of venous origin. This patient was successfully treated with conservative management.
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Figure 3a: Images obtained in 17-year-old girl involved in a motor vehicle collision. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow) in the pelvis. A right inferior pubic ramus fracture is also seen. (b) Transverse portal venous phase pelvic CT angiogram shows the area of arterial extravasation (arrow) to be increasing in size. (c) Transverse portal venous phase CT angiogram shows a distinct area of venous hemorrhage (arrow) is also present. As predicted, no contrast blush is seen in the region of the venous hemorrhage. (d) Conventional angiogram findings confirm the presence of the arterial hemorrhage (arrow).
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Figure 3b: Images obtained in 17-year-old girl involved in a motor vehicle collision. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow) in the pelvis. A right inferior pubic ramus fracture is also seen. (b) Transverse portal venous phase pelvic CT angiogram shows the area of arterial extravasation (arrow) to be increasing in size. (c) Transverse portal venous phase CT angiogram shows a distinct area of venous hemorrhage (arrow) is also present. As predicted, no contrast blush is seen in the region of the venous hemorrhage. (d) Conventional angiogram findings confirm the presence of the arterial hemorrhage (arrow).
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Figure 3c: Images obtained in 17-year-old girl involved in a motor vehicle collision. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow) in the pelvis. A right inferior pubic ramus fracture is also seen. (b) Transverse portal venous phase pelvic CT angiogram shows the area of arterial extravasation (arrow) to be increasing in size. (c) Transverse portal venous phase CT angiogram shows a distinct area of venous hemorrhage (arrow) is also present. As predicted, no contrast blush is seen in the region of the venous hemorrhage. (d) Conventional angiogram findings confirm the presence of the arterial hemorrhage (arrow).
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Figure 3d: Images obtained in 17-year-old girl involved in a motor vehicle collision. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow) in the pelvis. A right inferior pubic ramus fracture is also seen. (b) Transverse portal venous phase pelvic CT angiogram shows the area of arterial extravasation (arrow) to be increasing in size. (c) Transverse portal venous phase CT angiogram shows a distinct area of venous hemorrhage (arrow) is also present. As predicted, no contrast blush is seen in the region of the venous hemorrhage. (d) Conventional angiogram findings confirm the presence of the arterial hemorrhage (arrow).
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Arterial Occlusion
Six patients had findings of acute arterial occlusion at CT angiography (Table 2); three of these patients also had evidence of active arterial extravasation. Three patients had unilateral superior gluteal artery occlusion, two had unilateral internal iliac artery occlusion, and one had occlusion of both superior gluteal arteries. Both patients with internal iliac artery occlusion also demonstrated evidence of active arterial extravasation at pelvic CT angiography (Fig 4). These two patients underwent conventional angiography, which revealed both the internal iliac artery occlusion and the active hemorrhage. Coil embolization was successfully performed in both these patients. The four patients with superior gluteal artery occlusion, including one patient who also had active arterial extravasation, were successfully treated with conservative management.
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Figure 4a: Images obtained in 21-year-old man after motorcycle accident. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow). (b) Corresponding oblique maximum intensity projection image shows occlusion of the left internal iliac artery (arrow). (c) Conventional angiogram shows left internal iliac occlusion (arrow). Ongoing arterial hemorrhage (not shown) was also seen at conventional angiography. Comminuted left iliac bone fractures are best seen in a.
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Figure 4b: Images obtained in 21-year-old man after motorcycle accident. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow). (b) Corresponding oblique maximum intensity projection image shows occlusion of the left internal iliac artery (arrow). (c) Conventional angiogram shows left internal iliac occlusion (arrow). Ongoing arterial hemorrhage (not shown) was also seen at conventional angiography. Comminuted left iliac bone fractures are best seen in a.
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Figure 4c: Images obtained in 21-year-old man after motorcycle accident. (a) Transverse arterial phase pelvic CT angiogram shows area of active arterial extravasation (arrow). (b) Corresponding oblique maximum intensity projection image shows occlusion of the left internal iliac artery (arrow). (c) Conventional angiogram shows left internal iliac occlusion (arrow). Ongoing arterial hemorrhage (not shown) was also seen at conventional angiography. Comminuted left iliac bone fractures are best seen in a.
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Active Arterial Hemorrhage Size
In the 15 patients with active arterial extravasation, the area of the extravascular high-attenuating foci was measured on the arterial, portal venous, and delayed phase images (Table 3). We performed two separate comparisons of subsequent management by using the measured areas of extravascular hyperattenuation. The first comparison was that between the 11 (73%) patients who either underwent conventional angiography or died and the four (27%) patients who were successfully treated with conservative management. The second comparison involved only the 10 (67%) patients who underwent conventional angiography: The seven (70%) patients who underwent conventional angiography and required coil embolization were compared with the three (30%) patients who underwent conventional angiography that revealed no further evidence of active hemorrhage.
The first comparison revealed that the mean area of the largest focus of active arterial extravasation during all three phases was larger in the 11 patients who underwent conventional angiography or died than in the four patients who were successfully treated with conservative management and that this difference was significant on the portal venous phase (P = .03) and delayed phase (P = .006) images.
The second comparison revealed that the mean area of arterial extravasation for the seven patients with ongoing hemorrhage identified at conventional (digital subtraction) angiography during the arterial, portal venous, and delayed phases was actually smaller than that for the patients without ongoing active hemorrhage at digital subtraction angiography. These differences were not significant (P = .68, P = .54, and P = .34 for arterial, portal venous, and delayed phase images, respectively).
Associated Osseous Injuries
Fisher exact testing revealed significant differences in the frequency of arterial injury between the patients with more severe (types II and III) osseous injuries and those with less severe (types I and IV) osseous injuries (P = .008) (Table 4). A total of five (15%) of the 33 patients with more severe osseous injuries, compared with two (10%) of the 20 patients with less severe osseous injuries, underwent conventional angiography with the need for subsequent coil embolization.
Technical Quality
Twelve measurements of the attenuation coefficients of contrast-enhanced blood in the pelvic arteries were obtained in each patient, and a total of 612 vascular stations were measured (Table 5). For 312 (51%) of the 612 measured stations, the mean attenuation value for the pelvic arteries was greater than 250 HU. For 180 (29%) stations, the mean attenuation value for the pelvic arteries was between 200 and 250 HU. For 72 (12%) stations, the mean attenuation value for the arterial phase images was between 150 and 199 HU. For 48 (8%) stations, the mean attenuation value for the arterial phase images was between 100 and 149 HU. None of the stations had an attenuation value lower than 100 HU.
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DISCUSSION
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Differentiating between Arterial and Venous Hemorrhage
Given its capability to facilitate differentiation between active venous and active arterial hemorrhage, pelvic CT angiography may guide the clinical decisions for patients with blunt pelvic trauma. A large proportion of the patients who underwent pelvic CT angiography in this study had evidence of acute vascular injury. The majority of these patients had evidence of arterial injury with active extravasation. Three patients had isolated active venous hemorrhage, and two additional patients had evidence of both arterial and venous hemorrhage. The sole acquisition of portal venous phase images would not have enabled a confident differentiation between the two hemorrhage types unless the vessel of origin was readily identified. Although our experience was preliminary and limited to a small subset of patients, none of the three patients with isolated active venous hemorrhage detected at CT angiography required coil embolization of pelvic vascular injuries or surgical repair. Of equal importance is the increased confidence in diagnosing active arterial hemorrhage that we gained by using the arterial phase image findings. Although the source of hemorrhage is most commonly arterial, as in our study, confidence in the diagnosis of active arterial extravasation increases when this finding is identified on arterial phase images. Given the difference in clinical management based on the source of the hemorrhage, the ability to confidently discern arterial hemorrhage from venous hemorrhage is relevant in the setting of pelvic trauma (12,13,15).
Active Arterial Hemorrhage Size
In our study, the majority of patients with acute arterial injury underwent an emergent intervention. The majority of patients with evidence of active arterial hemorrhage underwent conventional angiography and embolization. However, many patients with no evidence of acute arterial injury and a subset of patients with active arterial extravasation were successfully treated with conservative management. It is therefore important to identify the predictors of the need for conventional angiography among patients in whom arterial hemorrhage is detected at pelvic CT angiography. In our study, the patients with arterial hemorrhage were more likely to subsequently undergo conventional angiography. As multidetector CT technology continues to progress, the sensitivity of this modality for the detection of arterial injury may increase. Even with use of 16–detector row CT technology, it has been shown in vitro that CT angiography may be more sensitive than catheter-based angiography—once considered the reference standard—for the detection of active arterial hemorrhage (24).
The size of the focus of arterial extravasation, the rate of growth of the extravasation across the multiple phases, and the location of the extravasation may be considered in clinical decisions. In our study, the areas of the foci of active extravasation were significantly larger in the patients who underwent an intervention than in those treated with conservative management. However, the area of the foci of active extravasation was not a good predictor of the need for embolization. This observation probably reflects the intermittent nature of arterial hemorrhage. In addition, a multitude of factors, including the patient's hemodynamic status, may affect the rate of hemorrhage during CT scanning. Estimation of both the rate of hemorrhage in patients with active arterial extravasation and the need for subsequent intervention is a topic that requires further research.
Associated Osseous Injuries
At our institution, the decision to request pelvic CT angiography as part of the thoracoabdominal CT examination is made by the trauma surgeon(s) and is often based on findings seen on the initially obtained pelvic radiographs in conjunction with the clinical findings. In this study, the presence of arterial injury was related to the severity of the associated osseous injury: More complex fractures were significantly more likely to accompany arterial injuries. Our experience did not reveal a significant difference in the need for coil embolization among the patients with more severe osseous injury, probably because of the low overall frequency of coil embolization. Findings on the initially obtained pelvic radiographs may be helpful predictors of arterial injury, as none of the patients without pelvic ring fractures had evidence of arterial injury in this study. Limitations in using pelvic radiography findings to triage patients to select those who will undergo pelvic CT angiography include the frequently poor quality of trauma radiographs. Also, although none of the patients with isolated acetabular fractures had evidence of arterial injury in this study, none of the fractures was substantially displaced; thus, a potential cause of vascular injuries was limited.
Technical Quality
The technical quality afforded by using pelvic CT angiography was adequate in the majority of patients, as 80% of the stations had mean attenuation values for the pelvic arteries of 200 HU or greater, which is considered indicative of a technically high-quality examination (25). It is possible that the technical quality of the CT scans would have been further improved if timing bolus or bolus-tracking techniques had been used in place of the standard delay technique. In the majority of patients, a standard scanning delay of 23 seconds proved to be adequate. Timing bolus or bolus-tracking techniques, although slightly more complex, may be considered to improve the likelihood of obtaining high-quality images, especially in elderly patients and patients suspected of having decreased cardiac output. We elected to use a fixed scanning time to avoid unnecessary delays in patient treatment.
Considerations in Implementing Pelvic CT Angiography
When considering performing pelvic CT angiography in patients with blunt trauma, several factors must be kept in mind. Because the sensitivity of pelvic CT angiography for the detection of arterial injury rivals that of direct catheter-based angiography, the clinical usefulness of CT findings of arterial injury, including hemorrhage rates, demands further investigation. However, we believe that differentiating between venous and arterial extravasation yields invaluable clinical information in cases of pelvic injury. Pelvic CT angiography can be integrated into trauma protocols without increasing intravenous contrast agent doses—but at the cost of higher radiation dose. However, patients who have blunt trauma with acute pelvic injury are often critically injured, so the benefits of rapid injury assessment outweigh the risks of radiation. With the intrinsically high contrast-to-noise ratio afforded with CT angiography, low-radiation-dose techniques may be used.
Limitations
The limitations of this study included the retrospective nature of the investigation and the lack of routine use of conventional angiography, which has long been considered the reference standard. Therefore, the diagnostic accuracy of pelvic CT angiography could not be assessed. However, a prospective trial incorporating conventional angiography might have exposed patients to unnecessary risks. Also, given the evidence that the sensitivity of multidetector CT for the detection of active hemorrhage rivals that of catheter-based angiography, the question of whether catheter-based angiography should remain the reference standard must be raised (24). Finally, given the retrospective design of this study, we were unable to directly correlate the CT findings with the subsequent clinical management owing to the myriad of clinical information that is considered in the treatment decision–making process. Given clinicians' reliance on CT findings, it is difficult to make conclusions about the value of these findings in predicting subsequent clinical management. With findings as critical as active arterial extravasation especially, the CT findings themselves may mandate certain clinical actions.
In conclusion, 64–detector row CT technology represents an important advance in trauma imaging and affords the ability to integrate pelvic CT angiography into the complete CT examination of patients with blunt trauma. Multiphasic CT image acquisition enables the distinction between arterial and venous hemorrhage, a differentiation of particular importance in the setting of pelvic trauma. Measurements of the areas of active arterial hemorrhage obtained with multiphasic CT may be used to predict subsequent clinical management.
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ADVANCES IN KNOWLEDGE
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- Pelvic CT angiography may be successfully integrated into routine trauma CT protocols by using 64–detector row CT with a single initial bolus of intravenous contrast material.
- The authors describe a method of differentiating between active arterial and active venous hemorrhage in blunt pelvic trauma.
- A comparison of the areas of active arterial hemorrhage revealed significant differences in area associated with subsequent clinical management on the portal venous phase (P = .03) and delayed phase (P = .006) images.
- Increasingly severe osseous pelvic injuries are shown to be associated with significantly increased (P = .008) rates of vascular in-jury.
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IMPLICATIONS FOR PATIENT CARE
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- Differentiation between active arterial and active venous hemorrhage in patients with blunt pelvic trauma may be used to triage patients for subsequent clinical management.
- The area of active arterial extravasation may be used to predict subsequent clinical management.
- The severity of osseous pelvic injury may help to predict the likelihood of vascular injury and aid in the triage of patients.
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FOOTNOTES
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Guarantor of integrity of entire study, S.W.A.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, S.W.A., B.C.L.; clinical studies, S.W.A., J.A.S.; statistical analysis, S.W.A.; and manuscript editing, all authors
Authors stated no financial relationship to disclose.
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References
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ABSTRACT
INTRODUCTION
