Blunt abdominal trauma: current imaging techniques and CT findings in patients with solid organ, bowel, and mesenteric injury.

Imaging plays a critical role in the evaluation of patients with blunt abdominal trauma. In most institutions, computed tomography (CT) is the modality of choice when evaluating such patients. The purpose of this review is to highlight current techniques in trauma imaging and to review CT findings associated with solid organ, bowel, mesenteric, and diaphragmatic injury. In particular, emphasis is placed on the use of multidetector CT technology (MDCT), especially 64-row detector CT. The role of various techniques, including the use of oral and intravenous contrast, as well as the potential benefit of delayed imaging, is discussed.

Blunt abdominal trauma: utility of 5-minute delayed CT with a reduced radiation dose.

PURPOSE: To retrospectively evaluate the utility of 5-minute delayed computed tomography (CT) of the abdomen and pelvis by using a reduced radiation dose in patients with blunt abdominal trauma. MATERIALS AND METHODS: Institutional review board consent was obtained, and written informed consent was waived. The study was HIPAA compliant. A total of 662 patients (497 men, 165 women; mean age, 40.5 years; range, 18-94 years) were identified who were evaluated with CT after blunt abdominal trauma during a 1-year period. Delayed CT scans were acquired 5 minutes after intravenous contrast material injection by using a decreased tube current of 100 mAs. Injury was identified in 106 patients. Two radiologists blinded to initial CT scan interpretation reviewed these cases to determine the quality and utility of delayed scans. Disagreement was settled by consensus. Delayed scans were considered useful when they aided in (a) characterizing initial CT findings, (b) identifying findings not present at initial CT, (c) excluding injury suggested at initial CT, and (d) increasing reader confidence with regard to initial CT findings. RESULTS: All delayed scans were diagnostic. Delayed scans were useful in 27% (12 of 44) of patients with solid organ injury, 5.9% (one of 17) of patients with bowel or mesenteric injury, 4.5% (one of 22) of patients with pelvic fractures, and in none of the patients with free fluid only. Overall, delayed CT was useful in 2.1% (14 of 662) of all patients (95% confidence interval: 1.0, 3.2) referred for evaluation following blunt abdominal trauma. Utility increased to 13.2% (14 of 106) (95% confidence interval: 6.8, 19.7) in the group of patients with injury or suspected of having injury after initial CT. CONCLUSION: If delayed CT scans are acquired when patients with blunt abdominal trauma are evaluated, selective, rather than routine, acquisition is recommended and a reduced radiation dose seems adequate.

Evaluation of blunt abdominal trauma using PACS-based 2D and 3D MDCT reformations of the lumbar spine and pelvis.

OBJECTIVE: The purpose of this study was to show the value of 2D and 3D reformations of CT data from abdominal and pelvic CT performed immediately at the workstation using a PACS-based software program to evaluate the lumbar spine and pelvis in patients with blunt abdominal trauma. MATERIALS AND METHODS: We reviewed the abdominopelvic CT scans and conventional radiographs of the lumbar spine or pelvis of 156 consecutive patients with blunt abdominal trauma. The CT data were compared with the radiographic findings and also with the findings of dedicated repeat CT of the spine or pelvis, when performed. RESULTS: CT depicted 80 fractures of the lumbar spine and 178 pelvic fractures. Radiography showed 40 fractures of the lumbar spine and 138 pelvic fractures. No additional fractures were identified on dedicated repeat CT. CONCLUSION: Conventional radiographs to clear the lumbar spine are no longer required when abdominopelvic CT data are available. CT and reformatted CT data show more fractures than radiography and miss no fractures compared with dedicated CT of the lumbar spine or pelvis. Having these images immediately available through the PACS workstation saves time for the trauma team in the management of critically ill patients.

Impact of MDCT angiography on the use of catheter angiography for the assessment of cervical arterial injury after blunt or penetrating trauma.

OBJECTIVE: The objective of our study was to assess the impact of the increasing use of MDCT angiography in the setting of blunt and penetrating neck trauma on the use of digital subtraction angiography (DSA) at our institution, a level 1 trauma center. MATERIALS AND METHODS: From January 2001 to December 2003, 57 patients were referred for CT angiography or DSA of the neck after blunt or penetrating neck trauma. All CT angiograms were acquired with a 4-MDCT scanner. The patients were divided into three groups on the basis of consecutive 12-month periods (2001, 2002, and 2003), and the initial imaging technique was recorded. The results of CT and digital subtraction angiograms were compared with operative findings and with clinical course, when available. RESULTS: In 2001, 12 patients were referred for imaging: nine patients were evaluated initially with DSA and three patients were evaluated with CT angiography and subsequently with DSA. In 2002 and 2003, 11 and 34 patients, respectively, underwent CT angiography as the initial imaging examination. During these 2 years, no patient underwent DSA as the initial diagnostic test, but five patients underwent DSA after CT angiography for the following indications: evaluation of nondiagnostic CT angiograms (n = 1), confirmation of findings when requested by the clinical service (n = 2), and catheter-guided therapy (n = 2). CONCLUSION: CT angiography has essentially replaced DSA as the study of choice for the initial evaluation of the neck vessels in the setting of blunt or penetrating trauma at our institution. CT angiography is adequate for the initial evaluation, allows appropriate triage of patients to conventional angiography or surgery for appropriate treatment, and can guide conservative management when appropriate.

Use of 3D imaging in CT of the acute trauma patient: impact of a PACS-based software package.

To evaluate the impact of a picture archiving and communication systems (PACS)-based software package on the requests for 3D reconstructions of multidetector CT (MDCT) data sets in the emergency radiology of a level 1 trauma center, we reviewed the number and type of physician requests for 3D reconstructions of MDCT data sets for patients admitted after sustaining multiple trauma, during a 12-month period (January 2003-December 2003). During the first 5 months of the study, 3D reconstructions were performed in dedicated workstations located separately from the emergency radiology CT interpretation area. During the last 7 months of the study, reconstructions were performed online by the attending radiologist or resident on duty, using a software package directly incorporated into the PACS workstations. The mean monthly number of 3D reconstructions requested during the two time periods was compared using Student's t test. The monthly mean +/- SD of 3D reconstructions performed before and after 3D software incorporation into the PACS was 34+/-7 (95% CI, 10-58) and 132+/-31 (95% CI, 111-153), respectively. This difference was statistically significant (p<0.0001). In the multiple trauma patient, implementation of PACS-integrated software increases utilization of 3D reconstructions of MDCT data sets.

Mesenteric lymph nodes seen at imaging: causes and significance.

With the advent of multidetector computed tomography, routine evaluation of mesenteric lymph nodes is now possible. For the first time, normal mesenteric nodes may be reliably identified noninvasively. Because of the increasing volume of cross-sectional imaging examinations being performed, lymph nodes in the mesentery are being detected with increasing frequency. This is often an unsuspected finding. Although the detected lymph nodes may be normal, there is a large number of disease processes that may lead to mesenteric lymphadenopathy. The most common causes of mesenteric lymphadenopathy are neoplastic, inflammatory, and infectious processes. Many of these causes may also result in lymphadenopathy elsewhere in the body. It is important to recognize mesenteric lymphadenopathy in patients with a history of a primary carcinoma because the lymphadenopathy affects the staging of the disease, which in turn will affect further management. In addition, mesenteric lymphadenopathy may be the only indicator of an underlying inflammatory or infectious process causing abdominal pain. The distribution of the lymph nodes may indicate the exact nature of the underlying disease process, and the correct treatment may then be instituted. Besides neoplastic, inflammatory, and infectious processes, many other disease processes may occasionally result in mesenteric lymphadenopathy.

Pancreas divisum: depiction with multi-detector row CT.

PURPOSE: To retrospectively evaluate contrast material-enhanced multi-detector row computed tomography (CT) in the depiction of pancreas divisum. MATERIALS AND METHODS: This study was approved by the investigational review board. Seventy-seven patients (46 men and 31 women; mean age, 51 years) underwent CT with a four-detector row scanner and endoscopic retrograde pancreatography (ERP). Section thickness was 3.2 mm, and the reconstruction interval was 3 mm. Two radiologists independently evaluated the CT data sets with picture archiving and communication system (PACS) workstations equipped with software for two- and three-dimensional postprocessing reformations; the radiologists were blinded to the clinical and ERP data. Pancreas divisum was diagnosed at CT if what the authors termed the "dominant dorsal duct sign" (the caliber of the dorsal duct was larger than that of the ventral duct) was present and if the dorsal and ventral ducts did not appear to communicate with each other at cine review of images. ERP findings were used as the standard of reference for determining the performance (sensitivity, specificity, positive and negative predictive values) of the radiologists' CT interpretations. Interobserver agreement was measured by using kappa statistics. RESULTS: For four of the 77 patients (5%), both radiologists considered that depiction of the pancreatic duct on CT images was not sufficient to enable evaluation of ductal anatomy. These patients were excluded from further analysis. In the remaining 73 patients, ERP demonstrated pancreas divisum in 10 (14%); both observers made the correct diagnosis in nine of these patients. In addition, one radiologist had one false-positive interpretation, whereas the other radiologist had two false-positive interpretations. Thus, for observer 1, the calculated sensitivity was 90% (95% confidence interval [CI], 60%-98%) and the specificity was 98% (95% CI, 91%-100%). For observer 2, sensitivity was 90% (95% CI, 60%-98%) and specificity was 97% (95% CI, 89%-99%). Interobserver agreement was excellent (kappa = 0.93). CONCLUSION: CT scans obtained with multi-detector row scanners and interpreted with PACS workstations enable depiction of pancreas divisum. This assessment is possible only when the pancreatic duct is visualized.

Mesenteric lymph nodes: detection and significance on MDCT.

OBJECTIVE: Unsuspected mesenteric lymph nodes are frequently found on abdominal CT scans in everyday clinical practice. What to do with these findings has not been well established. The purpose of this study is to document the incidence of mesenteric lymph nodes in a previously healthy population and to provide guidelines for further management. MATERIALS AND METHODS: We examined the CT scans of 132 consecutive patients (84 men and 36 women; age range, 12-90 years; mean age, 43 years) who presented to the emergency department after experiencing blunt abdominal trauma. Twelve patients were excluded because they had disease processes known to be associated with lymphadenopathy. All imaging was performed using 3.2-mm collimation on MDCT scanners with IV contrast material. Two radiologists evaluated the images by consensus and recorded the presence of mesenteric lymph nodes greater than 3 mm in the short axis. Lymph node size, number, and location (central, peripheral, or right lower quadrant) were documented. All studies were reviewed on a PACS workstation. RESULTS: Of the 120 patients with otherwise normal CT scans, 47 had mesenteric lymph nodes greater than 3 mm. Of these 47 patients, 22 (47%) had five or more lymph nodes detected. Twenty-five (53%) of the 47 patients had four or fewer nodes. The mean size of the largest nodes was 4.8 mm (range, 3-9 mm), and the mean size of the nodes found per patient was 3.6 mm (range, 3-6 mm). These nodes were identified only at the mesenteric root in 32 patients (68%), only in the mesenteric periphery in eight patients (17%), and only in the right lower quadrant in five patients (11%). Nodes were identified in more than one location in two patients (4%). CONCLUSION: Incidental finding of mesenteric lymph nodes is common, reflecting more widespread use of thin-collimation MDCT and PACS workstations. In general, these nodes are small, measuring less than 5 mm. Such nodes when found in an otherwise healthy population are clinically insignificant and require no further imaging.

Blunt abdominal trauma: performance of CT without oral contrast material.

PURPOSE: To retrospectively evaluate multi-detector row computed tomography (CT) without oral contrast material for depiction of bowel and mesenteric injuries that require surgical repair in patients with blunt abdominal trauma. MATERIALS AND METHODS: The investigational review board approved the study. Informed consent was waived. CT reports for October 2001 to September 2003 were reviewed and 1082 patients were identified who had undergone abdominopelvic CT with a multi-detector row scanner and without oral contrast material. Findings were divided into four categories: negative, solid organ injury with or without hemoperitoneum, free fluid only, and suspected bowel or mesenteric injury. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated by comparing CT findings with laparotomy reports and hospital course. RESULTS: CT findings were no intraabdominal injury (n = 932), solid organ injury only (n = 102), free fluid only (n = 34), and suspected bowel or mesenteric injury (n = 14). CT findings in patients suspected of having bowel or mesenteric injury were pneumoperitoneum with other secondary findings (n = 4), mesenteric hematoma and bowel wall abnormality (n = 2), mesenteric hematoma only (n = 4), and bowel wall thickening only (n = 4). In 11 patients, bowel or mesenteric injury was proved surgically. Thus, the study included 1066 true-negative, nine true-positive, two false-negative, and five false-positive results. Based on these data, sensitivity was 82% (95% confidence interval [CI]: 52%, 95%), specificity was 99% (95% CI: 98%, 99%), positive predictive value was 64% (95% CI: 39%, 83%), and negative predictive value was 99% (95% CI: 98%, 99%) for depiction of bowel and mesenteric injuries. CONCLUSION: Multi-detector row CT without oral contrast material is adequate for depiction of bowel and mesenteric injuries that require surgical repair. Results are comparable with previously reported data for single-detector row helical CT with oral contrast material.

Blunt trauma of the pancreas and biliary tract: a multimodality imaging approach to diagnosis.

Injuries of the pancreas, gallbladder, and bile ducts due to blunt trauma are relatively uncommon and difficult to detect but are associated with high morbidity and mortality, especially if diagnosis is delayed. Accurate and early diagnosis is imperative, and imaging plays a key role in detection. Knowledge of the mechanisms of injury, the types of injuries, and the roles of various imaging modalities is essential for prompt and accurate diagnosis. Early recognition of disruption of the main pancreatic duct is important because such disruption is the principal cause of delayed complications. Computed tomography (CT) can demonstrate pancreatic parenchymal injuries and complications such as abscess, fistula, pancreatitis, and pseudocyst. CT findings can also suggest disruption of the pancreatic duct; however, the ability of CT to indicate this finding depends on the degree of parenchymal injury. Magnetic resonance (MR) cholangiopancreatography allows direct imaging of the pancreatic duct and sites of disruption. Gallbladder injuries can be detected with CT, ultrasonography, hepatobiliary scintigraphy, or MR cholangiopancreatography. CT findings include a collapsed gallbladder, wall thickening, inhomogeneous mural enhancement, and pericholecystic fluid. Bile duct injuries can be suggested with CT, which may show ascites and associated liver injuries, and can be confirmed with hepatobiliary scintigraphy.