Tag Archives: CT

Using CT To Diagnose Extremity Vascular Injury

The traditional gold standard for diagnosis of vascular injury to the extremities has been a good physical exam plus conventional catheter angiography. However, using angiography always adds a layer of complexity and risk to patient care. The interventional team may not be immediately available after hours, there is typically a road trip within the hospital to deliver the patient for the study, and overall it is quite expensive.

With the advancements we have seen in CT angio techniques and scanner technology, some centers have been using computed tomography to evaluate for vascular injury. A few small retrospective studies have been done, but this month a larger prospective study was published.

Over a 20 month period, 635 patients with extremity trauma and a suspicion for vascular injury were entered into the study. A structured physical exam was performed, and any patient with “hard signs” of vascular injury were taken to the OR. 527 patients had no signs of vascular injury and were observed and released. The remaining 73 (most had soft signs of vascular injury) underwent CT angiography of the extremity.

The sensitivity and specificity of this test were 82% and 92%, respectively. Positive and negative results were nearly perfectly predictive. However, approximately 10% were inconclusive, usually due to bullet artifact or reformatting errors. These patients either underwent confirmatory conventional angiography or operation.

Bottom line: Angiography using multi-detector CT scanners is an excellent tool for evaluating potential extremity vascular trauma from penetrating trauma. The technology is available around the clock without a wait, and usually does not involve lengthy trips through the hospital. A good physical exam is imperative so patients with hard signs of injury can go straight to the OR. Equivocal studies must be evaluated further by conventional angio or an operation.

Reference: Prospective multidetector computed tomography for extremity vascular trauma. J Trauma 70:808-815, 2011.

Clinical Tip: The Flat Vena Cava in Blunt Trauma

Trauma patients who are hypotensive in the Emergency Department can only be transported to one of two places: the operating room or the morgue. With rare exception, they should never be taken outside the department (e.g. CT scan) because of the fear that they may arrest in an area that is not conducive to efficient resuscitation.

Sometimes patients are initially stable but decompensate later. Since most stable blunt trauma patients end up in CT scan, perhaps there is some telltale sign that can predict later deterioration. A recent Japanese paper looked at the “flatness” of the inferior vena cava as seen on the abdominal CT scan as a predictor of hemodynamic decompensation in the first 24 hours.

A small cohort of 114 patients was used in this prospective study. The vena cava was evaluated at the level of the renal veins. The flatness of the IVC was determined by dividing the transverse diameter by the anteroposterior (AP) diameter. A flat IVC was defined as a transverse to AP diameter ratio of more than 4:1. The ratio in normal patients was about 2:1. See the figure for details.

Patients who had a flat IVC required significantly more blood transfusions, crystalloid infusions within 2 hours of admission, and were more likely to proceed to the OR within the first 24 hours of their hospital stay.

Bottom Line: Assuming that you are only taking stable blunt trauma patients to CT, the incidental finding of a flat vena cava should increase your paranoia levels and lower your threshold for ordering blood and getting the trauma surgeons involved. 

Reference: Predictive value of a flat inferior vena cava on initial computed tomography for hemodynamic deteroration in patients with blunt torso trauma. J Trauma 69(6):1398-1402, 2010.

Emergency Medicine & Trauma Update – Bloomington, MN 10/28/10

“Torso Trauma Update” presented at 8:40AM.

For a copy of the slideset, click here.

Bibliography:

  • What is the utility of focused assessment with sonography in trauma (FAST) exam in penetrating torso trauma? Injury, in press, 2010.
  • CT of blunt abdominal and pelvic vascular injury. Emerg Radiology 17:21-29, 2010
  • More operations, more deaths? Relationship between operative intervention and risk-adjusted mortality at trauma centers. J Trauma 69(1):70-77, 2010

Diagnosing Facial Fractures With CT

Facial fractures are common after major blunt trauma. There are a number of diagnostic tests available for their diagnosis, including head CT, conventional facial imaging and facial CT.

Our preference has been to add a facial CT to the list of diagnostics in any patient with external evidence of facial trauma. Subjectively, it appeared that there were not many injuries being identified, and the vast majority did not require operative management. 

A review of the literature shows that head CT alone is sufficient for screening for significant facial fractures. A small retrospective series noted that the accuracy was 92%, with 90% sensitivity and 95% specificity. 

Bottom line: A head CT alone ordered for the usual indications is a very good screening test for facial fractures. If none are seen, it is unlikely that there are any fractures that require specific management. If fractures are seen, consultation with a facial surgeon is needed. However, unless the fractures involve critical areas (e.g. temporal bone near the middle ear) or are significantly displaced, the benefit of a facial CT scan is still very low since most will be treated without operation.

Reference: Computed tomography of the head as a screening examination for facial fractures. Marinaro et al. Am J Emerg Med 25, 616-619, 2007.

GI Contrast In CT Scanning for Blunt Trauma

Torso CT scanning has become a mainstay in the evaluation of major blunt trauma. The question of using GI contrast in these CTs arises from time to time. There is an ongoing battle between the ED physician/trauma surgeon, who want quick clinical and relevant results, and the radiologist, who wants nice pictures and a comprehensive list of diagnoses.

IV contrast is so helpful and immediately available that it is virtually a no-brainer to use. The only exception is in patients who have a known allergy to it. GI contrast is more complicated. Ideally, it should be given in divided doses over about an hour, and there just isn’t time for it in trauma patients.

We designed a prospective, randomized study more than 10 years ago that looked at groups of patients who either did or did not receive oral contrast. We studied 394 patients and looked a the need for laparotomy based on study results, delayed diagnoses, and nausea/vomiting.

Thirteen percent of the patients in each group vomited. There were two aspirations, both in the non-contrast group. There were 50 abnormal scans in the contrast group and 55 in the no-contrast group. Nineteen contrast and 14 no-contrast patients were taken to OR.

Most interesting, there were 6 bowel injuries in the contrast group and one was not seen by CT. There were 3 bowel injuries in the no-contrast group and all were seen on CT. We found that there were always other signs of injury, such as mesenteric stranding or bubbles. 

Bottom line: Oral contrast is not necessary in acute blunt trauma patients undergoing CT of the abdomen.