Seat Belt Sign – How Good Is CT for Intra-abdominal Injury?

Written by Alex Chen

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CT scan of the abdomen/pelvis had 100% sensitivity (95%CI 92.5-100) for detecting intra-abdominal injury in trauma patients with abdominal seat belt sign (ASBS). Both abrasions or ecchymoses over the seat belt area were associated with increased risk of intra-abdominal injury.

Why does this matter?
If you work at a trauma center, you are bound to see motor vehicle accidents coming in. One of the things we look for on our secondary survey is a seat belt sign which can indicate a higher risk of intra-abdominal injury. These patients are often observed or admitted due to the potential for missed injuries on initial work-up. In these times of worsening hospital crowding, anything that can allow us to safely discharge patients from ED is helpful.

“When in doubt, scan it.” -some wise ED attending
This was a retrospective case series conducted at a Level I trauma center in which they identified 425 ED patients with confirmed ASBS through chart review. 415 of 425 (97.7%) of these patients received a CT scan, and they found that the overall incidence of intra-abdominal injury was 38.1% in this cohort, with 13.6% undergoing exploratory laparotomy. Initial CT scan had a 100% sensitivity (95%CI 92.5-100) for detecting intra-abdominal injury. No patients in this sample that had an initial negative CT went on to have a positive finding on repeat CT. While the sensitivity looks great, just be cautious; the lower end of the confidence interval is 92.5%, and this was a retrospective case series which could have missed patients who had more subtle exam findings that excluded them from this study. Finally, if the patient’s abdomen remains extremely tender, even with a negative CT, don’t send them home.

Source
Patients with Abrasion or Ecchymosis Seat Belt Sign Have High Risk for Abdominal Injury, but Initial Computed Tomography is 100% Sensitive. J Emerg Med. 2020 Aug 18:S0736-4679(20)30660-0. doi: 10.1016/j.jemermed.2020.06.057. Online ahead of print.

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1 thought on “Seat Belt Sign – How Good Is CT for Intra-abdominal Injury?”

  1. dreyerc891@gmail.com

    As an ED physician (UK/NZ) with nearly 30 years experience, I have an increasing number of ‘I remember a patient who…’ (add on adverse outcome of your choice). I had a patient in their 20’s, middle back seat passenger, restrained by lap belt, positive ASBS, negative CT abdo who decompensated approximately 36 hours later (happily in the toilets of the surgical ward where they were a patient). At surgery small bowel perforation. Survived stormy post op course.

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