Isolated free fluid in trauma

Last revised by Craig Hacking on 27 Sep 2017

Isolated free fluid in trauma may or may not represent a significant injury, and this creates a diagnostic dilemma in determining appropriate treatment for these patients. 

The presence of isolated free fluid in trauma occurs in 3-5% of blunt trauma patients 1-4.

The concern is that this free fluid represents a sign of occult traumatic abdominal organ injury such as:

The location, volume and attenuation of free fluid can be helpful in determining its significance 1-4:

  • trace volume free fluid in females
  • trace volume free fluid in males
    • low volume of pelvic free fluid below the level S3 that was low-attenuating (mean 8.1 HU) was not associated with undiagnosed bowel or mesenteric injury in one study 4
    • larger volume (i.e. more than trace) of higher-attenuating free fluid (30-35 HU), especially if mesenteric, present in more than one or more peritoneal compartments or pelvic free fluid above the level of S3 is more indicative of occult injury 2,4

Isolated free fluid in trauma can often present a diagnostic dilemma and options for management are based on clinical conditions; options include proceeding for diagnostic laparotomy (becoming less common) or repeat CT scan in 12-48 hours with the consideration for oral contrast 1-2

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