pPOCUS in the Field – A Case of Mistaken Identity
A High-Impact Fall on the Slopes
Here’s the video I posted on Instagram about this case! 🎥🩺🚁
A few days ago, during a nighttime helicopter mission, we were dispatched to a 16-year-old snowboarder who had suffered a high-energy impact after falling on an icy slope. The ski patrol reported transient neurological deficits, raising concerns about a potential spinal injury. However, by the time we arrived, her symptoms had fully resolved.
While a resolved neurological deficit was reassuring, the mechanism of injury was significant enough to warrant further investigation. With that level of impact, internal injuries—especially abdominal trauma—couldn’t be ruled out.
The Role of pPOCUS in Trauma Assessment
After completing a thorough primary assessment, I reached for my Butterfly iQ3 Probe to perform an eFAST (Extended Focused Assessment with Sonography for Trauma) scan. The goal? Quickly assess for free intraperitoneal fluid and confirm the integrity of abdominal organs.
One of the first stops in an eFAST scan is Morrison’s pouch—the hepatorenal recess—where free fluid tends to accumulate due to gravity, making it a critical landmark for trauma assessment.
Free Fluid or Gallbladder? The Sonographic Challenge
As I swept the probe over the right upper quadrant, I immediately focused on Morrison’s pouch. And for a brief moment, I thought I had found free fluid—a finding that would have drastically changed our management plan. But something didn’t quite add up.
A closer look at the ultrasound loop revealed a well-defined, smooth, and ovoid structure—the gallbladder. In young, slim patients, the gallbladder can extend far enough into the scan window to mimic free fluid, especially when seen in an unfamiliar plane.
What looks like free fluid at first glance...
... turns out to be the gallbladder upon closer inspection—thankfully!
Key Sonographic Differences: Free Fluid vs. Gallbladder
Understanding the subtle differences between these two structures is critical to avoid unnecessary interventions or misdiagnoses. Here’s how to differentiate them:
✅ Free fluid:
Amorphous, lacks clear borders
Typically anechoic (black on ultrasound)
Shifts with patient movement
Can be seen pooling in dependent areas (e.g., pelvis, hepatorenal recess)
✅ Gallbladder:
Well-defined, smooth-walled, ovoid shape
May contain anechoic bile and occasionally internal echoes (sludge)
Does not shift with movement
Has a characteristic posterior acoustic enhancement due to fluid content
Clinical Context is Everything
Ultrasound alone doesn’t provide the full clinical picture. That’s why correlation with the patient’s presentation is essential. In this case, I expanded the eFAST scan to assess Coller’s pouch and the pelvis—both of which were free of fluid. The patient remained hemodynamically stable with an HR of ~70 and a normal blood pressure. Aside from some localized lower back pain, she had no significant abdominal tenderness and responded well to simple analgesia.
The Takeaway: Pattern Recognition and Clinical Correlation
pPOCUS is a powerful tool, but it’s only as good as the clinician interpreting it. In high-stress environments, it’s easy to misinterpret findings—especially when encountering anatomical variants. The gallbladder can be a common pitfall for less experienced users scanning Morrison’s pouch, but knowing its sonographic characteristics helps avoid misdiagnosis.
Always take a step back—does your ultrasound finding match the clinical picture? When in doubt, assess additional dependent areas for confirmation. Pattern recognition is key—train your eyes to distinguish true free fluid from normal anatomical structures.
Have you ever encountered a similar ultrasound pitfall? Let’s discuss in the comments below!
