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Dx: The W.E.S. Sign
Your intern made some ultrasound errors that are common in both comprehensive and focused biliary scans. Your intern noted that it was difficult to visualize the gallbladder via the subxiphoid or X-7 view, so she utilized the lateral approach instead. As she was scanning through the liver, she noticed a dark, anechoic, oval shaped structure that looked just like a gallbladder lumen. She froze the image and measured the anterior wall of the structure. Unfortunately, if you take a closer look at the image, you’ll note that the structure she was looking at was not the gallbladder, but instead, a massively dilated proximal ureter surrounded by renal parenchyma (top).
So, if that’s not the gallbladder, what is? In Figure 2, your intern thought she saw the typical ultrasound pattern of loops of bowel or stool near the liver, casting acoustic shadows farfield on the screen. When you take a closer look, you notice that she has captured an interesting sonographic finding called the W.E.S. sign (Wall-Echo-Shadow sign). If the gallbladder is completely filled with a very large gallstone, it will produce the W.E.S. sign. The large gallstone is abutted against the anterior wall of the gallbladder producing a bright white, hyperechoic curvilinear stripe with dark, acoustic shadowing farfield and posterior to the calculi (bottom).
You pat your intern on the shoulder and take the opportunity to praise her for a solid work-up, and for using beside ultrasound to enhance and expedite patient care. You teach her how to avoid making some common ultrasound errors, and you remind her that this is what residency is all about. She gives you a thankful smile and runs off to see the next patient, and you know that in the end, it’s still “all good.”
Click HERE to read more about Common Errors of Biliary Ultrasound
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. www.EMresource.ORG
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Based Training for the Maricopa Emergency Medicine Program in Phoenix, Arizona.