“Hey, save some pizza for me!” your resident exclaims as he joins the masses indulging in a late night treat from the ED administration. Over the past few months, the department’s “door-to-doc” times and “length-of-stay” times have improved enough to warrant a pizza party for the staff. “If all of you are stuffing your faces back here in the work room, who’s out there ensuring our metrics this month are going to be up to snuff?” you jest as you grab your third slice of cheesy goodness.
“It’s all good, Doc. I’ve got a quick case for you,” your enthusiastic intern states. “She’s in bed 10 and she’s all packaged up and ready for discharge. Her length-of-stay was definitely better than average!” In between bites of pizza, your intern summarizes the patient in bed 10 for you. She’s an otherwise healthy 42-year-old female who presents to the ED with right upper quadrant pain that started after dinner tonight. She’s been in town all weekend for a friend’s nuptials and thinks all of the eating and drinking is finally catching up with her. She denies any symptoms other than right upper quadrant (RUQ) and epigastric pain that has improved with some IV morphine that she received during her work-up. Her vital signs are normal, and her exam was only remarkable for RUQ tenderness to palpation. Your intern goes on to explain her differential for the patient’s presentation and expertly explains her reasoning for the work up that was initiated.
You review the results of the patient’s blood and urine tests and note that her CBC, CMP, and UA are within normal limits, and that her urine pregnancy test is negative. Your intern wheels over the ultrasound machine and pulls up the images she obtained at the bedside during her focused biliary scan. As the images are loading up, your intern states, “It’s all good. The wall of the gallbladder was a little thick, but there was no pericholecystic fluid, no sludge or gallstones, and the patient did not have a sonographic Murphy’s sign on exam.” She goes on to explain, “She has a bunch of stool and bowel gas that prevented me from getting a good subcostal or X-7 view, but the lateral approach worked just fine. Her common bile duct was normal and I didn’t see anything else that was concerning.”
You pull up the image where your intern measured the wall of the gallbladder, and this is what you see (top). You then have your intern pull up the images where she thought she saw stool and bowel gas (bottom).
What do the images show? Conclusion on NEXT page
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.
Common Errors of Biliary Ultrasound
More and more practitioners are using bedside ultrasound to obtain valuable data that can be used to enhance and expedite patient care. It is important to recognize the limitations of bedside ultrasonography and to stay current with the recent literature. Update your skills regularly and continue to challenge yourself by reading, scanning, and attending advanced courses.
1. Use a 5-1 MHz phased array or curvilinear transducer. Probes with smaller footprints are easier to maneuver in between the ribs.
2. The gallbladder can be visualized using three main views: the X-7 approach, the subcostal sweep, and the lateral approach.
3. For the X-7 approach, look for the gallbladder 7 cm lateral to the xiphoid process through the intercostal space.
4. With the subcostal sweep, start with the probe in a longitudinal fashion just lateral to the xiphoid process, with the indicator pointing towards the patient’s head. Aim the beams towards the patient’s right shoulder and sweep the probe laterally just underneath the costal margin until you visualize the gallbladder.
5. The lateral approach utilizes the liver as an acoustic window. Place your probe in a longitudinal fashion, along the anterior axillary line, with the indicator pointed towards the patient’s head. Glide anteriorly along the intercostal space, scanning through the liver, until you visualize the gallbladder lumen.
6. Assess whether or not the patient has a normal, dilated gallbladder (between 3-4 cm in the transverse diameter), evidence of cholelithiasis or sludge, gallbladder wall thickening > 3 mm, pericholecystic fluid, common bile duct dilatation > 6 mm, or a sonographic Murphy’s sign. Remember that contracted gallbladders (<3 cm in diameter) can appear to have thickened walls.
7. Remember that the right kidney lies adjacent to the liver. Large renal cysts and prominent hydroureters can be mistaken for the gallbladder if you are not careful. Always scan through the entire gallbladder and follow it’s neck until it joins the cystic duct and eventually the common bile duct to ensure you are visualizing the correct structure.
8. Often times, while scanning through the liver, loops of bowel will be visualized adjacent to the liver’s inferior edge. Stool will appear hyperechoic with prominent acoustic shadowing farfield on the screen. Do not mistake one of these loops of bowel for the gallbladder with an intraluminal stone.
9. Likewise, it is common to overlook a gallbladder filled with a large stone because its sonographic appearance is very similar to a stool-filled loop of bowel. Don’t be fooled by the W.E.S. sign (Wall-Echo-Shadow sign) signifying the presence of a large, and likely symptomatic, gallstone.
10. When in doubt, obtain multiple views from different angles, and reposition the patient as needed.
11. Remember that practice makes perfect. With bedside ultrasound there is no substitute for experience. The more ultrasounds you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is. Stay tuned for future articles on how to avoid common ultrasound mistakes.