Ultrasound
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“My 14-year-old has Gallstones!” At least that is what the mother of this teen tells you. He’s had abdominal pain off and on for a year, and it has been getting worse. An ultrasound done at an outside institution last week revealed a “gallstone”. Despite feeling better tonight, this pushy mom wants an admission and surgery. But his history is completely negative for gallstone risk factors. Plus, he’s just not sick. Against your better instincts you do labs. And they are negative as well. He won’t be admitted, not on your shift, but you’d like to see what they are talking about.
 
Using your ultrasound machine you get the following three images. What do you see? 
 
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Soundings by Brady Pregerson, MD & Teresa Wu, MD

“My 14-year-old has Gallstones!” At least that is what the mother of this teen tells you. He’s had abdominal pain off and on for a year, and it has been getting worse. An ultrasound done at an outside institution last week revealed a “gallstone”. Despite feeling better tonight, this pushy mom wants an admission and surgery. But his history is completely negative for gallstone risk factors. Plus, he’s just not sick. Against your better instincts you do labs. And they are negative as well. He won’t be admitted, not on your shift, but you’d like to see what they are talking about.

Using your ultrasound machine you get the following three images. What do you see? 
 
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Answer on next page
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Dx: Ultrasound Shows Gallbladder Polyp
 
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These images do NOT show a gallstone, but rather a gallbladder polyp. On ultrasound, a polyp differs from a gallstone in three ways. Polyps don’t usually cause acoustic shadowing posteriorly, they remain immobile despite patient repositioning, and often times, you can visualize the stalk connecting the polyp to the gallbladder wall. Image 1 (left) shows a cross section of the gallbladder with an echogenic polyp protruding from the right gallbladder wall (ignore the arrow). Using the centimeter markers on the right side of the screen, it probably measures about 0.4cm by 0.7cm. Note how it does NOT settle with gravity to the dependent part of the gallbladder lumen. Image 2 shows a slightly different view. Note the bright, hyperechoic region shooting farfield off the gallbladder wall. This ultrasound artifact is called acoustic enhancement, and occurs when sound waves pass through an anechoic structure like the gallbladder lumen. The “+” shaped calipers are measuring the gallbladder wall. Image 3 (right) shows the gallbladder in its long axis with the polyp now apparently suspended in mid-bile since the stalk is not seen. Again, notice how it does not settle with gravity. To the right of the gallbladder, note the dark acoustic shadow arising from a rib lying just below the inferior tip of the liver. 

Although gallbladder polyps are usually benign and usually asymptomatic, they can occasionally cause symptoms when fragments break off and cause ductal obstruction or spasm. It is also important to remember that polyps can be malignant. The incidence of this usually incidental finding is between one and five percent and they are even more rare in children. When you discover a gallbladder polyp, it is imperative to determine its size, and discern whether or not the patient may be experiencing symptoms related to the polyp. If the patient is asymptomatic and the polyp is less than 5mm, no further workup is warranted. For polyps between 5-10mm, patients should be advised to follow the size of the polyp with serial imaging at 6 and 12 months. Indications for surgery include size greater than 1cm or growing on recheck, concomitant gallstones, primary sclerosing cholangitis, symptoms suspicious for biliary colic, or pancreatitis.

Conclusion? This patient’s pain is more likely caused by dyspepsia than the polyp. An H2 blocker will work just fine.

Brady Pregerson manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit www.ERPocketBooks.com

Teresa Wu is the Director of Simulation Education and Training for Graduate Medical Education, and Ultrasound Faculty at Orlando Regional Medical Center in Orlando, FL.
 
 
 

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