One of the most common pitfalls in gallbladder sonography is confusion with the structure which abuts it in the right upper quadrant – the duodenum. This loop of bowel can easily be mistaken for the gallbladder especially if it contains a mixture of fluid and solid materials. So how can we tell them apart?
- has a bright (echogenic) wall
- is surrounded by liver
- attaches to the middle hepatic ligament
- is a contained structure
- can be traced to the portal vein
- has a darker (hypoechoic) wall
- is next to the liver, not in it
- cannot be traced to the middle hepatic ligament
- is a tubular structure
- does not connect to the portal vein
More images and explanation after the break!
Also, because of the presence of air within the duodenum, it often casts a ‘dirty’ shadow rather than a ‘clean, dark’ shadow from the acoustic shadowing of a classic gallstone. Check out the following images and see if you agree with the findings as labeled.
Some may argue that these pictures demonstrate the WES (wall-echo-shadow). There’s the hyperechoic wall, the anechoic bile and the stone is casting the shadow… however, the shadow’s all wrong. The “shadow” is NOT an anechoic area extending to the edge of the screen. Instead, it represents a ring-down artifact.
Therefore, going by all of the above criteria, the images are not that of a gallbladder or gallstone, but more likely the duodenum.