US vs the RUQ

By Dr. Michelle DiMare

Welcome back and Happy New Year!

While the gallbladder itself and the majority of its pathology are usually considered easily identifiable on basic bedside ultrasound, finding the common bile duct often earns top honors as our nemesis. We must be careful to not fall for a few classic, but potentially serious, gallbladder fakeouts…

Case 1: A 45 year old female presents to your hospital with a complaint of epigastric and RUQ pain, subjective fever, nausea and vomiting x 3 days. She tells you her twin sister had to have her gallbladder removed after an episode that seemed exactly like the illness she is having.

After a brief exam demonstrating mild tenderness in both the epigastric area and RUQ and a possible Murphy’s sign, you put the probe on the patient’s abdomen and see this…

US interpretation?

You quickly ascertain that this patient has stones with shadowing, a thickened GB wall and pericholecystic fluid. After an “official” sono, a surgery consult/rejection and some antibiotics, the patient gets admitted for acute cholecystitis.

Case 2: A few weeks later another 45 year old female presents with nearly the same complaint. She has epigastric pain, RUQ pain, nausea and vomiting and weirdly enough, she even looks like your other patient. After an even shorter abdominal exam than you did on the first patient, you again do a bedside sono and see this…

Because you’ve been there, done that, you know the surgery consult will want an “official” sono. You send the patient over to radiology and await the inevitable “critical finding” phone call…

20 minutes later, the phone rings and you are shocked to hear that the critical finding is actually that the patient is s/p cholecystectomy.

So what is the gallbladder looking structure you found on ultrasound??

It’s the Duodenum!!!

How to tell the difference?

1. Location

GB – within a fossa on the visceral surface of the liver, liver on both sides

Duodenum – medial to the liver, encircling the pancreatic head, liver on only one side

GB – connects in line with the main lobar fissure

Duodenum – no relationship to the main lobar fissure

2. Shape and wall

GB – an encapsulated structure in both longitudinal and transverse views

Duodenum – a true tubular structure, no blind end

GB – an anechoic structure (normal GB) with an ECHOGENIC wall

Duodenum – 5 concentric sonographic layers, like all GI structures, alternating hypo and hyperechoic

3. The Rolling Stone

For a patient with non obstructing gallstones (ie not lodged in the neck)

– Start with the patient in left lateral decubitus position

– Stones will sit in the neck

– Roll the patient so they are left side up

– Stones will slowly roll towards gallbladder fundus

– Debris/air in the duodenum will not move with change in position

4. Peristalsis

– obviously absent in gallbladder

The second RUQ fakeout, once again, demonstrates subtle differences between a non clinically significant variation in gallbladder appearance and a case of significant RUQ pathology.

The above US image demonstrates both walls of the gallbladder around a hypoechoic center. Without measuring, the walls appear thickened and mildly edematous and, in an appropriate clinical setting, would normally be concerning for cholecystitis. Or maybe not? If you actually measured the anterior wall of the gallbladder in this image, it would likely be less than 3mm. Even if it was more than 3 mm, given how contracted the gallbladder is, a slightly larger measurement would likely be a normal variant and not a sign of significant gallbladder disease.

How to tell the difference?

1. MEAUSURE!

Visually assess if the GB looks contracted
Get an actual numerical value for the wall, not a visual assessment

2. Look for other signs of cholecystitis

Stones
Pericholecystic fluid
Sono murphy’s sign

Finally, the case of the absent gallbladder which is actually right in front of you.

The image above demonstrates...

The WES or Wall Echo Shadow sign. In this condition, the gallbladder is tightly contracted around either a single large gallstone or around many small stones. Because of this, the lumen of the gallbladder is often not viewed and instead all you can see is the hyperechoic WALL, followed by the hypoechoic ECHO of the stone(s) and the dark SHADOW below that. Often times, while actively scanning, the wide band of shadow is the only sign that the gallbladder is being visualized. Because the GI tract often generates shadowing from bowel gas we tend to ignore shadowing that doesn’t look like its coming from a typical fluid filled gallbladder.

How to find this sign?

Always keep it in mind
Investigate all shadowing

Hope you enjoyed the first post of 2015!! Happy scanning!

References

Bortoff GA, Chen MY, Ott DJ, et al. Gallbladder stones: imaging and intervention. Radiographics. May-Jun 2000;20(3):751-66. Bortoff GA, Chen MY, Ott DJ, et al. Gallbladder stones: imaging and intervention. Radiographics. May-Jun 2000;20(3):751-66.
http://ultrasoundconnection.com/hot-tips-gallbladder-rolling-stones-sign-ultrasound/

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2 Comments

Ian deSouza · January 12, 2015 at 11:14 am

So….the RUQ symptoms in the case of the patient s/p cholecystecomy may be due to a pleural effusion???

dimare · January 12, 2015 at 2:53 pm

Good call deSouza. The image used for that case is actually from a patient who, in addition to being sp cholecystectomy, also has known CHF and was being evaluated for shortness of breath. In addition to the pleural effusion on this image, the rest of his lung US showed large bilateral pleural effusions and diffuse B lines.

Published by andygrock on January 12, 2015