Hey everyone, it’s Medicine Mondays again. Today is kind of a random post about “What is Bouveret Syndrome?”

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What is Bouveret Syndrome?

This is kind of random but recently I saw a case of Bouveret Syndrome, and interestingly New England Journal of Medicine just recently did an article about it. So today is kind of an educational day on what to look for in this interesting case, from both the clinical side and radiology side.

First things first:

What is it?

Bouveret Syndrome is a rare presentation of gallstone ileus. For those who don’t know, gallstone ileus is when a gallstone leaves the gallbladder and makes it way into the small bowel. Usually these gallstones are a 1 or 2 cm in size and their presence in the small bowel causes an ileus.

However, Bouveret Syndrome is a very rare variant of this. Rather than travel through the biliary tree, what happens is that the gallstone erodes through the gallbladder or the cystic duct directly into the small bowel, usually the duodenum. Rather than causing a small bowel ileus, it usually causes a gastric outlet obstruction. The reason for this is because this anomalous connection (cholecystoduodenal fistula) between the biliary tree and the small bowel is usually very proximal, involving the the 1st portion of the duodenum or even the pylorus of the stomach.

As you can imagine, usually these stones are also larger in size, something like 3 or 4 cm. I imagine their large size is what makes it impossible for them to pass through the biliary tree and causes the erosion and fistulous connection.

Clinical Presentation:

Unfortunately, there is no classic clinical presentation. However, usually its some variation of abdominal pain and right upper quadrant pain. From my understanding, it’s essentially a cross between cholecystitis, gallstone ileus, gastric outlet obstruction, or even small bowel obstruction so any or all of those presentations would have this in the differential as a zebra to be aware of.

The “Rigler triad” of gallstone ileus is helpful to remember: bowel obstruction, pneumobilia, and an ectopic gallstone

Imaging:

Usually, imaging for vague abdominal pain would start with an abdominal xray just to see what is going on. Identifying a gallstone and/or gastric distention would be helpful. In which case, depending on symptoms, you would probably move to an abdomen/pelvis CT or right upper quadrant ultrasound.

On a right upper quadrant ultrasound, you’re looking for a big posteriorly shadowing gallstone. However, the finding that is important for this particular entity would be ring-down artifact (not comet-tail) in the liver parenchyma. This is most compatible with air in the intrahepatic biliary tree (pneumobilia). There are many reasons for pneumobilia, such as gallstone ileus, or prior intervention. However, when you see a big gallstone, possible gastric outlet obstruction, and pneumobilia, you’re now on the trail for a zebra. The gallbladder itself may not be well visualized.

The CT usually clears things up. You should see a large gallstone with poor visualization of the gallbladder, but with pericholecystic inflammatory fat stranding. Then you’ll see the pneumobilia as well as the gastric outlet obstruction. All of these findings together tell the radiologist that this isn’t a run-of-the-mill cholecystitis or gallstone ileus. This particular entity, Bouveret Syndrome, is the top differential consideration, even though it’s relatively rare. Sometimes you can see oral contrast make its way into the gallbladder, which helps confirm the presence of the fistula.

Treatment:

Two options for treatment are ERCP or surgery, depending on symptoms and severity. However, endoscopic retrograde cholangiopancreatography (ERCP) is usually preferered and attempted prior to surgery because of advanced age or other comorbidities. The idea is to remove the offending gallstone via mechanical, electrohydraulic, or laser lithotripsy methods.

If surgery is required, usually removal of the stone (enterolithotomy) is performed. Removal of the gallbladder (cholecystectomy) may or may not be performed. Placement of a gallbladder drainage catheter (cholecystostomy tube) may be considered.

There is actually a really good article in Radiographics (July 2004) with good discussion and excellent pictures for those interested.

TL;DR

Sometimes we see zebras, here’s one called Boueveret Syndrome.

“When you hear hoofbeats behind you, don’t expect to see a zebra.”  — but you should still know what they are

-Sensei

Agree? Disagree? Questions, Comments and Suggestions are welcome.

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