Basic Gallbladder - HD

Normal Gallbladder Anatomy

As it pertains to the stenographic evaluation of the gallbladder.

Today I'd like to discuss normal gallbladder anatomy, congenital variations in the gallbladder, emphasize gallbladder ultrasound evaluation technique, and then review basic gallbladder disease entities including gallstone disease, porcelain gallbladder, acute cholecystitis, gallbladder polyps, adenomyosis, and the thickened gallbladder wall.

Now the gallbladder is a long oval organ that's positioned inferior to the liver and just immediately adjacent to the interlobular fissure.

Now, this fissure is a useful anatomic landmark when trying to identify the gallbladder.

The fissure is located immediately inferior to the gallbladder, and it, the gallbladder separates the liver.

It's a useful landmark to separate the liver into the right and left junction in trying to identify the fissure.

It's important to scan transverse images through the gallbladder to identify the ligamentum teres.

When this is identified, you can look for a linear echogenic line just to the left of the ligamentum teres, and this delineates the interlobular fissure.

Now, once this is identified, if you scan slightly inferior to this line, then it should lead you right into the gallbladder as demonstrated in this patient with a decompressed gallbladder into lobular fissure and ligamentum teres.

On a longitudinal view, the interlobular fissure connects the gallbladder to the right portal vein, and it's delineated by this linear echogenic line.

70% of scans you will see the interlobular fissure.

The upper limit for the normal gallbladder is four millimeters, four centimeters.

In transverse or short axis, it's important to note that the transverse or short axis dimension is the most important measurement.

When assessing gallbladder size, the gallbladder length can be quite variable, but in most instances, the upper limit of normal is 10 centimeters.

The normal gallbladder wall is typically less than three millimeters.

When a gallbladder is contracted, the echogenic mucosa and the hypoechoic muscularis become more apparent.

And visually the gallbladder may appear thickened.

However, when measured it is usually less than three millimeters.

Congenital Variations in the Gallbladder

There are quite a few congenital variations with the gallbladder.

More commonly, we see variations in the shape of the gallbladder, and this includes folds in the gallbladder, junctional folds, or Phrygian cap septations.

In addition, we can see congenital variations in the location of the gallbladder, including intrahepatic gallbladder or ectopically placed gallbladder, and we can see other anomalies like duplication of the gallbladder or agenesis of the gallbladder.

When folds occur near the gallbladder neck, they're referred to as junctional folds, and oftentimes we see multiple junctional folds near the gallbladder neck.

When gallbladder folds occur near the fundus of the gallbladder, they're referred to as Phrygian caps.

The gallbladder folds are composed of two walls.

They're thickened, and they change the outer contour of the gallbladder.

Now, unlike folds, septations are rare.

They appear thinner, and there's no indentation along the outer contour of the gallbladder.

Septations separate the gallbladder into segments that can communicate through small pores, illustrated longitudinal, and transverse images of a gallbladder containing multiple septations.

Now, this is a patient with cirrhosis, and on this initial image, you see that there's fluid anterior to this atrophic and nodular liver.

At a first glance, you might think that this is ascites or maybe even a loculated fluid collection, but with a second look.

And on the cine image, it's apparent that this fluid structure is an abnormally located gallbladder, but the gallbladder fundus and body positioned anteriorly and between the liver and the abdominal wall.

Other anomalies that we can see with the gallbladder include a duplication of the gallbladder.

This is an extremely rare anomaly, and in this patient we see that there is complete duplication of the gallbladder with two structures immediately adjacent to each other on longitudinal and transverse views.

This is a patient with a partial duplication of the gallbladder, and here we see two separate fundal segments, to my left, the ultrasound image showing the two separate fundal segments and the correlated CT image showing the same.

Gallbladder Ultrasound Evaluation Technique

Now technique is very important when we evaluate the gallbladder, and in general, patients fast for four to eight hours prior to the ultrasound examination.

Fasting is important because it ensures adequate gallbladder distension and it minimizes bowel gas.

Now we know that with fasting, we will obtain a better examination, but the lack of fasting is not a contraindication or an absolute contraindication for us to perform an ultrasound.

And oftentimes we can still get an adequate or diagnostic exam in a fasting patient.

When we start the gallbladder evaluation, oftentimes we start with a three to five megahertz sector transducer, and we scan the patient from both subcostal and intercostal approaches.

When we scan from a subcostal approach, the probe is positioned midline under the costal cartilage and drag to the right side.

When we're imaging from a subcostal approach, it's important to remember to have the patient inspire because deep inspiration improves our visualization of the gallbladder.

I cannot stress how important multiple views are.

Oftentimes when we evaluate the gallbladder, one view will display a pathology or a particular artifact, and it's important to have multiple views in order to distinguish these entities.

In addition, it's important to position the patient in multiple positions, including supine, left lateral decubitus, left posterior oblique, and upright positions.

Because the positioning allows us to determine mobility of stones and sludge, and it also allows us to determine non-mobility of polyps and tumors.

While we must evaluate the entire gallbladder, whenever we do a gallbladder ultrasound, it's really important for us to evaluate the neck in every single case because stones can be missed if the entire neck is not visualized.

I'll show you some examples of the importance of multiple views with technique.

This image illustrates low level internal echoes within the gallbladder lumen from reverberation artifact, which we oftentimes see when patients are scanned from a subcostal view.

A few moments later, scanning from a more lateral and superior approach in which the liver is used in an acoustic window, we eliminate that reverberation artifact.

It's important to visualize the gallbladder neck.

So on these images, longitudinal images of the gallbladder in patient presenting with right upper quadrant pain, there's an apparent stone free lumen within the gallbladder.

However, further interrogation of the gallbladder near the neck shows a stone with posterior acoustic shadowing.

Here's a different patient who presented to the emergency room with right upper quadrant pain, and this patient had gallstones that were visualizing the gallbladder neck, and a positive sonographic Murphy sign.

Our sonographer was puzzled regarding the Murphy sign with the comment that we see stones and they're all moving.

However, a closer evaluation of this patient shows that there were multiple stones, and I'm not showing you all of them lodged within the gallbladder neck, in the folds within the neck, and these were not mobile.

In this patient, it's important to evaluate the gallbladder neck.

Here's another patient with right upper quadrant pain, and on a longitudinal view of the gallbladder, we see that maybe there's a stone in the gallbladder neck, but further interrogation of this area then allows us to visualize the stone better with posterior acoustic shadowing.

To my left is an image of the gallbladder neck, a normal gallbladder neck, and I like to say that you should look for those junctional folds and look for the normal curves that you see in the gallbladder neck as it enters into the cystic duct, and then to the common bile duct.

If the images submitted to me and all of the images of my longitudinal images of my gallbladder look like this, to which I like to use the analogy, it looks like a teardrop, or if all of the images of the gallbladder neck have a rounded appearance and I never see those twists and turns, then that's my indication that I'm not seeing the gallbladder neck well, and we need to do a little bit more interrogation of the neck.

Gallstone Disease

Gallstone disease stones are present in 10% of the population.

75% are cholesterol and 25% are pigment stones.

The majority of patients with gallstones are silent, up to 80%, and they become symptomatic at a rate of 2% per year.

Symptoms rarely develop after an asymptomatic period of 10 to 15 years.

Gallstones are mobile echogenic intraluminal structures that shadow.

Shadowing from stones occur because of sound beam absorption by the stone and shadowing of gallstones is based on the size of the gallstone, not calcification or the composition of the gallstone.

It's common that very small stones, stones that are three millimeters or smaller may not show shadowing.

Here is a spectrum of the ways gallstones can appear, different size and appearances, echogenic luminal structures that shadow.

Now it's important for us to distinguish stones from other intraluminal pathology, and in order to do that, we have to understand some of the technical parameters that show shadowing.

One such parameter is the transducer frequency.

Sound is absorbed at higher frequencies.

And if we want to illustrate shadowing, one of the things that we can do is just increase our transducer frequency and that can transfer allow a stone that's non, a small stone that's non-shadowing to show shadowing.

The other thing that we can do if we want to show shadowing is set our focal zone at the depth of the gallstone, the focal zone is narrowest.

You know, at the level of the gallstone when set and there is increased power and absorption at that level.

And as a consequence, we can transform a stone that's not shadowing into a shadowing stone because small stones may not show shadowing.

If a patient has multiple small stones, we can position the patient so that those small stones are clumped together, and as a larger conglomerate, we can show shadowing.

The other thing that we can do is to deactivate real time compounding.

Real time compounding is a method that's used on many modern scanners in order to improve the image quality for the ultrasound images, however it results in decrease shadowing.

And because real time compounding is on many times when we scan, if we just turn it off, it's another way for us to show shadowing.

Here's a patient that was scanned in the supine position, and at a first glance, you might say that the lumen looks clear, or if you're looking a little carefully, you might see that there's a straight line in this gallbladder lumen, indicating that they're stones.

But notice that there's not any shadowing.

The same patient turned in a left lateral decubitus position.

We see those stones clump together, and now we can see clear posterior acoustic shadowing.

Without a doubt, we can say that this patient has multiple small gallstones.

A different patient with luminal echogenic contents.

The focal zone is intentionally set all the way down, not at the level of the gallbladder.

When the focal zone is optimized, we can begin to see a little bit of a vague posterior acoustic shadowing, indicating that this is a stone.

Same patient scanned with a six megahertz transducer, luminal echogenic content.

Maybe there's some vague posterior acoustic shadowing.

Not quite sure.

Same patient using a nine megahertz transducer.

And here we can clearly see that there's posterior acoustic shadowing.

Now, when the gallbladder is filled with stones, this is called the wall echo shadow complex, and it can be identified by looking for three arc shaped lines, followed by a shadow.

The first line is echogenic and it reflects the pericholecystic fat and the interface between the gallbladder wall and the liver.

The second line is a hypoechoic layer, which reflects the gallbladder wall or the gallbladder lumen, depending on which literature you believe.

And then the third line is an echogenic line, which reflects the stone, and all of this is followed by a shadow.

Here are images, longitudinal and transverse images of a patient with a gallbladder filled with stones, showing the wall echo shadow sign with the three arc shaped lines.

Here's a different patient with a gallbladder filled with stones, and we see the same thing, arc shape, echogenic line, hypoechoic arc echogenic line, followed by shadowing.

But notice that on the images to my left, the lines are very clear and distinct, and the images to my right, it's a little less distinct.

WES sign can appear crisp or indistinct, but what you need to do is just look for the three arc shape lines followed by the shadow.

And if you see this, then you can confidently diagnose that this is a gallbladder filled with stones.

Now, there are important pitfalls for you to be aware of or mimics of wall echo shadow sign, and important for us to distinguish.

So this is the patient with the wall echo shadow sign.

Porcelain Gallbladder

This is a patient with a porcelain gallbladder, and here you can see there's just a curvilinear echogenic wall followed by dense posterior acoustic shadowing that obscures the lumen and the back wall of the gallbladder.

This is a porcelain gallbladder.

I contrast this with this patient with emphysematous cholecystitis in which we see bright reflectors with dirty posterior acoustic shadowing from air within the gallbladder wall.

The other thing that we must be aware of or mindful of is that sometimes the gas filled bowel can appear like this, but the way that we distinguish it is there are echoes in the center of the lumen.

And on real time imaging, it's easy to distinguish this because you can see peristalsis from the bowel.

Porcelain gallbladder occurs in females greater than men, and the sixth decade of life, it's associated with gallbladder inflammation and in the majority of cases have gallstones.

Historically, there's been an increased risk of gallbladder cancers with estimates ranging from 12 to 61%.

However, the rate of cancer is significantly lower than previous estimates, and the incidence of cancer has been shown to depend on the pattern of the gallbladder wall calcification on pathologic studies with selective mucosal calcification having a risk of 7% of cancer and diffuse intramural calcification showing no risk of cancer.

This is a patient with a porcelain gallbladder.

Here we can see the echogenic wall from the calcified wall, but here the sound beam does penetrate the gallbladder, so we can see the back wall of the gallbladder.

In addition, we can see the stone within the gallbladder.

At the bottom is a different patient with a porcelain gallbladder, and here we see the dense wall with posterior acoustic shadowing, obscuring the lumen and the back wall of the gallbladder.

Gallbladder Sludge

Gallbladder sludge.

We commonly encounter it in pregnancy, in our inpatients in the ICU patients on TPN, bone marrow transplant patients.

The natural history for sludge is that 50% resolve spontaneously, 20% persist asymptomatically, five to 15% develop gallstones, and 10 to 15% become symptomatic.

Complications of sludge include stones, biliary colic, acalculous cholecystitis, and pancreatitis.

On imaging, we see low to high level non-shadowing reflectors within the gallbladder.

They're typically localized in the dependent portion and forms a bile sludge level, and some may form a mass like aggregate called a sludge ball or tumefactive sludge.

The lack of shadowing distinguishes sludge from gallstones and mobility distinguishes sludge from polyps or tumors.

So here a spectrum of appearances of sludge in the gallbladder with high and low echoes fluid sludge, bile levels in this patient.

The sludge has a similar echogenicity as the liver, and if this is the case and you can't use mobility to help distinguish motion, then it's important to use color doppler to ensure that there's no underlying mass.

This is a patient with tumefactive sludge that looks more mass like, but again, you can move the patient to show mobility and use color doppler to show that it's not a solid lesion.

Acute Cholecystitis

Acute cholecystitis is common.

We see it in 5% of patients presenting to the ER with abdominal pain.

It's caused by gallstones in greater than 90% of patients.

An impaction of stones in the cystic duct or gallbladder neck is the primary cause of acute cholecystitis.

What happens? The stone is impacted.

The neck gets obstructed, the gallbladder lumen distends.

The patient develops ischemia, secondary superinfection, and ultimately it can lead to necrosis of the gallbladder.

On ultrasound, the gallbladder wall is thick, the lumen is distended.

We see stones.

We see an impacted stone in the gallbladder neck or cystic duct.

The patient may have pericholecystic fluid and a positive sonographic Murphy sign or maximal pain over the gallbladder.

A spectrum of patients with pathologically proven acute cholecystitis.

Gallbladder Polyps

Gallbladder polyps are quite common and the majority of polyps are benign.

Cholesterol polyps make up 50 to 60% of polyps, inflammatory polyps five to 10%, adenomas less than 5%, and focal adenomyosis, gallbladder cancer and mets even smaller percentage of polyps.

Now, the typical gallbladder polyp or polyp lesion in the gallbladder appears as a non-mobile non-shadowing ball on the wall.

And I show different patients with gallbladder polyps.

It's been well documented that the management of polyps, if it's less than or equal to five millimeters, we don't follow up.

Between five and 10, we monitor to ensure stability and over 10 millimeters we recommend surgery.

However, Corwin looked at 346 patients with gallbladder polyps following patients for up to 11 and a half years on ultrasound, and they found no cases of gallbladder malignancy identified in these patients that we followed.

If the polyps for polyps between seven and nine millimeters, there was one neoplastic polyp and between greater than or equal to 10 millimeters, they found two neoplastic polyps.

And the recommendations were that if you have a polyp that's less than six millimeters, no additional follow up is required.

Adenomyosis

Adenomyosis is a benign condition that's unrelated to gallstones.

It's usually asymptomatic.

On pathology, we have mucosal hyperplasia and thickening of the muscular layer of the gallbladder with muscular mucosal herniation into the muscular layer called the Rokitansky-Aschoff sinuses.

These sinuses frequently contain cholesterol polyps, which create the comet tail artifact that we classically see with adenomyosis.

Patients can also present with diffuse wall thickening, focal or segmental annular thickening, a localized mass, and rarely we can see cystic or hypoechoic spaces in the gallbladder wall from the large Rokitansky-Aschoff sinuses.

This is a typical patient with gallbladder adenomyosis with a comet tail artifact in the superficial wall of the gallbladder and no other abnormalities.

We distinguish the comet tail artifact from gas.

The comet tail has a V-shape echogenic foci and gas has dirty shadowing in a more linear configuration.

This patient has adenomyosis with a focal mass cystic space and comet tail in the gallbladder fundus.

This patient presented with a mass on CT in the gallbladder fundus.

On ultrasound, we see a focal mass near the fundus, cystic spaces within the mass comet tail and twinkle artifact indicating prominent Rokitansky-Aschoff sinuses.

Thickened Gallbladder Wall

Gallbladder wall thickening, the differential for gallbladder wall thickening.

You can approach gallbladder wall thickening by thinking about the primary biliary causes, including conditions like acute cholecystitis, adenomyosis, gallbladder cancer, AIDS cholangiopathy and sclerosing cholangitis, and then the secondary or systemic causes including congestive heart failure, portal hypertension, pancreatitis, low albumin or protein, acute hepatitis, cirrhosis, and lymphatic obstruction.

This is a patient with HIV and lymphoma who presented with circumferential gallbladder wall thickening that was greater than one centimeter on CT and ultrasound.

And this was done on the same day.

The patient had normal albumin and protein.

The patient did not have hepatitis.

The ejection fraction was normal, and this was presumed gallbladder wall thickening from an AIDS cholangiopathy.

Follow up one year later and that resolved.

A different patient who presented with elevated lipase.

On the day of the ultrasound gallbladder wall thickening on ultrasound, the same day a HIDA scan was performed to exclude acalculous cholecystitis.

The HIDA scan was negative, and this was presumed gallbladder wall thickening secondary to acute pancreatitis.

This patient had CHF gallbladder wall thickening and abnormal pulsatile portal venous flow with a transient reversal of flow in diastole.

Alright, thank you.