Category: 3. Gallbladder & Common Bile Duct Ultrasound

Choledocholithiasis occurs when gallstones lodge in the bile ducts and bile can no longer flow, instead backing up into the liver. Most cases are symptomatic and require removal of the stones since ascending cholangitis (acute bacterial infection of the biliary tree) is a common complication with high morbidity/mortality.

Patients with choledocolithiasis usually present with biliary colic and obstructive jaundice, ascending cholangitis, and potentially acute pancreatitis (Hartung).

On ultrasound, look out for calculi in the gallbladder and/or CBD, and a dilated common bile duct. Any CBD wider than 5mm should raise suspicion, especially when paired with a suggestive history. However, with every decade of life past 50, the expected diameter increases by one millimeter. For example, a 60-year-old patient would be expected to have a CBD around 6mm, and a 70-year-old patient would be expected to have a CBD of 7mm.

Cholecystitis, or gallbladder inflammation, occurs when the gallbladder’s drainage ducts are obstructed and the gallbladder becomes inflamed/infected. Cholelithiasis is the most common cause and primary risk factor for developing cholecystitis, implicated in up to 95% of cases of cholecystitis (Liau). Other causes (acalculous cholecystitis) include sludge (fine bile crystals mixed with proteinaceous debris and fluids) or tumors.

Patients with cholecystitis most commonly present with acute RUQ pain, persistent over ≥ 6 hours, that may radiate to the right shoulder. Nausea, vomiting, and fever are also common. Lab abnormalities can include leukocytosis and increased liver function tests.

The cardinal physical exam finding for cholecystitis is the traditional Murphy’s sign on physical exam. With your fingers clasped under the right costal margin, a positive Murphy sign refers to a “catch” in the patient’s breath when asked to inhale deeply, indicating pain when the gallbladder touches the examiner’s fingers.

A Sonographic Murphy sign, however, refers to the presence of maximal tenderness when ultrasound probe pressure is applied over the visualized gallbladder on ultrasound. This is a very sensitive finding for cholecystitis (Bree).

Important secondary findings include cholelithiasis (gallstones), anterior gallbladder wall thickening >3mm, and pericholecystic fluid.

Other less specific findings are gallbladder sludge and gallbladder distension (>4cm transverse and >9cm longitudinal).

Here we’ll cover the most common patient presentations and ultrasound findings for cholelithiasis, cholecystitis, and choledocholithiasis. Ultrasound is by far the preferred initial imaging study for assessing RUQ pain, and boasts high sensitivities and specificities for cholelithiasis and cholecystitis (Revzin).

Cholelithiasis

Cholelithiasis refers to gallstone formation anywhere along the biliary tree. Gallstones are present in up to 10% of the population, and only about 1/4 of patients are symptomatic. When symptomatic, the most common finding is biliary colic (post-prandial RUQ pain, especially following a fat-rich meal). Pain may radiate to tip of the right scapula, a finding known as Collin’s sign. Nausea, bloating, belching, heartburn, and flatulence are also common (Bell).

Ultrasound is considered the gold standard for the detection of gallstones (Kothari), which will appear as highly hyperechoic collections with posterior shadowing within the gallbladder lumen. The stones may be gravity-dependent (“rolling stones”) and move within the lumen when the patient changes position.

Smaller stones may not be directly visible within the lumen, but may exhibit a “twinkling artifact” with color Doppler, pictured below. On the right, the tiny stone is visible in grayscale (green arrow).

Make sure the patient is fasting. Eating food will make the gallbladder contracted and you may not be able to visualize it. Tip: if possible, have your patient assume the left lateral decubitus position as this will bring the gallbladder more into the midline for your to scan.

• Position your probe in the epigastric midline with the indicator facing the patient’s head.
• In the midline, you will likely see the Main Portal vein in the long-axis, proximal to when it curves into the liver.

Slide laterally (slowly) along the costal margin, toward the patient’s right, until you can clearly see the Portal Triad (Portal vein, Hepatic Artery, and Common Bile Duct) in short axis.

• The Portal Triad seen in the short-axis is known as the “Mickey Mouse Sign,” where the Common Bile Duct (CBD) and Hepatic Artery are the “ears,” and the portal vein is the “head.”

Visualize the gallbladder and main lobar fissure (MLF).

• The gallbladder neck is attached to the Main Lobar Fissure (MLF). Search adjacent to the MLF, on the right of the screen, by rotating your probe clockwise as shown below.
• This view is known as the “Exclamation Point Sign,” with the portal triad as the “point” and the gallbladder as the “line” of the exclamation.

Evaluate for gallstones.

• Tilt/fan your probe superiorly and inferiorly as shown in the GIF to search for cholelithiasis.

Measure the anterior gallbladder wall thickness.

• Orient your calipers as pictured and measure the anterior gallbladder wall thickness.
• The normal anterior gallbladder wall thickness is <3mm
• Editor’s note: some resources use <5mm thickness to increase the specificity. Remember to use your hospital’s guidelines when measuring.

Evaluate the Common Bile Duct.

• Return to the short-axis view of the portal triad (“Mickey Mouse Sign”) described above.
• Use color Doppler to distinguish the common bile duct from the hepatic artery (proper). Flow will be seen in the hepatic artery, while the common bile duct will remain anechoic with no pulsatile flow.

Visualize the common bile duct in the long axis and measure the anteroposterior diameter.

• From the short-axis view, rotate your probe 90˚ counter-clockwise
• Once you have identified the common bile duct in the long axis, measure it from inner wall to inner wall as shown below.
• A normal CBD measurement is <5mm in the average population
• However, with every decade of life after 50, the expected diameter increases by one millimeter. For example, a 60-year-old patient would be expected to have a CBD around 6mm, and a 70-year-old patient would be expected to have a CBD of 7mm.
• Also, patients that have had their gallbladder removed (cholecystectomy) can have normal CBD measurements of <10mm.

• Tip: it can be difficult to visualize, let alone measure the CBD. Our quick tip is that if the CBD doesn’t appear wider than 50% the portal vein diameter, it is unlikely any bile duct pathology is present.

Ultrasound is the imaging modality of choice for most biliary tree pathologies. However, since the gallbladder is not fixed to the body wall like other GI organs, it can have a variety of positions in the right upper quadrant (RUQ), so getting a good view can be tricky. Here, we provide a way of imaging this somewhat challenging organ.

Ideally, your patient should fast prior to the exam, so the gallbladder will be dilated with anechoic bile. However, you will most likely have to image the gallbladder in an emergent setting, and fasting will not have been possible.