1. Biliary Disease
In this segment we are going to be talking about the identification and diagnosis of biliary disease using various image techniques.

2. Gallbladder and Biliary Tree
Imaging Studies Available
X-ray
Computed tomography
Radioisotope scan (hepatobiliary scan)
Ultrasound: the most sensitive study for gallstone
Evaluation of the gall bladder and biliary tree is possible utilizing a variety of different technologies. X-ray, Computed Tomography, Ultrasonography probably the most sensitive study for evaluation for gallstones, and Radioisotope or Hepatobiliary scans.

3. Gallstones
81% consist of cholesterol and are radiolucent (cannot be seen on plain films)
19% contain calcium and are radio-opaque (can be seen on plain films)
81% of gall stones are primarily made up of cholesterol and are therefore radio lucent on the plain radiograph. They cannot be seen on a plain x-ray. About 19% do contain some calcium and thus are radio opaque. They can be identified on plain radiograph.

4. Gallstones Size: can be very small (1-2 mm) to very large (several cm)
Shape: single stone – round, large
Multiple stones – small, faceted
The size of gall stones can vary tremendously from very tiny gallstones which may be only one or 2 mm size, to very large in size up to several centimeters in size. In fact you may have a single gallstone that will fill in entire enlarged gallbladder. If there is only a single stone the shape tends to be relatively round or gallbladder shape and fairly large. If there are multiple stones present they tend to be smaller, they also tend to have facets, or faceted junctions where the stones come together and rub together.

5. Gallstones Complications include
Obstruction of bile duct: commonly cystic duct and common bile duct
Cholecystitis (infection/ inflammation of the gallbladder)
Abscess (complication of cholecystistis)
Perforation:
peritonitis, inflammation infection of peritoneum
gallstone ileus, stone erodes into GI tract and causes obstruction
Complications related to gallstones can include such things as obstruction of the bile ducts. Most commonly stones involve the cystic duct, but less commonly seen but also identified would be obstruction of the common bile duct most often distally at the region of the ampulla of Vater. Cholecystitis, an infection or inflammation of the gallbladder is another potential complication. As a result of cholecystitis it is possible to develop an abscess in the region of the gallbladder or adjoining soft tissues of liver. Perforation of the gallbladder can take place. The result of this can lead to peritonitis which is of course an inflammation or infection of the peritoneum and peritoneal linings or we could have development of a gallstone ileus. This most typically happens if the gallstone erodes into the gastrointestinal tract and a large stone ultimately cause obstruction many times in the region of the distal small intestine in the region all the ileo-cecal valve.

6. Gallbladder Ultrasound Stones all appear ECHOGENIC (white)
May be either radiolucent or radio-opaque
Beyond stone is an acoustic shadow
Bile is HYPOECHOIC (black)
Polyps, neoplasm typically are isoechoic (equal echo density) to adjacent soft tissues
Ultrasound is our primary tool for evaluated for gallbladder disease. All gallstones will appear echogenic providing there of sufficient size to cause some disruption of the ultrasound beam. It doesn't matter whether these are radiolucent or radio opaque stones on x-ray. On ultrasonography they will be echogenic. Distal or beyond the stone on ultrasound there will be an acoustic shadow. Sufficient amounts of the ultrasound beam is reflected back at the gallstone that the area beyond the gallstone will appeared dark or have low echoes because of this obstruction to the beam. Bile when demonstrated will be hypoechoic and will be black due to the presence of its water-like content and the free passage of sound beams through it. A sufficiently large collection of bile will lead to through transmission beyond it as a result of the free passage of the ultrasound beam without interruption through bile. Polyps or neoplasms will typically be isoechoic or of equal density to the surrounding soft tissues, the tissues of the gallbladder wall or perhaps the surrounding liver.

7. Gallstones AP abdomen Several facetted calcified densities
Dense rim less dense center
Separate from renal calculi and costocartilage by different positions
Use oblique films, gallbladder anterior so move away from spine
Here is an example of a plain radiograph of gallstones. In this AP abdominal film showing the upper portions of the abdomen, we see several somewhat faceted gall stones present in the right upper quadrant. Note that they are in a relatively curvilinear distribution similar to what we would expect the gallbladder to appear as if you think back to anatomy class. These particular gallstones have a dense rim so more calcium around the periphery and less calcium in the central regions thus, the somewhat rim-like calcification. These can be separated from renal calculi or costal cartilage by varying the patient's position on the radiographic table, obtaining oblique films. In oblique films the gallstones will stick with the anterior portions of the abdomen, so if you roll the person up to the right side the gallstones will remain anterior structures.

8. Gallstones Ultrasound upper abdomen Longitudinal scan
Round echogenic structures in gallbladder
Acoustic shadowing
As mentioned earlier, ultrasound is an effective tool for evaluating the gallbladder. In this ultrasound of the upper abdomen in a longitudinal scan, we can identify the outline of the gallbladder and the presence of multiple echogenic foci within the gallbladder. Most of which show a band of lower attenuation posterior or lower echogenicity posterior related to an attenuation or disruption of the ultrasound beam as it strikes the strikes the solid gallstones. This is referred to as acoustic shadowing.

9. Dilation of Bile Ducts Causes include Stone (most common) Carcinoma
We can utilize our imaging techniques to evaluate for possible dilatation of the bile ducts. Causes for dilatation of the bile ducts include most commonly stones, but also obstruction and dilatation can as the result of neoplasm.

10. Dilated Common Bile Duct
Longitudinal US through liver hilum
Typical double channel sign
Dilated common bile duct (blue arrow) anterior to portal vein (red arrow)
Duct usually smaller than vein
Stone(not seen) distal in duct
This ultrasound demonstrates the presence of a dilated common bile duct just beneath the blue arrow, this seen anterior to the normal appearing portal vein indicated by the red arrow. This is sometimes referred to as a double channel sign in ultrasound. Typically, the common duct will be a much smaller structure then the adjoining vein. A stone was present in this particular case in the distal portion of the common duct, not included on this particular image.

11. Bile Duct Dilatation Axial CT mid-abdomen
Dilated common bile duct (arrowhead)
Dilated intrahepatic ducts
Round fluid structure anterior to kidney is distended gallbladder
In this CT scan of an individual with bile duct dilatation, in this axial mid CT abdominal location, we note a dilated common bile duct as indicated by the arrow head. We also note low attenuation or low density areas within the right and left lobe of the liver presenting dilatation of intrahepatic bile ducts. The round fluid structure seen anterior to the kidney represents a distended gallbladder, which is also noted to have a somewhat thickened gallbladder wall.

12. Common Bile Duct Stone Axial imaging lower than prior example
High density structure obstructing calculi (arrow)
Large round area gallbladder
In an adjoining image, somewhat more caudad in this patient demonstrates a high density structure which is the obstructing calculi down in the general location of the distal common bile duct ine the region of the ampulae of Vater. Note that the gallbladder is distended on this slice as well.

13. HIDA Imaging Radionuclide targeted to hepatocytes
Non filling of the common bile duct or gall bladder indicates obstructive process
Another technology for evaluation of possible bilary tree disease is HIDA scanning. In this normal HIDA examination, a radionuclide which is targeted to hepatocytes rapidly appears within the liver parenchyma and subsequently is noted to accumulate in the common duct, the various intrahepatic ducts, and the gallbladder and subsequently can be demonstrated to empty into the small intestine. Non-filling of the common bile duct or the gallbladder would indicate an obstructive process this is seen in chronic or acute cholecystitis.

14. Acute Cholecystitis
No filling of the gallbladder 60 minutes after injection of isotope
Rapid accumulation within the liver and bile ducts with spill into the doudenum
In this example we have an example of acute cholecystitis. We see rapid appearance of the radionuclide within the liver and the biliary tree and extension of the radionuclide out into the gastrointestinal tract. We however never identify the radionuclide accumulated within the gallbladder indicating obstruction of the cystic duct which in this case was as a result of acute cholecystitis.

15. Bile Leak Ida Scan Accumulation of isotope outside of the biliary tree
The Heptabiliary HIDA scan can be utilized for a variety of purposes. In this example an individual with complications following endoscopic cholecystectomy is noted to have accumulation of radionuclide not only within the liver, the biliary tree and the gastrointestinal tract, but also free within the peritoneal cavity indicating a leak as a result of the intervention.
Accumulation of isotope outside of the biliary tree

16. MR Cholangiography Stone
Emerging technology
Visualize stone as a filling defect in the common duct (blue arrow)
New technologies, including MRI imaging can be utilized for evaluation of all the biliary tree. MR cholangiography can be performed without contrast being necessary and in an example here from Michigan State at the blue arrow, we see a small filling defect in the water content of the common bile duct distally representing small calculi that are floating within the common bile duct. I hope you found this introduction to biliary imaging interesting.