Biliary Tract Sonography - SD

Introduction

I am Dennis Foley.

I'm a professor of radiology at the Medical College of Wisconsin and I practice in body imaging, which is a combination of mainly CT and ultrasound and also including MR.

And I'm here today to talk about biliary tract sonography and also discuss the other imaging tests that are used in conjunction with sonography to evaluate the biliary tract.

This presentation is to discuss biliary tract sonography and is to put the emphasis on a combination of biliary tract sonography and other appropriate imaging tests depending upon the initial sonographic findings and clinical aspects of the patient's presentation.

The first important statement to make is that sonography is really the initial imaging test in any patient who presents with right upper quadrant pain or jaundice.

So what we're again to discuss is the imaging pathway and the management of patients who have either choledocholithiasis either demonstrated or suspected on the basis of sonography biliary stricture demonstrated as a dilated biliary tract, and again, a clinical impression of possible stricture and malignant biliary obstruction demonstrated with dilated bile and pancreatic ducts as a double duct sign with either the inference or the demonstration of a pancreatic mass and other patients who present with tumors at other levels, including the hepatic hilum.

Anatomy of the Biliary Tree

To begin with, this is an anatomic demonstration of the biliary tree.

It shows you the common hepatic duct at the hilum.

The junction of the cystic duct draining the gall bladder with the common duct, which is usually below the hilum, and then the sub hepatic common duct, which extends into its intra pancreatic portion before joining the pancreatic duct immediately proximal to the ampulla.

This bile duct is actually physiologically very active and transports two to three liters of bile per day into the duodenum.

That mechanism is controlled by the sphincter of Oddi, which we will look at later.

Normal Dimensions of the Common Duct

Another issue is what is the normal dimension of the common duct and in generally accepted practice, it is stated that a bile duct under six millimeters is normal between six and eight millimeter in diameter is in a gray zone, but acceptable as normal and above eight millimeter in diameter is abnormal.

Sonographic Technique for Biliary Tract Imaging

Biliary tract sonography is best performed with a convex linear probe.

These days with modern instrumentation, compound imaging and harmonics helps to improve image quality.

A para sagittal plane directed from the hepatic hilum towards the ampulla is preferred and the patient may be better imaged if the right side is elevated approximately 20 to 30 degrees to give a better acoustic access, transverse imaging planes at the porta hepatis margin of the liver are utilized with a cephalad tilt to look at the intra hepatic ducts, generally through segment four to look at the left hepatic duct and segment five to look at the right intra hepatic ducts.

Subsequently, the common duct can also be imaged in a transverse plane.

As we progress towards a duodenum, the ability to see the sub hepatic duct depends upon the amount of gas in the distal stomach in the duodenum.

The reason that patients are fasted prior to studies is to decrease the amount of gas in stomach and duodenum, as well as have a distended gallbladder to enable better imaging of the gallbladder.

This is an image that shows you a parasagittal plain image of the common duct at the hepatic hilum.

Note that immediately posterior to the common duct is the transverse image of the right hepatic artery.

And behind that is the portal vein.

So that is the characteristic image that one should aim to demonstrate.

One can follow the common duct below the level of the hepatic hilum to the common bile duct and notice that the bile duct dilates in a fusiform manner below the hepatic hilum.

So it increases in dimension by several millimeter and then it narrows again as we progress towards the ampulla in the pancreas.

Here's a transverse image. We are below the hepatic hilum.

This is the arrow pointing towards the portal vein confluence.

Here's the pancreatic body and the pancreatic head.

Here is the gastroduodenal artery and posteriorly in the pancreatic head is the common bile duct, and if possible it is very nice to be able to demonstrate the common bile duct as far as possible towards the ampulla with ultrasound.

In addition, demonstrating as well the pancreatic duct, the use of color is useful in separating the intrahepatic arteries and veins from the ducts such as in this case we had the right portal vein as well as the right hepatic duct.

And then subsequently imaging through segment four.

Again with cephalad tilt, we are looking at the left portal vein, the left hepatic artery and the left hepatic duct.

The reason one can separate the hepatic artery from the portal vein is the increased frequency shift we see in the more faster flowing hepatic artery.

Both the right and left hepatic ducts should be less than two millimeter in diameter.

Physiology of Bile Flow

So to return to the physiology issue bile flow two to three liters per day monitored by the sphincter of Oddi or controlled by the sphincter of Oddi basal pressure in the biliary system, five to 15 millimeters of mercury and then intermittent phasic contraction with relaxation of the sphincter of Oddi causing passage of bile into the duodenum.

Cholecystokinesis are increased.

Bile flow is elicited by cholecystokinin either generally with ingestion of a meal.

This is accompanied by sphincter of Oddi relaxation so that increased bile flow occurs without dilatation of the biliary tract.

The sphincter mechanism that controls bile flow is the sphincter of Oddi and this particular schematic showing you the sphincter mechanism of the distal bile duct of the pancreatic duct and then a common sphincter to the level of the ampulla.

Examples of Dilated and Normal Bile Ducts

Here is a patient who has a dilated bile duct at the level of the porta hepatis.

Here is the hepatic artery cutting cross-section, the portal vein and the inferior vena cava more posteriorly.

One could follow this dilated bile duct into the pancreas and into its pre ampullary segment and demonstrate it immediately adjacent a normal dimension pancreatic duct.

However, notice that we do not demonstrate the conjunction of these two ducts immediately proximal to the ampulla, and it's really not possible with transcutaneous ultrasound to demonstrate that level of anatomic detail.

Here is a patient who has normal dimension bile ducts.

Notice that the maximum dimension is seven millimeter.

Notice again that the bile duct flares, as it were in dimension below the level of the porta hepatis and then is actually imaged into its intra pancreatic segment.

Again, this is the portal vein and here's the inferior vena cava.

And incidentally, just behind the inferior vena cava is an image of the right renal artery.

This patient ingested a fatty meal 45 minutes later was reimaged and you'll see that the bile duct in fact has decreased somewhat in dimension in this patient who has a cholecystokinin response.

And this indicates that we have satisfactory function of the sphincter of Oddi.

Intrahepatic Ducts

Just to reiterate, the intrahepatic ducts should be up to two millimeter in diameter.

Larger than two millimeter in diameter is considered to be abnormal.

The parallel channel sign is the demonstration of both ducts and intrahepatic vessels adjacent to each other, such that you will see the wall of the bile duct as well as the wall of the adjacent vessels.

The common bile duct, as stated earlier, is considered dilated when it's greater than eight millimeter in diameter.

Six to eight millimeter in diameter is considered a gray zone and less than six millimeter in diameter is considered normal.

Patients who have had cholecystectomies not infrequently have bile ducts, which are more than eight millimeter in diameter, but who do not have any functional symptoms and have normal liver function tests.

So to some extent, the bile duct performs a reservoir function after cholecystectomy.

Choledocholithiasis

Here's an example of a patient who has gallbladder calculi with some degree of acoustic shadowing, has a minimally dilated bile duct adjacent to the anterior wall of the gallbladder.

You see another shadow, which is a refractive shadow coming from the gallbladder wall.

This is not a shadow that's related to any impacting stone.

Slightly different angulation.

One demonstrates a ductal filling defect, which is echogenic with posterior shadowing, and this is consistent with a ductal calculus.

And here's another image which demonstrates nicely the ductal calculus.

Its size is being measured.

Notice that we have a slight degree of shadowing in this particular case coming from the duodenum and the echogenic content of the in the duodenum is due to admixed mucus and a small amount of air.

The sensitivity of sonography to detecting choledocholithiasis in general approximate 70%.

However, patients may have ductal calculi that are undetected.

This is most commonly due to the presence of ducts in the pancreatic or sub hepatic segment, which are obscured by overlaying bowel gas, or it could be due to the presence of small calculi, which are difficult to detect particularly in normal diameter ducts.

Also, it's important to remember that after initial passage of a ductal calculus into the common duct, there may be a time delay of up to 24 hours before there is some degree of dilatation the extrahepatic bile duct, and even up to 72 hours before the intra hepatic ducts dilate.

Another factor to remember is that intrahepatic ducts may not dilate in patients who have fibrotic livers, so that established cirrhosis may not allow intrahepatic biliary dilatation to develop.

Role of CT in Choledocholithiasis

The role of CT.

Here is a patient who has a dilated biliary system who has changes of acute cholecystitis and the sub hepatic common duct could not be demonstrated by sonography.

Notice that this patient has an abnormal gallbladder with a very thickened wall and also has some pericholecystic fatty stranding consistent with acute cholecystitis.

However, there is no finding of perforation, so that is demonstrating the acute cholecystitis.

Here is the dilated bile duct.

The more inferior duct demonstrates a filling defect, which is higher in attenuation than the bile.

And this is shown to better effect with a reformation showing you an obstructing calculus in the intra pancreatic segment of the bile duct in a patient who also has acute cholecystitis.

So the utilization of other tests occurs when sonography is unable to demonstrate the full extent of the biliary system and the test, which is most likely to be available and easy to perform, would be a CT scan.

Differentiating Calculi from Other Findings

This patient has intra hepatic bile duct echogenic content with posterior shadowing that looks as though these could be calculi in the bile duct.

But when one has a correlative imaging study in clinical history, one recognizes this as intrahepatic biliary ductal air in a patient who's had a sphincterotomy.

And then when re-looking at the sonographic images, you'll recognize that these shadows are relatively linear.

So the linear shadows with the posterior acoustic shadowing is a tip off to the possibility that this patient has intra hepatic biliary air and not calculi.

And then this is associated with the clinical history.

Here is a patient who at the porta hepatis has an oblong shaped fluid containing structure and adjacent to it or within it is an echogenic focus with distal acoustic shadowing.

And this looks very much like a calculus in the gallbladder neck.

In fact, this patient had a cholecystectomy and this represents a small biloma of serum in conjunction with a metallic clip related to cholecystectomy.

So pulse false positives in relation to biliary ductal calculi that should be remembered include pneumobilia related to prior sphincterotomy or a metallic clip artifact that occurs after cholecystectomy.

Here's an example of a patient with a calculus in the common hepatic duct, again with distal acoustic shadowing.

Again, note that this is a biliary system that does not appear to be dilated more distally.

Again, another calculus in the more distal segment of the duct.

Again, a non dilated biliary ductal system and with a slight degree of posterior acoustic shadowing.

But the real finding is the echogenic anterior margin of this calculus that indicates that we can make this diagnosis what should be done next.

Management of Choledocholithiasis

Here is a patient who has had a prior cholecystectomy.

So the initial study of choice, which is both diagnostic and in fact interventional is ERCP.

So here is an example of a intraductal calculus demonstrated following preliminary sonography.

Here is an another patient with an intraductal calculus And this patient is then treated by the gastroenterologist using a dilated balloon system to sweep the biliary ductal system and remove this calculus and do that in conjunction with a sphincterotomy.

So the management of choledocholithiasis really is determined by what the patient's surgical history has been.

If this patient has had a cholecystectomy, then it is appropriate to do an ERCP and in conjunction with the ERCP, do a stone extraction with sphincterotomy.

If the patient has not had cholecystectomy, then it would be more appropriate to consider a laparoscopic cholecystectomy in conjunction with surgical duct clearance that guided either by intraoperative laparoscopic ultrasound or a videofluoroscopic cholangiogram.

Indeterminate or Negative Ultrasound

What do we do in a patient who's had an indeterminate or negative ultrasound?

And this can occur in 30% or so of patients.

There are two options. One in the acute setting could consider CT scanning in the subacute setting, consider either MRCP or ERCP.

Of those two modalities it is considered that ERCP is more sensitive to small ductal calculi, but MRCP provides a global display and can diagnose other pathology.

So it may be considered to be a test which if available could be performed before consideration of ERCP.

Here is an example of a distal duct calculus immediately proximal to the ampulla demonstrated on MRCP in a patient who also has small calculi noted in the gallbladder in the region of the gallbladder neck.

This is the pancreatic duct.

And notice then as we go to a full volume MIP or maximum intensity projection display that you can demonstrate the distal duct calculus, slightly dilated biliary system calculi within the gallbladder intrahepatic calculi, which is slightly dilated and a normal diameter pancreatic duct.

Compare that to this patient who on ERCP has a limited view that demonstrates a small ductal calculus with distal acoustic shadowing in the distal common bile duct.

Adjacent to this is the portal vein.

Cholangiography can add to this information content as well by demonstrating both extrahepatic and intrahepatic ducts as well as a pancreatic duct.

But ERCP by its very nature is invasive and its utility is really in following the demonstration of the calculus with a stone extraction procedure.

Intrahepatic Calculi

Intrahepatic calculi, the associations are ischemia most often related to patients with liver transplant who have hepatic artery stenosis or stricture in cholangitis, such as can occur in patients with primary sclerosing cholangitis or some form of postoperative or post-traumatic stricture.

It can also occur in patients who have reflux in association with prior surgery such as hepaticojejunostomy, slow growing ductal neoplasm is another cause of intrahepatic stasis and the formation of intrahepatic calculi.

The imaging test for intrahepatic calculi, preferably sonography as the initial imaging test and once demonstrated, then a form of cholangiography either MRCP ERCP or PTC performed to delineate the full anatomy of the intrahepatic biliary ductal system and to plan an intervention.

Here's an example of a patient who intraoperatively has a sonographic demonstration of intrahepatic calculi.

This is a patient who's had a liver transplant who has formed intrahepatic calculi.

This is not a patient who actually had any hepatic artery stenosis, but liver transplant patients are more likely to develop a debris in their biliary system and to form calculi.

So this had migrated down into the extrahepatic duct.

Another example of intrahepatic debris or calculus is in this patient who's had biliary stent placement both in the right and left intrahepatic ducts in whom there has been debris or tumor ingrowth into the right-sided biliary ductal system into the stent itself.

So sonography is the initial study that should be utilized to detect intrahepatic calculi and also evaluate patients who may have debris or tumor ingrowth into stents.

Mirizzi Syndrome

Mirizzi syndrome is an unusual condition.

It is a impacted cystic duct calculus associated with per ductal inflammation.

The per ductal inflammation itself leading to a compressive effect on the common bile duct.

Sonography is not generally capable of making the distinction between an impacted cystic duct calculus and one in the adjacent common duct because they are immediately adjacent to each other.

So here's an example of a patient who's got a slight degree of intrahepatic biliary ductal dilatation and more distally.

One sees a calculus in this particular case immediately adjacent to a catheter which denotes the level of the common bile duct.

In this particular case, it is only when cholangiography is used that one recognizes that the calculus is in a cystic duct remnant and that's immediately adjacent to a slightly compressed common bile duct.

So the definitive diagnosis of Mirizzi syndrome is really made by a cholangiographic study rather than by a sonogram.

Biliary Strictures

The topic of common bile duct stricture After initial sonographic demonstration of a dilated biliary system, then the imaging test again become cholangiographic either MRCP or ERCP with endoscopic ultrasound.

And of those two imaging tests, MRCP magnetic resonance cholangiopancreatography would be preferred because it is non-invasive.

The management of a patients with strictures either distal or proximal on the biliary system is usually initially with a stent to relieve the biliary obstruction and then to plan a surgical procedure, either a choledochoduodenostomy for more distal strictures or an hepaticojejunostomy for proximal strictures.

In patients who may be difficult candidates for surgery for more proximal strictures at the hepatic hilum, then indwelling stents with intermittent balloon dilatation of the biliary ductal system is an alternative therapeutic technique.

Here's an example of a patient with a dilated common hepatic duct at the hepatic hilum.

Again, notice posterior to this is the portal vein and in between is the hepatic artery.

Here is another patient who had a dilated biliary system, only mild in degree, but it demonstrates very nicely the capability of MRCP to demonstrate a web-like stricture in this patient's biliary ductal system.

Notice here is the pancreatic duct.

So the anatomy of the stricture is best demonstrated I think by cholangiographic techniques, which also provide a relatively global display of the associated biliary system.

Iatrogenic Strictures

In terms of iatrogenic strictures, which is probably the most common cause of more proximal biliary ductal strictures have the hepatic hilum.

It is a laparoscopic cholecystectomy misadventure either due to poor surgical technique or due to ductal anomaly such that in this case such as this, the surgeon would mistake an anomalous right hepatic duct, a cystic duct and ligate it, causing intrahepatic biliary dilatation at least to the right lobe.

Here is an example of an aberrant duct draining from the liver into the gallbladder, directly removing the gallbladder and tearing that particular duct could lead to the presence of a bile leak and a biloma for harder biliary strictures.

Once initial diagnosis of a dilated system is obtained by sonography, then MRCP or in this particular case percutaneous cholangiography, would be the preferred imaging techniques to denote the location of the stricture and the intrahepatic biliary anatomy.

The management as stated earlier, usually antegrade stent placement as an initial technique to relieve jaundice followed by surgery, the appropriate surgical technique being hepaticojejunostomy.

If hepaticojejunostomy is not feasible, then this patient may be treated by continued placement of a antegrade stent with intermittent balloon dilatation to attempt to noninvasively treat this stricture.

Malignant Biliary Obstruction

Malignant biliary obstruction most commonly is due to pancreatic tumor, less commonly due to cholangiocarcinoma, may be due to central intrahepatic tumor such as hepatocellular carcinoma or metastatic disease, and can be due to hepatic lymphadenopathy at the hepatic hilum, either metastatic cancer such as colon cancer or malignant lymphoma.

Pancreatic Carcinoma

Here's an example of a patient with a dilated pancreatic duct and a dilated bile duct who also has an ill-defined mass lesion in the region of the pancreatic head.

Antec process, some degree of shadowing which may be due to fibrosis within this mass, but this represents the double duct sign with a high inference in a patient with painless jaundice of pancreatic carcinoma.

The next logical imaging step is a CT scan, which again delineates the pancreatic duct and the bile duct as well as this patient's pancreatic tumor mass.

The CT scan is useful not only for demonstrating the tumor as the cause of the biliary dilatation, but also as a staging procedure to determine if this patient is an operative candidate or not.

Here is an example of a patient with a pancreatic tumor that's causing dilatation of the bile duct and the pancreatic duct.

The CT scan shows you a dilated bile duct.

Here is a tumor mass in the inferior pancreatic head antec process immediately adjacent to the mesenteric vein sagittal plane view with ultrasound shows a dilated bile duct.

Here is a coronal plane which was generated from the same CT data that demonstrates a bilaterally dilated bile duct and the pancreatic tumor mass, the more distal normal dimension, common duct and pancreatic duct.

And the CT is nicely demonstrating the potential resectability of this tumor, which is contiguous two, but does not involve or invade the superior mesenteric vein.

So the imaging diagnosis of a pancreatic carcinoma is a demonstration of the primary tumor and the associated dilatation of the pancreatic and common bile duct, the double duct sign, and this can be performed by sonography.

The staging procedure is best done either by CT or MR, preferably by CT to demonstrate the features that may make this an inoperable tumor such as peripancreatic infiltration, lymphadenopathy, hepatic metastases or peritoneal tumor.

Lymphadenopathy, however, may be a rather late finding and it is not uncommon that at surgery metastasis are found in normal dimension lymph nodes.

In addition, hepatic metastasis and peritoneal tumors may be relatively small and undetected by preoperative CT scanning such that a patient who is deemed to be resectable by CT may have an initial laparoscopic procedure at surgery to determine if there are present or not peritoneal tumor seeds or small surface hepatic metastases that would make this patient unresectable.

And that is done prior to a definitive surgical exploration with a view to a Whipple procedure in terms of biopsy of pancreatic tumors.

Here is ERCP that demonstrates a dilated bile duct as well as an adjacent portal vein, which is normal in dimension.

Here is the tumor mass and then that tumor mass can be in fact sampled by aspiration techniques guided by the endoscope and ultrasound.

This particular patient was a different patient who has a stent in the biliary duct.

Here's another patient who's got a dilated pancreatic duct seen on a transverse image Whose tumor mass was localized nicely by ultrasound and in fact, percutaneous ultrasound in this particular case was used as the technique for obtaining both aspirate and core material for diagnosis.

It's been my own personal experience that percutaneous ultrasound is a mechanism for obtaining tissue from imageable pancreatic lesions is more efficacious than the endoscopic technique because one can obtain larger gauge aspirate and also core.

So image guided biopsy of either pancreatic carcinoma or cholangiocarcinoma if using endoscopic ultrasound can be by aspiration technique or by brushing by percutaneous ultrasound can be by aspiration technique or core.

And this can be directed either at a pancreatic tumor or for a cholangiocarcinoma can be directed more approximately at the hepatic hilum.

Provided we have a sufficient tumor target.

Central Cholangiocarcinoma

Central cholangiocarcinoma imaging diagnosis depends upon proximal duct dilatation and demonstration of a tumor mass.

Suffice to say that these tumor masses often are quite small and difficult to demonstrate by ultrasound staging depends upon demonstration of vascular encasement.

That is the intra hepatic portal vessels lymphadenopathy at the hepatic hilum and intra hepatic metastases.

Here is an example on sonogram of a patient with a very small strategically located cholangiocarcinoma surrounding a hepatic duct.

This duct in this patient contains a catheter that was in fact placed by a percutaneous technique prior to the sonogram.

The point of this study is to demonstrate how focal and in fact how subtle the cholangiocarcinoma is.

Here is another patient with central cholangiocarcinoma on CT scanning, demonstrated a dilated left and right intrahepatic biliary ductal system.

The adjacent vessels, the portal vessels on both the right and left side are in fact patent.

The best method of demonstrating the tumor is to do delayed CT scanning in this fibrous tumor that demonstrates enhancement of the tumor, which you now see to be extending into the second order branches of both the left hepatic lobe as well as adjacent to the right hepatic ducts.

As we go more posteriorly, we can see tumor mass at the hepatic confluence and the hilum, and this in fact is surrounding the hepatic artery.

On delayed imaging, you see contrast enhancement of tumor.

This is due to contrast diffusion into a fibrous tumor extending into the proximal right hepatic lobe to the level of the second order ductal branches.

So the CT scan was very useful in demonstrating extended tumor and involvement of second order branches making this a non operable tumor.

This is a reformation of a CT scan on the same patient following passage of percutaneous biliary stents.

This demonstrates as well the residual or not the residual, but the small component of tumor that we see in this particular plane.

Strategically located and obstructing both the right and left biliary ductal systems.

Notice the patient has an artifact which is generated from the biliary ductal stent that had been passed in this patient both at the hepatic hilum and we see this as well in the intra pancreatic common duct.

This patient had percutaneous cholangiography by sonographic guidance and subsequent placement of biliary stents.

We see these passed in both the left and the right hepatic lobe into the common duct and the pancreas and into the duodenum.

And then they were used as guidance for subsequent placement of these metallic stents, both in the right and left hepatic ducts.

Gallbladder Carcinoma

Gallbladder carcinoma imaging features are asymmetric mural thickening of the gallbladder tumor infiltrating liver or even adjacent intestine such as the right colon and not infrequently biliary obstruction due to central extension to the hepatic hilum sonographic image of a patient with the wall echo sign.

This is the anterior wall of the gallbladder bile and a large calculus.

This in conjunction with a hypoechoic soft tissue tumor infiltrating into the adjacent hepatic parenchyma.

Here's a CT scan showing you the calculus and showing you the tumor infiltrating into the adjacent hepatic parenchyma in this patient who has a small amount of ascites, a demonstration of a patient with invasive gall bladder cancer extending to the hepatic confluence who on CT scan has dilated left and right intrahepatic ducts.

But more interestingly, the same patient had a contrast enhanced sonographic study that demonstrated the same features.

Contrast agents are not available for use in the United States for this particular indication, but it does demonstrate the utility or potential utility of sonographic contrast agents.

In a case such as this.

Congenital Anomalies

Here is a patient who's got dilated intrahepatic biliary ducts, but when one looks closely, these are beaded and have small segments of cystic dilatation.

This is a patient who could have either primary sclerosing cholangitis or Caroli's disease.

As we go more anteriorly, we can see these rather prominent cystic dilatations more characteristic of Caroli's disease and here is a corresponding CT scan of this particular patient.

Patients with Caroli's disease may have coexistent congenital hepatic fibrosis or renal cystic disease.

Importantly, complications of Caroli's disease can include cholangitis and cholangiocarcinoma.

Another congenital anomaly condition is choledochal cyst, which is cystic dilatation, usually of the extrahepatic biliary ductal system.

The most common type one is fusiform dilatation of the extrahepatic duct.

Type two is a diverticulum of the extrahepatic duct.

And type three, a small distal choledochocele.

Type four is central intrahepatic duct dilatation.

And type five is Caroli's disease.

Here's an example of a patient who has a type one choledochal cyst, which you can see distal to the hepatic hilum.

Here's an example of a patient with a type four choledochal cyst that you can see at the hepatic hilum proximal to the cystic duct.

Patients with choledochal cyst may have anomalous biliary to pancreatic duct communication, such as you see in this reformatted CT study demonstrating pre ampullary connection of the pancreatic duct to the common bile duct.

It is considered that this may lead to retrograde passage of pancreatic juice into the biliary ductal system as a cause of biliary dysplasia and subsequent neoplasm.

Here is a patient with a choledochal cyst in whom there is a mass in the choledochal cyst.

This appears to be a type four choledochal cyst intrahepatic.

So cholangiocarcinoma is a potential consequence of both Caroli's disease and choledochal cyst.

Summary

So to summarize, biliary tract sonography should be the initial imaging test in any patient who presents with right upper quadrant pain or jaundice.

The major differential diagnosis being choledocholithiasis stricture or tumor.

The imaging for patients with choledocholithiasis initially should be sonography and if a positive may lead to immediate intervention by ERCP and endoscopic ultrasound.

However, if the patient has not had cholecystectomy, then more appropriately laparoscopic ultrasound and duct clearance by surgery should be considered.

The role of MRCP is that it is a more global display than ERCP And can be useful in patients with subacute or intermittent symptoms.

Endoscopic ultrasound is said to be slightly more sensitive than cholangiography in detecting small distal ductal calculi.

So as stated management of patients with intact gallbladders, laparoscopic cholecystectomy and duct clearance, those who do not have gallbladders ERCP in conjunction with sphincterotomy and stone extraction.

And remember that stone extraction of both extrahepatic and intrahepatic ducts can be performed with this technique.

But stricture after initial diagnosis by sonography imaging by MRCP or by ERCP and endoscopic ultrasound of the two MRCP favored more global in documentation management, either by stent or at least initially by stent to decompress the biliary system and subsequently by surgery.

And this should be applied to both proximal and distal biliary strictures for malignant biliary obstruction imaging by initially sonography whether it is a distal or proximal duct obstruction.

And then subsequently testing to demonstrate the stage and potential resectability of these tumors, most commonly by CT or possibly by MRI and then subsequently decompression if clinically appropriate, either by ERCP for more distal duct tumors and by percutaneous cholangiography for more proximal duct strictures.

So that is the end of this presentation.

I hope this has been useful for you in considering the anatomy and physiology of the biliary ductal system, the technique of sonography, the important sonographic findings that relate to stone stricture and tumor, and the role of other imaging pathways and management strategies in patients with biliary tract abnormalities.

Thank you.