Diseases of the Gallbladder and Bile Ducts - part 4 pot

124 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder The primary differential diagnosis of PSC is diffuse scleros- ing carcinoma of the bile ducts, which represents less than 10% of bile duct carcinomas [11]. Diffuse metastatic disease to the liver can cause multiple strictures of the intrahepatic ducts without biliary dilatation. Primary biliary cirrhosis can mimic PSC and is seen in middle-aged women. Recurrent biliary infections related to gallstones or surgical stricture produce similar findings. Sclerosing cholangitis can also be iatrogenic, occurring after infusion of chemotherapeutic agents through the hepatic artery [12]. Cystic biliary disease The etiology of cystic biliary disease is unclear (see Chapter 17). The disorder may be related to anomalous drainage of the pancreatic and biliary ducts and loss of the distal sphinc- ter mechanism [13]. The most commonly used classifi cation system for biliary cystic disease is the Todani modifi cation of the Alonso–Lej classifi cation. This system describes five types of cysts [13]. Type I is the most common (80 to 90%) and is a single cystic dilatation of the common hepatic duct, common bile duct, or both. Type II is a diverticulum of the common bile duct and accounts for 3%. Type III is a cystic di- latation of the common bile duct in the wall of the duode- num, accounting for 5%. Type IV is made up of multiple cysts involving the extrahepatic and/or intrahepatic ducts and accounts for 10% of cases. Type V is the variant known as Caroli’s disease. Type V is commonly associated with con- genital fibrosis and cysts outside of the liver. Complications include biliary obstruction, hepatic abscess, cholangitis, and bile duct cancer. The risk of bile duct cancer is increased 20 fold in this patient group. It is unusual for gall- stones to be found in association with biliary cystic disease. Choledocholithiasis Stones in the bile ducts either form there primarily or migrate there from the gallbladder. Primary bile duct stones are com- posed mainly of calcium bilirubinate. Bile stasis, dietary fac- tors, and bacterial or parasitic infection contribute to their formation, although their precise pathogenesis is unknown [14]. Single or multiple filling defects in the biliary tree charac- terize the presence of gallstones (Figs 6.4 and 6.5). Because contrast may obscure gallstones in the biliary tree, the con- trast should be diluted with normal saline for optimal visual- ization. Air bubbles or blood clots can obscure or mimic gallstones. Changing patient positioning while observing the filling defects under fluoroscopy helps to differentiate air Figure 6.3 Cholangiogram in a patient with primary sclerosing cholangitis demonstrates multiple long strictures (arrows) of the right hepatic ducts with areas of focal dilatation between the strictures. Figure 6.4 Multifaceted gallstones (arrows) appear as filling defects throughout the gallbladder and bile ducts. Chapter 6: Percutaneous biliary imaging and intervention 125 bubbles from stones. The air bubbles seek ananterior location and coalesce with one another. Blood clots are more diffi cult to differentiate from stones. Blood often enters the biliary tree during the puncture by the PTC needle. The suspected presence of blood clots requires repeating the cholangiogram in several days. The lytic prop- erties of bile and the passing of clots through the drainage catheter will have cleared blood clots from the biliary tree during that time. Gallstones sometimes become impacted within the bile ducts. In this form, they can be mistaken for a polypoid tumor [11]. Manipulation with a stone extraction basket or balloon may help differentiate between the two entities. Mirizzi’s syndrome occurs when a gallstone lodges in the cystic duct or gallbladder neck and causes extrinsic compres- sion of the common bile duct. The compression usually occurs at the lateral aspect of the common bile duct [15]. The patient develops jaundice because of common bile duct obstruction. Benign biliary strictures More than 90% of benign biliary strictures are the result of surgical trauma, most commonly cholecystectomy (see Chapter 10) [16]. Surgical strictures may be caused by duct li- gation or clipping, as is seen with emergency maneuvers to control massive bleeding. They can also result from thermal injury or injury to the small arteries that run within the com- mon bile duct wall [16]. Transection of the duct interrupts the delicate arterial blood supply to the ducts. This may be the reason for ischemia and stenosis sometimes seen with bili- ary–enteric bypass operations (Fig. 6.6). Torsion of the bile duct may also occur following choledochojejunostomy (Fig. 6.7). Figure 6.5 Multifaceted gallstones appear as filling defects above a benign anastomotic stricture (arrow) which developed in a patient who underwent biliary-enteric bypass for a laparoscopic cholecystectomy bile duct injury. Figure 6.6 A benign focal anastomotic stricture (arrow) is present in a patient who underwent biliary–enteric bypass for pancreatic cancer. 126 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder Benign biliary strictures are a common problem following orthotopic liver transplantation and occur in 3 to 22% of the patients (see Chapter) [17]. The etiology of anastomotic stric- tures in this group is not well understood. Postoperative fibrosis and possibly ischemia are felt to be the causes. Pro- longed cold ischemic time, hepatic artery thrombosis, surgi- cal interruption of the peribiliary arterial plexus, and chronic rejection are potential causes of nonanastomotic biliary stric- tures in the transplanted liver [17] (Figs 6.8 and 6.9). Postoperative benign strictures are usually short and have an abrupt change in caliber at the site of abnormality. There is ductal dilatation above the stricture. Intrahepatic abscesses may be present. A longer stricture should raise the suspicion of malignancy [6]. Nonsurgical causes of benign biliary obstruction include gallstone erosion into the main bile duct, pericholedochal abscess, blunt trauma, compression by pseudoaneurysm or pseudocyst, and pancreatitis (Figs 6.10 and 6.11). Malignant biliary strictures Distinguishing between malignant and benign strictures is difficult. Although certain cholangiographic features de- scribed in this section may suggest the presence of a malig- nant stricture, these features are not specific. Clinical information and results of noninvasive radiologic tests, such as CT, MRI, and ultrasound, may help to confirm a diagnosis of malignancy. CT, MRI, and ultrasound provide informa- tion about liver tissue surrounding the intrahepatic ducts and organs that surround the extrahepatic ducts. Results of these imaging modalities may be inconclusive, in which case a biliary biopsy may be helpful. Cholangiocarcinoma is a slowly growing tumor that usu- ally presents in the sixth decade of life (see Chapter 20). Pa- tients present at a younger age if the tumor is found in association with other diseases that predispose to cholangio- carcinoma, suchas primary sclerosing cholangitis and chole- dochal cyst disease. Figure 6.7 (A) Postoperative cholangiogram following biliary–enteric anastomosis in a patient who underwent hepatic trisegmentectomy for metastatic colon cancer. Torsion has occurred at the anastomosis causing obstruction (arrow) of the bile duct. (B)The biliary-enteric anastomosis (arrow) is widely patent following revision of the anastomosis. (A) (B) Chapter 6: Percutaneous biliary imaging and intervention 127 Figure 6.8 Multiple focal ischemic strictures following orthotopic liver transplantation. Figure 6.9 Ischemic stricture (arrowhead) involving a branch of the right hepatic duct following orthotopic liver transplantation for primary sclerosing cholangitis. There is gross dilatation of the bile ducts above the stricture and a large amount of debris within the ducts. Figure 6.10 Obstruction of the common bile duct (arrow) secondary to chronic pancreatitis. 128 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder Cholangiocarcinoma presents as long or focal bile duct strictures. It spreads through local extension along the bile ducts or into the liver substance [6]. The distal left or right main bile ducts and the common hepatic duct are the most common sites of involvement (Fig. 6.12). The tumor occurs at the junction of the left and right main hepatic ducts in 20.5 to 45.5%, the common bile duct i n 33 to 40.5% , and the cystic duct in 6% [6]. The differential diagnosis for intrahepatic ductal involvement of cholangiocarcinoma includes PSC and liver metastases (Fig. 6.13). Pancreatic carcinoma, ampulla- ry carcinoma, and chronic pancreatitis should be considered when the disease is confined to the distal common bile duct. Gallbladder carcinoma occurs more frequently in females and usually presents in the sixth and seventh decades of life (see Chapter 15). Choledocholithiasis is found in 80% of the patients [6]. Direct extension of the tumor is common and sometimes causes jaundice by obstructing the common he- patic duct (Fig. 6.14). The other common form of tumor spread is lymphangitic. Pancreatic carcinoma is the fourth leading cause of cancer death in the United States. It is the most common cause of malignant biliary obstruction in patients in their sixth de- cade of life or older. Pancreatic cancer causes compression and obstruction of the mid to distal common bile duct (Fig. 6.15). The contrast column passing through the tumor is typ- ically irregular, with a “rat tail” appearance. Narrowing is usually concentric. The site of obstruction may have a nipple- like appearance [6]. The proximal bile ducts are usually dilated. Most patients with ampullary carcinoma present in the sixth and seventh decade of life. Ampullary carcinoma on cholangiography appears as an irregular filling defect located in the distal most portion of the common bile duct. Metastatic disease from other organs causes biliary ob- struction when it involves the hepatic hilum, periportal lymph nodes, or peripancreatic lymph nodes (Figs 6.16, 6.17, and 6.18). Direct extension of tumor from adjacent organs, such as the stomach, may also cause biliary obstruction (Fig. 6.19). Tumor encasement can cause irregularity and dis- placement of the contrast column on cholangiography. Por- tal lymph nodes replaced by tumor may produce extrinsic compression of the contrast column. Bile leaks Most bile leaks are iatrogenic and occur following cholecys- tectomy, partial liver resection, or orthotopic liver transplan- tation. Uncomplicated bile leaks, such as cystic duct leak and Duct of Lushka leak following cholecystectomy, usually respond to biliary decompression with an endoscopic stent [18]. More extensive bile duct injuries require surgical Figure 6.11 A pancreatic pseudocyst causes obstruction (arrow) of the com m o n b i l e d u c t by ex t r in si c co mp re s s i o n. Figure 6.12 A cholangiocarcinoma causes a malignant stricture (arrows) of the common hepatic duct, left main hepatic duct, and the first two divisions of the right hepatic duct. Chapter 6: Percutaneous biliary imaging and intervention 129 Figure 6.13 Diffuse cholangiocarcinoma causes multiple strictures of the right intrahepatic ducts (arrows), left hepatic duct, and common hepatic duct. Figure 6.14 (A) Metastatic adenosquamous carcinoma of the gallbladder following biliary- enteric bypass causes obstruction (arrow) of the common hepatic duct. (B)A small amount of contrast passes through the biliary–enteric anastomosis showing marked thickening of the jejunal folds caused by tumor invasion (arrowheads). (A) (B) 130 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder biliary enteric reconstruction in the form of a Roux-en-Y anastomosis. Percutaneous methods can sometimes be used to treat a complex bile duct injury without surgery. More often, percutaneous interventions are performed prior to surgical repair to aid in identifi cation of the bile ducts intraoperatively. ERCP will demonstrate the abnormal bile duct in most cases of bile leak. PTC becomes necessary when a bile leak is occurring above a clipped or ligated common bile duct or when a common bile duct is transected and the intrahepatic ducts cannot be opacified in a retrograde fashion. Patients with a bile leak will usually have the biloma drained percutaneously first under CT or sonographic guid- ance. Successful repair of the bile leak requires careful re- view of all intraoperative and postoperative cholangiograms and knowledge of normal and variant bile duct anatomy. This is especially important in cases where an aberrant bile duct has been inadvertently divided and no longer communicates with the remainder of the biliary tree [19]. Cholangiography of the main biliary tree in such a case may lead the observer to believe that the entire biliary tree is intact. PTC is difficult in cases of bile duct leak because of the small caliber of the decompressed bile ducts. Successful needle ac- cess to the decompressed bile ducts may require many needle passes, increasing the risk of vascular injury. The decom- pressed bile ducts can more easily be found by injecting the biloma drain with contrast and observing for retrograde flow of contrast into the torn bile duct. Once a peripheral branch of the torn bile duct is identified, the duct can be accessed with a needle for subsequent catheterization and diagnostic cholan- giography. If this method of duct opacifi cation fails, ultra- sound can be used to direct needle passes into the portal region, increasing the chances of successful needle access to a decompressed bile duct [19]. The opacified biliary tree must be examined in multiple projections to be certain that all ducts are accounted for. Occluding the torn bile duct with a balloon occlusion catheter during contrast injection prevents rapid egress of contrast into the biloma, allowing maximal duct opacifi cation. The length of intact bile duct above the tear must be demonstrated if biliary enteric reconstruction is planned. Partial tears of large ducts or complete tears of small Figure 6.15 Pancreatic carcinoma has caused complete obstruction (arrow) of the distal common bile duct. An occluded endoscopically placed stent (arrowheads) is present. Figure 6.16 Pancreatic carcinoma metastasis to a portal lymph node (arrows) causes obstruction of the common hepatic duct. Chapter 6: Percutaneous biliary imaging and intervention 131 ducts may respond to biliary diversion techniques, either percutaneous or endoscopic. Percutaneous interventions in the biliary tree Introduction Image-guided instrumentation for percutaneous interven- tions in the biliary tree has improved greatly since the earliest interventions were first performed in the 1950s. Current in- dications for percutaneous biliary access include: (1) percu- taneous biliary drainage or stent placement for biliary obstruction; (2) biliary diversion as a definitive treatment for bile leakage or as a step to operative treatment; (3) gallblad- der drainage for the nonoperative candidate with cholecysti- tis; (4) percutaneous gallstone extraction or gallstone contact lithotripsy; (5) percutaneous access for brachytherapy for malignant bile duct obstruction; (6) percutaneous biliary bi- opsy; (7) transhepatic enteric access for jejunal feeding tube placement in the patient with a percutaneous biliary drain already in place [20]; (8) percutaneous choledochocholedo- chostomy in the patient with intrahepatic benign bile duct obstruction [21]; and (9) percutaneous choledochojejunos- tomy in the post-operative patient with an excluded aberrant bile duct and an existing Roux-en-Y limb [22]. Figure 6.17 Obstruction of the common bile duct (arrows) secondary to pancreatic carcinoma. Figure 6.18 Recurrent pancreatic cancer causes stricturing of the biliary bifurcation (arrows) following Roux-en-Y biliary–enteric anastomosis. Figure 6.19 Local recurrence of gastric cancer involves the common bile duct and duodenum. There is complete occlusion of the distal common bile duct (open arrow) and duodenum (closed arrows). 132 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder Percutaneous access of the biliary tree for biliary interventions Percutaneous access to the biliary tree becomes necessary when a biliary obstruction or leak: (1) fails to respond to en- doscopic treatment; (2) is located at or above the biliary bifur- cation where endoscopic therapy may be ineffective; (3) will be treated surgically and percutaneous biliary drainage cath- eters must be in place at the time of surgery to facilitate iden- tifi cation of the bile ducts; or (4) was in a favorable location to be treated endoscopically but ERCP was technically unsuc- cessful. ERCP (see Chapter 5) can be unsuccessful when the endoscopist fails to: (1) cannulate the ampulla because of un- favorable anatomy or tumor; (2) cross an obstruction or tear in the extrahepatic bile duct; or (3) pass the endoscope through the efferent limb of a biliary enteric bypass. When this occurs, the endoscopist attempts placing a nasobiliary tube before removing the endoscope. The patient is then transferred to the interventional radiologist for percutane- ous cholangiography and biliary drainage. The radiologist injects contrast into the nasobiliary drain to opacify the bili- ary tree (Fig. 6.20). This greatly simplifies percutaneous nee- dle access to the biliary tree for diagnosis and possibly intervention [4]. Lower procedure time reduces risk and ra- diation dose for the patient. The risk of vascular injury during percutaneous biliary in- terventions is greatest in the central portion of the liver, where the vascular structures are the greatest in caliber. Therefore, the biliary tree is best entered through a peripher- Figure 6.20 (A) The tip of a nasobiliary drainage catheter (arrows) was passed into the right biliary tree in a patient with cholangiocarcinoma involving the biliary bifurcation. (B) The nasobiliary drain was used to opacify the biliary tree for facilitation of right- sided percutaneous biliary drainage (arrows). The noncommunicating left biliary system (curved arrow) was accessed under sonographic guidance. Multiple radiopaque gallstones fill the gallbladder. (A) (B) Chapter 6: Percutaneous biliary imaging and intervention 133 al bile duct. In this manner, all central instrumentation will be done within the confines of the biliary tree. Once a peripheral bile duct is accessed with a 22-gauge needle, the needle is replaced with a temporary 3 French drainage catheter. Most of the bile is aspirated from the bili- ary tree. This avoids over-distension of the infected biliary tree when injecting contrast into the biliary tree for cholan- g i og r ap h y. A s p i r a t io n o f b i l e a l s o pr e ve nt s s pi l l a g e o f bi l e i n to the peritoneal cavity during catheter exchanges and tract dil- atation. Once the bile ducts are opacified, the cholangiogram is analyzed for the presence of any bile duct abnormalities. The percutaneous tract is then evaluated using a pullback contrast injection technique to see if a major vascular struc- ture has been transgressed [23,24]. A guidewire is left in place during this maneuver so as not to lose access to the bili- ary tree. The access is not used for biliary intervention if a major vessel has been transgressed. Once a favorable tran- shepatic tract is obtained, a curved tip catheter and guide- wire are negotiated through sites of leak or obstruction. W h e n t h e c a t h e t e r r e a c h e s t h e i n t e s t i n e , i t i s r e p l a c e d w i t h a n 8 French percutaneous biliary drainage catheter. If an ob- struction or tear cannot be passed, a straight or pigtail drain- age catheter is placed above the abnormal site. Left biliary drainage is necessary when a bifurcational oc- clusion prevents communication between the two ductal systems. A left-sided biliary drainage catheter is easier for the patient to care for by himself or herself because of ease of ac- cess. It is also associated with less leakage of ascites around the catheter. Left biliary access is best performed under sono- graphic guidance. The gallbladder can also be used as a portal of entry for in- terventions involving the common bile duct. Although the cystic duct is difficult to navigate, it may be used as an avenue for placement of an internal–external biliary drainage cathe- ter [25]. This method requires the obstructing lesion to be below the level of the cystic duct origin. Once cholangiography is performed and an abnormality is identified, a drainage catheter is often placed. Aggressive in- terventions, including balloon dilatation and biopsy, are avoided during the first patient encounter to avoid biliary sepsis. There are three types of drainage catheters available for draining the biliary tree. An external drainage catheter is placed above an obstruction, draining bile externally into a bag. An internal–external drainage catheter lies within the biliary tree and intestine and traverses the obstruction. Bile can drain externally into a bag or internally into the bowel or both. An internal drain is more often referred to as a biliary endoprosthesis or stent. It has no external component. The biliary stent crosses the obstruction and drains bile inter- nally only. It is usually placed endoscopically. Plastic, remov- able stents must be exchanged periodically, usually every 3 months. This avoids occlusion from bile salts and bacterial colonization. Metallic stents are permanent devices. They are used almost exclusively for unresectable malignant oc- clusions and usually remain patent throughout the patient’s life span. Ingrowth of tumor will occasionally occlude the stent, requiring coaxial placement of another stent. Metallic endoprostheses can be placed either percutaneously or endoscopically. The right internal jugular vein is an important portal of entry to the biliary tree in the patient with ascites and a ma- lignant biliary occlusion [26] (Fig. 6.21). The curved needle is directed from the inferior vena cava into the middle hepatic vein, across liver parenchyma and into the dilated biliary tree. A metallic stent is then placed across the malignant occlusion through the access and the jugular venous catheter is removed. Patients with ascites are at risk for ascites leakage around the percutaneous biliary drainage catheter. This is less of a problem with a drainage catheter placed via the left hepatic lobe rather than the right, possibly because of the right access being more dependent in the recumbent position. An ostomy bag can be placed temporarily around the catheter insertion site to collect ascitic fl uid and prevent skin breakdown. To stop the leakage of ascites around the catheter, a T-fastener set can be used to retract the liver surface against the abdomi- nal wall and seal off the tract from leaking [27]. For patients in whom percutaneous access is given up after a biliary stent is placed, cyanoacrylate glue can be injected into a transhe- patic tract to prevent leakage of ascites and bile at the end of the procedure [28]. Draining the isolated biliary system Occasionally, tumor, stricture or surgical clip prevents pas- sage of a percutaneous biliary drainage catheter from the left or right bile ducts into the intestine (Fig. 6.22). It then be- comes necessary to divert bile externally from the isolated biliary tree. Long-term external drainage of bile complicates medical management with fl uid and electrolyte loss. The bile can be rerouted back into bowel by connecting the drainage catheter externally to a T-tube [29], an internal–external PBD in the contralateral bile ducts [30,31] or a gastrostomy feeding tube [32]. A communication between the isolated bile ducts and the internally draining ducts may also be created using a sharpened guidewire. This results in an intra- hepatic choledochocholedochostomy [21]. An isolated left biliary tree can be drained directly into the stomach. This is done by transhepatic perforation of the left lobe of the liver into the lesser curvature of the stomach using fluoroscopic, endoscopic, and laparoscopic guidance. In a study of 35 patients who underwent hepaticogastrostomy, the mean patency rate was reported to be 234 days ± 252 [33]. The reintervention rate was 14%. Complications included cholangitis (20%) and gastritis (12%). Percutaneous treatment of bile duct fistulas Bile leaks following cholecystectomy are usually minor and arise from either the cystic duct stump or a transected bile [...]... loops in the needle path are noted The distance from the gallbladder to the anterior skin surface is usually 141 5.0 cm [48 ] The shortest route from the skin to gallbladder usually requires passage of the catheter through 1 cm of liver tissue Passing the needle through the window of liver tissue also stabilizes the guidewire during tract dilatation and limits the amount of bile leakage around the catheter... therapeutic approaches for the biliary tree and gallbladder by irradiation They further characterized the injury as “vacuolation, swelling, and necrosis of the epithelial cells of the ducts, and by a slow and atypical regeneration” eventually resulting in “biostasis and hemorrhage.” Warren later described the effects of radiation on normal tissue, including the gallbladder and biliary region, with similar... of the sensitivity and specificity of these techniques for the diagnosis of biliary tract stricture [44 ] They reported sensitivities and specificities of 50 to 66% and 93 to 100% for brush cytology, 42 to 67% and 100% for fine-needle aspiration cytology, 30 to 73% and 100% for bile cytology, and 30 to 100% and 100% for endobiliary biopsy forceps The Simpson atherectomy catheter is a percutaneous tool that... reports of radiotherapy for gallbladder and bile duct cancer focused on its use in the palliative setting, with an occasional cure reported In 1972, a report of over 1800 cases of gallbladder and EHBD carcinoma from the California tumor registry reported 24% of patients had received radiotherapy during the course of their disease [8] Green et al and Hudgins et al reported on the palliative benefit of radiation... area of active investigation Charged particles, such as protons and helium ions, have also been used in the treatment of gallbladder and biliary cancers In contrast to photons, the energy deposition patterns from charged particles are highly localized This is due to a disproportionate absorption of the majority of their energy at the end of their track range, the so-called Bragg peak The dose unit of. .. following X-ray therapy for gastric cancer in 1921; Case and Warthin reported on three cases in which X-ray therapy was used for treating malignancies in the upper gastrointestinal region in 19 24 [4, 5] From gross examination and histopathologic studies at autopsy, they concluded that the epithelium of the biliary tract, especially smaller ducts, could be injured 147 148 Section 2: Diagnostic and therapeutic... brachytherapy boost, and concurrent 5- uorouracil (5-FU)/mitomycin-C chemotherapy with or without a curative resection [ 54] Five patients underwent surgical decompression and the remaining seven had a biopsy or subtotal resection of the tumor Median survival for all patients was 17 months and 4- year survival 36% Four patients had no evidence of disease at 16, 30, 40 , and 64 months, respectively Alden and. .. patients, bile peritonitis was seen in 8.6% of the patients who had their T-tube removed with the modified technique Bile peritonitis was seen in 19.5% of the control patients who had the T-tube removed in a conventional manner (F) Use of a metallic endoprosthesis for the treatment of biliary strictures Over the last decade, the metallic stent has become a frequently used, permanent endoprosthesis for the. .. the 1950s radiotherapy became more commonly used in the treatment of gallbladder and biliary tract malignancies (collectively called the extrahepatic bile duct (EHBD) system) as a result of implementation of higher energy photons, initially with cobalt 60 and later linear accelerators [7] These high-energy X-ray sources permitted the delivery of therapeutic radiation doses at depth, while sparing the. .. guidewire and the arteriogram repeated This maneuver releases the tamponade effect of the drainage catheter on the injured vessel and usually discloses the bleeding site When an abnormal site is seen, the catheter is advanced into the artery and coils are deployed to bridge the site of injury Acute hepatic failure because of hepatic artery embolization is rare but may occur in the presence of advanced . 1 24 Section 2: Diagnostic and therapeutic approaches for the biliary tree and gallbladder The primary differential diagnosis of PSC is diffuse scleros- ing carcinoma of the bile ducts, which. diverticulum of the common bile duct and accounts for 3%. Type III is a cystic di- latation of the common bile duct in the wall of the duode- num, accounting for 5%. Type IV is made up of multiple. sclerosing cholangitis. There is gross dilatation of the bile ducts above the stricture and a large amount of debris within the ducts. Figure 6.10 Obstruction of the common bile duct (arrow) secondary