Management of Malignant Biliary Tract Obstruction



Management of Malignant Biliary Tract Obstruction


Raymond H. Thornton and Anne M. Covey


Malignant bile duct obstruction (MBDO) occurs when tumor within or adjacent to bile ducts impedes the normal passage of bile from the liver to the intestinal tract. Tumors of pancreobiliary origin, such as cholangiocarcinoma and gallbladder and pancreas cancer, are the most common causes of MBDO. Other etiologies include lymphoma and metastases from any primary neoplasm. Many benign conditions may also cause biliary obstruction. Differentiation of benign and malignant causes of bile duct obstruction is essential because treatments are different.


Obstruction of the biliary tree blocks the normal pathway for bile excretion, resulting in cholestasis (Greek chole, “bile,” + stasis, “standing still”). This leads to measurable biochemical derangements including elevation in serum bilirubin (conjugated hyperbilirubinemia), γ-glutamyl transpeptidase, and alkaline phosphatase. Physical signs and symptoms are often present, and many are explained by the absence of bile in the intestinal tract or the appearance of bilirubin and bile salts in the serum. The presence of one or more of these signs and symptoms of obstructive jaundice usually prompts referral for biliary drainage.


Jaundice, a yellowish discoloration of tissues caused by the deposition of bilirubin, may be first detected as scleral icterus when the total serum bilirubin level exceeds 2 to 3 mg/dL. Darkening of the urine (bilirubinuria) occurs with renal excretion of conjugated bilirubin. Light-colored, acholic stool is observed because of the absence of pigmented bilirubin breakdown products in the intestinal tract. Pruritus, a well-known but poorly understood symptom of cholestasis, is thought to be mediated by bile salt retention. Patients with jaundice may also experience constitutional symptoms including anorexia, nausea, and fatigue. Infection of obstructed bile ducts, termed cholangitis, is a clinical syndrome of broad spectrum ranging from low-grade fever to septic shock. Charcot described the triad of right upper quadrant pain, fever, and jaundice for diagnosis of cholangitis. To these, Reynolds added mental status changes and sepsis, for a total of five clinical findings suggestive of the diagnosis. Although cholangitis is relatively uncommon in MBDO when there has been no prior intervention to contaminate the biliary tree, it remains an important diagnostic consideration whenever a patient with biliary obstruction has fever.


Modern imaging capabilities permit robust noninvasive evaluation of the obstructed biliary tree. Regardless of which imaging modality is employed, certain observations about the pattern of biliary obstruction must be made. Chief among these observations is description of the point (or points) of biliary obstruction in anatomic terms. This can be accomplished by tracing dilated bile ducts as they pass from the periphery of the liver to the liver hilus and subsequently to the intestine, recognizing points of obstruction as sites where there is interruption or narrowing of dilated bile ducts. This is important because it facilitates preprocedural prediction of the cholangiogram so an optimal drainage procedure can be planned. Another key observation is evaluation of the patency of the portal vein and its intrahepatic branches. This is important because portal vein occlusion leads to atrophy of liver parenchyma, and drainage of atrophic liver segments will not result in recovery of liver function.


Sonographic examination is a common starting point in the imaging assessment, although overlying bowel gas can limit evaluation of the extrahepatic bile duct. Computed tomography (CT) and magnetic resonance imaging (MRI), including magnetic resonance cholangiopancreatography (MRCP), offer powerful cross-sectional and multiplanar anatomic methods to evaluate the biliary tree and surrounding structures. With this armamentarium of noninvasive imaging tests, it is now unusual to require diagnostic percutaneous cholangiography (PTC) for evaluation of MBDO.


Endoscopic retrograde cholangiopancreatography (ERCP) and biliary drainage (ERBD) are often preferred over percutaneous approaches in centers where skilled endoscopists offer this service. For patients with low bile duct obstruction (obstruction of the common bile duct or common hepatic duct not involving the biliary confluence), endoscopic techniques permit diagnosis and therapy without the need for percutaneous approaches or exteriorized drainage catheters. High bile duct obstruction (obstruction proximal to or involving the confluence of left and right hepatic ducts) is more often managed percutaneously by interventional radiologists, as are patients for whom ERBD is either not possible or unsuccessful. Interventional radiologic procedures used in the management of MBDO include PTC, percutaneous transhepatic biliary drainage (PTBD) and stent placement, and bile duct biopsy.



Indications


The indication for biliary intervention typically includes imaging evidence of biliary obstruction plus the need for diagnosis or treatment of one or more of the clinical manifestations associated with MBDO.




Percutaneous Transhepatic Biliary Drainage


In the presence of MBDO when ERBD cannot be performed, PTBD is indicated:



• For treatment of cholangitis. Hydration and antibiotic therapy are successful initial interventions for 80% to 85% of patients with cholangitis.1 Those with ongoing sepsis despite these therapies require urgent biliary decompression, and those who do respond to initial medical therapies frequently require subsequent biliary drainage.


• To relieve pruritus. Medical therapies including the bile acid–binding resins cholestyramine and colestipol, antihistamines, naloxone, and rifampin are variably effective treatments for pruritus related to cholestasis. Biliary drainage is an effective treatment2,3 when results of these medications are suboptimal, even when only one or two segments of the liver can be effectively drained. Following biliary drainage for this indication, symptomatic improvement is often observed within 24 hours.


• To relieve symptoms of jaundice. Symptoms such as nausea and anorexia may improve with delivery of bile salts to the intestine.


• To reduce serum bilirubin to facilitate administration of chemotherapy. Some chemotherapeutic agents require intact mechanisms of bile excretion for safe use, and others require dose modification when the serum bilirubin is elevated. To receive optimal chemotherapy at full dose, some patients may require biliary drainage to lower serum bilirubin.4


• Prior to surgery. Preoperative biliary drainage is highly controversial; many studies have shown it increases complication rates.5-8 One meta-analysis suggested neither positive nor negative outcomes in association with preoperative biliary drainage.9 Others have suggested improved postoperative results following internal drainage.1012


• In association with other percutaneous biliary procedures such as bile duct biopsy and placement of biliary stents or brachytherapy catheters




Contraindications


Percutaneous Transhepatic Cholangiography


Relative contraindications include:





Biliary Stent Placement




• All contraindications to PTBD


• Sepsis. PTBD with minimal manipulation is indicated for patients with sepsis and bile duct obstruction. If appropriate, stent placement can be considered after sepsis has resolved.


• Potential surgical candidate. Because determination of resectability presupposes knowledge of the diagnosis, metallic stents are not placed when the diagnosis is not known. Historically, biliary drainage catheters rather than biliary stents have been placed for preoperative patients. There is a trend in recent literature to suggest that stents can be safely used in preoperative patients with low bile duct obstruction.13-16 Because this represents a substantial change in approach, local surgical preferences should be sought and considered.


• Benign disease. Metallic stents are generally not used for treatment of benign causes of biliary obstruction.



Equipment


Either moderate sedation or anesthesia services can be used for performance of PTC, PTBD, and biliary stent placement. In either case, patient monitoring equipment including pulse oximetry and electrocardiographic monitors are required.


Owing to the length of biliary cases and proximity of the operator to the x-ray beam, modern fluoroscopic equipment capable of recording radiation dose should be used. Ceiling-mounted translucent leaded shields or leaded eyeglasses can be used as protective barriers in addition to leaded gowns.


Example equipment needs include:




Technique


Anatomy and Approach


Understanding the segmental anatomy of the liver is essential for interventional radiologists who perform biliary interventions. The Couinaud classification of liver anatomy (Fig. 134-1, A) is most useful in this regard. The liver is divided right from left by the plane that includes the middle hepatic vein and gallbladder fossa.




Left Hepatic Lobe


The caudate lobe is segment 1. The lateral segment of the left hepatic lobe comprises segments 2 and 3. Segment 2 is more superior and posterior, and segment 3 is more anterior and inferior. Therefore, left-sided biliary drainages often use segment 3 for access because it is ordinarily the most superficial and inferior portion of the lateral sector under the skin of the epigastrium. The medial segment of the left hepatic lobe, segment 4, is separated from the lateral segment by the umbilical fissure and falciform ligament.


The left hepatic duct is formed by the confluence of tributary bile ducts from segments 1 through 4. The lateral sector ducts (segments 2 and 3) have a typical appearance, joining to create an acute angle to form a single duct that subsequently receives the segment 4 and segment 1 branches, forming the left hepatic duct. The left hepatic duct is characteristically longer than the right. This anatomic fact is functionally important when MBDO is centered at or above the hilus, because progression of disease will usually involve second-order and higher biliary confluences on the right side before the same thing occurs on the left. In such a context, left-sided biliary drainage may be preferred.



Right Hepatic Lobe


The right hemiliver is separated into anterior and posterior segments by the plane of the right hepatic vein, and into superior and inferior segments by the plane of the portal vein. The posterior sector is composed of segment 6 (the posterior inferior segment) and segment 7 (the posterior superior segment). The anterior sector is formed by segment 5 (the anterior inferior segment) and segment 8 (the anterior superior segment).


The right posterior sector bile duct is formed by the union of the ducts from segment 6 and segment 7, and the right anterior sector bile duct is formed by the union of the ducts from segment 5 and segment 8. The right hepatic duct is formed by the union of the right posterior and right anterior sectoral ducts.


The confluence of the right and left hepatic ducts (the primary biliary confluence) forms the common hepatic duct. The common hepatic duct receives the cystic duct to form the common bile duct. The common bile duct receives the pancreatic duct close to the ampulla of Vater.


Important common variants of biliary anatomy must be understood (Fig. 134-1, B). Several of these involve variant insertions of the right-sided sectoral ducts. One common example occurs when the right posterior sectoral duct drains to the left hepatic duct instead of joining the right anterior duct. In certain hilar occlusions where this anatomic variant is present, drainage of the right posterior sector may confer drainage of 6 liver segments (segments 1-4, 6, and 7), whereas drainage of the anterior sector would accomplish drainage of only 2 segments (segments 5 and 8) in such instances. Therefore, careful study of preprocedure imaging and real-time scrutiny of the procedural cholangiogram for the presence of variant biliary anatomy is essential.



Pathologic Anatomy


As obstructed bile ducts pass from peripheral to central, they become larger in caliber, and this appearance can be appreciated by ultrasound, CT, MRI, and PTC. Sudden decrease in the caliber of a bile duct as it passes centrally is a clue to a point of biliary obstruction.


Biliary obstruction may cause one part of the biliary tree to be separated from another part, and this separation is termed isolation. The extent or degree of isolation may be characterized as complete or incomplete. In complete isolation, there is no obvious remaining connection between the segments of biliary tree that have been separated by the obstruction (Fig. 134-2). Contrast material injected into the bile duct during cholangiography stops at the point of obstruction, and catheter-guidewire manipulations are required to find the obliterated connection between completely isolated segments of bile duct. Incomplete isolation, on the other hand, occurs when disease has pathologically narrowed segments of bile duct that still remain in communication. This is depicted by passage of injected contrast material through areas of bile duct narrowing into other portions of the biliary tree (Fig. 134-3). Some refer to incomplete isolation as impending isolation to convey the likelihood that with time, disease progression will transform incomplete isolation into complete isolation (Fig. 134-4). Clinically, incomplete isolation is important because it is functionally equivalent to partial obstruction; when it is present, there are poorly drained segments of the biliary tree that are substrates for infection. Instrumentation or injection can contaminate such ducts with bacteria, leading to cholangitis.


Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Management of Malignant Biliary Tract Obstruction
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