Whereas surgery is still the gold standard for eradicating biliary and other intestinal tumors, percutaneous transhepatic biliary drainage, with or without placement of an endoprosthesis, has become an integral part of the treatment of biliary obstruction over the past 15 years[1,2]. Biliary drainage is a well-accepted means of palliation for malignant biliary obstruction that has been used both preoperatively and as the primary treatment in patients whose disease is deemed unresectable .
Role in Treating Different Tumors
Biliary obstruction is caused by a wide range of tumors, and therefore, therapy of the obstruction differs markedly, depending on the lesion involved. Ampullary carcinoma is preferably treated surgically with a Whipple procedure, and endoscopic biliary drainage is employed only in exceptionally high-risk patients or those with metastatic disease. In contrast, carcinoma of the pancreas is frequently treated by biliary drainage, as the majority of patients with this cancer present with advanced disease. In this situation, the drainage is often performed endoscopically, since the primary stricture is usually low-lying within the common bile duct.
High obstruction at the ductal confluence, which is beyond the reach of most endoscopists, may be caused by cholangiocarcinoma, gallbladder carcinoma, or adenopathy in the porta hepatis secondary to a variety of metastases. Biliary drainage is often the primary therapy for gallbladder carcinoma and adenopathy in the porta hepatis, since, by the time gallbladder carcinoma causes biliary obstruction, it is usually inoperative. Cholangiocarcinoma, when resectable, may be treated operatively with a hepaticojejunostomy. However, the majority of patients with a Klatzkin-type stricture at the bile duct confluence have more extensive intrahepatic disease at presentation that precludes curative surgical resection and/or pose too great a surgical risk.
Postoperative patients may also develop jaundice secondary to biliary obstruction. The concern in such patients is usually recurrent malignancy; however, a stricture may simply represent a late-presenting anastomotic stenosis. Benign anastomotic stenoses are well-treated by biliary drainage combined with balloon dilatation, whereas palliative drainage is the treatment of choice for recurrent disease .
Jaundice alone is not an indication for percutaneous transhepatic biliary drainage. The general indications for biliary tract drainage are jaundice associated with cholangitis, sepsis, pruritus, and nausea and vomiting leading to dehydration and malnutrition. In patients with these symptoms, biliary drainage offers significant palliation, and the benefits of the procedure outweigh the major risks, which include bleeding, bacteremia and/or sepsis, hepatic injury, and pneumothorax. Initial transhepatic cholangiography is necessary to define the extent of an obstruction, particularly with cholangiocarcinoma, and to plan for surgery.
Preoperative biliary drainage in patients who are jaundiced but otherwise asymptomatic, especially those with carcinoma of the pancreas, has not been found to be beneficial, but should be employed in the rare patient presenting with acute ascending cholangitis. Occasionally, the presence of a catheter in the extrahepatic bile duct may assist the surgeon in creating a biliary bypass, in which case preoperative endoscopic or transhepatic drainage may be considered.
Biliary drainage was first described in 1974 by Molnar and Stockum  and was popularized in 1978 by Ring, who developed a suitable catheter for internal drainage . Initially, external drainage was the treatment of choice, but it has the inconvenience of a catheter with bile draining into a bag. Prolonged external drainage of bile has the added disadvantage of electrolyte loss leading to metabolic imbalance. Occasionally, however, it may be necessary, particularly in patients who have high intra-abdominal or intraluminal pressures within the duodenum and who have persistent leaks alongside their catheter. Various techniques have been developed to readminister this "lost" bile enterically, but these are often quite difficult to tolerate.
Internal-External Catheters--As a result of these problems, internal drainage with an internal-external catheter became the standard therapy for nearly 10 years. These transhepatic catheters are designed with side holes both above and below the level of obstruction in the biliary tree; the tip of the catheter resides within the bowel, so that bile drains through the catheter across the obstruction and out of the side holes into the duodenum. Although biliary obstructions are usually complete, it is almost always possible for a trained interventional radiologist to negotiate through a stricture with a combination of guidewires and catheters under fluoroscopic guidance. With placement of an internally draining catheter, nutrition is improved, and metabolic imbalance no longer becomes an issue.
Most transhepatic biliary catheters are routinely changed every
2 months to avoid any chance of obstruction.
If such problems as deep pain, fever (> 101° F), or leakage around the catheter onto the dressing develop, they can be managed simply by exchanging the catheter for a new one. However, external-internal catheters are a potential source of bacterial infection, are prone to dislodgment and obstruction, and may be uncomfortable.
Furthermore, for many patients the external catheter is a constant reminder of their cancer. Less frequently, it may be regarded as a "lifeline," the device that saved the patient from death. Therefore, maintenance of the catheter becomes the main focus of the patient's life, and any problems that develop may be perceived as a threat to his or her existence. Both of these psychologically disruptive feelings encouraged the search for a truly internal device.
Early Internal Devices--The first devices to achieve this goal were a variety of endoprostheses, particularly the Carey-Coons stent (12 French [4 mm] in diameter), which is used for distal common bile duct strictures, such as that seen with carcinoma of the pancreas; and the Miller stent, a double mushroom design used for more proximal disease, as can be seen with cholangiocarcinoma. These devices were designed to be implanted following an initial trial of internal-external drainage. If internal drainage was achieved satisfactorily by capping an internal-external catheter (thereby forcing bile to flow into the duodenum), the internal-external catheter could then be exchanged for an endoprosthesis that was positioned over a guidewire, after which the percutaneous access site was allowed to heal over.
Because nothing protrudes externally from the patient's side, internal stents are generally tolerated much better by patients. However, the expected patency of these synthetic catheters is only on the order of 4 to 6 months. Radiologists originally used Teflon for these catheters, but this material was found to have a high rate of encrustation with sludge and bacteria, which are the predominant sources of catheter obstruction.
Metallic Stents--In the late 1980s metallic stents came into use (see Figure 1). These self-expanding stents may be introduced through a sheath the same size as the initial biliary drainage catheter. When deployed, they expand up to 10 mm (30 French) in diameter .
In essence, the theoretical advantage of metallic stents is that they provide a significantly larger lumen within the bile duct without creating a large access hole within the liver. It was believed that a much larger lumen would allow for a considerable increase in patency. Furthermore, metal is not reactive in the biliary tree, and progressively becomes incorporated into the wall of the bile duct over several weeks' time.
In reality, however, patency remains a problem with stented malignant biliary tract obstructions. Tumor ingrowth through the struts of the stent and overgrowth over the ends of the stent have proved to be major limitations of these newer devices.  The wider struts of the zigzag Gianturco Z stent appear particularly susceptible to tumor ingrowth. The woven mesh of the Wallstent design was first reported by European researchers to be better, but it, too, is susceptible to both tumor overgrowth and occasional ingrowth .
To avoid tumor overgrowth and ingrowth, stenting over an extended length of duct has been recommended. However, it does not totally solve these problems. Silicone coating of the stents has been proposed and tried in Europe, but no long-term data are available. Inspissated bile may obstruct these stents, despite their relatively large diameters.
Recent work suggests that the long-term patency of metal stents alone in the treatment of malignant obstruction is little more than 6 to 8 months [6-8]. However, in patients with carcinoma of the pancreas or gallbladder, whose survival is generally limited, this approach may provide sufficient palliation. Endoscopic stent placement has become the primary approach for most patients with carcinoma of the pancreas, since the obstruction tends to be low-lying in the bile duct. Also, this approach avoids the potential problems of hemobilia and pneumothorax associated with transhepatic drainage. As a technique, endoscopic retrograde stent placement may be less painful for the patient [2,3].