It has been shown in several studies that metal stents remain patent considerably longer than plastic stents -and despite the greater initial material costs, they are likely to be more cost-effective, at least in patients with a longer life expectancy. In a prospective study [1], 118 patients with inoperable malignant bile duct strictures were randomly assigned to receive either metal or plastic stents. There was no significant difference in the survival between the two groups, but additional days of hospitalization, days with antibiotics, and numbers of endoscopic retrograde cholangiopancreatography (ERCP) and ultrasound examinations were higher in the plastic stent group. Two independent factors for survival were American Surgical Association (ASA) classification and the number of hepatic metastases. The data for patency rate were inconclusive, and details of the plastic stents used were not given (size, number, type). In summary, metal stents proved to be more effective.The data reported by different groups for the patency rate vary: in one study, the patency rate of metal stents was higher than that of plastic stents [2], while in another it was almost equal, but the costs for plastic stents were lower [3]. In a third study, there was no difference, but the quality of life was better in the metal stent group [4]. Overall, optimal drainage is the most important aspect, regardless of whether metal or plastic stents are used to improve the clinical symptoms and survival [5]. In a prospective multicenter study conducted in Korea, the tumor characteristics and metal stent patency were evaluated in a cohort of 58 patients. Patency depended on the degree of stricture and time required for full expansion, but not on age, type of tumor, or length or location of the stent [6]. A European prospective multicenter study [7] including 111 patients presented an exact survey of the characteristics of metal stents in vivo. Insertion was successful in 98 %; two stents opened insufficiently, technical failure occurred in two, and one was misplaced. The median stent patency was 355 days, the median survival 174 days, and metastases had a negative impact on stent patency. Despite these excellent data for stent performance, this report lacks clinical data.A Japanese study of 67 patients emphasized the significance of malignant flow impairment; according to this study, the rate of recurrent stenosis and costs are higher in patients with obstructing metastases -particularly metastases from gastric carcinomas -than in those with obstructing hepatobiliary carcinomas [8].Since uncovered metal stents tended to suffer from tumor ingrowth, with occlusion after a certain time, new covered metal stents were developed. In a multicenter trial [9], experience with a silicone-coated stent was evaluated. Stent placement was satisfactory in 31 of 33 patients with different types of malignant biliary obstruction. After one month, the mean bilirubin levels had decreased from 150 µmol/l to 24 µmol/l. Early complications were minor: pain in two cases...
