Plastic biliary
endoprostheses relieved malignant
obstructive jaundice in 80% to 90% of the patients. The comfort of a completely indwelling
endoprosthesis should be offered to all palliatively treated
tumor patients, and external-internal
catheters should be reserved for the minority of patients who return with reoccluded
endoprostheses. These patients have bacterial flora that rapidly contaminates the
endoprosthesis and causes encrustations and reocclusions. Thus, a second
endoprosthesis also would reocclude quickly. The mechanism of reocclusion of
plastic and
metal endoprostheses is completely different. In
plastic endoprostheses, bacterial contamination causes decomposition of the bile and subsequent encrustation. In
metal endoprostheses tumor ingrowths between the struts of the
stent cause reocclusion.
Tumor ingrowths were observed in only 6.5% of
metal prostheses with a narrow woven mesh (Wallstent), whereas
prostheses with large distances between the struts (Gianturco
stent) had ingrowth rates of 19% to 50%. This fact shows that
tumor ingrowths can be reduced by narrowing the spaces between the metallic network, and, therefore, improvements in the design of the
metal stents should reduce the occlusion rate to or below that of
plastic endoprostheses, which currently have a lower encrustation rate. The major advantages of expandable
metal prostheses are the relative ease and the minimal
trauma of the implantation procedure. The Wallstent
endoprosthesis, in particular, can be inserted through a 7-F introducer sheath and offers the chance of single-step placement. The 30-day mortality rate, therefore, was only 5%. This is significantly lower than the 30-day mortality rate after insertion of
plastic prostheses (15% to 24%). Even simple external
catheter drainage procedures have a higher reported 30-day mortality rate (27%). Expandable
metal endoprostheses would be the most useful device if the occlusion rate could be kept under 10% in large series. Increasing the length of the
endoprostheses to 10 cm in the expanded state could also improve the long-term patency rates.