The endoscopic placement of bile duct stents is now widely used for the palliation of malignant bile duct obstruction. A variety of stents are now available but these can be broadly categorized as either plastic stents or self-expanding metal stents. Plastic stents are cheaper and can usually be readily exchanged. They are often used in patients who appear to have a poor prognosis and in patients who may have resolution of the obstructing lesion with chemotherapy. In contrast, metal stents are more expensive and are usually impossible to remove after deployment. However, the duration of stent patency is significantly longer for metal stents (6–12 months) than for plastic stents (3–4 months). Furthermore, patency of a blocked metal stent can be re-established by placing a second metal stent in the occluded stent or by placing a plastic stent within the metal stent. Plastic stents are usually obstructed by biofilms but metal stents are obstructed by tumor ingrowth through the wire mesh, tumor growth above or below the stent, encrustation of biofilms and sludge, stent malposition and stent migration. In the patient illustrated below, biliary obstruction was related to encrustation associated with bacteria and fungi.
A 78-year-old man was readmitted with jaundice, 6 months after placement of a self-expanding metal stent (80 × 10 mm) for an obstructing bile duct cancer. The cancer had been confirmed by endoscopic cytology and was judged to be irresectable by surgery. He did not have clinical features of cholangitis. Repeat endoscopic retrograde cholangiography showed pale tissue within the stent lumen that was thought to be due to tumor ingrowth (Figure 1). Biopsies were taken but only revealed inflamed duodenal-type mucosa (Figure 2, left). However, there were also numerous bacteria and fungi (Figure 2, right). A second metal stent was deployed within the original stent and the patient has remained symptom-free for a further 4 months. As encrustation within the stent may have been related to fungal overgrowth, he was also treated with fluconazole, 400 mg bd, for 2 weeks. Whether this was helpful remains unclear. Modifications that may prolong the patency of metal stents include the use of covered metal stents and the use of stents impregnated with either antibiotics or chemotherapeutic agents.