Many different therapies have been proposed for the treatment or palliation of esophageal carcinoma. These include resection, bypass, radiation therapy, laser ablation (neodymium/yttrium-aluminum-garnet), bougienage, chemotherapy, photodynamic therapy, bicap tumor probes, and feeding tube placement. Another palliative option consists of esophageal stents; previously rigid plastic stents were used, but now expandable metal stents are available.
Leroy d'Etoiles, a French surgeon of the 1840s, utilized a decalcified ivory tube as a stent. In 1885 Sir Charles Symonds placed a tube made of boxwood and German silver. He eventually utilized ivory as well [36-38]. This tube was held in place by strings that passed through the patient's nostrils and either looped behind the ears, or were attached to a mustache. In 1902 Gootskin modified the straight tube with a proximal inverted funnel and distal rim to mitigate against migration .
Traction placement, necessitating a laparotomy and gastrostomy to deliver the stent has now been replaced by pulsion techniques. A Celestin tube became the stent of choice before the advent of expandable metallic stents. This tube was modified by the placement of a wider proximal end to direct food and secretions into the tube lumen away from the native esophagus, especially in cases of local perforation or esophageal-airway fistulization. The proximal flare might also limit proximal migration of the stent. Various modifications included a collar (Souttar tube), funnel (Palmer tube), cup (Mousseau-Barbin tube), or tulip tip (Celestin tube) . The placement of all non-expandable metal stents had to be preceded by bougienage to a diameter 3F to 6F greater than the stent to be placed . Procedure-related complication rates approached 20%, with a mortality of almost 9% following placement of rigid endoprostheses. In comparison, expandable metal stents have fewer complications, decreased hospitalization time, and comparable results of palliation . One very unusual complication related to Celestin stents is fragmentation, with subsequent migration of the pieces, which have been known to cause obstruction or even bowel perforation [41,42]. These problems have not been associated with expandable metal stents.
The Nitinol mesh stent is made of knitted single strands of Nitinol elastic alloy wire, a heat-sensitive metal alloy that expands at body temperature. It is delivered in a gelatin mold and may take as long as a week to reach its maximum diameter . Because it is an open wire mesh, it is not suited for covering esophageal-airway fistulas. Its chief advantage is that of longitudinal flexibility [40,43].
The Wallstent is made of stainless steel that is intertwined in a double layer. Both coated and uncoated varieties have been manufactured, although only the coated kind is presently made . The coated variety is very effective in sealing esophageal-airway fistulas . The presence of flared ends (funnel shaped) makes this endoprosthesis a good choice in tumors that do not present a good proximal shelf to anchor a stent. These ends are not coated, even when the stent itself is
. The stent is mounted in a delivery tube and self expands within 24h . Alternatively, balloon dilatation may speed the attainment of the maximal diameter of the stent . Like all expandable stents, the prosthesis shortens considerably upon deployment. The presence of fixation hooks makes repositioning or removal difficult.
Gianturco Z stents are made of a stainless steel cage with wires in a zigzag pattern [36,39,40]. They may be covered with either silicone or urethane. Funnel-shaped ends are present at both proximal and distal ends. The deployment system is complex, consisting of a pusher tube and compression catheter. Prior to deployment, the esophagus must be dilated to at least 30F diameter. Although the stent is self-expanding, balloon dilatation may be needed to reach a satisfactory luminal diameter . Similar to the Wallstent, the coated Z stent is a good choice for covering esophageal-airway fistulas .
The Esophacoil is made of a flat wire coiled-spring arrangement of a superelastic nickel-titanium alloy [36,43]. It is wrapped over an insertion catheter. Pulling of restraining threads releases the stent. The Slinkylike configuration leads to marked shortening upon deployment (50%) . The device expands spontaneously in just a few seconds. The Esophacoil is particularly valuable in crossing tight and/or angu-lated strictures  because the radial force developed during its deployment is the greatest of all the stents. However, this very advantage may also lead to erosion of the esophageal wall, with resultant fatal hemorrhage.
The complications of esophageal stents are summarized in Table 2.1. Prior radiation and/or chemotherapy may lead to an increased rate of complications . There are many reasons for esophageal perforation to occur during or after stent deployment. Many stents require prede-ployment dilatation of the esophagus. This itself may cause a perforation. Angulated lesions cause eccentric mechanical forces to be placed upon the esophageal wall, especially with noncompliant stents . The considerable radial force developed by the Esophacoil may cause disruption of the wall.
Over the longer term, pressure necrosis may lead to perforation. The rate of perforation may reach as high as 14% for patients treated with rigid stents, although the numbers appear to be lower for the newer expandable stents [36,44-46]. The wire struts on some stents may lead to chronic esophageal ulceration or frank perforation .
Table 2.1. Complications of esophageal stents.
3. Migration (including fragmentation of Celestin tube)
4. Tumor ingrowth
5. Tumor overgrowth
6. Obstruction by food bolus
7. Tracheal compression
8. Stent infolding
The radiographic findings are often marked and easy to recognize. They include local extravasation of contrast agent or the presence of contrast in the mediastinum, pleural space, or subphrenic collections (Fig. 2.12). Pneumomediastinum or pneumothoraces may also be present. When perforations occur, they may be treated conservatively by leaving the covered stent in place or placing an overlapping stent to cover the perforation .
Malposition of a stent is usually the result of migration during or shortly after insertion. Other causes may include a discrepancy between the stent outer diameter and the maximum luminal diameter of the esophagus, inadequate anchoring of the prosthesis, too short a stent length, or deployment at the wrong level (seen in cases of inadequate predeployment localization of the stricture) . At radiography, there is lack of coverage of the stricture by the stent or continued filling of a perforation or fistula. Stents placed near the gastroesophageal (GE) junction or across angulated lesions are more prone to malposition, as are those placed in cases of abrupt change in luminal caliber or lacking
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