Intervention for Gastric Outlet and Duodenal Obstruction

Indications

The main indication for placement of gastroduodenal stents is obstruction of the stomach, duodenum, or proximal jejunum by unresectable malignant tumors. Advanced carcinoma of the pancreatic head is the most common malignancy causing obstruction in these regions. Other malignancies include cholangiocarcinoma, gastric carcinoma, and metastatic disease to the duodenum or proximal jejunum.

Anastomotic malignant obstruction after gastrectomy or esophagectomy is also an indication for stent placement. Although stent placement for benign obstruction is still under investigation, it may be a possible alternative treatment when coexisting morbidity involving the cardiopulmonary system limits surgical treatment.

Contraindications

The only absolute contraindication to stent placement is gastrointestinal (GI) perforation with peritonitis or tension pneumoperitoneum. Multifocal small-bowel obstruction has been reported as the main cause of clinical failure after stent placement. Therefore clear evidence of distal small-bowel obstruction is also a contraindication to stent placement. Patients with peritoneal carcinomatosis are at high risk for multifocal small-bowel obstruction.

Equipment

Gastroduodenal stents should be flexible enough to allow easy placement along a tortuous GI tract. They should not migrate after deployment and should be conformable in a way that does not permit distortion of the normal anatomy of the upper GI tract. They should have sufficient radial expansile force and diameters large enough to relieve the obstructive symptoms. In addition, such stents should not allow tumor ingrowth and mucosal hyperplasia. Available stents range from 18 to 22 mm in diameter and are mounted on 10F delivery systems 230 cm long for endoscopic placement and 160 cm long for peroral fluoroscopic placement.

Self-expandable metallic stents have virtually always been used in the stomach and duodenum. Many self-expandable stents composed of a variety of metal alloys with varying structures are available commercially. The development of stents woven from a monofilament of nickel-titanium alloy (Nitinol) is a major breakthrough because of their greater conformability and smaller delivery systems compared with stainless steel stents. Both covered and bare stents have been used in the stomach and duodenum. Covered stents have the advantage of resisting tumor ingrowth through the stent mesh wire, but are prone to migration and biliary obstruction. They are rigid and require a large delivery system and are thus difficult to deploy at distant locations along a tortuous delivery route. Advantages of bare stents over covered ones include greater flexibility, requirement for a smaller delivery system, and more resistance to migration.

Various stents dedicated to gastric outlet and duodenum are available, including the Wallstent enteral (Boston Scientific, Natick, MA) ( Fig. 89.1 ), Niti-S (Taewoong Medical, Gimpo, South Korea), Hanarostent (M.I.Tech, Pyeongtaek, South Korea), dual duodenal stent (S&G Biotech, Yongin, South Korea), Bonastent (M.I.Tech). The WallFlex enteral has been constructed using Nitinol to provide improved flexibility while maintaining lumen integrity, has looped ends to reduce risk of mucosal injury, and has a proximal flared end to minimize risk of stent migration. In some publications from South Korea, the use of various types of covered enteral stents ( Fig. 89.2 ) has been reported. The Niti-S stent and the Hanarostent are woven from a single thread of Nitinol wire. The stents are covered with polyurethane (Niti-S) or silicon membrane (Hanarostent). The diameters of the body of the stents are 16 or 18 mm, and both ends are flared, which increases the size to 20 to 24 mm. They are mounted on an 18F delivery system. These stents are highly flexible and exert adequate expansile force. Song et al. developed a nylon-covered stent (dual duodenal stent) that was designed to be placed coaxially. It is mounted on a very low profile (3.8 mm) delivery system. Other authors have introduced a new duodenal bare metallic stent (Bonastent M-Duodenal [Standard Sci-Tech Inc., Seoul, South Korea]), through which biliary stent placement is safe and effective for palliative treatment of malignant biliary and duodenal obstruction.

Stents designed for esophageal use have also been used in gastric outlet and duodenal obstruction. The Ultraflex esophageal stent (Boston Scientific) is knitted from Nitinol mesh wire, which slowly expands when deployed at body temperature, and is available in both covered and bare versions. It has significantly lower radial expansile force than the other stents, but it is highly flexible and thus can be placed across acutely angled stenoses.

Technique