Technology Insight: enteral stenting and new technology
Dia T Simmons and Todd H Baron* About the authors
Correspondence *Mayo Clinic College of Medicine, Division of Gastroenterology and Hepatology, 200 First St SW, Rochester, MN 55905, USA
Email baron.todd@mayo.edu
Summary
Self-expandable metal stents (SEMS) have gained acceptance for use in the gastrointestinal tract in order to relieve malignant luminal obstruction. In the upper gastrointestinal tract SEMS are used as an alternative to surgical bypass for palliation of malignant gastric-outlet obstruction. In the colon, SEMS are used to avoid colostomy during palliation and as a bridge to surgery for left-sided colonic obstruction. Enteral SEMS appear to be cost effective. This article reviews the latest in stent technology as well as the outcomes following their placement.
Review criteria
MEDLINE was searched in March 2005, using the following subject headings: "gastric outlet obstruction", "intestinal obstruction", "duodenum", "colon", "rectum", "colorectal" and "stents" or "self expandable stents"'. The review was limited to publications in English. Review articles that were identified by this query were searched for other relevant publications. Publications that were included in comprehensive reviews were generally not listed separately in this manuscript.
Keywords:
colonic obstruction, endoscopy, gastric-outlet obstruction, self-expandable metallic stent, surgical bypass
Introduction
Self-expandable metallic stents (SEMS)—tubular metal mesh stents that expand radially upon deployment—were initially introduced in the field of gastroenterology for the relief of malignant biliary obstruction. They were subsequently introduced for esophageal use. More recently, SEMS have been used to relieve luminal obstruction of the upper gastrointestinal tract, colon or rectum: in these situations SEMS are referred to as enteral stents (Table 1).1 This review highlights indications for enteral SEMS and relates data on efficacy, complications, and cost-effectiveness. Future directions for enteral stenting technology are also discussed.
Table 1 Commercially available enteral stents.
Full tableFigures & Tables indexDownload Power Point slide (185K)
Stenting for Gastric-outlet obstruction
Gastric-outlet obstruction (GOO) refers to mechanical or functional obstruction of the flow of gastric contents into the small intestine. Symptoms of GOO include early satiety, postprandial abdominal pain, nausea, vomiting, intolerance of oral feeding and weight loss. Malignancies most commonly producing GOO arise from cancers of the pancreas, gallbladder, biliary tree, stomach and duodenum (Figure 1). Malignant or benign anastomotic strictures and regional lymphadenopathy can also cause GOO. Historically, benign GOO was often a sequela of peptic ulcer disease. With the advent of effective antisecretory medications, peptic strictures are less common; therefore, we focus on malignant GOO.
Figure 1 Gastric-outlet obstruction after Whipple procedure.
(A) Endoscopic image showing tumor recurrence in the efferent limb of the gastrojejunostomy. (B) Fluoroscopic image showing the endoscope tip in the proximal efferent limb, and the guidewire across the stricture. (C) Fluoroscopic image taken immediately after deployment of a self-expanding metal stent (WALLSTENT® Colonic & Duodenal Endoprosthesis, Boston Scientific/Microvasive, Natick, MA). (D) Endoscopic view from the proximal end of the stent deployed at the gastrojejunal anastomosis.
Full figure and legend (24K)Figures & Tables indexDownload Power Point slide (74K)In well patients, surgery via gastroenterostomy is the traditional method for palliation of GOO. With unresectable cancer, the risks associated with surgical bypass and the possibility of postoperative delayed gastric emptying can outweigh the benefits. Conservative measures, such as nasoenteric tube feeding and venting gastrostomy, do little to relieve obstructive symptoms and do not allow patients the pleasure of oral food intake. Some patients develop recurrent malignant obstruction after palliative bypass. Endoscopic placement of SEMS can be a useful nonsurgical alternative for palliation of GOO (Figure 2). The first reported use of SEMS for malignant GOO was in the early 1990s.2
Figure 2 Malignant gastroduodenal stricture.
(A) Endoscopic view of a partially obstructing cancer in the gastroduodenal junction. (B) Endoscopic view immediately after deployment of a self-expanding metal stent (Ultraflex Precision Colonic Stent System, Boston Scientific/Microvasive, Natick, MA).
Full figure and legend (23K)Figures & Tables indexDownload Power Point slide (68K)An FDA-approved enteral stent (WALLSTENT® Colonic & Duodenal Endoprosthesis, Boston Scientific/Microvasive, Natick, MA) has been available in the US for nearly 10 years (Table 1). In some countries outside the US, additional dedicated enteral stents can be obtained, whereas in other countries no specifically designed enteral stents are available. Esophageal stents are less flexible and have shorter delivery systems than enteral stents, but have been modified for duodenal use. In Japan, for example, esophageal stents have been modified by the addition of a plastic tube to lengthen the stent delivery system. Custom sheaths have sometimes been used to cover the delivery system to prevent trauma to the mucosa.3, 4 Other esophageal stents that have been adapted for enteral use are the Gianturco Z-stent (Wilson-Cook Medical, Winston-Salem, NC) and the Ultraflex Esophageal NG Stent System (Boston Scientific/Microvasive, Natick, MA).
The goals of stenting for GOO are to restore functional continuity between the stomach and the intestine, allow oral nutrition and relieve symptoms by the least invasive means possible. When placing duodenal stents, one must consider the patient's risk of biliary obstruction,5 particularly in the setting of pancreatic cancer.1 After duodenal stent placement, access to the ampulla for endoscopic biliary stent placement is difficult, if not impossible. Therefore, prophylactic placement of a biliary stent prior to duodenal stent placement should be considered if there is a possibility of covering the ampulla.1 Once a duodenal stent has been placed, percutaneous biliary drainage can be performed if biliary obstruction occurs.
Contraindications to gastroduodenal stent placement include known or suspected enteral ischemia or perforation, inability to pass a guidewire across the stricture, and the usual endoscopy contraindications.
Early gastroduodenal stent complications, which occur within several days of placement, include bleeding and perforation. Late complications include distal STENT MIGRATION, and re-obstruction caused by TUMOR INGROWTH, reactive tissue hyperplasia, TUMOR OVERGROWTH, and food impaction; these late complications can usually be managed endoscopically. Patients must receive dietary instruction to avoid food impaction after stent placement. Late perforation is uncommon, but can occur.
Comparative studies of gastroduodenal stenting versus surgery
Fiori and colleagues6 published the only randomized trial to date of stent placement versus surgical bypass for palliation of malignant GOO. Eighteen patients with advanced, unresectable antropyloric stenosis were randomized to endoscopic stenting with 10 cm long covered SEMS (Ultraflex covered stent system, Boston Scientific/Microvasive, Natick, MA) or gastroenterostomy. Stent placement was technically successful in 100% of patients. The mean time to oral food intake was 2.1 days for patients who received stents compared with 6.3 days for patients who underwent surgery. Eight out of nine stent patients tolerated solids by day 3, whereas six out of nine surgical patients tolerated solids by day 7. Overall, stent patients fared better in terms of shorter procedure times, faster restoration of oral intake, and shorter hospitalization.
Nonrandomized prospective studies and retrospective studies have also compared surgical outcomes with endoscopic stent outcomes in GOO.7, 8 A major limitation of these studies is selection bias—surgical patients tended to have less advanced disease and longer life expectancy than the stent patients.
In 2004, Johnsson et al. published their prospective nonrandomized study of 36 patients, which compared treatment using endoscopic SEMS with open surgical bypass for malignant GOO.7 Surgery was performed when a radical dissection was considered, or if stent placement was not considered practical. Stents of 20 mm diameter (WALLSTENT® Colonic & Duodenal Endoprosthesis with UNISTEP® Plus Delivery System, Boston Scientific/Microvasive, Natick, MA) were placed in 21 patients, and 15 patients underwent open gastroenteric anastomosis. Technical success of stent placement was achieved in all 21 patients. Two stented patients underwent surgery, one for recurrent symptoms, and the other for massive hemorrhage. Repeat stenting was performed in two patients for tumor ingrowth. Food impaction was treated endoscopically in one stented patient. Among the 15 surgical patients, 1 underwent reoperation after 1 month for recurrent symptoms. Mean survival was 76 days in stented patients and 99 days in open surgery patients. At 1 month postprocedure, there were 15 surviving stent patients who could all eat or drink, of whom 11 (73%) could eat solid or pureed foods. In the surgery group, 9 of the 11 patients (81%) who survived beyond 1 month could eat or drink, but only 5 of these (45%) could tolerate solids. The authors attributed the delay in food tolerance among surgical patients, in part, to the slow recovery of motility functions associated with gastroenteric bypass. They concluded that enteral stenting was at least as efficacious as open gastroenterostomy for malignant GOO; it was less costly, and associated with a shorter hospital stay (7.3 days versus 14.7 days, respectively).
Mittal et al.8 retrospectively compared three methods of palliation for pyloroduodenal obstruction: endoscopic stenting, laparoscopic gastroenterostomy, and open gastroenterostomy. Patients were matched by American Society of Anesthesiologists grade, age and anatomic level of obstruction. Of 181 patients who had been treated between 1989 and 2002, the majority had undergone open surgery. After matching, there were 16 patients in the stent group, 14 in the laparoscopic surgery group and 16 in the open surgery group. The median time to oral fluid intake was up to 1 day after stenting, 4 days after laparoscopy, and 6 days after open surgery. In-hospital costs were lower for patients who underwent endoscopic stenting. As with other retrospective studies, there was some selection bias despite matching, because the endoscopic patients might have had more advanced obstruction.
Comprehensive reviews of gastroduodenal stenting
Case series on SEMS for GOO, published between January 1992 and September 2003, have been systematically reviewed.9 Criteria for inclusion included information on the technical success of stent placement and deployment, clinical success (relief of symptoms or improved food intake), and complications. A total of 32 case series comprising 606 patients were analyzed, of which 10 were prospective studies. Technical success was achieved in 589 patients (97%). Of those, clinical success was achieved in 526 (89%), an overall clinical success rate of 87%. Of the 526 clinical successes, dietary intake information was available for 401 patients; full diet was tolerated in 193 (48%), soft solids were tolerated in 158 (39%), and the remainder tolerated liquids only (13%). Pooled mean scores on the Gastric Outlet Obstruction Scoring System10 were 0.4 (almost no intake possible) at baseline and increased to 2.4 (ability to eat pureed or soft diet) postprocedure. Final symptom resolution was realized in a mean of 4 days.
Severe complications were observed in 1% of patients, including perforation and bleeding. There were no procedure-related deaths. Less severe complications included stent migration (5%), pain (2%), biliary obstruction (1%) and stent obstruction (17%).
Survival data were available for 458 patients, among whom the mean survival time was 12 weeks (range 1–184 weeks). Based on these results, some authors conclude that stents are the best palliative strategy if a patient's life expectancy is less than 6 months, whereas surgery might be a better option if the patient's expected survival is greater than 6 months.
What's new in gastroduodenal stenting?
Within the past 5 years, SEMS modifications have included partial coverings and various coatings to improve stent efficacy and reduce complications. Others have attempted to prevent stent obstruction by simultaneously placing stents within stents. On the horizon are stents that are more flexible and are less traumatic to tissue.
From the radiologic literature, 102 patients with inoperable, malignant, gastroduodenal strictures underwent placement of dual expandable nitinol stents; these stents allow the benefits of coating, but are less prone to migration.11 First, a partially nylon-covered nitinol stent was placed in the region of obstruction; a bare nitinol stent was then placed within the partially covered stent. Presumably, the curvature of the duodenum prevents migration, even with a covered stent. The technical success rate was 98% (100 of 102 patients) and the clinical success rate was 84% (85 of 101 patients). No perforations occurred. Stent migration occurred in two patients. Reintervention was required in one patient, because of tumor ingrowth (symptomatic recurrence). Five patients became jaundiced and were treated with percutaneous external biliary drainage.
Kim et al.12 reviewed 49 patients with malignant GOO who initially underwent placement of an uncovered stent (through the scope (TTS) Niti-S Pyloric Stent, Taewoong-Medical, Seoul, South Korea). Early restenosis (within 4 weeks of stent placement) occurred in seven patients owing to tumor ingrowth. Restenosis was treated with placement of a covered stent within the original uncovered stent. Early restenosis occurred more frequently at anastomotic stricture sites than at non-anastomotic stricture sites.
Summary for gastroduodenal stenting
The available literature shows that SEMS are efficacious for the palliation of malignant GOO (Table 2).13, 14 Dietary improvement after stenting is comparable with the improvement after surgical bypass, but allows an earlier return to oral intake, shorter hospital stay, and lower in-hospital costs.
Table 2 Summary of outcomes following enteral stent placement.
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Stent verus surgical approach to enteral obstruction
Endoscopic placement of enteral SEMS is typically performed using moderate sedation and analgesia, rather than general anesthesia, in an endoscopy or radiology suite. SEMS placement is generally associated with a shorter length of hospitalization compared with surgery. Either interventional radiologists or endoscopists place enteral SEMS. The interventional radiologist may be more adept with guidewires. The endoscopist has the advantage of working at close proximity to the obstructed lumen owing to the use of endoscopes.
The endoscopist places stents under direct endoscopic vision using fluoroscopic guidance. Generally, a flexible hydrophilic guidewire is first used to traverse the stricture to facilitate subsequent stent placement. With TTS devices, the stent delivery system is passed across the stricture after the stricture is traversed. With non-TTS devices, the endoscope must be withdrawn prior to passage of the stent system. The stent chosen should be approximately 4–6 cm longer than the stricture. Once the constraining sheath is released, SEMS undergo expansion and shortening.
Gross and histologic tissue changes occur as stents expand and become incorporated into the gut wall.15 Through pressure necrosis, the struts of the stent migrate into the mucosa and submucosa where a fibrous reaction occurs. The stent becomes embedded in collagen and fibrous tissue. A chronic lymphocytic reaction occurs in the normal tissue underlying the proximal and distal ends of the stent.
Surgical approaches involve resection or bypass of the obstructed segment of intestine. Temporary or permanent colostomy may be required for colorectal cancers. Few studies have directly compared laparoscopic and open surgical approaches with enteral palliation. Choi and colleagues retrospectively evaluated patients who underwent either laparoscopic (n = 10) or open (n = 10) side-to-side gastrojejunostomy for palliation of malignant GOO.16 The frequency of early postoperative complications was higher among open surgery compared to laparoscopic surgery (P <0.01). There was no significant difference in long-term morbidity, or mortality.
Colonic Stenting
Since the first reported use of self-expandable colorectal stents in 1991,17 their indications have broadened from palliation (Figures 3 and 4) to use as a bridge to surgical resection, in patients with potentially operable acutely obstructing colon cancer. In either situation, the main goals of stent use are to avoid emergency surgery, with its high mortality rate, and to avoid stoma creation.18 In patients with total left-sided colonic obstruction, a dual-stage operation is often necessary for operable cancers, including a temporary diverting colostomy followed by definitive colonic resection. In patients referred for curative surgery, stent placement as a bridge to surgery (described in 199419) permits bowel decompression, thorough bowel preparation, and a single-stage colon resection. Flexible transanal tubes placed proximal to the colon obstruction may also be used for short-term decompression.20, 21 Like SEMS, the cost-effectiveness of transanal tubes lies in permitting a one-stage operation. SEMS have the advantage of being completely internalized and expanding to create a wider lumen than may be achieved with tubes.
Figure 3 Malignant transverse colon obstruction.
(A) Endoscopic view of malignancy in the mid transverse colon with near-complete luminal obstruction. (B) Fluoroscopic image of the obstructed transverse colon. A pre-deployed colonic stent (Ultraflex Precision Colonic Stent System, Boston Scientific/Microvasive, Natick, MA) is positioned across the stricture. (C) Fluoroscopic image, taken after deployment of the self-expanding metal stent in the transverse colon. (D) Endoscopic view immediately after stent deployment.
Full figure and legend (22K)Figures & Tables indexDownload Power Point slide (67K)Figure 4 A 9 cm obstructive malignant stricture of the rectosigmoid colon.
(A) Endoscopic view of malignant rectosigmoid obstruction. (B) Fluoroscopic image during stent deployment. (C) The expanded self-expanding metal stent (Ultraflex Precision Colonic Stent System, Boston Scientific/Microvasive, Natick, MA) traverses the stricture. (D) Improved luminal patency after stent deployment.
Full figure and legend (26K)Figures & Tables indexDownload Power Point slide (70K)Proponents of stents as bridges to surgery recognize the potential quality-of-life benefit in avoiding a temporary or permanent colostomy, and reducing the number of surgeries required by the patient. Concerns have been raised regarding the possibility that stents could spread malignancy in curable cancers. A study from Tokyo reviewed the long-term prognosis of patients with resectable colorectal cancers treated surgically, with or without SEMS as a bridge to surgery.22 They found no significant difference in 3-year survival (50% versus 48%) or 5-year survival (44% versus 40%) between those treated with emergency operations compared to those given SEMS as bridges to surgery. These results suggest that implanted stents do not lead to spread of malignancy. Additional studies of long-term results after temporary use of SEMS in resectable cancers are needed.
In addition to the management of primary colon cancers, colorectal stents can be used to treat extrinsically compressing processes, such as pelvic cancers, regional metastases and lymphadenopathy. Covered stents have also been used to seal rectovaginal and rectourinary fistulas effectively.23
Contraindications to colorectal stent placement are similar to those for gastroduodenal stenting, and include known or suspected colonic ischemia or perforation, multiple sites of obstruction, and standard endoscopy contraindications.
Early colorectal stent complications, occurring within the first 24 h of placement, include bleeding and perforation. Perforation is associated with aggressive stricture dilation, occurring both pre-placement and post-placement. Tenesmus, pain, and fecal incontinence might occur after distal rectal stent placement. Late complications can include distal stent migration, and re-obstruction as a result of tumor overgrowth, tumor ingrowth, reactive tissue hyperplasia or fecal impaction.
The Ultraflex Precision Colonic Stent System, WALLSTENT® Colonic Endoprosthesis (Boston Scientific/Microvasive) and the Colonic Z Stent (Wilson-Cook) are colonic stents commercially available in the US. The TTS Niti-S Colorectal Stent (Taewoong-Medical Co., Ltd, Seoul, South Korea) and the Hanarostent Colorectal (MI Tech Co., Ltd. Seoul, South Korea are examples of colonic stents available outside the US (Table 1).
Comprehensive reviews of colonic stenting
The efficacy and safety of colorectal stents have been systematically reviewed.24 Case series from the beginning of January 1990 up to and including December 2000 were considered. Criteria for the pooled analysis were reporting of technical and clinical success of stent procedures, and reporting of complications and re-obstruction. In total, 598 patients were included in the analysis. The etiology of obstruction was malignant in 92% (n = 552), benign in 3% (n = 15), and not classified in the remaining 3% (n = 31). Obstruction was most frequently left-sided. Technical success (stent placement and deployment) was accomplished for 551 stenting attempts (92%). Failure of stent placement was attributed to obstruction, malpositioning and, in two cases, perforation. Clinical success, defined as colonic decompression within 96 h without the need for endoscopic or surgical reintervention, was achieved in 95% of the technical successes (n = 525), giving an overall clinical success rate of 88%. When assessed by indication, clinical success was slightly higher in the palliative stent patients (90%; 302 of 336 patients) than in the bridge-to-surgery group (85%; 223 of 262 patients). Of the clinically successful bridge-to-surgery patients, 95% (212 of 223 patients) went on to a one-stage colon resection within a mean of 8.9 days (range 2–115 days).
Complications included perforation, migration, re-obstruction, bleeding and pain. Perforation occurred in 4% of patients and was often associated with balloon pre-dilation of the stricture. Pain was reported by 5% of patients. Interventional mortality rate was 1% (3 of 598 patients).
Among the 551 technical successes, stent migration was observed in 10% (54 patients) and was managed with stent removal or replacement, or operation. Migration was associated with laser pretreatment, chemotherapy and benign disease.
Among the 525 patients in whom stents were clinically successful at relieving obstructive symptoms, the rate of re-obstruction was 10% (52 patients). Re-obstruction resulted from tumor ingrowth (62%; 32 patients), fecal impaction (25%; 13 patients) and migration (13%; 7 patients), and was more common among palliative patients. Bleeding occurred in 5% (27 patients). In most cases, bleeding resolved spontaneously within 24 h.
A pooled analysis by Sebastian et al. evaluated SEMS for the management of patients with malignant colorectal obstructions.25 Case series from January 1990 to May 2003 were included, if information on technical success (stent placed on first attempt, confirmed by radiograph), clinical success, outcomes and adverse events was reported. In total, 54 case series, representing 1,198 patients, were included.
For bridge-to-surgery patients (n = 407), stent placement was considered clinically successful when it was possible to perform a one-stage surgery without the creation of a stoma. In palliative patients (n = 791), clinical success was defined as colonic decompression within 48 h without the need for additional intervention. The technical success rate was similar in both palliative patients (93%) and bridge-to-surgery patients (92%). Success rates were higher if the obstruction was due to a colonic primary lesion (93.5%) rather than external lesions compressing the colon lumen (78%). Failure rates were higher the more proximal the colonic obstruction. Overall, clinical success was achieved in 88.6% (1,061 patients), with higher failure rates for externally compressing lesions. Cumulative technical and clinical success rates for palliated patients were 93% and 91%, respectively; for bridge-to-surgery patients the respective rates were 92% and 72%. This finding of higher clinical success rates among palliated patients is consistent with the aforementioned systematic review.24
Clinical failures were attributed to stent malpositioning or migration, proximal obstruction, stool impaction, perforation or persistent obstructive symptoms. Complications among all patients in the pooled analysis included perforation (n = 45; 3.8%), predominantly in the rectosigmoid colon, which often required emergency surgery (29 of 45 patients). There was an association between pre-dilation and perforation (16 of 45patients). Stent migration occurred in 11.8% of technical successes, typically within 1 week and usually distally. The migration rate in covered stents was 30.6%, and was significantly higher compared with that for uncovered stents (P = 0.04). The re-obstruction rate was 7.3%, occurring at a median of 24 weeks. Re-obstruction most often resulted from tumor overgrowth: additional causes included fecal impaction, mucosal prolapse, stent migration and peritoneal seeding. Re-obstruction occurred more frequently when uncovered stents were used rather than covered stents (7.8% versus 4.7%, P = 0.003). Most cases of re-obstruction were treated endoscopically. The cumulative intervention-related mortality was low (0.6%).
Cost-effectiveness of colonic stenting
As with gastroduodenal SEMS, endoscopic and radiologic placement of colonic stents for malignant obstruction seems to be cost effective.7, 8, 26, 27, 28 A formal decision analysis by Targownik and colleagues found that early colonic stent placement was less expensive than emergency surgery for acute malignant colonic obstruction.29 Notably, this analysis considered both inpatient costs and outpatient community costs, including the cost of stoma care. Most of the cost saving was attributable to avoiding a second colon operation to re-establish bowel continuity. This scenario assumes a clinical success rate of stent placement of 86% or higher.
Summary for colonic stenting
Colonic stents are useful for avoiding stoma surgery, therefore potentially improving quality of life. Overall, preoperative use seems to be cost effective, although clinical success rates are lower for preoperative than palliative use (Table 2). However, cost-effectiveness is predicated on the expertise of endoscopists and surgeons. Cost-effectiveness might vary according to the relative costs of endoscopic versus surgical procedures at individual institutions.
Conclusions
Prospective studies and pooled analyses have shown that endoscopic enteral stenting is safe and effective. Compared with open or laparoscopic surgery, enteral stents seem to be a more cost effective method of palliation for malignant GOO and colorectal obstruction. Stenting is also associated with a shorter time to symptom relief when compared with surgery. Additional intervention is required when stenting is later complicated by re-obstruction or migration. Therefore, if a patient's life expectancy is longer than 6 months, surgical palliation may be preferable. For patients with life expectancies of less than 6 months, however, palliative stenting is the optimal intervention. New stent designs and results from prospective randomized trials are in progress. Future enteral stents are expected to be more flexible, for easier placement, and less injurious to tissue.
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Competing interests
The authors declared no competing interests.
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Subject areas under which this article appears: Cancer | Therapy
