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Preoperative and Palliative Colonic Stenting
Colorectal cancer is the fourth leading cause of cancer death in the United States after lung cancer and carcinoma of the breast and prostate. Close to a million new cases of colorectal cancer are detected each year worldwide, and almost 500,000 deaths are attributed to malignant tumors of the colon and rectum. Up to 40% of these patients experience acute partial or complete obstruction, with up to 75% of colorectal cancers occurring in the left colon.
Other less frequent causes of colorectal obstruction include malignant infiltration from adjacent malignant tumors or metastatic involvement. Benign obstruction such as diverticulitis or other inflammatory bowel diseases and anastomotic or postirradiation strictures are rare.
Colonic cancer causing obstruction tends to be at a more advanced stage when first seen, and a higher proportion of obstructed patients (27%–40%) than unobstructed patients already have liver metastases, and only 50% are candidates for curative surgery. Acute obstruction of the large bowel usually requires urgent surgical treatment, and these patients generally are high surgical risks because of poor general condition related to dehydration and electrolyte imbalance. Mortality and operative morbidity are in the range of 10% to 20% and 40% to 50%, repectively. If patients can be treated electively, mortality rates drop to 3.5% to 7% and operative morbidity to 2% to 24%. Therefore for many years the standard treatment of acute malignant obstruction of the colon has been a two- or three-stage procedure (Hartmann procedure) with creation of a stoma. This treatment results in long hospital stays, and up to 62% of these patients never undergo closure of the colostomy. The best oncologic approach to obstructing carcinoma of the colon is primary resection without colostomy. To facilitate primary anastomosis and avoid colostomy, several techniques such as nasointestinal suction and lavage, colonic decompression with rectal-colonic tubes, lavage during surgery, and tube cecostomy have been used to relieve acute distention of the colon and rectum. However, nasointestinal suction and lavage require several days to become effective, rectal-colonic tubes may be impossible to place in severe tumor stenosis, and tubes may get obstructed. Balloon dilation and laser recanalization are no real alternatives. Therefore, self-expanding metal stents (SEMS) have been advocated to serve as a bridge to surgery (BTS) for rapid relief of obstruction and allow the patient to be prepared for elective tumor resection with primary anastomosis. Likewise, stents are used as a method of definitive palliation for colonic obstruction in patients who are not surgical candidates, thereby obviating the need for colostomy.
Indications
The primary indications for placement of endoluminal colorectal stents are for (1) bridge to surgery in patients with resectable colonic obstruction to single-stage surgical resection and (2) long-term palliative colonic decompression to avoid colostomy in patients with unresectable obstruction. Other less common indications are benign conditions such as preoperative stenting in diverticular disease ; rarely, anastomotic, ischemic, or radiation-induced strictures are treated with stents. Finally, colonic fistulas may be handled with covered stents.
Contraindications
Clinical or radiologic evidence of intestinal perforation and distal rectal lesions where a safe landing zone of at least 2 cm above the anal sphincter cannot be obtained are absolute contraindications to stent placement. Likewise tumors that cannot be passed by a guidewire and stent cannot be treated. Finally, colorectal obstruction that is too long or patients with multilevel obstruction should not be stented.
Equipment
Usually colonic stenting is performed in an emergency setting requiring an appropriately trained team of interventional endoscopists and/or radiologists and nursing staff for patient monitoring and administration of neuroleptanalgesia as well as high-quality fluoroscopy and endoscopic equipment at institutions where endoscopists provide this service. Standard angiographic and/or endoscopic catheters and guidewires must be available.
A variety of SEMS specifically designed for colonic use is available today ( Table 90.1 ). They are manufactured from stainless steel, Elgiloy (cobalt-chromium-nickel), or Nitinol (nickel-titanium). Postdeployment diameters vary from 18 to 30 mm, and typical unconstrained lengths are 6 to 12 cm (see Table 90.1 ). Most modern stents are flared at one or both ends to prevent migration, particularly in covered versions. For many SEMS, the delivery systems are designed so that they can be introduced through the anus over the wire (OTW) as well as through the endoscope (TTS). Colonic stents should be flexible enough to allow easy placement along acute curves and bends, particularly in the case of an elongated sigmoid colon or around the colonic flexures. The Enteral Unistep Colonic Wallstent (Boston Scientific), with a maximum diameter of 22 mm, was most frequently used until the early 2000s. In the late 2000s more atraumatic and flexible Nitinol modifications were introduced, such as the Ultraflex Precision Colonic Stent for OTW application and the WallFlex Colonic Stent with a 25-mm diameter for both OTW and TTS use (Boston Scientific), ( Fig. 90.1 ; see Table 90.1 ). For its atraumatic ends and proximal tulip shape (27/30 mm) to reduce the risk of perforation and migration, and the availability of both OTW and TTS systems, the WallFlex is currently being used at many institutions.
TABLE 90.1
Commercially Available Colonic Stents
| Manufacturer/Model | Material | Deployed Diameter (mm) | Deployed Length (mm) | Features | |
|---|---|---|---|---|---|
| Boston Scientific, Natick, MA | |||||
| Wallstent Enteral | Stainless steel Uncovered |
20, 22 | 60, 90 | Unistep Plus Delivery System 10F OTW and TTS Reconstrainable 39%–49% foreshortening during expansion |
|
| Ultraflex Precision Colonic Stent System | Nitinol Uncovered |
25 body/30 prox. flare | 57, 87, 117 | Only 22F OTW Proximal suture release Not reconstrainable 23% foreshortening during expansion |
|
| WallFlex Colonic Stent | Elgiloy (cobalt-chromium-nickel) Uncovered |
22 body/27 prox. flare 25 body/30 prox. flare |
60, 90, 120 | 10F Delivery OTW and TTS Reconstrainable 30%–45% foreshortening during expansion |
|
| Cook Endoscopy, Winston-Salem, NC | |||||
| Evolution Colonic | NitinolUncovered | 25 body30 flared ends, dog-bone shape | 60, 90, 120 | 10F TTS system Reconstrainable Controlled release-delivery system |
|
| ELLA-CS, Hradec Králové, Czech Republic | |||||
| SX-ELLA Colorectal Enterella Stent | Nitinol Uncovered |
22, 25, 30 | 82, 90, 113, 135 75, 88, 112, 123, 136 |
15F OTW All models are repositionable |
|
| M.I.Tech, Seoul, South Korea | |||||
| HANAROSTENTColon/Rectum“Single Layer” | Nitinol Uncovered |
Body: 22, 24, 26 Flared ends: 28, 30, 32 Dog-bone shape |
60, 170 | 10.2F OTW and TTS Partly reconstrainable |
|
| HANAROSTENTColon/Rectum“Dual Layer” | Nitinol Uncovered |
Body: 22, 24 Flared ends: 28, 30 Dog-bone shape |
60, 170 | 10.2F OTW and TTS Partly reconstrainable Inner layer increases radial forceDesigned to resist tissue ingrowth |
|
| HANAROSTENTColon/RectumTwin Layer | Nitinol Partly covered with silicone |
Body: 20, 22, 24 Flared ends: 26, 28, 30 Dog-bone shape |
60, 150 | 10.2F OTW and TTS Partly reconstrainable Silicone membrane between inner and outer mesh |
|
| HANAROSTENTCHOOSTENTColon/RectumAsymmetric | Nitinol Fully covered |
Body: 22, 24 Flare: 30, 32 Dog-bone shape |
60, 170 | OTW 8mm/24F Repositionable with lassos on both ends |
|
| Taewoong Medical, Seoul, South Korea | |||||
| Niti-SD Enteral Colonic Stent(D-Type) | Nitinol UncoveredNonflared |
18, 20, 22, 2426, 28, 30 18, 20, 22, 2426, 28, 30 |
60, 80, 100, 120, 140, 150 for all diameters 60, 80, 100, 120, 140, 150 for all diameters |
OTW 16FOTW 18FTTS 10.0FTTS 10.5FAll models with markers at both ends and in the middle | |
| Niti-SS Enteral Colonic Stent(S-Type) | Nitinol Fully covered (silicone) or partly covered, with both or distal flared end bare |
1820, 2224, 26, 28 18, 20Dog-bone shape |
60, 80, 100, 120, 140, 150 for all diameters 60, 80, 100, 120, 140, 150 for all diameters |
OTW Delivery system16F (18mm diameter)20F (20,22mm diameter)22F (24,26,28mm diameter)TTS 10.5.F delivery system for all diametersAll models have flared ends and have markers at both ends and in the middle.Removable (green suture) | |
| Niti-SCOMVIEnteral Stent (Flare) | Nitinol triple layer partly covered, with PTFE membrane | 18, 20, 22, 24, 26 | 60, 80, 100, 120 | 10.5F TTS only Triple layer PTFE membrane between two bare nitinol stents Flare uncovered to reduce migration |
|
| Niti-SCOMVIEnteral Colonic Stent | Nitinol Covered Triple layer PTFE membrane between two bare stents |
18, 2022, 2426, 28 18, 20, 22 |
60, 80, 100, 120 for all diameters 60, 80, 100, 120 |
OTW Delivery systems:14 F (18,20mm diameter)16 F (22,24mm diameter)18 F (26,28mm diameter)TTS10.5F delivery system for all diameters | |
OTW, Over the wire; prox., proximal; PTFE, polytetrafluoroethylene; TTS, through the scope.
∗Not available in the United States.
The Colonic Z-Stent (Cook Endoscopy, Winston-Salem, NC) has been discontinued. Instead a 10F TTS Nitinol version has recently been released, but to date no wide experience has been published (see Table 90.1 ). The Hanarostent (M.I.Tech, Seoul, South Korea) in covered and uncovered version has flanges on either side to prevent migration (see Table 90.1 ).
The Niti-S colorectal stent (Taewoong Medical, Seoul, South Korea) is available in three versions: (1) a straight uncovered version (D-Type), (2) a covered design in a dog-bone shape with bare flared ends to prevent migration (S-Type), or (3) the COMVI type, which is a triple-layer stent with short bare flanges on each side and a polytetrafluoroethylene (PTFE) membrane in between the inner and outer Nitinol stent meshes. (see Table 90.1 ). Both Hanarostents and Niti-S stents have been used in Asia and also in Europe.
The SX-ELLA colorectal-Enterella stent (ELLA-CS, Hradec Králové, Czech Republic) is repositionable and retrievable, thanks to a plastic loop at the distal end. This device may be particularly suited for benign or rectal lesions. However, apart from treating malignant fistulas, iatrogenic perforations, or postsurgery leaks, covered stents do not seem to have a significant advantage, and have not gained wider acceptance because no overt advantages and a higher migration rate have been found. Today, mainly uncovered Nitinol stents are used and have almost replaced stainless steel and Elgiloy for their nonferromagnetic properties (magnetic resonance imaging compatibility), shape memory, and high elasticity/flexibility.
A biodegradable stent is also offered by ELLA-CS for the treatment of benign disease, but there is only limited experience with the stent.
Drug-eluting stents for reducing tumor ingrowth and overgrowth of stents are still in an experimental stage.
Technique
Approach
A radiologic diagnosis of acute colonic obstruction is made by plain film radiography and computed tomography (CT) ( Fig. 90.2 ). Barium enema, colonoscopy, and biopsy can help to determine the exact location and nature of the obstruction. CT is also the method of choice for staging and may provide important information about the presence of multiple stenoses or concomitant small-bowel obstruction in peritoneal carcinosis that have to be ruled out before placement of colonic stents. CT colonography may be of additional value.
The stenosis can be negotiated (1) primarily with radiologic techniques alone, with optional endoscopy reserved for difficult cases, (2) with hybrid endoscopic-radiologic methods, and (3) endoscopic stent placement with assisted fluoroscopic guidance, probably the preferred method at many institutions where endoscopists are the main providers of gastrointestinal stenting. Lesions in the ascending colon and transverse colon to the splenic flexure are best handled with a combined endoscopic-fluoroscopic approach to overcome the tortuosity of the colonic flexures.
Technical Aspects
Fluoroscopic Guidance/Radiologic Technique (Over the Wire)
Patients are best treated under mild sedation and are placed in a left lateral position on the fluoroscopy table at the start of the procedure. A high-torque (7F) angiographic catheter (Headhunter or Cobra type) or a guiding catheter is placed in the colon, and the colonic segments are best negotiated with a catheter-guidewire combination ( Fig. 90.3A–C ). Water-soluble contrast material is used to outline the bowel lumen and the area of the stricture. Conventional or hydrophilic guidewires, or both, may be used. Once the stricture has been passed with the catheter-guidewire assembly, the lesion is best defined by injecting contrast material through a catheter with multiple side holes and rotating the patient to an optimal position for stent insertion. For stent placement, an exchange-length super-stiff wire (Amplatz Super Stiff, Lunderquist [Boston Scientific]) is placed well beyond the lesion. After advancing the stent to the desired location under fluoroscopic control, the stent is released ( Fig. 90.3D ). If acute bends or kinks have to be passed or an elongated rectosigmoidal arch reduces forward pushability, a stiff large-bore guiding catheter (Flexor Ansel guiding sheath or Mullin sheath [William Cook Europe, Bjaeverskov, Denmark]) may be helpful to advance the stent assembly to the desired location.
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