New Developments in Colonic Stent Technique and Techniques: How
Since its original description by Dohmoto in the early 1990s, the technique of preoperative colonic stenting has remained unchanged. Preprocedural imaging with a plain radiograph (to rule out colonic perforation) and computed tomography scan to obtain more information about additional sites of colonic obstruction and stage of the disease are suggested. Prophylactic antibiotics should be considered in patients with complete obstruction as the introduction of air may induce microperforation and bacteremia. The patient is placed in the left lateral position and sedation is rarely required.
Typically, colonic stent placement can be performed by a radiologist under fluoroscopic guidance alone, or by an interventional gastroenterologist using a combination of direct endoscopic visualization and fluoroscopic guidance. When radiologic placement is planned, the colonic obstruction is located fluoroscopically using water-soluble contrast medium and the stricture is passed with a guidewire, over which the stent is inserted into the obstruction and released under fluoroscopic guidance.[17,22] Using the combination of endoscopic and fluoroscopic guidance, the distal end of the obstruction is documented endoscopically. If the stricture is not too tight and the endoscope can be easily passed through, fluoroscopy is not necessary to complete the procedure (endoscopic guidance alone). If the tumor cannot be traversed with an endoscope, the length and configuration of the stenosis are demonstrated fluoroscopically by injecting water-soluble contrast. When a lumen is identified, the obstruction is negotiated with a guide wire. Then the stent is deployed under direct endoscopic and fluoroscopic guidance using a 'through-the-scope' stent-delivery system. If the stent-delivery system cannot fit through the operating channel of the endoscope, then the endoscope is removed over the wire and the stent is delivered over the wire and deployed under fluoroscopic guidance.[17,22]
The advantages of the endoscopic approach are the ability to biopsy the lesion, the ease of passage of the guide-wire through a tortuous and long sigmoid colon, the ability to detect distal additional polyps, and to add stiffness during advancement and deployment of the stent if a through-the-scope system is chosen. These advantages are specially recognized when the obstruction is proximal to the rectosigmoid, or in patients with very angulated rectosigmoid anatomy.[17,22] There are no randomized clinical data, however, formally comparing fluoroscopic guidance with endoscopic/fluoroscopic guidance for the placement of colonic stents.
An additional benefit of colonic stenting preoperatively is to allow for a preoperative colonoscopy to exclude synchronous lesions. In one study, 57 patients with acute neoplastic colon obstruction, who recovered from an acute colon obstruction by an effective stent placement and who had a resectable cancer, underwent a preoperative colonoscopy. Self-expandable metallic stents (SEMS) were placed in 50 of 57 patients (87.8%). Thirty-one of 50 patients had a resectable cancer (62%), and a complete preoperative colonoscopy was possible in 29 of 31 patients (93.4%). A synchronous cancer was detected in three patients (9.6%), changing the surgical plan.
There have been new developments in colonic stent design. The traditional SEMS available for endoscopic placement in the colon in the US had included esophageal and tracheobronchial stents such as the Wallstent (Boston Scientific, Natick, Massachusetts, USA) and the Gianturco Z stent (Wilson-Cook, Winston-Salem, North Carolina, USA).
Recently, because of increased awareness of the role of colonic stenting in the preoperative and palliative setting, an increasing number of dedicated colonic stents have been introduced into the clinical setting ( Table 1 ).[17,22,25] The Enteral Wallstent (Boston Scientific, Natick, Massachusetts, USA) is delivered using a 10 Fr through-the-scope (TTS) delivery system that fits through a 3.7-mm working channel of an endoscope. The diameters of the fully deployed stent ranges are 20 or 22 mm, and the lengths are either 60 or 90 mm. As a result of issues relating to stent complications including occlusion with fecal matter, migration and even perforation, newer colonic stent designs have been introduced. These include a dedicated Wallflex colonic stent that comes with a larger diameter (25 mm) and longer lengths (6, 9, 12 cm), and can be delivered TTS or over a guide-wire, and the Ultraflex Precision Colonic Stent system (Boston Scientific, Natick, Massachusetts, USA), which also has a larger 25-mm outer diameter in a variety of lengths (57 mm, 87 mm and 117 mm) but is delivered over a wire rather than through the endoscope. These newer colonic stents have a larger diameter to prevent occlusion with fecal matter, a 30-mm proximal flare to prevent migration, are made of a more flexible Nitinol stent to maintain lumen integrity despite tortuous anatomy, and contain a looped ending to decrease the risk of colonic perforation. The other commercially available stent in the US is the Colonic Z-stent (Wilson-Cook, Winston-Salem, North Carolina, USA), which is made from stainless steel. It also has a flare (35 mm) and an increased diameter (25 mm) and comes in a variety of lengths (40, 60, 80, 100 and 120 mm). It is not yet clear whether covering is useful, as covered stents appear to migrate more frequently, are more rigid and require a larger delivery system. There have been no prospective randomized trials comparing the different available stents, either uncovered or covered, in the setting of preoperative colonic stenting.
The development of silicone-based removable enteral stents (e.g. Polyflex, Boston Scientific, Natick, Massachusetts, USA) has led to their increased use for the endoscopic management of benign anastomotic strictures, especially in the esophagus. Their potential application for preoperative stenting in the colon is limited by their rigid introducing system, however, which confines their deployment to the lower sigmoid and rectum. Most of the experience with these newer stents in the colon has been for anastomotic strictures or anastomotic leaks, and not for preoperative stenting for malignant colonic obstruction.
Curr Opin Gastroenterol. 2007;23(05):544-549. © 2007 Lippincott Williams & Wilkins
Cite this: Preoperative Colonic Stenting: How, When and Why? - Medscape - Sep 01, 2007.