Rectal Stents for Obstruction

An alternative to surgical intervention in those presenting with obstruction may be endoscopic stenting to allow patency of the bowel lumen. Given the high morbidity and mortality associated with emergent surgery for colorectal obstruction, self-expandable stents (SEMS) were initially used to convert an emergent surgery to an elective surgery [95]. Placement would allow for rapid decompression and the ability to stabilize the patient with minimal sedation and less cost [96] . This evolved to utilizing SEMS for bridging to definitive surgery or for palliative therapy [97-99].

A SEMS procedure entails placement of a metallic stent across the tumor with the aid of endoscopy, fluoroscopy, or both [100] (Figs. 24.1 and 24.2). Over the course of 24-72 h, the stent expands and becomes incorporated into the tumor by pressure necrosis [96]. Technical success and clinical rates have been demonstrated to be as high as 98.7 and 95.9 % respectively, and 93 and 91 % respectively in the palliative setting [92]. Following stent placement, patients are able to be

Fig. 24.1 (a) Malignant stricture. (b) Guidewire through stricture. (c) Stent deployment. (d) Guidewire through stricture. (e) Stent deployment. (f) Final stent placement.

Placement of a self-expanding metallic stent in an obstructing colon cancer with the aid of endoscopy and fluoroscopy

Fig. 24.2 In situ stent of obstructing colon cancer

Resuscitated and optimized for any potential subsequent surgical procedure without the need for diverting stoma placement [96, 101-103]. Retrospective studies have demonstrated that stent placement is associated with increased rates

Of primary anastomosis during subsequent operations and shorter hospital stays [92, 103, 104]. Additional advantages to SEMS include the use of covered stents for colovaginal or colovesical fistulae as well as patients having the ability to undergo chemoradiation with the stent in place [96, 105, 106].

Contraindications to the use of colon and rectal stents include perforation and certain characteristics of the tumor that could increase risk of perforation including a long segment of tumor or significant angulation of the colon or rectum [107]. Tumors must be able to be traversed with a guidewire in order for successful stent placement. Additionally, tumors cannot be located within 5 cm of the anal verge to allow for placement of overlapping stents and to prevent the development of pain, tenesmus and incontinence after placement [108 ] . SEMS is also not indicated in patients with obstruction due to external compression such as metastasis [94].

Although the overall mortality rate of SEMS is low at 1 % [92], complications of SEMS do exist including perforation, migration, reobstruction and bleeding. Perforation rates have been reported to occur in 3.8 % of patients [109]. Although the exact mechanism is unclear, it has been proposed that early perforation is due to balloon predilation, rapid expansion of the balloon or the stent, or guidewire manipulation [109]. Late perforation, occurring less frequently, may be due to friable tissue and poor vascularity particularly in previously irradiated tissue. Additionally, certain chemotherapeutic agents have been associated with an increased risk of perforation [89]. Migration, although typically less serious than perforation, occurs at a rate of 10 % [110 ] . This is likely due to the tortuosity of bowel and its lack of fixation to adjacent structures and organs in addition to active peristalsis [31, 111, 112]. Tumor shrinkage following chemoradiation, balloon dilation or poorly-sized stents have also been proposed to cause stent migration [110]. Covered stents have been found to have increased rates of migration due to a decrease in tumor ingrowth when compared to the more commonly used uncovered stents [113]. Bleeding occurs in approximately 5 % of patients who have undergone stent placement [109].

A number of retrospective reviews from single institutions have reported primarily positive outcomes. The first randomized trial comparing colostomy to SEMS demonstrated 57 % longterm patency until death [114]. Fiori et al. published another small series of 22 patients with similar morbidity and mortality between colostomy and SEMS groups [115]. A multicenter RCT from the Netherlands was closed prematurely due unacceptably high perforation rate in the SEMS group [116]. A Cochrane Review of five randomized trials evaluating colorectal stents and emergent surgery in malignant colon obstructions, including two of the three previously mentioned, concluded that SEMS has no advantage over emergent surgery. Emergent surgery demonstrates higher clinical success with no differences in overall complication or 30-day mortality rates between the two groups. However, SEMS is safe in this setting with acceptable rates of complications, and the advantage of shorter length of hospital stay [117]. Table 24.3 Summarizes several of the studies evaluated in this review [114-116118, 119 ] . Thus, although SEMS has not been demonstrated to be superior to traditional surgical approaches to malignant bowel obstructions, it may be useful in select patients.

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