The use of a CO₂ inflator is highly suggested during colonic stent insertion: in theory this technique reduces gastrointestinal distension and the risk of perforation and then it induced the patients’ tolerance [19]. There were no data about the prevention of risk of complications by inflation with air and CO₂. In the absence of a CO₂ inflator, inflation during progression to the stenosis and during progression to the stenosis and during the implantation of the prosthesis must be as small as possible [19]. A washing pump is useful for facilitating progression to the stenosis [19].

SEMS classified to uncovered or covered according to the presence of meshwork of the stent is bare-wire or covered with polyurethane to prevent tissue ingrowth into the stent. Various types of SEMS are released by many commercial companies (Table 6.2). Most of SEMS are made with wire of Nitinol: a metal alloy of nickel and titanium.

The choice of SEMS is mostly depended on the preference of endoscopists. Covered stent is designed for preventing the tumor ingrowth through the mesh of stent, though it developed the similar number of events between covered and uncovered stents. Surprisingly, it has more frequent event of late migration than uncovered stent. There are no differences of technical success rates, clinical success rates and early complications between covered and uncovered stents. Therefore, most experts recommend that uncovered SEMS is the first choice for the malignant colorectal obstruction in guideline [18, 19]. The appropriate length of SEMS is determined by measured the length of stenosis of obstructive lesion, and then constantly should be at least 3–4 cm longer than the stenosis.

SEMS placement is usually performed by using either the through the-scope (TTS) or the over-the-guidewire (OTW) method . Most of all SEMS insertion is done with colonoscope under use of fluoroscopic guidance: TTS method. OTW method is done using fluoroscopic guidance with or without colonoscopic images. The success rates of technical and clinical are comparable between TTS and OTW method [15, 17, 18, 21, 31–34]. Recently most experts recommended that colonic stent placement might be useful under circumstance of combined with endoscope and fluoroscopic guidance (Fig. 6.1).

First step catheterization : The colonoscope was advanced to the obstructive distal site and a guidewire preloaded on the endoscopic retrograde cholangiopancreatography catheter was introduced under endoscopic and fluoroscopic guidance. After passing through the lesion, the catheter was advanced over the guidewire to the proximal end of the stricture. Second step evaluation of the lesion: The guidewire was removed and a soluble contrast medium was injected to determine the length and morphology of the lesion. Third step insertion of the stent: The catheter was then replaced by the guidewire. SEMS delivery catheter was then advanced through the working channel of the colonoscope over the guidewire until the catheter was positioned across the obstructive site. Final step SEMS deployment: Upon the release of stent delivery catheter, stent deployment began proximally and progressed distally with some static traction forces for preventing proximal migration as monitored by colonoscopy and fluoroscopy. After the deployment of the SEMS, the delivery system and guidewire were removed (Fig. 6.2). The type of inserted SEMS was decided by the endoscopists during the procedure [15].

There are some considerations during catheterization as below. In case of easy positioning of the endoscope in front of the stenosis (left colon, transverse, rectum), the use of flexible catheter with a single or dual channel with long (>450 cm) flexible (or fully flexible) hydrophilic guidewire tip allows the placement of stent TTS under fluoroscopy, combining safety and efficiency [19]. In difficult catheterization, the stenosis is lateralized, or angular, or the position of the endoscope is unstable (recto-sigmoid colon, sigmoid colon, splenic and hepatic flexures), the stenosis is right or the stenosis is tortuous. These situations require the help of a pre-curved adjustable catheter, or a rotary sphincterotome, and the use of “J” guide wire technique, or a thinner guide wire (0.018 or 0.025 in.) [19]. The materials and techniques used in this situation are the same as those used for endoscopic retrograde cholangio-pancreatography (ERCP). The use of biliopancreatic catheterization materials and long non-traumatic hydrophilic guides is advocated [19].

Early complications evaluated between 2 and 7 days after SEMS insertion. The serious complications of SEMS insertion are very good with an immediate mortality rate of below 1% in most published studies (average 0.6%) [16–19, 35–49]. SEMS insertion caused early complications such as perforation (0–12.8%), migration (0–13%), and less frequently bleeding (0–3.7%) [18, 19]. Last two complications are managed by conservative cares with colonoscopy. However, perforation usually need to emergent surgical treatment and is the most common cause of early mortality. Perforation is also bad prognosis factors of oncologic outcomes.

Late complication might be related to the results at 30 or 7 days [15, 39, 50]. The 30 days mortality rate was 9% with half of the deaths related to poor prognosis of cancer [19]. The late complications occurred 16–31% of patients [15, 22]. The rate of late perforations ranged from 1 to 7% [19]. The risk factors of late perforation are associated with the type of stent use, the presence of peritoneal carcinomatosis, and chemotherapy including anti-angiogenic therapy [15, 18, 19, 22, 51]. The suspected mechanism may be that inhibition of vascular endothelial growth factor (VEGF) results in tissue hypoxia, which leads to tissue necrosis and perforation at the tumor site [15]. Therefore, we should be considered the increased risk of perforation for patients administered with chemotherapy after SEMS insertion. However, patients who have undergone stenting for palliation could be safely treated with chemotherapy without anti-angiogenic agents (bevacizumav, aflibercept and regorafenib) If a patient is considered for chemotherapeutic treatment with anti-angiogenic agents, it is not recommended to use palliative SEMS insertion in high risk of patients with perforation [18]. Baron et al. proposed that stent-related perforation may result from different causes: (a) guidewire or catheter malpositioning; (b) dilation of stricture before or after stent placement; (c) stent-induced perforation (tumor and non-tumor local perforation); and (d) proximal colonic distension because of inadequate colonic decompression or excessive air insufflation [18, 52]. The rate of late migration ranged from 1.0 to 12.5% and this risk is closely related with the types of stent: covered stent occupied the most proportion of late event and also small diameter SEMS (<24 mm) [15, 18, 53, 54]. Some studies reported that chemotherapy might be associated with late migration of SEMS by the mechanism of tumor shrinkage [18, 31, 50]. Stent re-obstruction occurred due to tumor in/overgrowth and also during the long-term follow up period. The use of uncovered SEMS is risk factor for tumor ingrowth [44]. Suh et al. presented that less than 70% stent expansion within first 48 h is predictive marker for estimating the occurrence of re-obstruction [55]. Both migration and re-obstruction can be managed with colonoscopic methods. Stent replacement and stent reopening by a stent-in-stent have been reported as first choice in the majority of studies, with satisfactory outcomes (clinical success rates 75–86%) [15, 18, 22, 56].

After SEMS insertion, we should evaluate the immediate and late complications like as careful and precise interview of abdomen symptoms and physical examination of peritonitis, abdomen supine and erection or simple abdomen for kidney ureter and bladder (KUB). Also, the serial assessment for regression of obstructive symptoms and signs should be performed within 48 h after SEMS insertion. The symptoms and signs of obstruction are improved after SEMS insertion and then oral intake slowly try with sips of water. There are no other symptoms and signs after water intakes, sequential diet try to start with soft diet like low residual diet. If fecal material is hard consistency in patients with distal obstruction, stool softener should be prescribed for preventing stool impaction.

Several studies reported that the median patency duration of palliative SEMS was 106 days (range 68–288 days) [14–16, 18, 57]. Although consensus follow up schedule for SEMS is not existed, it might be performed concordance with regular surveillance for colorectal cancer. However, if the patients with SEMS have symptoms and signs of obstruction, we should be investigated the complications.

Some studies present that synchronous colorectal tumors occur in 3–4% of patients with colorectal cancer [58–60]. Preoperative CT colonography and colonoscopy through the stent appear feasible and safe in malignant colorectal obstruction and there are no data discourage their use in some studies [61–64].

There are many studies about the clinical efficacy of SEMS insertion for patients with malignant colorectal obstruction. SEMS placement gains the better short-term outcomes to decompress obstructive symptoms compared with emergent surgery. SEMS insertion additionally can avoid the emergent surgery with stoma creation which has the high morbidity and mortality.

The various causes of colonic strictures includes inflammatory bowel disease (Crohn’s and ulcerative colitis), anastomotic leakages, ischemia, malignancy, radiation injury, nonsteroidal anti-inflammatory drugs (NSAIDs), and as a consequence of diverticulitis [65]. The etiology-specific prevalence of colonic strictures is not known for all of these conditions but is as high as 13.5% in Crohn’s disease [65]. Colorectal strictures induced by non-malignant conditions were managed with various treatment modalities, especially balloon dilatation. Ballooning reduces the symptoms and signs of benign strictures like constipation, abdominal pain and vomiting and also prevents the secondary perforation induced strictures. Balloon dilatation is the simple and easily used modality and relatively safe and effective.

Before endoscopic ballooning dilatation abdomen pelvic CT should be taken for precise evaluation of the site, length, and morphology of strictures. The contraindication is active inflammation like abscess of CD, long length segment of stricture and fistula of CD due to complication of perforation and re-operation needed. In rectum, endoscopic ultrasound and MRI also helpful evaluation methods but it is not inevitable. Bowel preparation is done depends on the severity of stricture; if there is no symptoms of complete obstruction, routine bowel preparation should be taken and patients with partial or complete obstruction take the enema. Also, sedation was administered as necessary depending on patient tolerance. The diameter of balloon was first chosen the larger size than the diameter of stricture and then changed more big size balloon than first size. There are no definite final size of balloon diameter, duration time of balloon inflation, and the number of repeated balloon inflation. It depends on the severity of stricture. Most of all TTS balloons were used for dilatation with or without under the fluoroscopic guidance. Dilation was performed with balloons ranging in diameter from 18 to 25 mm [68].