In my next lecture, I'm very proud and happy to introduce Uzma Siddiqui. She's a professor of medicine and the associate director of the Center for Endoscopic Research and Therapeutics at the University of Chicago. And in addition to being a prominent researcher, excellent clinician, she's a dedicated educator and mentor. And I frequently have heard say to my patients that she taught me everything I know as I was her trainee in an advanced endoscopy fellowship. And I truly am thankful for everything that she's done for me. So with that, Uzma, thank you so much, and we look forward to your talk. Good afternoon, everyone. I want to thank the ASGE and our great course directors, Drs. Chapman and Raju, for inviting me here today to discuss colonic stenting. Here's a list of my disclosures. We'll start by just discussing a typical consult to the GI doctor where colonic stenting would be requested. You have a 75-year-old patient with multiple comorbidities. They've noticed for the past couple of weeks they haven't passed any stool. On physical exam, they have a very distended abdomen. A CAT scan is done that shows that there is an obstructing lesion, potential malignancy in the sigmoid colon with proximal colonic dilation, and there is no obvious metastases noted. And the question becomes, should this patient undergo colonic stenting as a potential bridge to surgery, or since this is potentially curable disease, should the patient undergo emergency surgery right away? And I'm hoping over the course of this lecture to try to delineate when stenting may be more useful and also highlight the fact that these cases can be complex and definitely warrant a multidisciplinary discussion. Let's talk a little bit about malignant obstruction from colon cancer. As many of you already know, colon cancer is the second most common cancer in the United States. Less than 15% are going to present with obstructive symptoms, and those who are diagnosed with cancer and present with colonic obstruction as their initial symptom have a five-year survival rate that's less than 30%. Most of the time, patients are going to complain of obstipation, bloating, abdominal distension, and sometimes nausea, vomiting. The diagnosis will be made on a contrast-enhanced CT where you see an obvious transition point in the sigmoid consistent with a mass lesion and then proximal colonic dilatation. The other thing the CAT scan is helpful for is to rule out any metastases or peritoneal carcinomatosis, which would then impact potentially your decision-making. Historically, surgery has been performed for both curative and palliative purposes. The issues with emergency surgery, though, in the setting of malignant bowel obstruction is that the mortality rates can be up to 20%. You can have up to 50% morbidity rates with resultant anastomotic leaks, wound infections, and abscess formation. And in up to 40%, they may need a permanent colostomy. So elective surgery is preferred because you can increase your chances of a primary anastomosis, give the chance to adequately stage a tumor, do a complete colonoscopy prior to resection, minimize the patient's nutritional status, and other comorbidities. So that's where we see the benefit of colonic stents because now you're going to have the ability to convert an emergency surgery into an elective one, potentially minimize adverse event rates, reduce morbidity and mortality related to emergency surgery, and potentially avoid the need for colostomy and additional surgery. So let's discuss the technique of placing a colonic stent. When we talk about colonic stents, we're talking about self-expandable metal stents or SEMs. In the colon, these stents are uncovered. They are deployed along a 10 French catheter. So you do need a scope that has a therapeutic accessory channel. So that includes your T1, T2 upper scopes if the lesion is very distal or a colonoscope. They come in 22 and 25 millimeter diameters, and I usually prefer the 25 millimeter size. The lengths are 6, 9, and 12 centimeters. You usually want the stent to extend one and a half to two centimeters above and below the stricture to allow for some shortening over time. And when you're discussing follow-up, diet, and care with the patient and the referring team, you want to make sure you explain that the stent may take a couple days to get to its maximal diameter, and usually I advance the patient's diet slowly once I place the stent to give it that time for expansion. So how do I like to place a colonic stent? First, I put the patient in the left lateral position on the fluoroscopy table. If the tumor is distal, then I like to use a therapeutic channel upper endoscope. I then pass an 035 guide wire through a large diameter extraction balloon that I would use with any ERCP, and then I'm going to use endoscopic and fluoroscopic views to maneuver across the stricture and then inject contrast. Sometimes like you see here, when there's this large mass obstructing the lumen, it may be difficult to actually figure out where the stricture and lumen opening is to pass your wire. If that's the case, then I may blow up the balloon just distal to the tumor, inject a lot of contrast, and then use fluoroscopy to help me guide my wire through the stricture. But once I have a wire through the stricture and I pass my balloon catheter over it, then I inflate the balloon and I start injecting contrast, and I start pulling back on the balloon catheter until I feel some resistance, because then I know that is the proximal end of the stricture, and I can visualize my balloon and scope position on fluoroscopy so I know where the end of my stent should be. Then I can put the stent over the wire and deploy it. I'm using, again, fluoroscopic and endoscopic views. The fluoroscopic views are for ensuring that the proximal end of the stent is fully opened on fluoro, and then endoscopically, I can watch the distal end open up, and on the final fluoro image, I want to inspect it carefully to make sure that there is a waste, and then endoscopically, you'll see a lot of stool coming through. A few technical considerations, again, you want the stent to extend a couple centimeters proximal and distal to the stricture because they are going to foreshorten a little bit, and if there is a turn in the colon, I like to have my stent make that turn so that it's not pushing up against the mucosa. Do not dilate the stricture prior to stent placement. I'll show the data later, but that will increase your risk for perforation. Stents are prepped with enemas prior to the procedure. They do not need prophylactic antibiotics, and sometimes we will have an NG tube in place if the patient's vomiting. Here's a video where you see the stent catheter has already been passed over the guide wire and through the stricture, and then under fluoroscopic guidance, your goal is to look at the proximal end of the stent and make sure that it opens fully so you know you're in the proper position. Now, as with all other types of stents, the tendency as you deploy them is to have them get sucked into the stricture, so you always have to hold some constant back pressure to maintain your position, and here you see after the proximal stent looks good on fluoroscopy, the distal end of the stent can be verified on endoscopic views. Now let's look at the outcomes of colonic stent placement especially in comparison to surgery. Now looking at stenting as a bridge to surgery this concept was first introduced 20 years ago but it still continues to be a little controversial. The original studies comparing stenting to early surgery were looking at just successful decompression of the colon and decreasing those complications I mentioned earlier from emergency surgery. But more recently the shift of focus in studies is to look at the longer-term oncologic impact. Now the vast majority of data looking at this topic are meta-analyses rather than randomized control trials. So that means that you have a varied mix of patients, indication, expertise of the endoscopist and which surgery was performed and that's why we have some conflicting results. Before we look at the guidelines and studies let's just go over a few definitions that are used in the majority of the literature related to colonic stenting. Usually when we're talking about stenting for malignant bowel obstruction most of the time it refers to left-sided obstructions that are distal to the hepatic flexure but also more than five centimeters proximal to the anal verge so we are not including rectal tumors. Colonic stenting is performed with uncovered stents and again depending on the experience and volume of the center technical success rates can approach 90%. The indication for stenting that's very important it's not always clear in some of the studies but is it done for palliation or as a bridge to surgery in a curative scenario and then there are multiple emergency surgery options which again makes it a little confusing that include diverting ostomy, Hartman's pouch, subtotal colectomy, with or without anastomosis and resection and washout with and without a primary anastomosis. Over the years there have been a number of different guidelines throughout the world. One of the more commonly cited ones was published in 2014. It was a joint ASGE ESGE guideline on colonic stenting and they made a few recommendations again based mainly on meta-analyses and a few randomized controlled trials but they suggested that prophylactic colonic stent placement is not recommended in potentially curable but obstructing left-sided colorectal cancers. CEMS can be an alternative to emergency surgery in really high-risk patients i.e. elderly and those which are more than ASA class 3 and CEMS is recommended as the preferred treatment for palliation of malignant obstruction. Now interestingly back in 2014 the guidelines suggested that colonic stents should not be used as a bridge to elective surgery and that was based on the data in the decade prior to this guideline coming out and it included a few randomized controlled trials that were prematurely closed because they showed increased adverse outcomes in the stent group. But we've seen a change in guidelines from 2014 to 2020 and again we have seven more meta-analyses that have come out in that time frame although there are a few new prospective randomized controlled trials. The issue is that a lot of these meta-analyses are based on some similar studies so that still causes a lot of heterogeneity with respect to indication stage of disease, stenting expertise, what surgeries were done, the perforation rates, and what was the adjunctive treatment. But there was enough new data that the European Society guidelines that were updated just this year now say that stenting as a bridge to surgery should be discussed and it is a potential option in patients with potentially curable left-sided obstructing colon cancer. So despite the variation in the meta-analyses that were looked at, the newer data did show some short-term and long-term advantages of colonic stenting over emergency surgery that included lower morbidity rates, higher proportion of primary anastomosis, and lower permanent stoma risk. If you looked at hospital stay and quality of life, the data was still pretty sparse and therefore not really conclusive on that regard. And then just this year there was a randomized controlled trial that looked at the long-term oncologic effects after stenting as a bridge to surgery versus emergency surgery and it showed no difference between the two groups in terms of overall survival, time to progression, and disease-free survival. So the final conclusion on colonic stenting and curable malignant bowel obstruction is that you do need a multidisciplinary discussion but stenting is considered a viable option in 2020. We've talked about colonic stenting for left-sided obstruction but what about stenting in the proximal colon? Currently there's no prospective trials so the limited data we have shows that when you compare stenting in the proximal colon to surgery there really aren't huge differences in morbidity, mortality, and hospital stay. What we do see is that stenting in this area has a lower clinical success rate and lower patency rates. So while it can be done safely it is definitely one of the more difficult procedures and you want to make sure that you feel comfortable and have enough expertise in colonic stenting to take on these more challenging cases. This is an example of a patient I had with a hepatic flexure obstruction. As you can see by the significant amount of scope looping that it was very difficult for me to make it to the area of obstruction and then subsequently the patient came back two more times with an occluded stent. So it definitely supports the limited data that we have shown but the European guidelines do suggest that you should consider colonic stenting for obstruction in the proximal colon if able. In terms of palliation of malignant bowel obstruction it's a little bit more clear-cut that stenting has a distinct advantage compared to surgery. You have shorter hospitalization, lower ICU rates, shorter time to start chemo, decreased stoma formation. If you have peritoneal mets then you definitely have lower technical and clinical success rates with stenting because oftentimes there's not just one transition point that can be stented and have improvement in symptoms. The patient may have a tacked down bowel. You have increased complication rates and decreased stent patency if the stent fails after you put it in. And then also with extracolonic malignancy we also see in the data and in my own clinical experience that typically you may have lower clinical success rates and higher rates of migration because the stent doesn't have any obvious intrinsic structure to adhere to and it may not be strong enough to open up against a lot of extracolonic tumor. But in terms of stenting and palliative malignant bowel obstruction the conclusion would be that stenting is the preferred treatment. What happens if your colonic stent is placed successfully but then it becomes occluded or migrates? Well your next step is going to depend on you know what the indication for the stent placement was. If this is a curative setting then the patient should just go for surgery if the stent fails. If it's a palliative setting and the stent occludes then you can always place a new stent inside the old one and if the stent migrates you can just replace it. When is a stent not indicated? The main contraindication for stent placement is perforation as you see in these images. In the CAT scan there's air and fluid outside the sigmoid indicating a perforation and on the x-ray there's free air under the diaphragm so again you do not want to put a stent in the setting of perforation. Also sometimes we get consulted for a patient that's on chronic narcotics, their colon's dilated, filled with stool, they're constipated and they ask for a prophylactic stent placement or the patient may have a colon tumor and again they have colonic dilatation but they're passing gas having normal bowel movements so there is no guideline or clinical practice that supports prophylactic placement of stents. You need symptoms and imaging to confirm that there is a malignant bowel obstruction. Also again in peritoneal carcinomatosis, tumors that are very low in diverticulitis or again this chronically dilated colon you don't need to put a colonic stent in. So what are some of the adverse events that are associated with colonic stenting? The thing that you always worry about especially if you're using it as a bridge to surgery is perforation because then you're going to have tumor seeding and this patient went from potentially curable to now advanced disease. Overall the complication rate can be around 20 to 30 percent. Perforations can occur in up to 15 percent and then you also see the silent micro perforations that may not be noted until the time of surgery, migration, stent failure, and reocclusion. Colonic stenting in general is a fairly safe procedure but there are definite risk factors associated with perforation with SEMS placement. The first thing is dilation. Do not dilate when you place a colonic stent. The other issue is the experience of the endoscopist. There have been multiple studies and they show that if the endoscopist has performed a low volume of cases anywhere from 10 to 40 anything less than that or they're not familiar with ERCP stricture management skills using balloons, wires, fluoroscopy, then those endoscopists tend to have higher rates of perforations and in fact the European Society guidelines also suggest that whoever is doing colonic stenting needs to be competent in both colonoscopy and fluoroscopic techniques and do it on a regular basis. Other risk factors that have been shown to play a role in increasing rates of perforation include putting in stents and benign indications, stent types, and also receiving anti-angiogenic therapy like Avastin. Multiple studies including this meta-analyses have shown that your rate for perforation is definitely much higher if the patient is receiving anti-angiogenic therapy and in fact most guidelines suggest that you should not place a colonic stent in patients while they are receiving this type of therapy. It is okay for other standard chemo but not Avastin or anti-angiogenic therapies. So you've been consulted for placement of a colonic stent. What are the questions that you need to ask yourself before you attempt the stent procedure? First question is always is this really an obstructive malignant tumor? We often get consulted on patients that maybe have some sort of mass like lesion but the CAT scan also says there's a ton of inflammation, stranding, and it looks like acute diverticulitis. So in those cases you do not want to place a stent because you have an increased risk of perforation. If it's an urgent situation and there is a tumor but you haven't gotten a tissue confirmation it's okay to place the stent and you can take a biopsy at the same time if the stents clinically indicated. Is the stent being placed in a situation where it's a potentially curable tumor that may go to surgery or is it a palliative situation where there is metastatic disease that's obvious on CAT scan? Because again then the discussion with your surgeons is going to be a different one. Palliation more straightforward to go for the stent. If it's potentially curable disease it's a little bit more involved discussion based on the patient's comorbidities, age, and overall clinical status. And are there any contraindications to placing the stent? It is very important to make sure you review that CAT scan and make sure there is no evidence of perforation prior to placing a colonic stent. Ask the patient and the oncologist if there's any plans to put the patient on an anti-angiogenic drug. Are they on it currently or are they going to be on it in the next few weeks? And again avoid if there's a benign etiology. Where is the tumor located? Is the obstruction in the left colon which you know is easier to reach higher clinical and technical success rates with colonic stenting or is it in the proximal colon which is known to be more difficult to reach and place your stent successfully? So do you have the expertise and the skill set to attempt stenting in that area? Also if the lesions in the rectum colonic stenting is not going to help, all the data shows that you need to have five centimeters distance from the anal verge to the obstruction. And I'll end with a few take-home points. So you're going to place a colonic stent only if imaging and symptoms suggest a malignant bowel obstruction and you have a target site. The data overall does not show a major difference between stenting versus surgery and you always need to make these decisions in a multidisciplinary fashion which takes into account the available expertise at your center. In the curative setting you definitely have to consider the age, comorbidities and nutritional status of your patient but stenting is a viable option. In the palliative setting it's more clear-cut that stenting should be the preferred method if expertise is available and you can minimize your perforation risk with increased experience of the endoscopist, avoiding dilation and avoiding stenting in patients who are on anti-angiogenic therapy. And with that I'll stop. Thank you.

Uzma Siddiqui

colonic stenting

malignant bowel obstruction

self-expandable metal stents

indications

complications