Okay, I'm tasked now with taking you through the small intestine. I'm going to speed this up a little bit just so we can get back on time, but I will try to focus on a few things that particularly are relevant to EOE. The small intestine, as was covered earlier this morning, is the longest part of the digestive tract, and the diseases that we see as gastroenterologists, actually it only makes up a very small fraction of the diseases we see. Most of what we see is in the upper digestive tract or in the colon. But nonetheless, important diseases, and we'll cover celiac sprue, obscure GI bleeding, small bowel obstruction, and mesenteric ischemia, or lack of blood flow to any part of the digestive tract. So who's heard of celiac disease? Probably everybody's heard of it. We're obviously in a, we live in a society now that almost values gluten-free food, and the important thing to realize is that celiac disease is not as common, it's not uncommon, I should say, but it's not as common as perhaps is the perception in terms of the need for a gluten-free diet, and we'll talk about the distinction of what celiac disease is versus what we call a gluten-sensitive upper digestive or lower digestive symptoms. So it's an autoimmune disease of the small bowel, it's really similar to EOE, it's driven by a dysfunction in the immune system, and it's due to the exposure of gluten, which is a protein, a gliadin protein within gluten that's stimulating an abnormal immune response in the small bowel. The underlying cause still is not clear, but there is a genetic predisposition to this. What is gluten? Well, again, it's a protein that's found in wheat, barley, and rye, and it's what gives that doughy consistency to these grains when we consume them. It is, however, found in other agents, it's an emulsifier, and it can be in cosmetics. If you're truly a patient with celiac disease, you have to be very vigilant, and we'll talk about why in a moment. So the spectrum of celiac disease, it can be asymptomatic. Patients may not know that they have celiac disease, and they may present with a very subtle laboratory abnormality on the routine physical exam. They may not have digestive symptoms at all. That's one end of the spectrum, however, the far end of the spectrum where they have florid celiac disease, they have malabsorption, they have weight loss, they may have growth failure as a child, and they may develop bone loss or other signs of malnutrition because of their inability to normally absorb food. The diagnosis is really reliant on two things. One is a blood test. There's a couple of different blood tests that we can do to help screen and identify patients with celiac disease, but the gold standard is really endoscopic biopsies of the small intestine. Here's what the endoscopy looks like. You saw the normal duodenum earlier, and this is a very subtle, mild case of celiac disease where the folds are slightly flattened, particularly in the proximal duodenum. They also may have scalloping. You see these punched-out linear furrows on the folds. That can be a sign, and sometimes it's just, frankly, nodular, and this would be a more florid case endoscopically. It can appear normal, by the way, so that's why it's often recommended for us to do biopsies if we suspect celiac disease, even if it looks normal. The treatment of celiac disease is get rid of the gluten, all of it. It has to be almost complete, strict gluten. You can't have a piece of bread today and think, oh, well, it's just one piece of bread, you know, wheat bread. It really is a complete avoidance of gluten, which is very different than gluten-sensitive enteropathy, which is more related to, which is much more common than celiac disease. So that's why a lot of people have this sensitivity to gluten, but they don't actually have the immune damage to the intestine. The gluten itself is more the sugar that goes along with the gluten in breads and other wheat products that stimulates the abnormal symptoms in patients with gluten-sensitive enteropathy. Okay, next we're going to cover obscure GI bleeding. Jennifer talked briefly about the upper GI bleeding and the conditions we see there, and later John is going to talk about lower GI bleeding. Well, obscure GI bleeding means it is not within the reach of an upper endoscope or within the reach of a colonoscope. And I want to highlight for you this 10 percent. Ten percent of GI bleeding, that is patients that are in the hospital for GI bleeding, have an obscure source. In other words, it's not in the upper digestive tract within the reach of a standard endoscope, and it's not within the reach of a colonoscope. That means it's somewhere in that mid-gut. It can be occult, meaning that it's a slow blood loss, or it can be overt, which is usually those hospitalized patients where they're passing gross blood and requiring blood transfusions. These are the causes of obscure GI bleeding or mid-gut bleeding, and it can be Crohn's disease with ulcerations. It can be an ulcer further down in the small intestine that is within the reach of an upper endoscope. It can be vascular abnormality, something we call a dullifois lesion, or here is a vascular ectasia. There's a congenital anomaly that often presents in children called the Meckel's diverticulum, which is in the ileum, or the distal small bowel, and it's failure of closure of the omphaloduct during development of the individual, and it's not uncommon. Upwards of 2 percent of the population will actually have a retained Meckel's diverticulum, and a small percentage of those can actually result in bleeding, and of course, you could have tumors that are present in the small bowel that could be bleeding. So how do we evaluate them? Well, we're always going to repeat an upper and lower endoscopy in patients that come in with GI bleeding, just to make sure it's truly obscure and not within the reach of those standard endoscopes, and then we have this great tool called a capsule endoscopy. It's basically a small capsule that the patient swallows. It transmits signals to electrodes on the patient's surface, and it captures digital images which are stored on basically a drive that the patient wears all day long. The capsule typically takes anywhere from 6 to 12 hours to traverse the entirety of the small bowel, and so you can actually image, in the vast majority of patients, the entire small bowel with this capsule. You can see on the capsule endoscopy signs of active bleeding. You could identify tumors in the small bowel. You could identify abnormal blood vessels or the angioictasias, or even ulcers within the small bowel. So it's a great first test in patients with obscure GI bleeding to help identify if and where they are bleeding in their small bowel. It still requires a bowel preparation. The patient usually has to take some cleanse to clean out the small bowel to adequately examine that. It only is really good for examining the small intestine for the most part. They do make a colon capsule, which is designed for colon cancer screening. It cannot yet, anyway, cannot yet take biopsies, and it's a long reading time. You can imagine sitting in front of a computer for eight hours looking at these images is not practical, and this is a great application of artificial intelligence, where a computer can actually screen the images and identify abnormalities and highlight to the person reading the capsule endoscopy, which is typically a gastroenterologist. There is a risk of the capsule getting stuck in the small bowel, and that is up to 1 percent of cases, depending on the clinical circumstances. So we always want to make sure it's an appropriate test and a safe test, and there are ways for us to determine if it's a safe test for them to have. So beyond those tests, we have, as John talked about earlier, dedicated enteroscopes. These are really specialized instruments that are designed to go deep into the small bowel, and they can actually go forward, deep into the small bowel, or they can come retrograde through the colon and then into the downstream aspect of the small bowel. It is not done very frequently, and these are the devices here. There's one that we call a double-balloon enteroscope. We have one that's another company that makes a single-balloon enteroscope, and then we have a rotational scope, which is, I like to tell my fellows, it's like a drill, and the drill is just drilling you all the way down the course of the small bowel as the small bowel is pleated behind you on the scope. So the endoscope is with a balloon-assisted enteroscopy, and I'll show you a cartoon of this. It's advanced down the small intestine by serially inflating and deflating these balloons, and the small bowel is pleated like an accordion onto the endoscope behind the viewing section as you're making progress forward. And as I mentioned, it can go either antegrade through the mouth or retrograde through the rectum and into the distal small bowel. So this is how it works. So the endoscope is advanced with the balloon, and you can see when both balloons are then inflated, the endoscopist pulls back, and the small bowel is pleated or accordioned onto the upstream part of the sheath of the balloon and the scope. Rotational endoscopy is really just a clockwise rotation of that spiral device that's on the scope. It's currently not available in the U.S. It is available in other parts of the world. It was at one point available in the U.S., but it's been removed from the market for modification and hopefully redeployment at some point. And essentially, the spinning of that spiral drags the scope down, much like a screw would lead to advancing into whatever structure it's engaging. So this shows you how much scope can sometimes be in the patient under fluoroscopy. It goes deep down. And why is it important to have these tools? Because you can actually apply treatments, or you can actually do biopsies with an endoscope as opposed to the capsule where you cannot do that. And here, a bleeding source is treated with coagulation, and here's a small tumor that could be biopsied and or confirm what the underlying histology is of that structure. So we also have a radiology test that can help us. I won't go into that in detail, but we have both nuclear medicine as well as angiography and CT scans that can help the endoscopist localize, and in some cases, treat the underlying source of bleeding. Here an interventional radiologist has identified bleeding or extravasation of contrast, and they can place these coils in that vascular structure to stop the bleeding. And then very rarely, surgery is necessary. So the third disease state to talk about in the small bowel is small bowel obstruction. As you know, when the esophagus is obstructed, there is nothing getting down, right? The patient can't swallow their saliva, they have to spit up their saliva, they can't get any liquid down. Well, any place in the digestive tract that results in obstruction is not a good thing. And in the small bowel, which is perhaps one of the more common areas of the digestive tract that does get obstructed, the patient is often vomiting, they're in severe pain, the abdomen is distended, and it is a medical emergency, and they almost always have to be in the hospital. So the most common cause of obstruction in the small bowel is adhesions. Typically, from anybody that's had previous surgery on the abdomen will have scar tissue, which we call adhesions. And those adhesions can lead to trapping of loops of intestine, and that kinking or trapping can lead to an obstruction. And sometimes it's just transient. Most of the time, it's just transient where a piece of food gets lodged there, and with decompression and conservative management, it can resolve and get better on its own. But in some cases, it does require surgery to remove that. Another common cause is a hernia. If a loop of bowel gets into that hernia sac, if it's in the groin or even in the abdomen, if there's an abdominal surface, if there's a hernia, that loop of bowel gets trapped in there, that kinking and torsion on that loop of bowel can cause an obstruction. A tumor can cause a mechanical obstruction if it grows large enough. Intussusception is where there's laxity in the connective tissue holding the intestine in a straight line, and that you can see that the — much like a puzzle or a trapped puzzle the intestine can sort of accordion inside of itself, and that can lead to an obstruction. That's called an intussusception. And strictures, which occur in Crohn's disease, is a classic example. Here you can see an endoscopic image of a stricture in the small bowel, and this might be a radiographic image where you can see a blockage at the very end of the small intestine with upstream dilation of that small bowel, the narrowing of the small bowel, and downstream from that is the colon. And finally, bezoars, which are non-digestible contents. Here you see a bezoar, a phytobezoar of hair that a patient has consumed, often in psychological illness, that result that's undigestible and leads to an obstruction anywhere in the digestive tract, but most commonly it's going to be in the small bowel. We diagnose small bowel obstruction with X-rays. Here you can see dilated loops of small bowel with air fluid levels. That's fluid in the small bowel. And we should not typically see these air fluid levels if the intestines are working properly. A CT scan is another imaging modality that we can use to not only confirm these dilated loops of fluid in air-filled bowel, but we can usually identify where in the small bowel that blockage is and potentially identify whether it's a tumor or a stricture of any other kind, say from Crohn's disease, that's causing the blockage. The treatment for small bowel obstruction is to decompress the digestive tract by having the patient have a nasogastric tube to suction any chyme or contents out, and that helps to lessen the patient's pain, also decreases their need to vomit, and will help restore the motility of the digestive tract, because whenever the intestines are stretched and distended, the motility is abnormal. We do need to correct their electrolytes and give them IV fluids, because many of these patients, because they've been vomiting so much, have disorders of both of those. Many small bowel obstructions, as I alluded to earlier, may resolve on their own, especially if it's from adhesions, but if it's a tumor or some other non-reversible source, or if it's a complete obstruction that's not getting better, then surgery may be necessary where they actually resect the area of bowel that's obstructed and connect them back together. The last disease state I'm going to cover is mesenteric ischemia, and the way to think about this is it's like a heart attack or stroke of the intestinal tract, and it can happen both ways. So you can have angina, where you have blockages in the heart that aren't causing a heart attack, but the patient gets angina because their blood flow under stress isn't adequate, and then when they relax, it gets better. We have a similar condition in the digestive tract, where you can have intestinal angina after eating a large meal. The blood flow demands are increased, but the narrowings in the mesenteric arteries are such that the patient gets a lot of abdominal pain, so it's angina of the abdomen. And likewise, if there's a sudden blockage, much like a heart attack or stroke, then they can have basically a necrosis of the intestine. So any interruption of blood flow to the intestine is essentially termed mesenteric ischemia. It can be either acute or chronic. With acute, it is typically a blood clot or a sudden obstruction of the blood flow. These patients present with acute, severe pain and shock. If it's chronic, then they often have chronic narrowings, but not complete occlusion of the blood flow to the intestine, and they often have postprandial abdominal pain and weight loss. They get weight loss because the pain hurts when they eat, so they stop eating as much. And so they almost always have significant weight loss. And with acute mesenteric ischemia, with the blockage, these patients often have a surgical emergency because the gut is going to die, and that will then lead to necrosis and perforation. And early identification and management is critical to prevent the patient from becoming septic and really approach death. So the diagnosis of mesenteric ischemia does rely a lot on imaging as well, either vascular imaging, CT angiography, MR angiography, or a Doppler ultrasound of the vasculature. The treatment in some cases can be interventional radiology, where they can go in and place a stent or do a balloon angioplasty to open up a blockage or a thrombectomy to clear out acute blockage. But as I mentioned, if it looks like necrosis has occurred and there is dead gut, then surgery is necessary. So that's a quick fly-through of small bowel disease. Questions you have about that? Oh, yes, one right here. How often does EOE prevent you from being able to get down an NG tube? Well, that's a good question. Yeah. Or maybe other strictures. It's a good question. And I haven't had a case where EOE has really precluded putting an NG tube down. But there are patients where placing an NG tube down is difficult. It may not go in the right place. It may go in the lungs. And sometimes you have to even have a gastroenterologist come to help facilitate placement of the NG tube to direct it visually into the stomach. One issue I did, I wanted to, I told you I was going to connect EOE to some of these things. And I passed, I was going so fast I forgot. But one of the things about celiac disease is that there's a connection between celiac disease and EOE. In fact, there's a much higher incidence compared to normal population of patients with celiac disease having esophageal eosinophilia and maybe even EOE disease itself. There are different immune mechanisms, but maybe the immune dysfunction is connecting. And there's also a connection, by the way, with inflammatory bowel disease. And so we'll maybe talk about that when we talk about inflammatory bowel disease. Any other questions?

small intestine

celiac disease

gluten-free diet

capsule endoscopy

mesenteric ischemia