This is small and large intestine. You guys heard me talk about before. So I'm an IBDologist. I do mostly inflammatory bowel disease, and by mostly, about 99% of my practice. So the stomach can get involved with Crohn's disease, so can the esophagus. It's quite rare. But the small and large intestine are two of the biggest organs that cause problems for my inflammatory bowel disease patients. And so it's a part of my career to get a very, very deep understanding of this organ system. That being said, I also do a lot with other diseases of the small and large intestine to help out my colleagues. So we just got through with our picture here. So we're going to move now from the stomach into the small intestine, which is made up of three different parts, the duodenum, the jejunum, and the ileum. The duodenum is going to be your shortest part. Then you've got your jejunum, which is your longest part, and then your ileum. And so let's sort of start by focusing on the duodenum. So duodenum is actually quite an important organ. It's got four different parts, the bulb, the descending, the horizontal, and the ascending. Typically when we do an endoscopy, we're getting to D2. We're getting to the descending part of the duodenum, and it's sometimes difficult for us to get further, or we don't necessarily have a need to go any further. So we don't always get to D3 or D4. Now there are ways for us to get to D3, D4. We can sometimes use a longer scope. We do that sometimes when we're concerned about specific pathology that may be deeper down or if somebody's having an unexplained bleed, which we'll talk about a little bit later. But in the general practice of doing an EGD, you'll typically hear GI doctors refer to the bulb and the descending duodenum. The bulb is that very first part when you get right past that pylorus. The pylorus, again, is the connection of the stomach to the duodenum, and the bulb can be an area where you can get inflammation, you can get ulcerations, and it can be a little bit tough to find it because sometimes the scope doesn't want to stay in the bulb. And so if you've got somebody bleeding with a bulb ulcer, we have different techniques that we can use to try to keep the scope in there because the way that the duodenum works is you can kind of see that it has a sharp turn here. So when you're entering in with a scope, you typically will fold the scope over because an upper endoscopy scope is very pliable. You'll typically fold it over, and then it'll give you a quick view or an immediate view of D2. Coming back out, you can very quickly pop. You'll see this with any first-year fellow, second-year fellow, third-year fellow where they'll quickly pop out from D2 and all of a sudden they're back in the stomach. So there's a process in learning how to really hold yourself in that bulb. It is not a long organ. As you can see, it's about 12 inches in length at largest, but plays, like I said, really important role inside of the body. The other thing that can happen is the duodenum is going to fall very close to things like the aorta, and so that, especially D4. So you've got to understand, we're just showing you here in this picture this one part, and we're specifically looking at the GI tract, but we have all the other organs that are over here. There are some organs in the GI tract that aren't really around anything that's major or vast, and then there are other organs in the GI tract that land right smack in the middle. D4 is one of those organs that, you know, when a surgeon, when a vascular surgeon calls you because they've got a bleeder and they're wondering about a fistula, that's not one that you want to see. The last thing you ever want to see in your career is a connection between the GI tract and an aorta. It's not good. The other thing you have is you have the lungs around here. So these are different areas where problems may occur. So as we talk about the duodenum here, you heard me say before that the pancreas and the gallbladder liver are going to form their connections into the small intestine, and the small intestine that we're speaking of is the duodenum. So within the duodenum, you have this area called the ampulla of vader, and that's going to lead you into your progression of the common bile duct, which is like that pancreas, which I told you before is that small organ structure that's sometimes hidden by everything else. But again, is where a lot of our acids and enzymes are produced. And then the gallbladder, and then again, right lying over the gallbladder is going to be your liver. And then as we follow along here, we've got the bile duct and the pancreas, which are going to empty into the duodenum, and then that's going to allow all of those enzymes into there to break down food and allow us some degree of absorption. One of the very important things for us to understand is that iron, for any of you, I don't know if any of you here today do iron supplementation or anything like that, iron's absorbed in the duodenum. Really important when you're talking about gastric bypass patients or anybody who's had an upper GI surgery. Now in every single field in the body, we talk about iron deficiency in the GI tract, because iron has to be lost. So there's only certain ways it's going to be lost. Either it's coming out of your body through an orifice, and that means either you're bleeding, which I would like to think no, or you're a female and you have a menstrual cycle, or it's coming out of your urine, or it's coming out of your GI tract. It's either going to come out this way or this way. But you don't necessarily see blood all of the time. You can be iron deficient and not necessarily know that you're bleeding. But iron deficiency is a symptom. Every GI fellow has to understand this concept. It is not a disease state. You have to understand why is the iron not being absorbed? So having this idea that it's absorbed in the duodenum is really important. When my fellows try to talk to me about they're iron deficient, or if I get a referral, they're iron deficient because of their Crohn's disease that's in their small bowel. That's because the Crohn's disease is active and bleeding, not because the iron's not being absorbed in the small intestine, in the ileum. It doesn't get absorbed there. So this is the area where it gets absorbed. So if you're having an iron absorption problem, you could have an autoimmune disease. We call that pernicious anemia. Or you could have some sort of, like I said, a surgery wherein that iron's not going to get there. You see this a ton in gastric bypass patients who really suffer from it. And no matter how much an insurance company tells you that oral iron is the treatment, oral iron is not going to help in those types of situations. At the end of the day, though, with regards to iron, you have to figure out what it is that is the problem there, or else you're just going to end up keep giving them iron and it's not going to go up. It's also where lots of other nutrients begin their absorptive process and then continue that on into the jejunum, which is the 8 to 10 feet in length part of the body. So for those of us that had to do anatomy in med school, when we would do the GI tract, the jejunum just goes everywhere. Like I said, it's not connected to anything. So if somebody was to lacerate or get in a car accident, jejunum can be the part of the intestines that spill out because they're not adhering to anything. They're like a jumbled up maze, right, in like a little box. They're housed within the outer lining of the large intestine. And then they're just going to, you know, be lost out there. They are extremely thin organ and is highly susceptible to injuries, not industry, might be susceptible to industry. But there's no clear demarcation between the jejunum and then when it enters into the ileum, we'll talk about the ileum in a second, the jejunum is largely responsible for the absorption of nutrients, carbohydrates, fats, proteins, minerals, and even some vitamins and is largely lymphatic and there's a huge capillary network and there's a huge vascular network. But like I said, at the end of the day, it's a very, very thin organ system. When you look at all parts of the small intestine, whether or not it's the duodenum, the jejunum or the ileum, you look at villi. And villi are really important. They look like a pillow. Sometimes people will use that term to describe it. But the colon doesn't look like this and the stomach doesn't look like this. This is how if you're doing a colonoscopy, you'll know immediately you're in the ileum if you're seeing this. They're like these little protrusions of the mucosa and they're the villi. If the villi aren't present, you may have some other underlying pathology. They help increase the surface area because, again, what's the purpose of the small intestine? It's absorption. And you see here that if it was stretched out, it would be the surface of a tennis court. So then, like I said, the jejunum does not have a specific demarcation into the ileum. They'll go into one or the other. You heard me say that you could live without an intestine. You can live without some ileum. So the ileum is about 8 to 15 feet, let's say 300 centimeters in length. And you could lose about 100 centimeters of ileum and be okay, about 100, 110 centimeters of ileum. After that, you get something called short gut where you really start to have a problem with absorptive processes. You don't want to lose any jejunum. I could tell you horror stories about when people start to lose a lot of their small intestine, then we're starting to go down the discussion of small bowel transplant. But it's not compatible with being able to live life without something like that being done. And the ileum is responsible for, again, ongoing absorption of nutrients, but specifically fat-soluble vitamins. So think about duodenum, iron. You can leave here kind of getting this, like duodenum, iron, ileum, AD, E, and K, and B12, and then jejunum, everything else. So jejunum is ultra-important. But these fat-soluble vitamins become really important as you're looking at them. We do a lot of looking at vitamin D and vitamin B12, A and E. Sometimes we'll check for, as gastroenterologists, we don't typically check for K, just so you guys know. Nobody orders a vitamin K level. You order an INR, typically, which isn't an end-all, be-all, because you could still, as you'll hear in the liver side, have an elevated, or a normal INR, but be vitamin K deficient, or vice versa. But that's typically how we do vitamin K. A and E play really important roles inside of the body with vision, and skin, and all of that, and they're very big antioxidants. B has a huge role in fatigue, and pain, and obviously bone health. And B12, super, super important for fatigue. There's a neurologic component to B12, and it's friend folate, and the way that those go. And now let's get into the large intestine, which is near and dear to my heart, but not exactly the smartest organ in the body. So the large intestine, I told you, its main role is reabsorption of water. It's about four to five feet in length, and it's the elimination mechanism. It's the dumpster. So the GI tract is a box. When we do colonoscopies, gastroenterologists sort of learn to do things backwards. So we're like, oh, the first part's the rectum. It's not, right? We got to think about it from top to bottom. So the first part is the cecum, and then it goes up into the ascending, over to the transverse, down into the descending, the sigmoid, and then the anus. All of these parts of the colon are responsible for very similar traits. You will see different individuals that can lose one part of the colon and not another. The one area you really need to keep is the anus, because that's what's going to allow you to do proper defecation. And peristalsis, again, becomes really important here. And as we talked about segmentation, the colon in and of itself is segmented, as you can see here. And so this is where there's that constant sort of mixing and propelling and coordinated contractions to move food through here while reabsorbing water. If you reabsorb too much water, you can get constipated. If you don't reabsorb enough water, you can have diarrhea. And the last part of the colon is the rectum and anus, and this is where defecation's going to occur. So the rectum is, again, it's your dumpster. That is its role inside of the body. And the rectum can hold a large amount of stool. You have an external anal sphincter and an internal anal sphincter and then a dentate line. And what's nice about this is that you have, in proper GI health, you can retain stool until you have to go to the bathroom. Now, what happens is that stool starts to descend. It's going to alert your external anal sphincter. That's why sometimes when you have to have a bowel movement, you have to sort of clutch down. You still have control over it, but your body's telling you it's time to go there. And then the internal anal sphincter is under involuntary control. So once you release, once you open up the external sphincter, then the dissension of stool is able to occur. And you can see here the process of defecation, which is an entire field in of itself now in GI that, you know, there's an anal rectal angle and then that angle stretches out and you get to send through the pelvic floor. But we are seeing a ton of pelvic floor dysfunction, both in men and women now. And sometimes this process and the way that you're sitting and the way that we're trying to defecate can affect that ability to go. Sometimes you feel like you're relaxing and you're trying to expel, but it's not necessarily happening and you can't get the stool out. And so all of that is part of how the process of elimination happens. But in a coordinated method, it will go smoothly. I will tell you, there's no normal number of bowel movements. There's no normal number of times per day. Normal is what your normal is. So if some patient comes to my office and says to me, I'm having one bowel movement every other day, but that's completely normal for me, I'm not going to call them constipated. If I have somebody else who says I have three to four bowel movements a day, but that's my normal, I'm not going to call them, you know, as having diarrhea. Normal has to be a normal range for you as an individual. And then we go from there. So with that, I will take questions on small and large intestine. When a physician is doing a colonoscopy and they decide to go into the ileum, what exactly are they looking for? Different things. Number one, I think, if I'm being transparent and fully honest, sometimes you're doing it to make sure that you still have a skill, because it's a skill set that you need to keep up, right? So sometimes you're doing it, like I'll do it sometimes just to make sure that I'm still good at doing it. And that's in when you're just doing like a screening colonoscopy. Otherwise you could make the argument that sometimes people are doing it because they are looking for any evidence of adenocarcinoma or something that can still, because you can still get small bowel cancers. So getting a quick look in the TI can help eliminate that thought. If you have any symptoms that are unexplainable, diarrhea, iron deficiency, constipation even to some extent, you want to go in there to make sure that there is an inflammatory process going on. So you want to make sure that you're not going to go in there and see ulcers, which would be consistent with something like an underlying inflammatory bowel disease or Crohn's disease. If you have one of those diseases, you're always going to go in it. But I think that going in there and taking a look and just showing that it's normal. The other reason is that when you're doing a colonoscopy, as you have already heard, people don't want to have these done all of the time. So let's say you didn't go in there and a year or two later, something happens. And then we as a GI are seeing that patient now, and we just want to make sure that the GI was, that the terminal ileum was checked and it wasn't. Then we're now left with an incomplete examination. So sometimes it's a preventative step, but it should be a part of our educational experience. It's an advantageous skill to have. Obviously for somebody like me, going into the ileum is ultra important when I'm doing anybody with inflammatory bowel disease. But I think that I sometimes will see endoscopists who are doing a screening colonoscopy only do a colon and then reach the cecum. I see it with my fellows and I'm like, absolutely not. Get into the terminal ileum and show me you can do it. Because again, you just never know what you're going to find. And there's no reason why you shouldn't go into it either. Of course, if there is a reason to not push further, you should never push into a terminal ileum. You should never push into an organ that's scarred, especially because like I told you, the jejunum is really thin, so is the terminal ileum. So it's really easy to perforate these organs with a blunt object such as an endoscope. I was just curious, are you using ultrasound for any of your IVT patients? That's a great question. So intestinal ultrasound is an up and coming field in the United States. In Europe, and honestly throughout the world, this has been commonplace. So yes, there are a few of us that are in the process of training right now. There's about five centers in the country. Out here in Chicago, University of Chicago runs an intestinal ultrasound program. And then I am in the middle of my training. So you go, just like you guys are here, I will be sitting in a classroom very soon. But part of the training is that they make you go do four weeks at centers that have ultrasound. So I've done two of my weeks, and then I'll do two more. The way that ultrasound is working, as you think about this, with regards to the APP question that was asked earlier, the IBIS organization, which is intestinal bowel ultrasound, has really deemed that they only want MDs and DOs to learn it right now. And that's because it's a brand new field in the United States. And so the only way to educate appropriately is to have actual physicians do it. And so that's right now the only people doing it. And then hopefully enough of us learn it, and then we'll start teaching it to fellows and bring up additional courses. But I absolutely wholeheartedly, what did somebody say to me recently? One of my other colleagues in IBD said, oh, you drank the ultrasound Kool-Aid. Sure, I did. I got into it because, you know, different people will tell you if you get into it. It's amazing. As you just heard me talk about the different layers, ultrasound is really important in the large and small intestine because it'll help us delineate things like diverticulitis, colon cancers. But in the field of IBD, where I'm using it, fistulas, thickness, and we use the thickness to determine whether or not a medication is working or our patients are doing any better. You can do it in pregnant patients. You can do it in obese patients. You can do it in the office in five minutes. So yeah. But I will be certified by DDW, so that's pretty cool. And then you've got to get your institution to buy you an ultrasound machine, which is super easy.

IBD specialist

small intestine

large intestine

inflammatory bowel diseases

iron absorption

defecation