Health and medicine
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Matthew McPheeters.
Want to join the conversation?
- I don't think that erythrocyte sedimentation rate (ESR) is a good indicator of IBD inflammation because it is affected by other factors such as the albumin concentration, or the size, shape, and # of red cells. ESR can indicate anemia, but hemoglobin and RBC count are more direct. True?(2 votes)
- [Voiceover] All right, so let's talk about how to diagnose Inflammatory Bowel Disease, or IBD for short. So, Inflammatory Bowel Disease is a group of disorders that's caused by an inappropriate inflammatory response that results in chronic intestinal damage. And, there are two types of inflammatory bowel disease: Crohn's Disease and Ulcerative Colitis. And, Crohn's disease and Ulcerative Colitis can be distinguished from one another based the on the location of the inflammation and the pathalogic changes. So, the location of the inflammation here becomes really important for the clinical presentation of the disease. So, it this clinical presentation that will drive the diagnostic work up that will ultimately lead to a biopsy which will determine the pathology that makes the diagnosis of Crohn's Disease or Ulcerative Colitis. Now, unfortunately there's no single blood test or physical exam maneuver that can diagnose either of the types of Inflammatory Bowel Disease. Instead, the diagnosis is made through a process that includes the clinical presentation, certain labratory findings, radiographic findings, and then finally the pathologic diagnosis. So, let's start with the history and physical exam. So, I just mentioned the the location of disease in general will dictate the clinical presentation. So, where do these lesions in Crohn's Disease and Ulcerative Colitis occur? Well, in Crohn's Disease the lesions are discontinuous and they can occur anywhere from the mouth to the anus. However, the most common locations are the terminal illium, the large intestine which is also known as the colon, as well as then other areas in the small intestine. So, how do these locations of inflammation tend to present? Well, let's start with the most common location and that's the terminal illium, which is the last section of the small intestine before it enters into the colon. Now, if you imagine a box over the abdomen, kind of like this, you can see that the terminal illium is largely located in the right lower quadrant of the individual. So, this is someone, you're looking at the person so this is gonna be their right side, and in the lower part of the abdomen. So, it makes sense that inflammation of the terminal illium often results in right lower quadrant abdominal pain. And, inflammation in this area may also result in diarrhea that may or may not be bloody. Now, other parts of the small intestine may also be involved. And, if enough of the small intestine is involved, which is the location where our nutrients are absorbed from the GI tract primarily, you can get malabsorption which can result in poor nutrition. So, this can cause weight loss and fatigue. Now, the second most common location of inflamation is the colon, which is just another way of saying the large intestine. Now, the colon is mainly responsible for reabsorbing the water from the stool. So, if it's inflammed and not working properly one can expect that the water will not be reabsorbed so there's gonna be, once again, this diarrhea which may or may not be bloody. And then, another common presenting symptom, although it's not necessarily related to a specific location is just this general inflammation can result in a fever which is usually fairly mild. And then, there may be some other symptoms that are caused by some of the complications of Crohn's Disease that we'll discuss in a minute. And, these can be things like bowel obstruction that can lead to something known as obstipation, which is the inability to pass stool or gas. Or, you can have these fistulas that can result in some fairly severe perianal pain as well as infection. Now, for Ulcerative Colitis the lesions occur instead of in this discontinuous kinda skip manner of Crohn's Disease they can occur in a continuous manner. And, it typically begins in the rectum and then kinda just moves backwards through the large intestine and almost never leaves the large intestine. So, similar to Crohn's Disease if the large intestine is inflammed in Ulcerative Colitis the most common presentation is this diarrhea with some diffuse crampy abdominal pain. And, it's also important to note that this diarrhea in Ulcerative Colitis is often bloody, not always but fairly frequently bloody and it's more frequently bloody than in Crohn's Disease although bloody diarrhea can occur in either type of Inflammatory Bowel Disease. Now, there are a few signs and symptoms of Crohn's Disease and Ulcerative Colitis that are not associated with the location of the inflammation and these are known as Extra-Intestinal Symptoms. So, one of these extra-intestinal symptoms can be skin disease such as these red tender nodules that are known as Erythema Nodosum. They can also include joint pain that often seems to migrate between different joints such as the shoulders, elbows, hips, and knees as well as redness of the eyes, and liver disease. Now, these extra-intestinal symptoms in Crohn's Disease and Ulcerative Colitis are actually pretty important because the GI symptoms of the disease can be fairly non-specific, I mean there's a lot things that can cause right lower quadrant abdominal pain and diarrhea. However, there are not many diseases that will cause these abdominal symptoms or these GI symptoms in association with some of these extra-intestinal symptoms. So, if they're happening together that's actually a fairly specific sign that someone might have Inflammatory Bowel Disease. Now, since the history and physical is fairly non-specific the next step in this diagnostic work up is to perform some laboratory studies. And, these studies tend to be fairly similar between Crohn's Disease and Ulcerative Colitis. So, let's once again bring in this diagram of the GI tract. So, the first set of laboratory findings are these markers of inflammation. And, this includes an increased white blood cell count, which is known as Leukocytosis, as well a couple of other very non-specific markers of inflammation that include an increased sedimentation rate and an increased C-reactive protein. Now, these findings here are very non-specific, meaning any sort of inflammatory condition in the body can cause these findings. However, they're very sensitive for Inflammatory Bowel Disease, meaning that if someone doesn't have an increased sedimentation rate or an increased C-reactive protein the process that's going on is likely not Crohn's Disease or Ulcerative Colitis. And, another labratory finding in Crohn's Disease and Ulcerative Colitis is anemia. And, anemia is a low hemoglobin count. And, hemoglobin is an important component of red blood cells. Now, there are a couple reasons why anemia can occur in Crohn's disease and Ulcerative Colitis. In Crohn's Disease if this terminal illium is involved then the body is not able to properly absorb the vitamin B-12, which in this vitamin is necessary to produce red blood cells. So, if there's low vitamin B-12 then it can result in anemia. Also, I mentioned that both Crohn's Disease and Ulcerative Colitis can have bloody diarrhea. If this bloody diarrhea is occuring frequently and over long periods of time that blood loss can kinda be addative and add up and that blood loss can result in anemia. Then, the last category of laboratory findings to mention is that f malabsorption. So, I mentioned earlier that if enough of the small intestine and even parts of the large intestine are inflammed and not working properly then body isn't able to absorb all the nutrients it needs to in order to survive. This is known as malabsorption, so it's what causes that weight loss and fatigue in Crohn's Disease and Ulcerative Colitis. However, if the body is in a state of malabsorption and getting very poor nutrition there's some blood tests that can also be a marker of that. And, one of the most common ones is a low albumin level. And, albumin is just an important protein in the body and when it's low it's a sign of malabsorbtion. So, similar to the history and physical exam the laboratory findings of Crohn's Disease and Ulcerative Colitis are fairly non-specific. But, they're very sensitive for Inflammatory Bowel Disease, meaning if these findings, if none of these findings are present chances are someone does not have Inflammatory Bowel Disease and you won't move on to the next step in the diagnostic work up. However, if these findings, especially the markers of inflammation, are present then we'll move to the next step in the diagnostic work up which is obtaining imaging studies. Now, a number of radiographic studies can be performed to aid in the diagnosis of Crohn's Disease and Ulcerative Colitis, including CT and MRI. However, one of the studies that's used is something known as a Barium Enema. Now, Barium is a contrast dye that is inserted through the rectum into the intestines and as it fills up the intestinal lumen an X-ray is taken to look at the abdominal cavity. And, this is a normal Barium Enema study. You can see a nicely outlined large intestine and when this study is performed in either Crohn's Disease or Ulcerative Colitis there are some characteristic findings that represent some of the underlying pathology of the two diseases. Now, there are a lot of things going on in this image, but what I want to point out is that you'll notice that the inflammation is occuring in both the large intestine as well as parts of the small intestine and it's intermixed by fairly normal looking sections of intestine. So, this is characteristic of Crohn's Disease, which are those skip lesions that occur both in the large intestine and the small intestine. Whereas the findings of Barium Enema for Ulcerative Colitis are fairly different. So, in Ulcerative Colitis you'll get this continous lesion that only involves the large intestine. So, notice that there's no gaps of inflamation, the entire intestine is involved and then you get a fairly normal small intestine afterwards. And so, it's these radiographic findings that lead to the next step in diagnosis, which is to obtain a biopsy to then formalize the diagnosis of Crohn's Disease and Ulcerative Colitis. So, a number of different procedures can be performed to obtain a biopsy and the decision for the type of procedure is largely based on where the locations are for biopsy. So, say if Crohn's disease is suspected and the lesion is in the first part of the small intestine then an endoscopy, or a camera is put down the throat into the esophagus and through the stomach can be performed because that's the best way to get to the first part of the small intestine. Whereas in Ulcerative Colitis where the inflammation is contained only in the colon then the procedure is most likely going to a sigmoidoscopy or a colonoscopy where a camera is inserted through the anus and rectum to obtain a biopsy. But, regardless of the type of procedure the steps are the same and it's twofold, there's the visualization of the lesion and then the biopsy for microscopic pathology. So, in Crohn's diease on visualization the lesions grossly will look something like this. And, this is known as a "cobblestone" appearance. And, it's called this because pathologists kind of think these lesions look somewhat like a cobblestone path in which the intestinal wall has numerous intersecting lesions to make this kind of cobblestone pattern. And, once this gross appearance is seen a biopsy of the intestinal wall is taken to look at under the microscope. And then, the characteristic microscopic findings of Crohn's Disease are this Transmural Inflammation in which the inflammation caused by the disease goes through all three layers of the intestinal wall: the mucosa, the submucosa, and the muscularis externa as well as these noncaseating granulomas which is demonstrated here. And, these granulomas are a sign of chronic infection. Now, Ulcerative Colitis has a very different gross appearance. You can see the walls look much more smooth because of the continuous lesion and they have what's described as "friable" appearance. And, what friable means is that if you were to touch the wall it kind of looks like it would easily bleed or parts of it would just slough off. And so, when this is seen a biopsy is once again taken to look at under a microscope where it reveals the hallmark lesion of Ulcerative Colitis which is inflammation contained only in the mucosal and submucosal layers, which is very different than Crohn's disease. So, once this pathologic specimen has been taken and you see the hallmark findings of one or the other a diagnosis of Crohn's Disease or Ulcerative Colitis can finally be made.