During this 20-25 minute pre-recorded lecture, Dr. Bhavana Bhagya Rao discusses the topic of diarrhea. This in-depth review will provide an update on this topic for your clinical practice as well as supplement your learning for the ABIM Gastroenterology and Hepatology boards. CME pre-requiste of live Q & A webinar, 8th Annual Mount Sinai Intensive Board Review in Gastroenterology & Hepatology on Oct 6. Hello everyone, my name is partnered all and over the next 2025 minutes, I wish to give you a broad overview about how to approach the topic of diarrhea for the sake of the Gi boards. So let's start with a few basics. How do we define diarrhea? So it's one of three parameters that need to be met. One increased tool frequency while keeping in mind that the normal range can vary from three bowel movements a day to three volume. It's a week number two altered stool consistency. And this is where the bristol stool chart comes into play where in types 5 to 7 would classify under diarrhea. And the technical definition is when the stool weight It's more than 200 g or volume is more than 200. Mhm. With regards to classifying diarrhea, one approach is duration based. So here we talk about acute persistent chronic with acute being diarrhea lasting less than two weeks and chronic being more than four weeks and persistent falling in that interim category. This classification is useful because oftentimes when you're talking acute diarrhea, you're thinking about infectious causes and oftentimes this is self limited. Um and hence does not require much of the world cup chronic diarrhea is what we'll see in our clinics and consult settings more often. Um and its usually noninfectious causes that require additional work up, chronic diarrhea can be sub categorized into the following. So the two big buckets are inflammatory and non inflammatory on the non inflammatory that can be watery, fatty or functional diarrhea and the subcategories. Under watery diarrhea are osmotic and secretly now understanding this classification is useful because in the boards, when they describe the patient history in the question stem, they're going to try to lead you down one of these parts and identifying what type of diarrhea it is. Will help you narrow down the differential and then reach the diagnosis, differentiating between inflammatory and non inflammatory area is pretty straightforward. So an inflammatory cases, patients are going to have new coid or bloody stools, abdominal pain, rectal pain, tennis, Miss, fevers. Uh, these are usually smaller volumes tools and the stool samples will contain elevated laughter, Ferron cal protecting and then there's the presence of Lucas sites and a cold blood. But as non inflammatory, does not have any of these features among inflammatory. The common etiologies we encounter our IBD invasive infections such as entra toxic Andrew hemorrhagic and invasive equal. I see death is key make or radiation colitis and certain drugs like checkpoint inhibitors as well as en sets when they cause severe ulceration can cause inflammatory diarrhea. Under non inflammatory fatty diarrhea is easier to distinguish. So they'll give you a case where the patient has greasy stools which are difficult to flush and the state aurea is technically defined when there is more than eight g of fecal fat President in 24 hours to a sample. When you suspect this. You can do a quick screening test with a qualitative Sudan staining, after which the gold standard would be doing a stool five determination over 72 hours. Um And this is having had the patient on a high fat diet in the preceding 48 to 72 hours. The question they also talk about patient having fat soluble vitamin deficiencies. So that would be A D. E. K. And in terms of the theologies. Fatted areas encountered when there is some amount of malabsorption. So any small bowel pathology but in the absorptive uh capacity of the small ball is compromised. Can cost tutorial automatic digestive process. So this is usually where there is pancreatic insufficiency or an inability of the pancreatic enzymes to exert their fullest potential. These are the ideologies of statutory. Um Mhm. What re diarrhea is a bigger bucket and under this falls secretly versus osmotic secretary is typically large volume diarrhea. So more than one liter of stool in 24 hours. It continues even in a fasting state. The ph is usually normal. Unlike osmotic diarrhea where there's an acidic ph because reducing substances are present in the stool and perhaps the biggest way to distinguish between the two that we heavily lean on is calculation of the stool osmotic gap. Now in the boards they may give you values of stool electrolytes for a patient and then expect you to calculate the gap. Um And that's the formula that you can use and an osmotic gap more than 100 to 1 25 strongly suggests an osmotic diarrhea. Uh But as a gap less than 25 to 50 is gonna make you think about secretary gas is also useful to know that if you have a measure stool osmolarity and if it's less than 200 million possums packaging, then the suspicion is maybe this is factitious because it's been diluted with water or urine or it just may be an incorrect collection of the stool sample. Osmotic diarrhea causes, you know, any dissect right intolerance, Common one being lactose intolerance. Uh, but a secretary diarrhea is uh, you know, it's a big umbrella term which a lot of ideologies fall under and we'll discuss a few of them in the upcoming cases. Now. Now we once stood how to define and classify diarrhea. Let's jump right into some cases which are going to address these board favorite ideologies that they love to quiz us on Case. One is about a 20 year old college senior who comes with the complaint of episodic abdominal pain, bloating and diarrhea occurring over the last two years. Pain is in the lower abdominal and it is improved with bowel movements. He says he passes several lose or liquid stools on the days he has pain And these symptoms occur at least 1-2 times per week. And in between episodes he's pain free and his tools are formed. He finds that he has more episodes when he's anxious or stressed about school. He denies any other G. I symptoms. He's not on any medications, has not tried any special diets. He has no other significant medical surgical history uh and a normal physical exam. And also recent labs including CBc cmp, thyroid studies, inflammatory markers and celiac serology. These were all un remarkable. So what is the most likely diagnosis for this patient functional diarrhea? I. B. S. Celiac disease Or just normal bowel habits over 20 year old. This is a useful juncture to discuss functional bowel disorders. So the couple of paradigms we talk about is pain constipation, diarrhea. Now in the absence of pain, if someone just has constipation that would fall on the functional constipation in the absence of pain. Only diarrhea gives a diagnosis of functional area. But if pain is present then we're talking irritable bowel syndrome and that can be I. D. S. C. On I. D. S. De. Depending on, you know which end of the spectrum patients fall on. Or sometimes patients can have I. B. S. M. Or a mixed picture with alternating constipation and diarrhea to make a diagnosis of I. B. S. They need to meet the room for diagnostic criteria which is recommended donald Payne on average at least one day per week in the last three months and this pain needs to be associated with two or more of the following. It has to be related to defecation Where in either it's improved or worsened with defecation. No two, it has to be associated with a change in the frequency of stool as well as the farm of stool. And these criteria need to be met for the last three months with symptoms having originated at least six months before making this diagnosis. So with that in mind, the correct answer for this patient is I. B. S. D. It's not functional diarrhea because he does have pain. It's not Celia. His theology is phenomenal and you know, presence of pain with diarrhea is never normal bowel habits for a young man and he does meet the room for criteria based on the presence of the pain which is associated with a change in stool form. And it is improved with defecation and also the frequency and duration of his symptoms helping meet the criteria going forward. You put him on a low fat map diet and with that he has significant improvement in his abdominal pain. But he comes back eight months later because of worsening diarrhea. He says now five out of seven days a week. He has diarrhea with significant cramping, abdominal pain and bloating. And again the pain does improve after defecation. He has about three episodes of Type six tools. So that's mushy stools on the days. These symptoms are active. He has now become more anxious about leaving the house because of these symptoms. He does undergo a colonoscopy with random biopsies, which showed normal mucosa. So at this stage for his worsening symptoms. What medications would you advise? Allah citron Hello, Oxendine click annotate on masala. Me the answer here is a low oxygen. So both Alice citron and L. Occident are approved for I. B. S. D. But ellis citron is only approved for women and it doesn't apply to him. Play content is actually approved for my BSC. So I. B. S. Constipation and masala means what we used for. You know I'll see the colitis and he had a normal colonoscopy so that would be inappropriate here Let's move on to case two. So here a big family goes to Mexico for vacation and they all unfortunately developed acute gastroenteritis. They all have similar symptoms with the duration of illness being about five days and nobody took antibiotics and rightfully. So the question is which family member has the highest risk of developing post infectious ideas is that the 22 year old daughter with depression. The 35 year old son with arthritis, 64 year old mom with hypothyroidism are the 85 year old grandpa with a history of cabbage, interestingly about 20% of I. B. S. Patients actually described having an acute infectious broad room and post infectious I. B. S. Is usually diarrhea predominant. The different risk factors that can predispose the patient to development of post infectious I. D. S. Are adverse life events? Concomitant depression, hyper Congresses, female gender smoking and then a prolonged duration of initial illness, Interestingly. The one factor that seems to reduce your risk for post infectious ideas is being older than 60 years of age. So in this scenario, the 22 year old daughter is the one with the highest number of risk factors because of her young age, female sex and concomitant depression. So that will be the answer. In this case case freezer of a 46 year old white man who comes with chronic diarrhea along with lethargy hand arthritis and weight loss. His wife also says that his memory is not what it used to be. Exam shows diffuse them for no empathy. Apache, hyper pigmented skin, nystagmus and systolic murmur. We do an upper endoscopy which shows for me macrophages in the original biopsies. Lab work reveals below serum Kentucky and is HIV is negative and the Sudan stain on the fact is positive. So what is the diagnosis here? Amyloidosis, systemic lupus tv of the bills disease. This is actually a case of ripples. This is caused by the bacteria. Trough rima Ripley vehicles is a multi system process. So you'll have joint symptoms, chronic diarrhea malabsorption, weight loss and often neurologic symptoms as well because it's malabsorption, I've you're gonna see features like low serum Claritin as well as high fecal alfa one anti trips and levels which all suggests that there's protein losing occurring and then the positive Sudan stain shows that they're losing fat in school as well. Um The characteristic finding is the former macrophages in the lamb inappropriate of the small bowel and then these would stay positive for periodic acid Schiff sting. So this is a board favorite for sure. Treatment of ripples involves intravenous set Jackson for about two months because they need to tackle the neurologic symptoms, Followed by one year of Bactrim therapy. Moving on to case four. So now we have a 52 year old man who recently moved to us mainland from Puerto rico. He is complaining of fatigue malaise abdominal cramps along with diarrhea and dyspepsia. Labs revealed mild anemia with macro psychosis. His stool studies for infectious organisms is negative. He also undergoes an entire a Skopje and this is an image of his proximal, judging him. It may not project as well, but essentially what we're seeing here is scalloping of the mucosa. So what is the likely diagnosis? So here are the likely diagnosis is tropical screw. The thing to remember here is the question stem is gonna allude to the patient coming from or traveling to the screw belt which comprises Puerto rico cuba, the Dominican republic Haiti India and the Middle East. Now the chronic form of tropical screw requires at least two years of residents in that endemic area, but the acute form can occur even with the shorter exposure to that place. Um In chronic prove patients usually have three phases where initially it's just fatigue and abdominal discomfort, but in phase two is when the diarrhea dyspepsia and the r word malabsorption develops and by phase three people have mac ascetic megillah plastic anemia as well. Treatment for tropical screw involves a prolonged course of debt recycling. And these patients also require for lead supplementation because of concomitant deficiency. Cases five and six are slight variations of each other. So this talks about patient with Crohn's disease, who has undergone resection of his D. I. For structuring complications and thereafter develops non bloody diarrhea. Now in case 5 75 cm of the D. I. has been affected But it's in case 610 cm. Now what is the diagnosis and bought these cases? Is it the same if so what is it? The diagnosis is actually not the same in both these cases. And to understand this answer, we need to think about the intra hepatic circulation of buying a little bit. So when less than 100 centimeters of the terminal William is respected, then there's still enough amount of the ilium left to be able to continue reabsorption of bile and maintain the intra hepatic circulation. Often some amount is bile is going to spill into the colon and binding the colon. Works as a secret ago causes irritation and leads to diarrhea. So in this scenario the diarrhea that's occurring is because of the bile acid. So bile acids stimulated and the treatment for that would be bile acid binding resins such as polystyrene or cholesterol. In the second scenario where more than 100 centimeters of the ilium gets respected. Then there's not enough absorptive surface left to re absorb all the bile and so eventually deliver is not able to compensate and make enough bile acids. And so the intra hepatic circulation gets impacted and the amount of bile um decreases. So essentially these patients develop a bile acid deficiency because of which they have fat malabsorption and that is the kind of diarrhea they developed. So in this scenario is more steel Pretoria. And so the treatment approach here is not to give bile acid binding lessons because already there's very little bile acids available in the system. Rather you need to put them on a low fat diet so that their diarrhea is not exacerbated and you need to supplement the diet with medium chain triglycerides because this is the only kind of fatty company that can get absorbed directly without the need for bile. In the small understand Finally we come to K7 where we're talking about a 65 year old man who comes for the evaluation of abdominal bloating distension and diarrhea over the last six months. Um he has no other gi-related symptoms. His medical history is notable for diabetes, no other relevant surgical or family history In terms of labs. He has a normal cbc cmp, thyroid levels, inflammatory markers, negative celiac serology ease his agency is eight. He has borderline low B 12 vitamin D deficiency and elevated followed, he had a ghost Nigerian colonoscopy with biopsies, which are normal stone studies for infections is negative and he has normal fecal elastics and fecal fact his cats can only show small bowel diverticular, so what is the most likely diagnosis for this Gentleman symptoms? I. B. S. D. Celiac disease? Small intestinal bacterial overgrowth or pancreatic insufficiency. Working through the options here. So this is not a case of I. V. S. D. Because he does not have abdominal pain which is one of the most important criteria. Celiac disease is unlikely because his theologies were negative and his E. G. With biopsies were negative. Pancreatic insufficiency is wrong because his fecal last days and fecal fat levels were normal. So this is most likely cibo you know the question stem does describe to risk factors for siebel which is small bowel diverticular and diabetes. Also the lab trends of elevated folded low B. 12 and vitamin D. All of this um is consistent with the diagnosis of cibo. Sasebo is just basically excessive bacteria in the small Einstein symptoms can be varied and vague ranging from abdominal pain, discomfort, bloating, diarrhea, flatulence, weight loss and in extreme cases to Pretoria. Um there'll be some laboratory clues like the low B. 12 elevated for late um and then vitamin mineral deficiencies and in severe cases they can be protein losing as well and that's where patients can be high profile human ate. The question stem is going to describe certain risk factors or predisposing factors for cibo. This could be structural like post op ed hessians, small bowel diverticular or structures blind intestinal loops. So maybe a patient who has undergone bariatric weight loss surgery and has a long ruling or they can be motility problems in the intestine, such as chronic intestinal pseudo obstruction, connective tissue disorders, poorly controlled diabetes. Or maybe the patient is on longstanding medications like opiates or anti Colin objects. A useful diagnostic test for cibo is the breath test. And the board does like questioning us on trying to interpret these breath tests. So either with glucose or galactose breath test, there are two parameters that are being assessed and that is the hydrogen level as well as the meet him. Now. The test is considered positive at the hydrogen level Rises more than 20 parts per million from the baseline within 90 minutes of administering the test. Or the test is positive if the meeting 11 is more than 10 parts per million at any point during the test. So let's look at the graph below. And this is the graph which was there in my board exam uh two years ago. So here at zero you can see the grass in of hydrogen is marked in blue. The graph of meeting levels is in orange. So at when the bachelors was given hydrogen level was measured at 10 parts per million. And at 90 minutes it had risen to about 20 parts per million. But the criteria is not met because the rice has to be equal to or more than 20 from a methane standpoint. Um, throughout the 90 minutes the level has been less than 10 parts per million. And so that's why even from a methane standpoint, the criteria is not met. So this is the negative breath test for cibo. Now, if the tests have been positive then to treat cibo, the variety of antibiotics that can be used including the fax um in a taxi cycling. But the thing to remember is if the methane competent is positive, then we should add neo mason to the regimen as well now because we're restricted by time. I cannot go over video cases for all the theologies but I do want to leave you with some high yield polls. So the whole question of diarrhea would classically be this way there will be a history and physical stem which will describe characteristics that will help you narrow down whether this is an acute was just chronic, whether it's inflammatory and non inflammatory, watery or fatty diarrhea. Then they may talk about a patient having undergone upper endoscopy or colonoscopy. They make sure you his to pathological images and then ask you to further narrow down your diagnosis. Um in particular when they give you upper endoscopy biopsies. One thing that they're asking you to identify our history path is villas entropy. So pictures on the right, they show you pictures of normal grips above as well as the villus atrophy below and well it's a trophy is caused by all these different etiologies listed in the table. But there are going to be certain buzzwords included in the question which will help you narrow down your defenses. So let's review some of these high yield pearls. So number one went off about Celia they're going to describe in Tripathi little lymphocytic infiltration. Um The other thing they can question you on is okay you diagnosed the patient with celiac. There aren't a gluten free diet but they have continued diarrhea. So in that scenario first thing we need to make sure is they are being compliant or they're not having any inadvertent exposure. The other thing we should do is test for microscopic colitis. Um you know because there is an association between these two diseases and this also holds the other way around. I suppose you've diagnosed a patient with microscopic colitis and they're not responding to put a snack therapy that we need to make sure that they don't have celiac as well. Um The others explanation for continued diarrhea in a patient with celiac, especially long standing would be refractory Celia and maybe this is now converted to indirectly cell lymphoma. In which case we're going to have to get close item entry on the pathology specimens to help identify that. Another quick thing that they like to ask with regards to celiac is they describe the skin manifestations of dermatitis have better farmers. Um And in particular on a skin biopsy. Those patients will have linear I. G. A deposition treatment for dermatitis. Her performers is also a gluten free diet. All in the factory cases you can use the app. So uh but they talk about whipple's disease to be said patients would have multi system findings. And then the classic is the periodic acid shifts positive macrophages in the lab, inappropriate common variable immunodeficiency. They described patients with recurrent infections, low serum immunoglobulin levels and then classically absent plasma cells on the biopsy in autoimmune enteritis. Um They may describe patient having anti intra site antibodies. And then on biopsy these patients will have increased grip a prosthetic bodies or absent goblet cells. But a case of amyloid. They'll talk about a patient with a chronic inflammatory conditions such as rheumatoid arthritis. Um With now diarrhea as well as any other end organ manifestation, like a new heart failure. And the key here is the congo red staining which shows apple green pirate fringes. They love to talk about medication induced diarrhea. So common culprits insets. Uh Michael. Finally marketing so this may be a patient who received a kidney transplant who has diarrhea to look for this medication on their medalist and the other board favorite is almost certain. So this is the one arab agent which can cause a collagen. This type of screw. Um Hence the common cause of diarrhea in terms of cases of giardia, there'll be an exposure or travel history. And then uh you can use stool tests to identify the agent in terms of tropical screw again there'll be the travel history to the endemic screw belt region. Uh And these patients will have low foliate levels. In a case of collagen screw, they might show you pictures where then there is the sub epithelial collagen band thicker than 10 micrometer in the small bowel. And then when they discover case of cibo, you know there will be risk factors of predisposition and the lab parameters will show low B 12 high for lead. And then they may ask you interpret the glucose or laterals. Breakfast. Okay I hope you found that quick review useful. Um And I wish you good luck for your boards.