Diarrhea is defined as having stools that occur more than three times a day and are looser than usual, specifically 200 grams in 24 hours is considered diagnostic but as you can imagine trying to measure the weight of stools in everyone referring diarrhea would be a mess literally so first off…the causes of diarrhea, we can divide them into acute and chronic causes for a start; acute diarrhea is defined as lasting less than four weeks and is often caused by infections that are usually either viral or toxin mediated, typically they will resolve spontaneously. Chronic cases are cases lasting more than four weeks, they need to be further divided into either organic of functional causes and the difference between them is that organic causes can be detected or quantified through testing while functional causes cannot. Examples of organic causes include celiac disease inflammatory bowel disease like ulcerative colitis or Crohn’s disease, we can also have bacterial and parasitic infections, pancreatic insufficiency and of course intestinal neoplasms, on the other hand functional causes of chronic diarrhea include irritable bowel syndrome, lactose intolerance, food allergy and abuse of drugs or alcohol. How then can we begin to narrow down the causes when we encounter a patient with diarrhea, let’s first tackle how to distinguish functional from organic diarrhea, firstly the duration of organic ranges between weeks and years while functional is over six months, secondly the volume of organic diarrhea is usually larger than in functional.
Next we look for the presence or absence of blood. Functional will never have blood while organic often does, we can also ask about the timing, organic doesn’t have any specific pattern but may wake the patient up at night, well functional is usually in the morning and will not wake the patient up, this is also closely tied to stress where organic diarrhea doesn’t have much association to stress, functional diarrhea often coincides with stress extra symptoms like fever, arthritis and skin lesions are often seen in organic causes but not commonly seen in functional causes. The last two are weight loss and a cramping pain, organic usually has weight loss while functional only has it alongside anorexia and cramping pain is usually present in an organic cause but not as frequently seen in a functional cause although it is there, often after making the distinction between organic and functional, you want to evaluate whether it’s a small or large bowel problem, small bowel related diarrhea usually has a higher volume and a lower frequency and is often yellow or even gray in color, large bowel related diarrhea instead often is very frequent with a low volume and much more frequently features blood and mucus, after addressing these two questions, you would then look at doing a follow-up based on your findings including potential esophageal dude and Oscar pee or colonoscopy and biopsies so that’s it for the clinical side of things but it’s worth knowing about the different types of diarrhea based on the pathophysiology. First off we have osmotic diarrhea where there is an increased concentration of osmotically active solutes in the lumen and so water remains in the lumen, here the causes are malabsorptive diseases like celiacs disease or things like osmotic laxatives, interestingly the symptoms will resolve if the patient casts the osmotic gap here is often greater than 100 million miles per kilo, next is secrete REE diarrhea where we have active secretion of water and electrolytes into the lumen via activation of adenylate of guanylate cyclase, usually this type is caused by bacterial endotoxins such as with E coli and cholera, here there is no response to fasting and no osmotic gap. Third is oxidative diarrhea resulting from extended inflammatory to the intestinal mucosa, it may often feature blood and mucus and it will not respond to fasting. Lastly we have diarrhoea of altered motility where we have an increase in peristalsis and therefore less time for reabsorption.