Back To CoursePathophysiology Textbook
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A great many song, commercial, and joke has been made about the contents that will be expelled, no pun intended, in this lesson.
All joking aside, what we'll talk about may look simple but has a lot more consistencies to it than most people expect and can actually be deadlier than you suspect.
Diarrhea is a type of bowel movement resulting in watery stools. You knew that. But believe it or not, what you may not know is there's actually more than one type of diarrhea. The next time you get diarrhea, try to figure out which type you have as you're sitting on the toilet. At least it'll make the experience a bit more fun!
So, there's osmotic diarrhea, which can occur if things that can't be absorbed by the intestines draw water out of the body or cause the retention of water within the intestinal lumen, the open part of the intestines. Eating too many grapes or enjoying lactose intolerance are two prime examples of this type of diarrhea. The good thing about this type of diarrhea is that many times you'll just get it out of your system once or twice, and it will stop on its own until the next time you drink too much grape juice. In a basic sense, osmotic diarrhea occurs because the pump pushing water into the body is not strong enough to do so against the larger forces of osmosis holding the water back in the lumen.
But when the pump actually actively pumps water out of the body and into the intestines, then it's called secretory diarrhea. It's actually not that big of a secret. In this type of diarrhea, the water is being secreted out into the intestines. The end result is a massive and potentially deadly secretion of water and resulting dehydration of the body. Causes of secretory diarrhea include bacterial toxins, such as the cholera toxin, certain laxatives, and even tumors.
There are other types of diarrhea, including exudative and inflammatory, where there's blood, mucus, and pus in the stool that can be associated with inflammatory bowel disorders, such as ulcerative colitis and Crohn's disease. These things can increase the fluid content of the stool and even the osmotic forces, predisposing to diarrhea. If that wasn't bad enough, the inflammation in these diseases causes irritant receptors in the bowel to constantly fire off signals telling your brain you need to always go to the bathroom, even if only a tiny bit of bloody mucus ends up coming out.
If the blood coming out of the rear end is bright red, it's called frank blood or hematochezia. Again, hematochezia is fresh, bright red blood being passed as a result of bleeding occurring in the lower gastrointestinal tract, such as the colon. It can also occur if there is massive upper GI bleed. This should be contrasted with melena. Melena is dark tarry, digested blood coming from the upper digestive tract, such as the stomach and duodenum.
Finally, certain neurological and metabolic conditions, stress, or even some types of food and drugs can decrease the amount of time ingested food and water has for absorption into the body, leading to diarrhea due to what's known as motility disorder. In this case, the pump works just fine; it's simply that the digestive content is rushing by way too quickly for the pump to catch it all. This occurs because the muscles of the GI tract do not contract and relax back and forth properly like a jaw in order to 'chew' the food in the intestines. Instead, they quickly flush the food down through the entire tract like a conveyor belt.
Prolonged or severe diarrhea can cause the loss of bicarbonate, potassium, and magnesium from the body. Sodium levels may increase or decrease, depending on the cause. All of this can actually cause serious problems, such as arrhythmias of the heart and metabolic acidosis.
If you need to go see the doctor for diarrhea, they may not perform any tests if they think it's something simple. Otherwise, they may take blood samples to look for the electrolyte imbalances mentioned before, stool samples, and even use instruments to look inside of your GI tract to figure out what is going wrong. Treatment would have to be specific to the cause, including the famous Pepto-Bismol, which contains bismuth subsalicylate, as well as antibiotics, intravenous fluids, and potentially even surgery if a tumor is causing the diarrhea.
By the way, no one is exactly sure how Pepto-Bismol works - although we know it helps to decrease inflammation and neutralize bacterial toxins. Which is a nice segue to an important clinical point: in some cases of diarrhea, the last thing you want to do is to give an anti-diarrheal. That is because if there are dangerous types and amounts of toxins building up in the intestines, you actually want them to leave your body by way of diarrhea as opposed to building up to deadly amounts thanks to anti-diarrheals.
We can't end this lesson without considering the flip-side of diarrhea - good old constipation! Yay!
Constipation is defined as difficulty passing stool or abnormally infrequent amounts of bowel movement. Having less than three bowel movements per week is one of the criteria for fulfilling a diagnosis of constipation.
Constipation can have many causes, such as dehydration, damage to the innervation of the intestinal tract, a cancer blocking the movement of stool within the digestive tract, not enough fiber, and a whole lot more.
Diagnosis is usually made by taking patient history, a rectal exam, and visualization of the tract through endoscopy, among other things.
Treatment is specific to each cause and may include things like increased fluid intake, increased dietary fiber, or in more serious cases, medications and surgery.
Now that we finally got this lesson's contents out of our system, no pun intended, I think we need to look over some things an additional time just in case.
Diarrhea is a type of bowel movement resulting in watery stools. Many different kinds of diarrhea exist, including osmotic, secretory, inflammatory, and exudative. The latter two may involve something called frank blood or hematochezia. Hematochezia is fresh, bright red blood being passed as a result of bleeding occurring in the lower gastrointestinal tract, such as the colon. This should be contrasted with melena. Melena is dark tarry, digested blood coming from the upper digestive tract such as the stomach and duodenum.
In contrast to diarrhea, constipation is defined as difficulty passing stool or abnormally infrequent amounts of bowel movement.
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Back To CoursePathophysiology Textbook
20 chapters | 274 lessons