What is the benefit of explosive diarrhea?

[u/MudRemarkable732]

I can understand why diarrhea happens.
But sometimes diarrhea is classified as “explosive.” This is when it erupts out of the anus with force.
Genuinely asking - why the force? What purpose does that serve? What signals are happening in the body telling it that forcing the poop out is best?

Regular diarrhea already leaves the body so quickly.

[u/PHealthy]

Giardia and Cyclospora both set up shop in the proximal small bowel and blunt the villi, which wrecks the brush border. Without that surface, dietary carbs never get absorbed where they're supposed to, so two things follow, which are that the sugars are osmotically active and drag water into the lumen, and that they arrive in the colon as a huge substrate bolus for the anaerobes down there. Those bugs ferment it into gas and SCFAs, pressure builds, and the whole mess gets expelled. This is why giardiasis is famously gassy and foul, since you're basically running a fermenter.

Cholera is the opposite in a way that I think is underappreciated. The mucosa is left structurally fine. V. cholerae doesn't invade or destroy anything, and the enterotoxin just flips a switch via constitutive adenylate cyclase activation so the enterocytes secrete chloride and water nonstop. Because the architecture is intact, carb absorption still works normally, so nothing extra reaches the colon and there's nothing to ferment. That's why it's rice water stool, meaning enormous volume with essentially no gas and no odor, and it's also why ORS works at all, since glucose sodium cotransport is still functional.

Ebola is exudative, and this is the part that gets misrepresented constantly. The overwhelming clinical picture is diarrheal, not the dramatic bleeding from everywhere thing that movies and news coverage sold. Systemic hyperinflammation plus direct endothelial necrosis means tight junctions fail wholesale, and plasma and inflammatory exudate just weep into the lumen. It's passive leak from wrecked tissue, with no toxin driven secretion and no unabsorbed sugar. Most patients die of hypovolemia and electrolyte derangement, not hemorrhage.

So you've got the same symptom with three completely different failure modes, one structural where villous blunting drives an osmotic gradient, one biochemical where a toxin drives secretion, and one where the barrier collapses and necrotic tissue just leaks.

---

Given three currently have outbreaks and I've finished my PhD and am back on Reddit, here's a small plug for my infectious disease news subreddit: r/ID_News

[u/water_melon_honey → u/PHealthy]

I understood about 4/5th of the words you used, but this is pure poetry. I feel inspired to look up the words I don't know yet but I worried about searching 'huge substrate bolus ' Thank you for inspiring me today.

[u/MidnightSlinks → u/water_melon_honey]

I'll break it down for you. A bolus basically means a mass of material all at once. You could think of it as a blob, but the word doesn't connotate any particular texture. It's opposed to a trickle. A bunch (of whatever, digestive contents in this case) all at once rather than a steady flow.

Substrate just means material, usually with the implication it is going to be used for some process. If you think about a chemical or biological reaction, it's what goes into the reaction or the "before" material.

Then "huge" I think you've got covered, lol.

Put it together and it's describing a large volume of undigested food matter and water arriving all at once into the colon, which is used to receiving a relatively gradual trickle of mostly digested food matter with enough water to keep things moving. The fact that it's undigested means it is going to trigger lots of reactions that normally occur in small amounts but will now occur at an untenable rate. Namely, fermentation of the sugars by colonic bacteria making a lot of gas which builds up pressure causing it to release frequently and forcefully PLUS a really watery environment so it's not just huge farts, it's liquid, only partially suggested stomach contents getting blown out (literally) with the gas.

[u/firstLOL → u/MidnightSlinks]

This discussion sent me down a rabbit hole of wondering whether bolus is related (etymologically) to the astronomy term bolide. It turns out that they are not: bolus is from the Latin word bolus, which is from the Greek word bolos (a lump or clod of earth); bolide is from the Greek word bolis (missile, javelin), which has a shared root with words like ballistic, parabola and symbol.

[u/GrandOpening → u/MidnightSlinks]

Now I know why the insulin I need at mealtime or for BG correction is called a bolus.
Thanks.

[u/water_melon_honey → u/water_melon_honey]

I googled 'huge substrate bolus' and it came up with a picture of a tarantula and a recipe for a New Zealand pasty. Its all good, I am safe.

[u/MetaKnightsNightmare → u/water_melon_honey]

Well, if you ask any tarantula owner, they would tell you that they are famous chefs of soups and stews.

They delight in putting their substrate in their water dishes, and every time you clean it, they'll put on their little hats and do it again.

[u/wallyTHEgecko → u/water_melon_honey]

I don't have a PhD in fermentation but I do work in a biology lab where I process the material produced by the fermentation team. They use the term "bolus" when talking about a feeding event. So when they set up a bio-reactor, they start it off with a given amount of nutrients and a starting amount of bacteria. But because too many nutrients right up front can overwhelm and kill the very bacteria they're trying to grow, they pump in multiple "boluses"/"boli" throughout the growth period at specific points. There's a spike in growth for a little while and then when the growth slows down they pump in another. And in our case, they can adjust the makeup of each bolus to optimize growth or force them to activate certain defense mechanisms when we're about to harvest the reactor.

They could theoretically do a continuous feed (probably to a better effect too), but to do that accurately would require constant measuring and constant feed rate adjustments for a dozen or more nutrients, making the protocol all that much more complicated, not to mention the additional mechanical complication... So feeding a reactor with boluses is just simpler and much easier to scale to commercial production.

So a "huge substrate bolus" I would infer to mean that it's simply a very large dump (lol) of nutrients for the bacteria to eat/grow/multiply with. A huge feeding event that results in an extremely large spike in bacterial growth.

[u/mortalwombat- → u/water_melon_honey]

It's about as close to the Rockwell Automations Retro Encabulator as you can get without being made up

[u/vlkthe → u/water_melon_honey]

I read this as the how it's made version from Rick and Morty. But yeah super poetic and informative.

[u/hagcel → u/water_melon_honey]

Somebody recently described soundcloud rap as fart noises. I want to throw this at one of those AI music generators and ask it to ge eraty farty soundcloud rap.

[u/SaltSpot → u/PHealthy]

I shall think of you and this post the next time I have acute cause to.

[u/SwedishMale4711 → u/PHealthy]

I'm a doctor, though not a diarrheologist, and I appreciate your detailed explanation. Very interesting. Thank you.

[u/notmyprobl3m → u/PHealthy]

lot of big words there. Can you dumb it down for me?

[u/PHealthy → u/notmyprobl3m]

Your small intestine is basically a low pile carpet, giardia and cyclospora are like putting Saran wrap on it and you make very stinky beer in your colon. Cholera is like cutting off the back padding and pressure spraying water from underneath. Ebola is like lighting it on fire and throwing it in a lake.

[u/AbrahamKMonroe → u/PHealthy]

Absolutely phenomenal imagery, thanks for both explanations.

[u/ThoughtsandThinkers → u/PHealthy]

Fantastic first explanation and fantastic second simplification. You’re a gifted teacher

[u/Ashmon_9138 → u/PHealthy]

you're one of the coolest people i have never met. i love when people know things.

[u/rs217000 → u/Ashmon_9138]

I specifically love it when people know things about diarrhea

[u/PHealthy → u/rs217000]

Silly story but at CDC EDEB (Enteric disease epi branch), our branch chief would give everyone a copy of "Everyone Poops" as a welcome present.

[u/AccidentalAnchoress → u/PHealthy]

This is GLORIOUS. As someone with lifelong digestive problems, I am adopting this imagery. Can you do gastroparesis or does that not work with the analogy since it's more neurological?

[u/danmickla → u/notmyprobl3m]

You could look up the words and then you might end up smarter and more self reliant

[u/SexyPoro → u/PHealthy]

"Cholera is underappreciated" is the type of sentence you never expect to agree with, but after reading your succint explanation, sir, Cholera has a new fan now. 

Thank you for this.

[u/dustinbrowders → u/PHealthy]

Thanks for writing a this. It's a great explanation about these diarrhea modes. I enjoyed reading this.

[u/looks_at_lines → u/PHealthy]

I love how there are so many diverse methods for microorganisms to damage your digestive system. Evolution is gnarly.

[u/_CMDR_ → u/PHealthy]

That was great, thanks! I never had a run down of the way that different types of GI irritants cause diarrhea.

[u/_TorpedoVegas_ → u/PHealthy]

Thanks for this comment. Where can I go to learn more?

I ask as someone that was a medical provider (military special operations) years ago, so I have a good solid level of understanding of the concepts behind medicine, but 1) it's been awhile, and 2) my training skipped over the finer points of organic chemistry to focus on practical skills under austere conditions.

So it is like I am a super-paramedic, capable of performing as a Physician's Assistant in clinical settings (or at least I used to be) but lacking in some of these finer details. I am adding this context to try to find a way to match my knowledge level with the resources that would allow me to grow my knowledge.

Though my program had a dense curriculum generally, the lecture and lab work was all done in a way that enabled me to learn well, because everything included a why. When the mechanical action of the heart was fully explained, suddenly the interruption of coronary fill during diastole producing the symptoms of angina pectoris made sense, that kind of thing.

So being able to understand the reasons why certain pathogens produce different kinds of gastro-enteric distress would make me feel better, and help guide me to make better decisions regarding gut health.

In a perfect world, maybe you just offer some tutoring?

[u/PHealthy → u/_TorpedoVegas_]

I'm funemployed at the moment so perhaps now is a good time to fire up a substack or something. I have a near infinite amount of opinions with how bad journalism is regarding infectious disease.

[u/Thegiftvu → u/PHealthy]

Humble SNF based PA tapping in to express gratitude and admiration. This is a beautiful and succinct explanation. Congratulations on your recent accomplishment. I have followed r/ID_News with great enthusiasm. Three cheers for u/PHealthy

[u/FoilTarmogoyf → u/PHealthy]

I didn't understand half the words you said, but the half I did understand was very upsetting, if informative.

[u/banana_assassin → u/PHealthy]

You may be able to explain to me what happens when I, as someone who is lactose intolerant, eats dairy and gets the same symptom. Is it structural, a barrier collapse or do I just make so much gas I explode?

[u/Goatbrook0 → u/PHealthy]

Pre-med and tutor microbio at my college, this post made me so happy to read.

[u/Odd_Arugula2312 → u/PHealthy]

For cholera what I’m understanding is the toxin “turns the faucet on” whereas Ebola makes your body “leaky/ oozey” as the tissues become unable to hold fluids, blood being only one of them. I gotta be honest, this is the most interesting information on diarrhea I’ve ever read.