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Cards In This Set
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What is the normal water content of stool?
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60-85%
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What is the water content of stool in diarrhea?
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>85%
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What are the 2 mechanisms of pathophysiology of diarrhea?
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1. Abnormal motor function2. Abnormal fluid and electrolyte transport (increased secretion/decreased absorption)
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GIve 3 examples of abnormal motor function that causes diarrhea
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1. Hexoaminidase B deficiency (Sandhoff disease)2. IBS3. Anorectal disease
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Most water is absorbed in the small intestine/large intestine.
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Small intestine, even though the only job of the large intestine is to absorb water.
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Low volume diarrhea is usually a problem of the ________
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Large intestine (colon)
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High volume diarrhea is usually a problem of the ________
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Small intestine(b/c the SI absorbs the most water, so if it's not functioning correctly, the diarrhea will be very large volume)
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What are the relative concentrations of Na, K, HCO3-, and Cl in the stool?
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Na and Cl are relatively low in the stoolK and HCO3- are relatively high in the stool
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What does the concentration of electrolytes in the stool indicate for diarrhea?
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If there is diarrhea, can end up with hypokalemia (low K+ in the blood) if there's increased secretion/decreased absorption of K+ since there is norm a lot of K+ in the stool anyway, and can also end up with metabolic acidosis b/c of the loss of HCO3- since there is norm a lot of HCO3- in the stool anyway
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How can decreased absorption occur and lead to diarrhea?
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If something is wrong with the small bowel in which it absorbs less than 50% of what it usually does, the amount of fluid entering the colon will overwhelm the colon's absorptive capability, and we get diarrhea.
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How can increased secretion occur and lead to diarrhea?
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Neurotransmitters, hormones, bacterial endotoxins, inflammatory mediators, cathartics can all cause increased secretion. Increased secretion of Cl- and water occur through changes in cAMP, cGMP, and ionized Ca2+. Mediators work by direct enterocyte stimulation and indirectly via enteric nervous system.
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T/F. Stool osmolality will always be lower than plasma osmolality.
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FALSE! It will always be equal to plasma osmolality, without exception. The only way that it will be different than plasma osmolality would be if it had been artifactually altered. The whole goal of the gut is to make the osmolality of the stool equal to the osmolality of the plasma.
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In normal intestinal physiology, what is re-absorbed and what does the re-absorbing?
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Colonocytes re-absorb Na+ and water
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Normally, stool pH is ________ because ______
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5-7, because stool is bicarbonate rich.
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If stool pH is acidic, what does this indicate?
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Carbohydrate malabsorption, because bacteria in the gut break down non-absorbable carbohydrates into short-chain fatty acids, which are acidic and are excreted to make the pH of the stool < 4.
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