Diarrhea Isotonic Only! Loss of Acids or bases! - USMLE Forums
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Old 07-06-2010
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GIT Diarrhea Isotonic Only! Loss of Acids or bases!

is ALL diarrhea considered loss of isotonic saline (even osmotic diarrhea? because in kaplan physio he just mentions diarrhea is loss of isotonic fluid)? and is diarrhea a loss of acids(H+) of bases(HCO3-)? thx
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Old 07-06-2010
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I don't think so coz there is even exudative diarrhea.
somebody should put some light on this.
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Old 07-06-2010
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Info There's no rule for diarrhea

Diarrhea is not a single disease entity. There are hundreds of causes of diarrhea. So it's not appropriate to generalize the concept.

Certainly it cannot be isotonic all the time because as you said in osmotic diarrhea the stool is hypertonic (or hyperosmolar). In fact there is something called the osmolar gap which we can get by knowing the difference between the serum osmolality (normally isotonic) and the stool osmolality and if it is increased you think of the presence of non-absorbable sugars in the stool such as the case in malabsorption diarrhea.

As for the acidic and basic content of diarrheal stools, that also differs from cases to case. The intestinal fluid content can be acidic in small bowel diarrhea or basic in large bowel diarrhea but there's no rule for that.

Diarrhea (in physiology) is usually thought of as causing Normal Anion Gap Metabolic Acidosis See This Thread. Which means is it causes loss of bicarbonate and retention of chloride (the other name is hyperchloremic metabolic acidosis). However, that's not a rule also because sometimes you have increased chloride content in the stool and that results in metabolic alkalosis.
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Quote:
Originally Posted by Sabio View Post
Diarrhea is not a single disease entity.....etc
thanks
from which compartment does the mainly loss of fluid happen?
like in cholera it is mainly from the intra cellular fluid becausa of detruction of mucosa of small intestine?
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gr but most questions on osmolarity dont tell you what type of diarrhea it is, so i guess we should assume it is isotonic then, unless otherwise stated?
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Default Secretory diarrhea

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Originally Posted by Kabutar111 View Post
thanks
from which compartment does the mainly loss of fluid happen?
like in cholera it is mainly from the intra cellular fluid becausa of detruction of mucosa of small intestine?
Once again it depends on the type of diarrhea. As you said you have luminal epithelium sloughing and more importantly an enterotoxin that causes increased intestinal secretion (secretory diarrhea).
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Default Look for clues

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Originally Posted by Androide89 View Post
gr but most questions on osmolarity dont tell you what type of diarrhea it is, so i guess we should assume it is isotonic then, unless otherwise stated?
USMLE questions will not usually ask you to assume things, they always give hints, like in this case they always give hints in the history about the kind of diarrhea that patient might be having.
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Acid-Base-, Gastrointestinal-Tract-, Physiology-

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