Digestive system question

[Spectar]

Hey everyone I'm having some trouble figuring this question out:

An individual seeks medical attention because he has been experiencing watery diarrhea for several days. This condition is most likely the result of:
A. an overactive stomach.
B. an underactive large intestine
C. an overactive small intestine
D. an underactive small intestine.

This is an EK question- they say the answer is B. because the large intestine's primary purpose is water absorption. The problem I'm having with that explanation is that even though the PRIMARY PURPOSE of the large intestine is water reabsorption, the small intestine still absorbs most of the water - I think the answer should be D. going by which part of the digestive system absorbs the most water. If this type of question were to come up on the MCAT which would be the correct answer?

Thanks

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[MiddleDefense93]

I think the primary role of small intestine is to absorb nutrients from food, and the primary role of large intestine is to absorb water.

 

[Spectar]

I think the primary role of small intestine is to absorb nutrients from food, and the primary role of large intestine is to absorb water.

Yeah definitely I agree for primary roles. But the small intestine ends up absorbing more water in general even though the primary role is different.

 

[the Mannis]

perhaps there would be other problems happening with an underachieve small intestine; thus if a patient is only experiencing water diarrhea, then the large intestine answer makes sense while you would expect there to be other problems caused by an underactive small intestine besides deficient water absorption

 

[yeasureyoubetcha]

Hey everyone I'm having some trouble figuring this question out:

An individual seeks medical attention because he has been experiencing watery diarrhea for several days. This condition is most likely the result of:
A. an overactive stomach.
B. an underactive large intestine
C. an overactive small intestine
D. an underactive small intestine.

This is an EK question- they say the answer is B. because the large intestine's primary purpose is water absorption. The problem I'm having with that explanation is that even though the PRIMARY PURPOSE of the large intestine is water reabsorption, the small intestine still absorbs most of the water - I think the answer should be D. going by which part of the digestive system absorbs the most water. If this type of question were to come up on the MCAT which would be the correct answer?

Thanks

Most of what the LI does is water reabsorbption, however, thats pretty much all thats left in the GI by the time contents get there. Water is reabsorbed everywhere. Therefore, the SI absorbs far more fluid than the LI. I would suspect some sort of infection causing the secretory diarrhea. Secretory diarrhea is due to poor absorbtion in the small intestine. This causes fluid to be osmotically drawn out into the SI lumen. Its a poor question though

 

[Medical Muse]

The way the question is written, choices B, C, or D, could be correct. If it was a small volume of diarrhea, then it could be the large intestine that is responsible. If it was a large volume of diarrhea, then it could be either an overactive or underactive small intestine issue depending on the cause of the diarrhea. For example, cholera activates secretory systems, which would be considered an overactive small intestine. Cryptosporidium, on the other hand, interferes with small intestine absorption, which would be considered an underactive small intestine. Without a few more details in the question, you can't know for sure.

SpectreDoc, you hit on a very important point, that while the large intestine has a primary role of water absorption, the small intestine does the vast majority of water absorption. Similarly, the loop of Henle is known for solute and water reabsorption in the kidney, but the vast majority occurs in the proximal tubule.

My guess is the question was written to ask about which organ has a "primary" role in water absorption. You won't see a question that vague on the actual MCAT.

 

[Terry Toma]

I think it just comes down to the volume of diarrhea. If it's a massive amount, it has to be a small intestine issue. If they don't specifically tell you that it is a huge amount, it could be a large intestine issue.

But yeah, as mentioned, probably nothing this vague on the real test. Sounds like you understand the concept.