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Old 09-29-2012
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Arrow Gyrus Daily Questions; Internal Medicine #39

A 54-year-old male presents with 1 month of diar-rhea. He states that he has 8 to 10 loose bowel movements a day. He has lost 8 lb during this time. Vital signs and physical examination are normal. Serum laboratory stud-ies are normal. A 24-h stool collection reveals 500 g of stool with a measured stool osmolality of 200 mosmol/L and a calculated stool osmolality of 210 mosmol/L. Based on these findings, what is the most likely cause of this pa-tient’s diarrhea?

A. Celiac sprue
B. Chronic pancreatitis
C. Lactase deficiency
D. Vasoactive intestinal peptide tumor
E. Whipple’s disease
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Old 09-29-2012
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fecal osmotic gap is 10<50 so it s about a
secretory diarrhea . I m with d as the other answers refer to osmotic diarrhea.


+ substantial weight loss
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D. Vasoactive intestinal peptide tumor

Quote:
Stool osmolal gap (or stool osmotic gap) is a calculation performed to distinguish among different causes of diarrhea.
A low stool osmolal gap can imply secretory diarrhea, while a high gap can imply osmotic diarrhea.[1]
It is calculated with the equation 290 − 2 * (stool Na + stool K).[2] The 290 is the value of the stool osmolality. The stool osmolality is usually not directly measured, and is often given a constant in the range of 290 to 300.[3]
A normal gap is less than 50.[4]
High osmolal gap causes of osmotic diarrhea include celiac sprue, chronic pancreatitis, lactase deficiency, and Whipple's disease.
Low osmolol gap causes of secretory diarrhea include toxin-mediated causes (cholera, enterotoxigenic strains of E. coli) and secretagogues such as vasoactive intestinal peptide (from a VIPoma, for example). Uncommon causes include gastrinoma, medullary thyroid carcinoma (which produces excess calcitonin), and villous adenoma.
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The answer is D.


This patient has a stool osmolality gap (measured stool osmolality – calculated stool osmolality) of <50 mosmol/L, suggesting a secretory rather
than an osmotic cause for diarrhea.

Secretory causes of diarrhea include
toxin-mediated diarrhea (cholera, enterotoxigenic Escherichia coli) and intestinal peptide–mediated diarrhea in which the major pathophysiology is a luminal or circulating secretagogue.

The distinction between secretory diarrhea and osmotic diarrhea aids in forming a differential diagnosis.

Secretory diarrhea will not decrease substantially during a fast and has a
low osmolality gap.

Osmotic diarrhea will generally decrease during a fast and has a high (>50 mosmol/L) osmolality gap.
Celiac sprue, chronic pancreatitis, lactase deficiency, and Whipple’s disease all cause an osmotic diarrhea.
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Old 09-29-2012
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The answer is D.


This patient has a stool osmolality gap (measured stool osmolality – calculated stool osmolality) of <50 mosmol/L, suggesting a secretory rather
than an osmotic cause for diarrhea.

Secretory causes of diarrhea include
toxin-mediated diarrhea (cholera, enterotoxigenic Escherichia coli) and intestinal peptide–mediated diarrhea in which the major pathophysiology is a luminal or circulating secretagogue.

The distinction between secretory diarrhea and osmotic diarrhea aids in forming a differential diagnosis.

Secretory diarrhea will not decrease substantially during a fast and has a
low osmolality gap.

Osmotic diarrhea will generally decrease during a fast and has a high (>50 mosmol/L) osmolality gap.
Celiac sprue, chronic pancreatitis, lactase deficiency, and Whipple’s disease all cause an osmotic diarrhea.

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