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GI > Approach to Diarrhea > Flashcards

Approach to Diarrhea Flashcards

1
Q

What is the normal stool pattern in the US? What is the main composition of stool?

A

3 BM/day to 3 BM/week is normal

Mostly made of water

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2
Q

What is the definition of diarrhea?

A

Increase in stool weight greater than 200 gms/24 hrs

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3
Q

What is the main purpose of the small intestine? What cells are specially designed for these tasks?

A

Villus cells: Specialized for absorption

Crypt cells: Sepcialized for secretion

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4
Q

What is the main purpose of the large intestine?

A

Mostly absorption of fluid and electrolytes

–No villous architecture

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5
Q

How much water is absorbed where in the bowels?

A

9L of fluid enters the bowel

  • ->90% is absorbed in the small intestine
  • ->90% of the remaining water is absorbed by the colon
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6
Q

Through what pathway is most of the water resorbed?

A

Paracellularly

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7
Q

What are the two key carriers and pumps in the GI tract?

A

SGLT1

Na/K ATPase

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8
Q

What is the purpose of the Na/K ATPase?

A

The Na/K ATPase is the key driver for absorption! Found on the basolateral membrane, it
Creates the gradient necessary for fueling a lot of the transmembrane carrier proteins (like SGLT1)

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9
Q

What drug is the Na/K ATPase sensitive to?

A

Digitalis

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10
Q

What is the role of the SGLT-1 carrier protein?

A

On the apical surface. It uses the gradient created and moves sodium and glucose together through the lumen and into the cell.

Mostly found in the villous areas

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11
Q

What are the predominant transport proteins in the crypts??

A

Na/K-2CL transporter on the basolateral membrane moves those ions INTO the cell.

  • Cl channel allows chloride to enter the lumen
  • Na+ follows the balance the negative charge
  • This keeps the stool moist
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12
Q

What happens in CFTR mutation?

A

The chloride channel in the apical channel is mutated, preventing movement of Cl- and thus Na+
–>constipation

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13
Q

What is the main intracellular signaling molecule regulating all of this?

A

cyclic AMP

  • ->Increase
  • ->more secretion
  • ->decreased absorption
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14
Q

What factors can activate cAMP formation intracellularly?

A 
NE
Somatostain
VIP
Prostaglandins
Also, bacterial toxins
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15
Q

What are the four broad mechanisms of diarrhea?

A
  1. Osmotic
  2. Secretory
  3. Inflammatory
  4. Dysmotility
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16
Q

What are some key clinical hallmarks that would make you think of osmotic diarrhea?

A
  1. Ceases with fasting
  2. Increase in stool osmotic gap (>100)
    - -(290-2*(Na+K))
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17
Q

What could cause osmotic diarrhea?

A

Sorbitol/lactulose
Milk of magnesia
Lactose intolerant people
Malabsorption of fat (steatorrhea)

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18
Q

What is the pathophysiology behind secretory diarrhea?

A

Hormone or toxin commandeers the normal mechanism of secretion by increasing intracellular cAMP
Ex: Vibrio cholera, gastrinomas, VIpomas, some laxatives

19
Q

How do you treat cholera? Why?

A 
Gatorade ORT (glucose + salt + water)
-->Because the Na/Glucose cotransporter (SGLT1) is NOT controlled by cAMP!
20
Q

What are the clinical hallmarks of secretory diarrhea?

A
  1. Fasting has no effect

2. No change in stool osmotic gap

21
Q

What is lubiprostone?

A

A drug that activates chloride channels on the apical membrane, good for chronic constipation

22
Q

What is the mechanism behind inflammatory diarrhea?

A

Mucosal ulceration and inflammation–>exudation of blood, lymph, mucus into the bowel lumen
–Epithelial cells destroyed

23
Q

What is an example of noninfectious inflammatory diarrhea?

A

Crohn’s disease

24
Q

What are the clniical hallmarks of inflammatory diarrhea?

A
  1. Bloody, mucoid stool
  2. Fever
  3. fecal leukocytes
25
Q

What can infectious agents can cause inflammatory diarrhea?

A

EHEC (O157:H7)
C Difficile
Shigella, Campylobacter, salmonella, yersenia

26
Q

What is the mechanism behind dysmotility type diarrhea?

A

Abnormal intestinal transit time=diarrhea

27
Q

What is the archetypal scenario with dysmotility diarrhea?

A

Post surgical

  • -Pyloroplasty, causing dumping syndrome
  • -Vagotomy
28
Q

What is dumping syndrome?

A

Large volumes of fluid and nutrients rapidly enter the duodenum

  • -fluid shifts, stim of intestinal motility and decreased transit time
  • -hypertonic chyme=osmotic diarrhea
  • -Rapid bowel distention=secretory diarrhea
29
Q

Which chronic disease are associated with dysmotility diarrhea?

A

scleroderma and diabetes

30
Q

At what point do you differentiate between chronic versus acute diarrhea?

A

over and under 3 weeks

31
Q

What is the most common cause of acute diarrhea?

A

INFECTIOUS!! Mostly norovirus

32
Q

What would make you think acute diarrhea was something BESIDES norovirus?

A

The fact that they came to the doctor!

  • Travel history/camping (ETEC, salmonella, shigella, giardia)
  • Recent hospitalization (C Diff)
  • Immunodeficiency (cryptosporidium)
33
Q

IS norovirus an inflammatory or noninflammatory diarrhea?

A

NONinflammatory

34
Q

What is the difference between inflammatory and noninflammatory diarrhea in terms of clinical presentation?

A
  • -Inflammatory is bloody, mucoid, and small volume. pt is toxic and febrile
  • -Noninflammatory diarrhea is mostly water, large volume
35
Q

Examples of common causes of inflammatory diarrhea?

A

Shigella, Salmonella, Campylobacter, All EColi except ETEC

36
Q

Examples of common causes of noninflammatory diarrhea?

A 
Norovirus
Cholera
Giardia
EteC
Staph
37
Q

How do you evaluate acute diarrhea?

A

Mostly by checking hydration status. and severe abdominal pain (think toxic megacolon 2ndary to infection)

38
Q

What are some diagnostic tests to consider in acute diarrhea?

A
  1. Fecal leukocytes+culture: If positive, bacteria or IBD. If negative, think viral
  2. Toxin or antigen detection
  3. KBD for toxic megacolon
  4. Endoscopy for pseudomembranes
39
Q

What should you eat if you have diarrhea?

A

Increase intake of salt, potassium, and carbs

Don’t eat milk products or things that increase intestinal motility

40
Q

When should you not give antidiarrheal agents?

A

If inflammatory diarrhea, will worsen situation!

41
Q

What are causes of chronic diarrhea?

A
  1. IBS
  2. Medications (digoxin, magnesium antacids, sweeteners like sorbitol or fructose)
  3. Too much caffeine! Fiber?
42
Q

What is the single most valuable test in the case of chronic diarrhea?

A

48 hr stool collection
If low volume, IBS
r/o laxatives
Calculate osmotic gap

43
Q

What do you want to make sure you do in a physical exam on someone with chronic diarrhea?

A
  1. Weigh the pt
  2. Skin exam
  3. Anorectal exam
44
Q

What other diseases do you want to consider in chronic diarrhea? How do you diagnose them?

A
  1. Celiac’s disease (serum tissue transglutaminase and biopsy)
  2. Microscopic colitis (colon biopsy, shows up in middle aged peeps)

GI (27 decks)

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