Pathophys of Diarrhea

Question 1

Where in the villi does
1. Absorption
2. Secretion
occur?

Answer 1

1. Near the tip

2. Crypts

Question 2

4 mechanisms of diarrhea

Answer 2

Osmotic/malabsorptive
Secretory/disordered electrolyte transport
Altered intestinal transit
Inflammatory

Question 3

Osmotic/malabsorptive diarrhea

Answer 3

Caused by poorly/non absorbed solutes/anions/cations/sugars
Colon and small intestine cannot maintain an osmotic gradient
Increased osmolality in the lumen leads to obligate retention of water
Diarrhea disappears with fasting or ceasing consumption of the offending agent

Question 4

Secretory/disordered electrolyte transport diarrhea

Answer 4

Increased secretion of anions and/or inhibition of Na absorption
Stimuli can be from the lumen, subendothelial space, or systemic circulation
May also be due to congenital absence of transport molecules
Diarrhea contines in fasting state

Question 5

Altered intestinal transit diarrhea

Answer 5

Rapid intestinal transit causes diarrhea with secretory and osmotic components
Slow intestinal transit may lead to small bowel bacterial overgrowth (can lead to deconjugation of bile acids causing fat malabsorption and secretory diarrhea)

Question 6

Inflammatory diarrhea

Answer 6

Exudative and protein losses
Also get osmotic diarrhea secondary to loss of absorptive surface
And secretory diarrhea secondary to inflammatory mediators
Damage may be direct or immunologic

Question 7

Fecal calprotectin

Answer 7

Neutrophil cytosolic protein, released during degranulation
Highly resistant to degradation
Correlates with inflammation
Not specific for IBD, but useful for monitoring disease activity

Question 8

How to replace fluids in severe diarrhea

Answer 8

IV Ringer’s lactate or normal saline with additional K and NaHCO3 as required

Question 9

Crohn’s disease

Answer 9

IBD that may affect any part of the GI tract
Inflammation penetrates the lining of the GI tract and often causes ulcers to form
Transmural
Skip lesions (spots)
Can result in stenoses/fistulas
Smoking is bad for it
Extra GI manifestations

Question 10

Ulcerative colitis

Answer 10

IBD exclusively located at the large intestine always affecting the rectum and some or all of the colon in continuity
Never affects the small intestine nor the anus
Mucosal
Continuous
No stenoses
Smoking helps
Extra GI manifestations