mechanisms of diarrhea

Question 1

definition of diarrhea

Answer 1

> 200 gms or mls per 24 hour period

patient as to be eating, high fiber diet can easily get over 300, does not factor in consistency or frequency, Water- 1 cup= 230 gms

Malabsorptive diarrhea- inadequate nutrient absorption, associated with steatorrhea, relieved by fasting

Exudative diarrhea- inflammatory disease, purulent/bloody stools, continues with fasting

lots of overlap

One BM every 3 days–> 3 BMs everyday
More than 3 lose/watery stools a day, clear increase

Question 2

Small bowel diarrhea

Answer 2

Functions to absorb most water, nutrients, minerals, sugars, and proteins

Watery diarrhea, large volume and less frequent

Abdominal cramping, bloating, gas and wt loss
Evidence of malabsorption, vitamin or nutrient deficiencies, fever is rare, rare stool WBCs or occult blood

Question 3

large bowel diarrhea

Answer 3

Stoarage and some fluid/electrolyte absorption
Inflamed dysfunctional colon/rectum cannot perform this function

Frequent small, regular stools

Tenesmus (rectal dry heaves), painful BMs, fever, bloody mucoid stools, RBCs and WBCs on stool smear

Question 4

osmotic diarrhea

Answer 4

neither smal intestine nor the colon can maintain an osmotic gradient against serum- (aka the GIT osmolality is always the same as the serum)

Unabsorbed ions that remain in the lumen cause osmotic diarrhea

osmotically active ions act to pull water into the lumen of the bowel to maintain an intraluminal osmolarity of 290 mosm/kg

Ingestion of poorly absorbed ions or sugars or sugar alcohols (mannitol, sorbitol, magnesium, sulfate, and phosphate)

monosaccharides but not disaccharides can be absorbed- disaccharidase deficiency will prevent absorption, lactase deficiency most common

disappears with fasting or cessation of the offending substance, electrolyte absorption is not imapired in osmotic diarrhea, electrolyte concentrations in stool water are usually low

Question 5

secretory diarrhea

Answer 5

many causes- either net secretion of anions (chloride or bicarbonate), or inhibition of net sodium absorption

The most common (cause is infection)
enterotoxins- interact with receptors and modulate intestinal transport, block specific absorptive pathways in addition to stimulating secretion
Inhibit Na+/H+ exchange in both the small and large intestine
Peptides produced by endocrine tumors

Question 6

acute diarrhea causes

Answer 6

infection responsive for most acute diarrhea

food allergies/poisoning/meds/ initial presentation of chronic diarrhea

Question 7

Chronic diarrhea causes

Answer 7

Fatty diarrhea- malabsorption syndromes, mesenteric ischemia, mucosal diseases (celiac disease whipple)
Short bowel syndrome
Small intestinal bacterial overgrowth
Maldigestion (inadequate luminal bile acid concentration, pancreatic exocrine insufficiency)

Inflammatory- chrons and celiac etc

Question 8

diagnosis of diarrheas

Answer 8

history (turtles)
fever- infectious
food history (6 hours- ingestion of toxin, staph or bacilus), at 8-14 houts (c perf), more than 14- viral or bacterial

Colume status, systemic diseases (dermatitis herpetiformis in celiac disease, erythema nodosum or arthritis in IBD

Question 9

stool electrolytes

Answer 9

the bowel cannot maintain an osmotic gradient with the serum
Osmolality of colonic fluid contents is in equilibrium with body fluids (290 mosms)-
osmotic gap= serum osm- est stool osm (290)
almost all of the osmotic activity of stool is accounted for by electrolytes- unlike serum where proteins plan a role, there

Secretory diarrhea- small osmotic gap
Osmotic - osmotic gap is really high

rarely negative