General Medicine Lecture 3 Diarrhea

Front 1

What causes diarrhea on the molecular level?

Back 1

An increase in osmotic particles in the feces which results in an increase in fecal water content

Front 2

What are the 3 types of diarrhea (i.e. what are the 3 mechanisms)?

Back 2

1) Secretory
-Secretion outpaces absorption
2) Malabsorption/ maldigestion
-Failure of food particles to be assimilated or ions to be absorbed
3) Exudative
-Leakage of blood or protein into gut lumen

Front 3

How much water do horses ingest daily? Cows? Neonates?

Back 3

Horses: 4-6% BW
Cows: 7-10% BW
Neonates: need 10% BW
- Will drink 20-25% BW if unlimited water available

Front 4

*The total daily amount of all fluid entering the gut roughly equals ____________________.

Back 4

The animal's ECF volume

Front 5

How much water that goes into the gut is absorbed before excretion?

Back 5

99%

Front 6

Where does the majority of intestinal secretion occur? What cells are responsible?

Back 6

Upper GI, by cells in crypts of Lieberkuhn's

Front 7

Where does the majority of intestinal absorption occur?

Back 7

Along the villi of the jejunum and ileum (some occurs in colon)

Hint 7

Along

Front 8

What part of the intestine has a 'reserve capacity'?

Back 8

The colon has a reserved capacity to handle extra water, diarrhea occurs when this reserve capacity is overwhelmed or colon is diseased

Front 9

Compare the reserve capacities of horses, small ruminants and cattle and hence the hydration of the feces?

Back 9

Small ruminants (pelletted feces) > horses > cattle (80-85% water)

Front 10

What are the two "cycles" of the intestines?

Back 10

1) Front (secretion) to back (absorption) in whole GI tract
2) Bottom (crypt) to top (villus) of each microscopic intestinal segment

Front 11

True or false. Sheep and goats commonly get diarrhea.

Back 11

False, have a high reserve capacity so the small intestine and stomach has to be messed up OR colon damaged to get diarrhea

Front 12

What electrolyte is used as crypt cells divide to form the mature absorptive cells on the villus?

Back 12

Takes in large amounts of NaCl from the interstitium

Front 13

Why is chloride excreted into the intestinal lumen?

Back 13

After crypt cells take in NaCl during division, the Na is recycled back into the ECF by the Na/K pump and much of the K+ leaks back into the ECF leaving a negative net charge in cell--> Cl- diffuse out of cell into intestinal lumen

Front 14

What promotes the facilitated diffusion of luminal Na into the villus cells?

Back 14

Villus cells pump Na out of their ICF into the interstitium by basolateral Na/K pump, creating low [Na] in the cell so Na diffuses into cell from lumen

Front 15

How is Na+ transported from the intestinal lumen into the villus cells?

Back 15

-Na/Glucose co-transport
-In exchange for H+ or K+ while Cl enters in exchange for HCO3-

Front 16

What happens to the bicarbonate that is released from the intestinal villus cells in exchange for Cl?

Back 16

Recycled by the body by absorption of CO2 from the combination of luminal H+ and HCO3

Front 17

What are the 3 processes that break large food particles down into small particles?

Back 17

1) Mechanical
-teeth, stomach
2) Hydrolytic
-stomach acid
3) Enzymatic
-Starts in mouth w/ amylases
-pepsin, trypsin, lipases- pancreas or intestinal brush border, stomach

Front 18

Adequate digestions requires the presence of necessary enzymes, time for them to act and _____________.

Back 18

Thorough mixing of ingesta

Front 19

What are the 4 major sites of endogenous enzymatic digestion?

Back 19

1) Mouth
2) Stomach
3) Cranial duodenum
4) Small intestinal brush border

Front 20

What is the major site of microbial digestion for ruminants? Horses?

Back 20

Ruminants: Rumen
Horses: colon

Front 21

The most widely known example of secretory diarrhea is caused by what?

Back 21

Cholera and cholera-like toxins, including the heat-labile toxin (LT) of E. coli

Front 22

The cholera and cholera-like toxins (+ heat labile toxin of E. coli) enters the cell and appears to do what 2 things?

Back 22

1) 40% stimulates adenylate cyclase --> increase intracellular cAMP--> phosphorylation of membrane ion channels --> Cl secretion enhanced and Na loss begins to occur across apical membrane
*2) 60% stimulates the enteric nervous system, which in turn stimulates crypt cell division (increasing rate of Cl loss and pushing off the absorptive apical epithelium-the dividing cells take up lots of NaCl) so cells are changed from 20% secretory and 80% absorptive to 50/50

Front 23

True or false. Cholera is a major cause of secretory diarrhea in small animals.

Back 23

False, Cholera doesn't effect the species we deal, but cholera-like toxins do

Front 24

Inflammation can cause ______ intestinal secretion.

Back 24

increased

Front 25

Maldigestion can be the result of poor _______ or _______, or poor ________ or ________.

Back 25

Poor chewing or mixing, or poor digestive enzyme or acid production

Front 26

What are the 3 areas of production that can result in maldigestion when damaged?

Back 26

1) Gastric ulcers
2) Parasitic or microbial damage to gastric pits or villus cells
3) Liver or pancreatic disease

Front 27

What is a major cause of mild maldigestive diarrhea in large animals?

Back 27

Inadequate microbial digestion due to die-offs in the normal population and feed changes
----> large undigested particles draw water into the bowel

Front 28

What are the 2 causes of malabsorption?

Back 28

1) Loss of surface area of the gut
2) Thickening of the gut wall

Front 29

What causes a loss of surface area of the gut resulting in malabsorption?

Back 29

Occurs acutely w/ microbial or toxic damage; with time, blunted villi may form, leading to physiologic, chronic malabsorptive diarrhea

Front 30

What are 4 causes of thickening of the gut, resulting in malabsorptive diarrhea?

Back 30

1) Neoplasia
2) Fibrous reactions
3) Inflammatory cell infiltrates
4) Edema

Front 31

What are the 3 causes of edema (which can result in malabsorptive diarrhea)?

Back 31

1) Vasculitis
2) Hypoproteinemia
3) Passive congestion of blood vessels or lymphatics

Front 32

How do alterations in intestinal motility lead to osmotic diarrhea?

Back 32

By affecting digestion and absorption

Front 33

What are the sequelae to slowed transit or an atonic gut?

Back 33

Slow transit is often accompanied by poor mixing cycles, meaning that food particles are not brough into contact w/ the brush border for digestion or absorption. Also microbial fermentation in an atonic gut leads to production of osmotic particles

Front 34

What are the sequelae to increased gut motility?

Back 34

May decrease the amount of time available for absorption

Front 35

What are the digestive repercussions of ostergia in cattle or haemonchus in sheep?

Back 35

Can damage the acid secreting part of the intestine resulting in maldigestion

Front 36

What is the primary cause of exudative diarrhea?

Back 36

Usually result of inflammatory processes affecting the bowel.

Front 37

What is an example of acute exudative diarrhea? Chronic?

Back 37

Acute: Hemorrhagic gastroenteritis
Chronic: Johne's disease

Front 38

What is the mechanism of action of exudative diarrhea?

Back 38

Loss of mucosal integrity, leading to leakage of protein, plasma or blood into the gut lumen, or an abnormal build-up of pressure and protein in the tissue (as occurs w/ lymphatic obstruction)

Front 39

Blood and protein are poorly digested beyond the _______ and hence act as osmotic particles.

Back 39

Cranial duodenum

Front 40

______ diarrhea are usually more severe than other types, because they reflect a more severe degree of tissue damage.

Back 40

Exudative diarrhea

Front 41

What are 5 disease processes that could cause thickening of the bowel and result in obstruction of lymph passage?

Back 41

1) Neoplasms
2) Tumor
3) Inflammatory bowel disease
4) Non-neoplastic infiltrates
5) Edema

Front 42

True or false. An increase in peristalsis with a decreased intestinal transport time has the potential to decrease time for absorption to take place in the gut, so it causes diarrhea.

Back 42

False, it is unlikely that this alone can lead to diarrhea, but if another mechanism is operative, this can exacerbate fluid and electrolyte loss

Front 43

How does a decrease in peristalsis or mixing motility cause diarrhea?

Back 43

Promotes bacterial overgrowth and fermentation. This can lead to diarrhea through inflammation or the generation of secretagogues or osmotic compounds

Front 44

What is the primary purpose of mixing ingesta in the intestines?

Back 44

Mix stuff w/ enzymes secreted at brush border or mucosa w a larger amount of stuff in lumen and increase contact b/w luminal contents and gut so absorption can happen

Front 45

How is the fecal volume affected by small intestinal disease in small animals? Large intestinal disease?

Back 45

SI: increased
LI: Normal

Front 46

Is mucus present when diarrhea is caused by small intestinal disease in small animals? LI?

Back 46

SI: rare
LI: common
-Mucus is a large intestine lubricant, if irritated it over lubricates

Front 47

How does blood in the stool appear with small intestinal disease in small and large animals? Large intestinal?

Back 47

SI: melena
LI: fresh (hematochezia)

Front 48

How often does tenesmus (straining) occur with small intestinal disease in small and large animals? LI disease?

Back 48

SI: rare
LI: common

Front 49

How often does vomiting/colic occur with small intestinal disease in small and large animals? LI disease?

Back 49

SI: occassional
LI: rare

Front 50

What "type" of diarrhea does salmonellosis cause (secretory, maldigestive/malaborption, exudative)?

Back 50

Causes ulcers in GI tract, knocks out the brush border, affects digestion, but also affects absorption and if bad enough animals bleed or leak protein into GI tract so exudative, and malabsorptive/ maldigestive

Front 51

How often is there fat present in stool in small animals with small intestinal disease? LI disease?

Back 51

SI: Occasional
-normally digested in SI
LI: No

Front 52

How common is undigested food present in the stool with small intestinal disease in small animals? LI disease?

Back 52

SI: Occasional
LI: Rare

Front 53

How common is urgent defacation with SI disease in small animals? LI disease?

Back 53

SI: uncommon
LI: common

Front 54

How common is gas with small intestinal disease in small animals? LI disease?

Back 54

SI: occasional
LI: Rare

Front 55

How common is weight loss in small animals with small intestinal disease? LI disease?

Back 55

SI: common
LI: rare