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76 Cards in this Set

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Define diarrhea.
Abnormal frequency and liquidity of fecal discharges.
What are 5 consequences of diarrhea?
Dehydration
Electrolyte imbalance
Hypoglycemia
Acidosis
Impaired growth or death of animal
What ions are lost in diarrhea?
Na+
Cl-
HCO3-
What ions are retained in diarrhea?
H+
K+
What are 3 reasons for acidosis with diarrhea?
Decreased HCO3- absorption from gut
Decreased H+ excretion from kidneys
Anaerobic glycolysis leading to ketoacidosis
What causes extracellular hyperkalemia with diarrhea?
Acidosis causes intracellular K+ to be exchanged for extracellular H+
What species typically does not exhibit hyperkalemia with severe diarrhea?
Horse
What is the major site of digestion and absorption in carnivores?
Small intestine
What is the major site of digestion and absorption in the horse and pig?
Large intestine
Where do digestion and absorption take place in ruminants?
Digestion primarily in rumen
Absorption in small intestine
Luminal digestion in carnivores is carried out by enzymes from what locations?
Saliva, pancreas, liver, gut mucosa
Brush border enzymes
About how many liters of fluid will a calf normally secrete into the gut lumen per hour?
6 liters per hour (large volume)
Where do the progenitor cells for the villi enterocytes originate from?
Crypts
What is the functional role of the crypt cells?
Secretion
What do the crypt cells actively secrete?
Cl- and HCO3-
(Na+ and H2O passively follow)
What is the functional role of the villi enterocytes?
Absorption
What do the villous enterocytes absorb?
Electrolytes, water, nutrients
What are 4 potential mechanisms of small bowel diarrhea?
Malabsorption
Hypersecretion
Increased mucosal permeability
Hypermotility
Which mechanism of small bowel diarrhea is of questionable plausibility?
Hypermotility
True or false: most diseases one mechanism or another of causing diarrhea, but rarely in combination.
False – most diseases utilize more than one mechanism of causing diarrhea.
What are 2 general ways of causing malabsorption diarrhea?
Destruction of enterocytes
Interference with enterocyte function
Which agents selectively kill crypt enterocytes?
Parvovirus
BVDV
Irradiation
Radio-mimetic cytotoxic drugs
Which agents selectively kill villous enterocytes?
Rotaviruses
Coronaviruses (TGE)
Coccidia
E. coli (some strains)
Gluten-sensitive enteropathy (hypersensitivity)
What is the response of villi that have lost enterocytes?
Villous contraction/ atrophy
Crypt cells move out to cover remaining surface area
What agents interfere with enterocyte function or cause effacement of enterocytes?
EPEC (enteropathogenic E. coli)
Cryptosporidia
Giardia
Congenital lactase deficiency
Why are the effects of malabsorption and maldigestion frequently exacerbated in young mammals?
Lactose in milk is not absorbed and passes undigested into the colon where it is fermented and osmotically pulls fluid into the bowel lumen.
What is the difference between a secretagogue toxin and a cytotoxin?
Secretagogue toxins cause the crypt enterocytes to secrete massive amounts of electrolytes and water.
Cytotoxins induce tissue injury and induce an inflammation-induced hypersecretion.
What organisms produce secretagogue toxins?
ETEC (enterotoxigenic E. coli)
Vibrio cholera
Rotavirus (possibly)
Secretagogue toxins bind to receptors on the cell and cause increased levels of intracellular ______ which activates adenylyl cyclase. This brings about an elevation of ________, which increases Cl- and bicarbonate secretion.
Calcium
cAMP
Which organisms secrete cytotoxins?
EHEC (enterohemorrhagic E. coli)
Salmonella (some species)
Shigella
Clostridium difficile
Inflammatory hypersecretion is dependent on activation of______________ (cell type) and mediators derived from ________________.
Neutrophils
Arachidonic acid
How can prostaglandins influence the gut?
Cytoprotective
Alter local blood flow
Affect tone of intestinal musculature
Stimulate enteric nerves
What prostaglandin directly stimulates enterocytes to secrete fluid and electrolytes?
PGE2
What prostaglandin stimulates neural reflexes to promote intestinal secretion?
PGI2 (prostacyclin)
ACUTE exudation from increased mucosal permeability is a relatively unimportant mechanism of diarrhea, with the possible exception of ______________ enteritis.
Clostridial
CHRONIC enteric protein loss can be important. Name 4 conditions you might see this with.
Chronic enteritis
Intestinal neoplasia
Ulcers
Lymphangiectasia
How will a protein-losing enteropathy cause diarrhea?
Increased relative osmolality of intestinal contents pulls fluid into the intestinal lumen.
What are 2 distinct mechanisms that account for the loss of plasma proteins into the bowel?
Direct secretion of proteins by enterocytes
Passive diffusion of proteins between enterocytes
Name 4 general but distinct types of protein losing enteropathies.
Infiltrative bowel disease
Bowel edema
Intestinal lymphangiectasia
Chronic blood loss with severe ulceration
Name an infiltrative bowel disease in the cow.
Johne’s disease
Name an infiltrative bowel disease in the horse.
Equine granulomatous enteritis
Name an infiltrative bowel disease in the dog.
Lymphoplasmacytic enteritis
Some protozoal/ fungal infections also
What neoplasm diffusely infiltrates the bowel?
Predominantly lymphosarcoma
What are 2 causes of chronic bowel edema?
Portal hypertension and hypoproteinemia
What is intestinal lymphangiectasia?
Obstruction of intestinal lymphatics leading to a backup of lymph drainage in bowels
Congenital lymphangiectasia is well-recognized in _________.
Dogs
Acquired lymphangiectasia occurs in association with what other diseases?
Chronic lymphadenitis (i.e. in Johne’s disease in cattle)
Secondary to lymphosarcoma (or other metastatic tumors) in dogs
Granulomatous lymphadenitis
Large bowel diarrhea refers to disease or dysfunction of the __________ or __________.
Cecum
Colon
The large bowel has a considerable absorptive function in _____________, but only the proximal portion of the colon contributes to resorption in ________________.
Herbivores
Carnivores
If the colon surface epithelium is denuded and the crypt cells left intact, in what time frame will the attenuated cells line and cover the remaining surface?
Within minutes
What is the main difference between the small intestine and the colon architecture?
There are no villi in the colon
What agents may destroy colonic enterocytes?
Bile salts and fatty acids
Invasive bacteria (Salmonella, Clostridium difficile, Treponema), certain viruses
Drugs and toxins - NSAIDs
Parasites
What are 4 specific causes of large bowel hypersecretion?
Bile salts
Fatty acids
Bacterial endotoxins
Inflammation
Where are bile salts absorbed primarily?
Ileum
High doses of bile salts cause __________ of luminal enterocytes.
Necrosis
What do low doses of bile salts cause to colonic luminal enterocytes?
Hypersecretion, but not by COX metabolites
Will COX inhibitors enhance or decrease bile salt mediated injury to colonic mucosa?
They will enhance damage. Prostaglandins have a protective effect on the colonic mucosa.
Name three conditions that may cause steatorrhea.
Exocrine pancreatic deficiency
Deficiency of bile
Excessive gastric acidity
Do secretagogues or cytotoxins cause colonic hypersecretion?
Both do
In what species are secretagogues more important in the large bowel than in the small bowel?
Horse
In addition to important agents of inflammatory hypersecretion in the colon such as C. difficile and Salmonella, _______________ has also been recognized as an important cause of colitis and diarrhea in cats and dogs.
Tritrichomonas foetus
Which bacteria are most commonly associated with acute fibrinous colitis in the horse?
Clostridium difficile
Salmonella
Which bacteria are most commonly associated with acute fibrinous colitis in the pig?
Brachyspira hyodysenteriae
True or false: Other mechanisms such as hypersecretion are usually more responsible for diarrhea than acute exudation of proteins.
True
Name 2 important infiltrative large bowel diseases that may cause chronic protein loss.
Granulomatous colitis
Diffuse lymphoma
Name 2 chronic gastric disorders that can impair gastric acid production.
Chronic gastritis
Mucosal atrophy (atrophic gastritis)
Define achlorhydria.
An abnormal deficiency or absence of HCl in the gastric juice
What are 2 ways decreased gastric acid production leads to maldigestion/malabsorption?
Gastric enzymes not being activated
Increase in pH allows bacterial overgrowth, which compete for nutrients and destroy brush border
Name 2 general causes of protein losing gastropathy.
Chronic gastritis
Mucosal hypertrophy
What are 2 endocrine disorders that will cause increased gastric acid secretion?
Hypergastrinemia (i.e. from gastrinoma)
Excessive histamine from mast cell tumor
What are 3 ways increased gastric acid production will cause maldigestion/ malabsorption?
Precipitation of bile salts
Denaturation of pancreatic enzymes
Injury to mucosa
What is hypertrophic gastropathy in ruminants caused by?
Ostertagiasis
Which of the following is NOT characteristic of hypertrophic gastropathy in ruminants:
a. Chronic gastritis
b. Mucosal hypertrophy
c. Hypergastrinemia
d. Achlorhydria
e. Ascites
E – ascites; Ruminants get dependent edema and “bottle jaw”
What are the gross lesions you might see with ostertagiasis?
Abomasal edema, coalescent nodules in abomasum, mucosal hyperplasia, “Moroccan leather” appearance
What are 2 causes of exocrine pancreatic insufficiency?
Congenital exocrine pancreatic hypoplasia/ juvenile atrophy
End-stage pancreatitis
What is the mechanism of diarrhea in exocrine pancreas insufficiency?
Malabsorption/ maldigestion
Bacterial overgrowth to some degree