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