L31: Diarrhea

Question 1

what is osmotic D+

Answer 1

excess amounts of poorly absorbable, low MW substances that remain in the intestinal lumen = excessive amounts of osmotically active solutes are retained in the intestinal lumen

Question 2

what things can cause osmotic D+

Answer 2

ingestion of poorly absorbable substrates; excessive amounts of salt/laxatives/cathartics; sugar alcohol; Na salts; hydrophilic colloids

Question 3

both malabsorption & maldigestion lead to water retention in the ?

Answer 3

intestinal lumen

Question 4

inadequate production of digestive enzymes by pancreatic acinar cells

Answer 4

exocrine pancreatic insufficiency

Question 5

what could cause exocrine pancreatic insufficiency

Answer 5

immune mediated pancreatic acinar atrophy or secondary to chronic pancreatitis

Question 6

lactase deficiency in the brush border that occurs when lactase activity falls to ~10% of its peak activity

Answer 6

lactose intolerance
D+ occurs then when more lactose is consumed than what the animal can digest

Question 7

what occurs in lymphangiectasia (lymphatic obstruction) in dogs

Answer 7

• engorged lymphatics have a narrow rim of small lymphocytes and expand the villi
• absorption of all nutrients is compromised
• increased venous/lymphatic pressure due to malformation of lymphatic drainage

Question 8

symptoms of lymphangiectasia (lymphatic obstruction)

Answer 8

• malabsorption of lipids and loss of plasma protein into lumen
• dilated/ruptured lacteals compress surrounding blood vessels
• chronic D+, wasting, hypoproteinemia, lymphopenia, hypocalcemia, hypocholesterolemia
• peripheral edema, ascites, hydrothorax

Question 9

excessive/uncontrolled ion transport causes this kind of D+

Answer 9

secretory

Question 10

what mediators stimulate Cl- secretion via CFTR

Answer 10

• bacterial toxins (cholera, E.coli)
• fatty acids
• bile acids

Question 11

how does cholera cause D+

Answer 11

cholera toxin activates Gproteins which activate adenylyl cyclase which activates cAMP; elevated cAMP levels open CFTR channel; water and Na follow paracellularly

Question 12

what type of D+ is unaffected by fasting, why?

Answer 12

secretory b/c the CFTR is activated by toxins/agents even without digesta present

Question 13

how is it that nutrient absorption in the SI stays relatively normal during secretory D+

Answer 13

b/c Na-dependent nutrient absorption (SGLT-1) occurs in SI

Question 14

occurs when pancreatic acinar cells are slactingggg

Answer 14

exocrine pancreatic insufficiency (not enough digestive enzymes being made)