Diarrhea

Question 1

what are the 5 descriptors of diarrhea?

Answer 1

1. duration (acute is less than 14 days, chronic is 14 days or longer)
2. frequency
3. volume
4. appearance
5. associated weight loss

Question 2

describe the frequency, volume, urgency, and associated weight loss with small bowel diarrhea

Answer 2

frequency: normal to mildly increased
volume: normal to increased
urgency: absent
weight loss: common

Question 3

describe the frequency, volume, urgency, and associated weight loss with small bowel diarrhea

Answer 3

frequency: markedly increased
volume: normal to increased
urgency: often present
weight loss: uncommon

Question 4

what else may diarrhea be accompanied by? (11)

Answer 4

1. abdominal distension or pain
2. borborygmus
3. dehydration
4. flatulence
5. halitosis
6. melena
7. hematochezia
8. P/U P/D
9. tenesmus
10. vomiting
11. weight loss

Question 5

what are the 4 main pathophysiological mechanisms of diarrhea?

Answer 5

1. osmotic
2. secretory
3. increased mucosal permeability/inflammation
4. deranged motility

diarrhea can result as a combination of these mechanisms!

Question 6

describe osmotic diarrhea (5)

Answer 6

1. due to large amounts of poorly absorbable osmotically active solutes in the intestinal lumen
2. occurs with malabsorptive disorders, where maldigested/malabsorbed nutrients remain within the intestinal and osmotically attract water, altering intestinal microflora and carbohydrate fermentation, which further increases the number of osmotically active particles
3. a differential diagnosis is exocrine pancreatic insufficiency (EPI)
4. electrolyte absorption is unaffected, so fecal water contains very little unabsorbed sodium or potassium
5. a hallmark of this cause is the resolution of diarrhea when the patient stops ingesting the poorly absorbable solute or the EPI is resolved

Question 7

describe secretory diarrhea (5)

Answer 7

1. due to abnormal ion transport in intestinal epithelial cells
2. abnormal mediators resulting in changes in cAMP, cGMP, calcium, and/or protein kinases lead to decrease in neutral NaCl absorption OR increase in Cl- secretion
3. mediators include: endogenous enteric hormones or neuropeptides, inflammatory cell products, bacterial enterotoxins, laxatives, fatty acids, and bile acids
4. key features: small osmotic gap and diarrhea persists despite fasting because the diarrhea is caused by abnormalities that have nothing to do with diet
5. differential diagnoses include: enteropathogenic E. coli, inflammatory bowel disease

Question 8

describe diarrhea due to increased mucosal permeability/inflammation (2)

Answer 8

1. causes loss of fluids, electrolytes, proteins, and RBCs into intestinal lumen
2. differential diagnoses include” erosive or ulcerative enteropathies, inflammatory bowel disease, or neoplasia

Question 9

describe diarrhea due to deranged motility (3)

Answer 9

1. abnormal ileal and colonic motility patterns may contribute to clinical signs of IBD
2. platelet-activating factor (synth and released from several immune cells) may stimulate giant migrating contractions (GMCs)
3. 2 major motor abnormalities include: suppression of phasic contractions like the MMC, and stimulation of GMCs, both of which lead to ultrarapid transit of secretions and undigested food into the colon, increasing the osmotic load and resulting in diarrhea

Question 10

describe protein losing enteropathy

Answer 10

a syndrome characterized by abnormal loss of serum and proteins into the GI lumen

Question 11

what are the 3 broad mechanisms of plasma protein loss through the GI tract?

Answer 11

1. physical or functional lymphatic obstruction: plugs the pipes and leads to backleak out of lymphatics into gut, often congenital, so rareish
2. release of cellular mediators that alter vascular permeability, leading to fluid egress into tissues
3. mucosal inflammation (erosive.ulcerative or nonerosive): leaky gut! most common

Question 12

how is a diagnosis of PLE most commonly made? in what 4 breeds is PLE more common?

Answer 12

detecting panhypoproteinemia (especially albumin); more common in german shepherds, yorkies, rottweilers, and border collies

Question 13

describe albumin (4)

Answer 13

1. main protein maintaining oncotic pressure; transports hormones, fatty acids, and ions (CALCIUM)
2. synthesized in the liver and is a negative acute phase protein
3. in health, there are enteric losses due to sloughing of enterocytes and normal secretions
4. in PLE, protein wasting can reduce protein pool by up to 60% and hepatic synthesis cannot keep up so serum/plasma albumin can drop below 2mg/dL

Question 14

describe globulins (3)

Answer 14

1. all non-albumin proteins, most are synthesized in the liver but gamma are synth by plasma cells and lymphocytes
2. positive acute phase proteins
3. differential diagnosis for globulin decrease includes PLE, exudative dermatopathies (burns), and hemorrhage

Question 15

describe cholesterol (3)

Answer 15

1. most common steroid in the body, derived from dietary sources, part of all lipoproteins
2. bile is main route of excretion
3. differential diagnoses for low cholesterol include: decreased absorption (malabsorptive and maldigestive diseases like PLE and EPI), decreased production, and altered metabolism

Question 16

describe calcium (4)

Answer 16

1. only 1% of calcium is found in serum/plasma and of that, over half is free ionized calcium, 35-45% is protein bound to albumin, and 5-10% is complexed with anions
2. important for muscle and nerve function
3. main organs for calcium homeostasis are intestines (ileum, absorption), and kidneys (excretion/reabsorption)
4. differential diagnoses for total hypocalcemia include: decreased protein binding, abnormal PTH, decreased absorption of calcium, loss of calcium, or toxicosis