B5.020 Evaluating the Patient with Diarrhea

Question 1

diarrhea definitions

Answer 1

frequency: >3 times/day
weight: >200 g/day
duration: acute < 2 weeks
chronic >4 weeks
osmotic gap: outside of normal 50-100 mmol/kg range

Question 2

osmotic gap calculation

Answer 2

osmotic gap = 290-2(Na+K)

Question 3

characteristics of acute diarrhea

Answer 3

most are infectious, and self limited
some drug related (primarily antibiotics)
most do not present to medical care

Question 4

categories of chronic diarrhea

Answer 4

fatty, inflammatory, watery (osmotic or secretory)

Question 5

important components in history of a patient with diarrhea

Answer 5

onset
pattern
duration
epidemiology
stool characteristics
other symptoms
aggravating/mitigating factors
iatrogenic/factitious considerations
systemic diseases

Question 6

systemic diseases associated with diarrhea

Answer 6

hyperthyroidism
DM
collagen vascular diseases
tumor syndromes
AIDS
Ig deficiency

Question 7

physical exam components important in a patient with diarrhea

Answer 7

general
fluid balance
nutrition
skin
thyroid*
chest*
heart*
abdomen*
anorectal
extremities
* = carcinoid?

Question 8

routine lab tests for chronic diarrhea

Answer 8

CBC

chem screen

Question 9

stool analysis components for chronic diarrhea

Answer 9

weight
electrolytes (osmotic gap)
pH
fecal occult blood
stool WBCs
fat output
laxative screen (urine too)

Question 10

secretory diarrhea osmotic gap

Answer 10

osmotic gap <50

Question 11

osmotic diarrhea osmotic gap

Answer 11

> 100

Question 12

algorithm for secretory diarrhea

Answer 12

exclude infection
exclude structural disease
selective testing
cholestyramine trial for bile acid diarrhea

Question 13

how to exclude structural disease

Answer 13

radiographs
sigmoidoscopy/colonoscopy with biopsy
CT abdomen
small bowel biopsy

Question 14

algorithm for osmotic diarrhea

Answer 14

stool analysis

• low pH=carb malabsorption
• high Mg=laxatives

Question 15

how to test for carb malabsorption

Answer 15

breath H2 test (lactose)

lactase assay

Question 16

inflammatory diarrhea algorithm

Answer 16

exclude structural disease

exclude infection

Question 17

fatty diarrhea algorithm

Answer 17

exclude structural disease

exclude pancreatic exocrine insufficiency

Question 18

gastric causes of chronic diarrhea

Answer 18

dumping syndrome

Question 19

small intestinal causes of chronic diarrhea

Answer 19

celiac, Whipple’s, lymphoma, abnormal motility

Question 20

large intestinal causes of chronic diarrhea

Answer 20

villous adenoma, IBD, IBS, AIDs related infection

Question 21

pancreatic causes of chronic diarrhea

Answer 21

chronic pancreatitis, islet cell tumors

Question 22

systemic/metabolic causes of chronic diarrhea

Answer 22

hyperthyroidism, hypoparathyroidism, Addison’s disease, diabetes, Carcinoid syndrome

Question 23

minimum laboratory evaluation in most patients with chronic diarrhea

Answer 23

CBC w dif
CRP and ESR
thyroid function tests
serum electrolytes
total protein and albumin
stool occult blood

Question 24

common causes of osmotic diarrhea

Answer 24

lactase deficiency
primary bile malabsorption
antacids (MgSO4 and other Mg salts)

Question 25

common causes of secretory diarrhea

Answer 25

infectious- rotavirus, adenovirus, calcivirus
infectious/endotoxin- vibrio cholera, E.coli, bacillus cereus, clostridium perfringens
neoplastic- tumor, villous adenoma in distal colon
laxative abuse

Question 26

what are some issues with breath H2 test

Answer 26

some people are low hydrogen producers

potential false negatives

Question 27

what is melanosis coli

Answer 27

small patches of pigmentation in colon
macrophage breakdown in histology
often associated with laxative abuse
damaged cells express pigmentation

Question 28

what lab finding would be indicative of inflammation?

Answer 28

ESR or CRP

Question 29

sorbitol malabsorption

Answer 29

unabsorbed sorbitol in colon can lead to fermentation and symptoms

Question 30

how might you distinguish between osmotic diarrhea and secretory diarrhea simply by behavioral manipulation

Answer 30

osmotic diarrhea responds to fasting, secretory does not

Question 31

what foods can cause osmotic diarrhea?

Answer 31

various absorbed carbohydrates, including sugar alcohols when taken in large quantities
resembles lactose intolerance

Question 32

what might low serum electrolytes suggest about diarrhea

Answer 32

secretory in nature

Question 33

what is Indomethacin

Answer 33

nonselective COX1/2 inhibitor which suppresses prostaglandin synthesis

Question 34

why do villous adenomas cause diarrhea

Answer 34

secretion of PGE2

thus can be treated by Indomethacin

Question 35

mechanism for PGE2 causing diarrhea

Answer 35

activates cAMP in enterocytes

downstream phosphorylation opens CFTR channel constitutively

Question 36

McKittrick Wheelock sydrome

Answer 36

villous adenomas secrete electrolytes and mucin
leads to secretory diarrhea, dehydration
common presentation: hyponatremia, hypokalemia, and elevated creatinine

Question 37

metformin associated lactic acidosis

Answer 37

drug accumulation usually due to impaired/failed renal function
treatment: consists of vital function support and drug removal

Question 38

how does metformin cause lactic acidosis

Answer 38

decreases hepatic glucose production, thus decreases utilization of lactate

Question 39

metformin associated diarrhea

Answer 39

usually with initiation
mechanism- altered transport of serotonin or histamine, local metformin concentration in enterocytes, increased bile acid exposure in the colon, or an altered microbiome