Diarrhea, Lymphocytic colitis Flashcards
Clinical definition of diarrhea?
Incr in frequency, volume, or urgency of defecation
+/- change in consistency
Nml stool frequency?
3 BM per week up to 3 BM per day
Physiologic definition of diarrhea?
> 200 gm stool output per day
Normal amount (liters) of input into the gut?
8.5L
2L from ingestion, 6.5L from secretions
The small intestine absorbs __L of fluid, and the colon absorbs __L.
7L
1.4L
How much fluid is excreted form the gut?
0.1L
What is the basis of nml fluid absorption?
Na+ uptake
Receptors in small intestinal villi?
Na+ / glucose co-transporter
Na+ / H+ exchanger (NHE)
Receptors in Large intestinal crypts?
epithelial Na+ channel (ENaC)
Pathophysiology of Diarrhea?
- Increased intraluminal fluid
2. More rapid transit through GIT
Increased Intraluminal Fluid: Pathophysiologic Mechanisms?
- decr absorption (osmotic mechanism, fluid drawn into gut)
- incr secretion (active secretion of electrolytes + fluid into lumen)
- inflammation (inflammatory mediators stimulate secretion)
comprise most stool osmolality
electrolytes
What causes compromise of epithelial barriers?
cell death, caused by inflammation
**results in incr intraluminal fluid
How does ingestion of unabsorbable solutes affect the GIT?
incr intraluminal fluid via osmotic mechanism
Causes of Osmotic Diarrhea:
Non-absorbable carbohydrates
Non-absorbable electrolytes (laxatives)
Types of Non-absorbable carbohydrates?
lactose (milk, yogurt, cheese, etc.)
sorbitol, mannitol (diet soda, gum, candy)
lactulose (Rx for hepatic encephalopathy)
Types of Non-absorbable electrolytes?
Mg2+ compounds (MOM, Maalox, Epsom salts)
Golytely (PEG)
Fleets phosphosoda prep
The key to all secretory diarrheas is:
excessive Cl- secretion into the gut
oral rehydration formula for the treatment of cholera and other secretory diarrheas is based on:
exploitation of the Na/glucose co-transporter
By including glu in high salt drink, Na+ absorption can continue despite cAMP inhibition of Na+ absorption by NHE
Secretory Diarrhea Mediators:
Bacterial Enterotoxins?
Cholera toxin (cAMP)
E. coli LT (cAMP)
E. coli STa (cGMP)
Yersinia toxin (Ca2+)
Secretory Diarrhea Mediators:
Neurohumoral agents?
VIP (cAMP)
ACh (Ca2+)
Serotonin (Ca2+)
Secretory Diarrhea Mediators:
Immune mediators?
Histamine (cAMP)
Prostaglandins (cAMP)
Chemical irritants that cause secretory diarrhea?
Bile, arsenic, caffeine, ETOH
Neuroendocrine tumors that cause secretory diarrhea?
VIPoma
carcinoid
medullary carcinoma of thyroid
How does fasting affect osmotic diarrhea?
How does fasting affect secretory diarrhea?
O: resolves with fasting
S: persists with fasting
Which form of diarrhea is associated with flatulence?
osmotic
pH of stool in osmotic diarrhea?
pH of stool in secretory diarrhea?
O: <5.3
S: 6-7
osmolar gap in osmotic diarrhea?
osmolar gap in secretory diarrhea?
O: >125
S: <50
**=230-2(Na+K)
Pathophysiology of Inflammatory Diarrhea:
Stimuli?
Parasites Food allergy Celiac sprue Salmonella Whipples IBD GVH Shigella Rotavirus
Pathophysiology of Inflammatory Diarrhea:
Immune-mediated mechanisms causing enterocyte cell death?
complement, cytokines,
cytotoxic T-cells, mast
cells, neutrophils, etc.
inflammatory mediators induce…
Intestinal Secretion
what stimuli directly induce enterocyte death?
Amoeba Shigella Rotavirus Giardia Cryptosporidium
What are the consequences of inflmm diarrhea?
Villous atrophy
Malabsorption
Acute Diarrhea:
Duration?
Etiology?
Prognosis?
<3 weeks
infectious
self-limited
Acute Diarrhea:
Pathophys?
Management?
secretory or inflammatory
supportive
Most Common Causes of Infectious Diarrhea in the US?
Viral E. coli Campylobacter Salmonella, Shigella Giardia Cryptosporidium (AIDS) C. difficile (antibiotics)
Most Common Causes of Infectious Diarrhea in the 3rd world?
Viral (rotavirus, norovirus) Campylobacter E. coli Vibrio cholerae Entameba histolytica Salmonella, Shigella Cryptosporidium (infants)
Most common cause of traveler’s diarrhea?
enterotoxigenic E coli
Who is affected by traveler’s diarrhea?
travelers to third world
Prophylaxis Recommendations for traveler’s diarrhea?
eat only cooked foods
drink only bottled beverages, avoid ice
wash hands before meals
consider peptobismol QID
Trx for traveler’s diarrhea?
po fluids + anti-diarrheals for symptom control
if severe, ciprofloxacin 500 mg BID x 3 days
What type of acute diarrhea is likely viral or toxin mediated?
Non-bloody diarrhea without dehydration
What type of acute diarrhea is likely bacterial?
bloody (dysentery) diarrhea without dehydration
Treatment of diarrhea without dehydration?
fluids and peptobismol
Treatment for bloody diarrhea with dehydration?
IV fluoroquinolone (cipro)
hospitalization
IV fluids
C. diff risk factors?
Antibiotic usage
Extremes of age
Hospitalization or institutionalization
How does C. diff induce diarrhea?
Cytotoxins A & B
How is C diff diagnosed?
pseudomembraneous colitis on endoscopy
Stool assay for Toxin A (+/- B)
How is C diff treated?
stop the offending abx (if possible)
metronidazole or vancomycin po
cholestyramine to bind toxins
Chronic diarrhea:
Duration?
Etiology?
> 3 weeks
infectious
immune-mediated
malabsorption
Chronic diarrhea:
Pathophys?
osmotic, secretory (no mucosal injury)
Inflammatory (mucosal injury)
What types of chronic diarrheas are associated with NO mucosal injury?
- maldigestion/malabsorption syndromes
- hypermotility (thyroid, IBS, etc)
- Neuroendocrine malignancies
- factitious (laxative abuse)
Clinical features of lactase deficiency?
- osmotic diarrhea
- flatulence
- acidic stool pH
Clinical features of bacterial overgrowth?
secretory diarrhea (due to conversion to unconjugated bile acids)
osmotic diarrhea
gas
IBS is a disorder of
motility and pain perception
Symptoms of IBS?
- abdominal pain
- bloating
- no weight loss, bleeding, malnutrition, anemia
Treatment of:
IBS w/ diarrhea?
IBS w/ const?
anti-cholinergic medications (diarrhea)
5-HT receptor antagonists (constipation)
What types of chronic diarrheas are associated with mucosal injury?
- chronic infections (HIV, parasites, sprue)
- allergic/immune-mediated (celiac, Crohn’s, ulc colitis, etc)
- malignancies (colon CA, lymphoma)
What are the 2 types of microscopic colitis?
What are the associated symptoms?
Collagenous colitis
Lymphocytic colitis
Chronic watery, non-bloody diarrhea in adults
Treatment for microscopic colitis?
Bismuth
Aminosalisylates
steroids
What are the features of Behcet’s disease?
- generalized vasculitis
- Oral and genital aphthous ulcers
- Uveitis
- GI tract ulcers
- Non-erosive arthritis
Trx of Behcet’s?
immunosuppressants
What are “red flags” in a patient with chronic diarrhea?
- Unintentional weight loss
- Nocturnal diarrhea
- Signs of malnutrition (muscle wasting)
- Rectal bleeding
What is the ddx of there are no red flags + flatulence?
lactose intol
bac overgrowth
What is the ddx of there are no red flags + pain with BMs?
IBS
What is the ddx if Red Flags Present or Initial Studies Abnormal + weight loss?
IBD
hyperthyroidism
malabs
malignancy
What is the ddx if Red Flags Present or Initial Studies Abnormal + bleeding?
malignancy
infection
IBD
