Diarrhea Flashcards
What is the “textbook” definition of diarrhea?
Why is this not a good definition?
>200 grams or 200mL per 24 hour period
- Difficult to accurately measure
- Patient has to be eating
- High fiber diet can easily get over 300 gm/d
- Does not factor in consistency or frequency
How does Robbins define…
- Malabsorptive diarrhea:
- Exudative Diarrhea:
- Malabsorptive diarrhea:
- Inadequate nutrient absorption
- Associated with steatorrhea
- Relieved by fasting
- Exudative Diarrhea:
- Due to inflammatory disease
- Purulent, bloody stools
- Continue during fasting
What four phases of nutrient absorption are disturbed in malabsorption?
- Intraluminal digestion: break down of proteins, carbohydrates, and fats
- Terminal digestion: Hydrolysis of carbohydrates adn peptides by disaccharidases and peptidases into the brush border
- **Transepithelial transport: **Defects in transport of nutrients, fluid, and electrolytes across SI epithelium
- Lymphatic transport: Defects in lipid absorption
What are some “practical” definitions of diarrhea and normal bowel movement
- Normal BM: One BM every three days to 3 BMs every day
- Diarrhea:
- More than 3 loose/watery stools per day
- Clear increase in frequency and decrease in consistency over baseline
What history clues do you look for in diarrhea?
- Consistency: Liquid > Loose > Soft > formed
- Urgency
- Incontinence – lose control of full BM (not always diarrhea)
- Nocturnal BMs – BM wakes patient up
- Flatuphobia – Fear of poop/fart combo
How much fluid is excreted in feces per day?
<100mL
Small bowel
- Absorptive function:
- Diarrhea characeristics:
- Symptoms:
- Fever?
- Absorptive function: Absorbs most water, nutrients, minerals, sugars and proteins
- Diarrhea characeristics: Watery diarrhea, large volume, less frequent
- Symptoms: Abdominal cramping, bloating, gas and weight loss (evidence of malabsorption/deficiencies)
- Fever?: Rare (Rare stool WBCs)
Large Bowel
Absorptive function:
Diarrhea characeristics:
Symptoms:
Fever?
- Absorptive function: Storage and some fluid/electrolyte absorption (decreased function with inflamed dysfunctional colon)
- Diarrhea characeristics: Frequent, small, regular or bloody mucoid stools,
- Symptoms: Tenesmus (rectal “dry heaves”), painful BM
- Fever?: Yes (RBCs and WBCs on stool smear)
How is osmotic diarrhea due to an abnormal gradient?
- Neither the SI nor the LI can maintain an osmotic gradient against serum
- Unabsorbed ions that remain in the lumen:
- Osmotically active ions act to pull water into the lumen of the bowel
- Maintain an intraluminal osmolality = 290 mOsm/kg
What types of molecules can lead to osmotic diarrhea?
- Ingestion of poorly absorbed ions or sugars or sugar alcohols
- Mannitol, sorbitol, magnesium, sulfate, phosphate
- Monosaccharides but not disaccharides can be absorbed
- Lactase deficiency is most common (loss of nutrient transporter)
Disaccharide deficiency will _______(induce/prevent) malabsorption
Disaccharide deficiency will prevent malabsorption
How is osmotic diarrhea treated? Why does this work?
- Disappears with fasting or cessation of the offending substance
- Electrolyte absorption is not impaired in osmotic dirrhea
- Electrolyte concentrations in stool water are usually quite low
What are the general causes of secretory diarrhea?
What is the most common specific cause?
Either net secretion or anions or inhibition of net sodium absorption
The most common cause is infection
How do enterotoxins play a role in secretory diarrhea?
- Interact with receptors and modulate intestinal transport
- Block specific absorptive pathways, in addition to stimulating secretion
- Inhibit Na+/H+ exchange in both the small intestine and colon
Define…
- Acute Diarrhea:
- Persistent Diarrhea:
- Chronic Diarrhea:
- Acute Diarrhea: ≤ 14 days
- Persistent Diarrhea: 14-28 days
- Chronic Diarrhea: > 28 days
What causese acute diarrhea?
- Infection responsive for almost all acute diarrhea
- Bacteria, Parasites, Protozoa, Viruses
- Food allergies
- Food Poisoning
- Medications
- Initial presentation of chronic diarrhea
What are some causes of chronic diarrhea?
- Fatty diarrhea
- malabsorption; mesenteric ischemia; mucosal disease
- Inflammatory diarrhea
- diverticulitis; infectious diseases; IBD
- Watery diarrhea
- Osmotic diarrhea; carbohydrate malabsorption; osmotic laxatives; congenital syndromes
What diagnostic things should be found in a history for diarrhea?
- Tenesmus
- Nocturnal waking
- Gas/bloating
- Blood in stool
- Flatuphobia
What are some risk factors for diarrhea?
- Recent and remote travel
- Pets (turtles)
- Drinking from mountain streams
- Family history
- Autoimmne conditions
What items in a person’s diet can be a risk factor for diarrhea?
Sorbitol, caffeine, large amounts of high fructose corn syrup (HFCS), alcohol intake
What medications changes can lead to diarrhea?
NSAIDs and Olmesartan can cause sprue like illness
What does a fever + diarrhea indicate?
- Invasive bacteria
- Enteric viruses
- Cytotoxic organism (C. Diff or Entamoeba histolytica)
- Ischemia
- IBD
What is the significance of diarrhea beginning:
- Within 6 hours of food ingestion:
- 8-14 hours since food ingestion:
- More than 14 hours since food ingestion:
- Within 6 hours of food ingestion:
- Suggests ingestion of toxin
- Staph. Aureus; Bacillus Cerus
- 8-14 hours since food ingestion:
- Suggests infection with Clostridium perfringens
- More than 14 hours since food ingestion:
- Can result from viral or bacterial infection (non-specific)
What exposures can be risk factors for diarrhea?
- Recent antibiotic use or chemotherapy exposure
- Exposure to ill family members or outbreaks
- Nursing home residence
- Occupational exposure (health care, day care)
What is done in a physical exam for a patient experiencing diarrhea?
- Initially focused on volume status
- Signs of other systemic diseases
- Abdominal tenderness/mass
- Rectal exam (fistula, bloody stool)
When do you order stool for pathogens?
In general, when patient is very ill or has risk factors for infection
What is the purpose of ELISA or DFA microscopy in diarrhea? (how sensitive/specific is this method?)
Checks for:
- Giardias and Crytposporidium in stool
- Greater than 90% sensitivity
- Approaching 100% specificity
How is the osmotic gap measured?
How does it differentiate between secretory diarrhea and osmotic diarrhea?
- Osmotic Gap = Serum Osm – Est Stool Osm (290)
- (2 x ([Na+] + [K+])) ~ 290 mmol/L
- In secretory diarrhea: Osmotic gap < 50 mOsm/kg
- In osmotic diarrhea: Osmotic gap > 100 mOsm/kg
What does it mean if the osmotic gap is negative?
Poorly absorbed multivalent anion, such as phosphate or sulfate (more anions are pulled in to try and balance)
For what reasons would someone have excessive laxative ingestion?
How can surreptitious laxative ingestion be found out?
- Reasons: Eating disorders, Munchausen syndrome, secondary gain
- Finding out:
- Stool can be analyzed for laxatives by chemical or chromatographic methods
- Large osmotic gap (suggests magnesium ingestion)
- Negative osmotic gap
What are the more common causes of chronic diarrhea that should be pursued early?
- Celiac disease (caucasians)
- Thyroid disease
- IBD
- IBS
When is endoscopy indicated in diarrhea cases?
Most appropriately used for persistent and chronic diarrhea or patients with significant lab abnormalities
When is the 72 hour stool collection (for fecal fat) useful?
What findings are abnormal?
Only useful for chronic diarrhea (impractical most of the time)
- 7-14 g/day is considered abnormal but not diagnostic
- >14 g/day is considered indicative of fat malabsorption
