Diarrhea Flashcards
Diarrhea Definition
Normal BMs: vary from 3 per day to 3 per week
Multiple definitions for diarrhea are used:
- ↑ Frequency of stools w/ ↓ consistency and ↑ volume
- ≥ 3 loose or watery stools
- Stool weight > 200gm per day (
- Not very meaningful clinically as people are not weighing their stool
- May be higher w/ high-fiber diets
Acute vs. Chronic
Diarrhea
-
Acute Diarrhea
- Generally 2 wks or less in duration
-
“Persistent” Diarrhea
- > 14 days up to 4 wks in duration
-
Chronic Diarrhea
- Loose stool w/ or w/o ↑ frequency for > 4 wks

Acute Diarrhea
Overview
- > 90% of cases are infectious in etiology
- ↑ Duration ⇒ ↑ likely to be non-infectious
- Viral or bacterial cause
- Frequently self-limited and very common
- 1 episode/person/yr in Western countries
-
Outbreaks are common
- Food or water contamination
-
High-risk groups:
- People who care for infants
- Small children
- Travelers
- Immunocompromised individuals
Acute Diarrhea
Elderly Population
Elderly are not more commonly affected
Deaths due to diarrhea occur most commonly in the elderly
-
Physiologic changes
- Abnormalities in water homeostasis
- ↓ Thirst perception
-
Volume depletion leads to ↑ risk for falls
- Orthostatic hypotension
- Electrolyte disturbances
- Delirium
Acute Diarrhea
Differential Diagnosis
-
Infectious Diarrhea:
- Pathogens causing mucosal inflammation can range from mild to severe presentation
- Pts often present w/ watery diarrhea progressing to bloody diarrhea
-
Non-infectious Diarrhea:
Most of these are more likely to present w/ chronic diarrhea- Irritable bowel syndrome
- Inflammatory bowel disease (IBD)
-
Ischemic bowel disease
- Ischemic colitis or mesenteric vascular insufficiency
- Carcinoid syndrome, thyrotoxicosis
- Partial bowel obstruction
- Fecal impaction w/ overflow diarrhea
- Food allergies
-
Medications and over the counter supplements
- Oral magnesium
- Donepezil hydrochloride
- Tube feedings
- Liquid medications
- Chewing gum w/ non-absorbable sugars (sorbitol)
Acute Diarrhea
Microbiology
-
Viral infections
- Most common cause
- Noroviruses, rotaviruses, and adenovirus
-
Bacterial infections
- Cultures positive in ~ 1.5-5.6% of cases
- Can cause severe diarrhea
- Salmonella
- Campylobacter
- Shigella
- Enterotoxigenic E. Coli ⇒ most common cause of acute traveler’s diarrhea
- Clostridium difficile
- Protozoa do not frequently cause acute diarrhea
Acute Infectious Diarrhea
Classification
- Classify by clinical presentation as noninflammatory vs. inflammatory
- A lot of overlap w/ invasive versus noninvasive classification
- In general (w/ 2 exceptions)
- Invasive organisms ⇒ inflammatory picture
- Noninvasive organisms ⇒ noninflammatory picture
Non-inflammatory
Acute Diarrhea
-
Etiology
- Usually viral, but can be bacterial or parasitic
- Generally these are non-invasive infections agents
-
Pathophysiology
- More likely to promote intestinal secretion w/o sign. disruption in the intestinal mucosa
-
History and exam findings
- N/V
- Absence of fever
- Abdominal cramps
- Larger volume, watery, non-bloody stool
-
Lab findings
- Absence of fecal leukocytes
-
Common pathogens
- Rotavirus, Norovirus
- Enterotoxigenic E. coli
- Vibrio cholerae
- Giardia, Cryptosporidium
-
Other
- Generally milder disease
- Severe fluid loss can occur, especially in malnourished pts
Inflammatory
Acute Diarrhea
-
Etiology
- Generally invasive or toxin-producing bacteria
-
Pathophysiology
- More likely to disrupt mucosal integrity
- May lead to tissue invasion and destruction
-
History and exam findings
- Fever
- Abdominal pain, tenesmus
- Smaller volume, bloody stool
-
Lab findings
- Presence of fecal leukocytes
-
Common pathogens
*Classified as noninvasive pathogens in micro- Salmonella (non-Typhi species), Shigella, Campylobacter
- Enterohemorrhagic E. coli*
- Enteroinvasive E. coli
- Clostridium difficile*
- Entamoeba histolytica, Yersinia
-
Other
- Generally more severe disease
Antibiotic-associated Diarrhea
- Pts currently or recently on abx can develop diarrhea
- Alteration in the normal intestinal flora caused by abx use
- Watery, non-inflammatory diarrhea
- DDx is C. difficile
- See fever, high serum WBC, stool WBCs, etc. w/ C. diff
Acute Diarrhea
History
-
Travel Hx
- Traveler’s diarrhea: acute-onset of diarrhea occurring during or shortly after travel
- Work exposure (ex. Works in day care center)
- Pets (ex. Salmonella associated w/ pet turtles)
- Fever
-
Food consumption or preparation
- Raw or undercooked meats and dairy products
- Contaminated fruits and vegetables
-
Pregnancy
- 20x ↑ risk of developing listeriosis from meat or unpasteurized milk
-
Timing of onset of diarrhea
- Generally starts within 6 hrs of ingestion of pre-formed toxins (S. aureus, B. cereus, or C. perfringens)
- Any recent changes in medications
Acute Diarrhea
Evaluation
-
Generally clinical investigation not necessary
- Short duration, good prognosis, and most commonly viral etiology
- 20-40% of the time no cause will be found when evaluated
-
Indications for evaluation of etiology of acute diarrhea:
- Profuse watery diarrhea and hypovolemia
- Frequent small-volume, bloody stools w/ mucus or bloody diarrhea
-
Illness longer than 48 hours
- Worsening or not improving
- Hospitalization
- Recent use of abx
- Age > 70 years
- Immunocompromised individual
-
Systemic illness
- Fever > 101 F o
- Severe abdominal pain
- Diarrhea in pregnancy because listeria is a possible cause
Acute Diarrhea
Diagnostic Tests

Acute Diarrhea
Treatment
-
Supportive treatment (general approach)
- Oral or intravenous hydration
- Perspiration replacement drinks (ex. Gatorade) ok if not volume depleted
-
Symptomatic treatment
-
Dietary changes
- Clear liquids, soft and low-fiber foods ⇒ aids hydration & provide some calories
- Avoid dairy ⇒ risk of temporary lactose intolerance due to mucosal injury
- Avoid caffeine and alcohol ⇒ both ↑ intestinal motility
-
Anti-motility agents
- Ex. Loperamide, diphenoxylate-atropine [Lomotil], tincture of opium
- Can ↓ frequency of stools
- Should be used only in acute diarrhea w/ no blood or fever
-
Empiric antibiotics
- Generally do not give if pt is not severely ill
-
Avoid abx for enterohemorrhagic E. coli
- No clinical benefit
- ↑ risk of hemolytic-uremic syndrome due to ↑ release of Shiga toxin
-
No clinical improvement in Non-typhoid Salmonella
- May actually prolong bacterial clearance
-
Dietary changes
Chronic Diarrhea
Epidemiology
- Chronic diarrhea is common
- Lifetime prevalence (developed countries) 2-7%
- Prevalence in elderly 7-14% (w/ functional disorders included)
- Very broad differential dx
- Can classify by type
- Infectious causes are unusual in the US
- Very common in developing world
Chronic Diarrhea
Classifications
- 5 main cetegories:
- Secretory
- Osmotic
- Steatorrhea
- Inflammatory
- Dysmotility
- Some conditions have fndings from multiple categories
- Consider factitious causes if etiology remains unclear despite work-up
Chronic Secretory Diarrhea
-
Description
- Large volume, watery diarrhea (>1 liter/ day)
- Continues despite fasting
- Usually painless
- Occurs both day and night
- Uncommon cause of chronic diarrhea
-
Pathophysiology
- Derangements in fluid and electrolyte transport across the enterocolonic mucosa
-
Differential Diagnosis
- Drugs, non-osmotic laxatives, bile salts
- Chronic ethanol ingestion
- Cholera / bacterial toxins
- Neuroendocrine tumors: Zollinger-Ellison syndrome (gastrinoma), Vasoactive intestinal peptide-producing tumor (VIPoma), and carcinoid
- Bowel resection, mucosal disease (ex. Crohn’s) or enterocolic fistula
-
Diagnostic factors
- Dx usually made by hx and trial of stool monitoring during fasting
- Little or no osmotic gap (< 50 mOsm/kg)
Chronic Osmotic Diarrhea
-
Description
- Watery diarrhea
- Generally stops w/ fasting
-
Pathophysiology
- Ingested, poorly absorbable, osmotically active solutes draw more fluid into the colonic lumen than can be absorbed
-
Differential Diagnosis
- Carbohydrate malabsorption (lactulose or fructose)
- Osmotic laxatives (Mg, PO4)
- Sugar alcohols (mannitol, sorbitol, xylitol)
-
Diagnostic factors
- Dx usually made by careful diet history
- High osmotic gap (>125 mOsm/kg)
- Low stool pH suggests carbohydrate malabsorption (due to carb fermentation)
- High stool Mg output suggests Mg ingestion
Steatorrhea
Steatorrhea defined by stool fat exceeding the normal 7gm/day
-
Generally malabsorption of fats and nutrients
- ↑ stool output d/t osmotic effects of fatty acids
-
Congenital
- Membrane transport defects of small bowel enterocytes
-
Acquired
- Extensive damage or resection of small bowel causing ↓ absorptive area
- BM are greasy or oily and foul-smelling
- Often associated w/ weight loss
- Can lead to nutritional deficiencies
-
Differential Dx:
-
Intraluminal maldigestion
- Chronic pancreatitis leading to pancreatic insufficiency (when ≥90% of pancreatic secretory function is lost)
- Cystic fibrosis or pancreatic duct obstruction
- Bacterial overgrowth in small intestine
- Chronic pancreatitis leading to pancreatic insufficiency (when ≥90% of pancreatic secretory function is lost)
-
Mucosal malabsorption
- Etiologies including Celiac disease (i.e. celiac sprue), tropical sprue, Whipple’s disease and short bowel syndrome
-
Intraluminal maldigestion
- Lab findings depend on severity and which nutrients are deficient
Inflammatory Diarrhea
- Bloody, mucous diarrhea w/ frequent, urgent small stools
-
Differential Diagnosis:
- Inflammatory bowel disease
- Infectious colitis
- Invasive bacteria

Dysmotility Diarrhea
-
Rapid transit often occurs w/ diarrhea as a secondary or contributing phenomenon
- 1° Dysmotility is unusual etiology of true diarrhea
- Can have features of secretory diarrhea ± mild steatorrhea
- Soft to watery stools
-
Differential Diagnosis:
-
Hypermotility
- Hyperthyroidism, carcinoid syndrome, and drugs (prostaglandins and prokinetic agents)
-
Dysmotility
- DM (often w/ peripheral and autonomic neuropathies), scleroderma
- Irritable Bowel Syndrome
-
Hypermotility
Irritable Bowel Syndrome (IBS)
Overview and Epidemiology
- “Functional” bowel disorder
- Characterized by altered bowel habits and abdominal pain
- Without detectable structural abnormalities
- Diarrhea and constipation predominant forms
- Prevalence in North America is 10-15%
-
2-3x more common in women
- Women make up 80% of those w/ severe IBS
- IBS affects all ages but most pts have their first sx before age 45
Irritable Bowel Syndrome (IBS)
Clinical Manifestations
-
Pain or abdominal discomfort ⇒ key sx
- Crampy and episodic
- Relieved w/ defecation
-
Altered bowel habits ⇒ most typical feature
- Constipation alternating w/ diarrhea ⇒ most common pattern
- Many w/ constipation or diarrhea as predominate sx
- Altered BMs interspersed w/ nl stools
- Urgency and feeling of incomplete evacuation
- Small volume
- Mucus in stool (~ 50%)
- Stops during sleep
- Exacerbated by emotional stress or eating
- Abdominal distention
- ↑ Belching and flatulence
- Dyspepsia, heartburn, N/V (25-50%)
-
Not consistent w/ IBS:
- Large-volume diarrhea
- Bloody diarrhea
- Nocturnal diarrhea
- Greasy stool
- Weight loss

Irritable Bowel Syndrome (IBS)
Pathophysiology
Poorly understood
Mechanisms proposed:
-
Abnormal gut motor and sensory activity
- Quantitative differences vs healthy controls
- Ileum, colon, rectum hyperreactive to stimuli
- Meals, distention, stress
- Ileum, colon, rectum hyperreactive to stimuli
- Visceral Hypersensitivity
- Enhanced perception of visceral events
- Intestinal contractions and gas
- Seen in esophagus, stomach, duodenum, and ileum
- Enhanced perception of visceral events
- Quantitative differences vs healthy controls
- Central neural dysfunction
- Mucosal inflammation
- Luminal factors
-
Psychological disturbances and/or stress
- Sensitive to psychological stress ⇒ sx exacerbation
- Up to 80% of IBS pts may have psychological sx
- IBS sx can occur after a GI infection
Irritable Bowel Syndrome (IBS)
Diagnosis
-
Rome III Criteria
- Recurrent abd pain or discomfort on 3+ days/month in the last 3 months ass. w/ ≥ 2 of the following:
- Improvement of pain w/ BM
- ∆ in frequency of stool
- ∆ in form or consistency of stool
- Recurrent abd pain or discomfort on 3+ days/month in the last 3 months ass. w/ ≥ 2 of the following:
- Perform hx and PE (including rectal) to assess for other causes
- Pt needs further work-up if sx not consistent w/ IBS including:
- Rectal bleeding, nocturnal or progressive abdominal pain, weight loss
- Lab abnormalities: anemia, electrolyte disturbances, elevated inflammatory markers;
- Fhx of IBD or cancer
Irritable Bowel Syndrome (IBS)
Treatment
-
Dietary modification
- Careful diet hx for triggers
- Caffeine, gas-producing foods, fermentable saccharides [fructose, high-fructose corn syrup, wheat], lactose
-
Stool-bulking agents
- Fiber
- Physical activity may help
-
Antidiarrheal agents (if diarrhea predominant IBS)
- Loperamide
-
Antidepressants
- May help in pts w/ depressive sx
Factitious Causes
Diarrhea
- Up to 15% of cases of unexplained diarrhea
- DDx: Munchausen syndrome or eating disorders
- Most typical pt is a woman w/ hx of psychiatric illness
- Disproportionately w/ hx of career in health care
- May add water or urine to stool, self-administer laxatives w/ or w/o other medications like diuretics
- Hypotension and hypokalemia are common findings
Chronic Diarrhea
History
- Onset and duration
- Continuous vs. intermittent sx
- Presence of nocturnal diarrhea
- Duration of diarrhea
- Stool characteristics: watery, bloody, greasy
- Fecal incontinence vs. diarrhea (or both)
-
Aggravating factors
- Stress
- Specific foods (ex. Milk)
-
Alleviating factors
- Diet changes
- Prescription or OTC medications
- Prior work-up done
- Abdominal pain (IBD, IBS, mesenteric vascular insufficiency)
-
Epidemiology
- Travel
- Exposure to contaminated food or water
- Family members w/ similar illness
- Weight loss (Malabsorption, IBD, ischemia, and neoplasm)
- Previous operations, radiation therapy
- Medications and supplements
-
ROS for systemic causes
- Hyperthyroidism, scleroderma, tumor syndromes, DM
- Risk factors for HIV or other immunocompromised conditions
-
Hx of eating disorders, secondary gain, or history of malingering
- Potential markers of factitious diarrhea
Chronic Diarrhea
Physical Exam
Most likely will not provide a specific dx
May be helpful for fluid status and nutritional status
- Mouth ulcers or perianal disease ⇒ suggests IBD
- Rash or flushing
- Abdominal mass
- Findings of hyperthyroidism or thyroid mass
Chronic Diarrhea
Systemic Labs
- CBC to assess for presence/type of anemia
- Leukocytosis ⇒ suggests inflammation
- Eosinophilia can be associated w/ neoplasm, allergy, collagen-vascular diseases, parasitic infection, and eosinophilic gastroenteritis or colitis
- CMP ⇒ fluid/electrolyte status, nutritional status, liver problems, Dysproteinemia
Chronic Diarrhea
Stool Analysis
Quantitative stool collection vs spot stool collection
-
Fecal osmotic gap
- Sodium and potassium concentrations in stool water ([Na+] + [K+])
- Osmotic diarrhea ⇒ osmotic gap > 125 mOsm/kg
- Secretory diarrhea ⇒ osmotic gap < 50 mOsm/kg
-
Stool pH
- Value of < 5.6 consistent w/ carbohydrate malabsorption
-
Fecal occult blood testing
- ⊕ consistent w/ IBD, neoplasm, celiac disease or other “sprue-like” syndrome
-
Fecal leukocytes
- Suggest inflammatory diarrhea
-
Excess stool fat
- Directly measured or w/ Sudan stain
- Can see large and numerous fat globules if malabsorption or maldigestion
-
Laxative screening
- Perform if chronic diarrhea w/ no clear diagnosis