1. Diarrhea and Malabsorption
Internal Medicine Update & Review Course
Don Schoch, M.D.
February 10, 2018

2. Conflicts
None

3. Incidence
Acute diarrhea in US
0.65 episodes per person per year
Chronic diarrhea
5% of the US population per year

4. Commonly considered a decrease in the consistency of the stool
Definition
A symptom, not a disease
General criteria
Commonly considered a decrease in the consistency of the stool
Consistency is determined by the ratio of the water binding ability of stool solids to total stool water.
Stool solids: dietary fiber and bacterial cell walls
Specific criteria (not absolute)
More than three bowel movements a day
Stool weight over 200 grams a day
Small bowel delivers from 1 to 1.5 liters of water to the colon a day. Normal water absorption is 90%.

5. Pseudodiarrhea
Formerly hyperdefecation
Definition
More than 3 bowel movements a day
Normal stool weight
May be more common that chronic diarrhea
Seen with irritable bowel syndrome, anorectal disorders (proctitis), and fecal impaction

6. Determine if patient is having true diarrhea
Take a detailed history
Patients use the term diarrhea to describe a variety of symptoms
Bristol stool chart is helpful
Other possibilities
Pseudodiarrhea
Fecal incontinence
Fictitious diarrhea

8. Determine if patient is having true diarrhea (cont.)
Evaluation
Check abdominal roentgenogram (KUB)
Ask for an assessment of stool burden
Stool chart in hospital
Have patient use a “hat”
Record time, volume, consistency

9. Pathophysiology
Excess stool water
Osmotic diarrhea
Normal colonic mucosa can’t maintain an osmotic gradient
Increased non absorbed stool contents increases stool water
Common agents causing this
Poorly absorbed anions and cations
Magnesium, phosphate, sulfates
Poorly absorbed sugars
Mannitol, sorbitol
Polyethylene glycol (GoLYTLEY, MiraLAX)
Used clinically

10. Pathophysiology (cont.)
Osmotic diarrhea
Clinical feature
Stops when fasting or when ingestion of agent stops

11. Secretory diarrhea
Mechanism
Net secretion of anions
Net inhibition of Na absorption
Causes
Infection is the most common cause.
Complex diarrhea
Most causes of diarrhea are a combination
Diarrhea is rarely just osmotic or secretory.

12. Clinical classification
Time course
Acute
Less than four weeks
Usually infectious
Viral being most common
Chronic
Fatty diarrhea
Inflammatory diarrhea
Watery diarrhea
Secretory
Osmotic

13. Evaluation
Acute
Most patients do not require evaluation or intervention.
Exceptions
Poor oral intake
Vomiting
Immunocompromised

14. Initial evaluation
When it lasts more than a few days or is complicated
Labs
CBC
Renal panel
Stool studies
Fecal leukocytes
Stool cultures
Limited value in outpatients with negative fecal leukocytes

15. Evaluation (cont.)
Acute diarrhea
Clostridium difficile toxin
History of antibiotics
Institutional setting
Cryptosporidium and Giardia lamblia ELISA tests for antigens
Abdominal roentgenogram (KUB)

16. Chronic diarrhea
More complex than acute diarrhea
Rely on the categories to focus the evaluation
Stool studies (partial list)
Stool occult blood testing
Osmotic gap
Stool electrolytes
Fecal leukocytes
Stool fat
Qualitative
Quantitative
Stool weight

17. Osmotic gap
290 mOsm/kg – 2(Na + K)
Small gap (< 50 mOm/kg)
Poorly absorbed electrolytes
Large gap (>100 mOm/kg)
Ingestion of a poorly absorbed substance
Doesn’t involve measuring stool osmolality

18. Norovirus
Causes acute diarrhea
Highly contagious
Sources
Eating contaminated food and drinks
Touching contaminated surfaces
Person to person contact

19. Norovirus (cont.)
The leading cause of illness from contaminated food
Including raw shellfish
Common cause of epidemics in the US
Notoriety due to recent cruise ship outbreaks
Also seen in day care, camps, schools, health care facilities
Clinical features
Diarrhea, nausea, abdominal cramps, and vomiting
Lasts 24 to 48 hours
No specific treatment is available.

20. 55 year old female presents with abrupt onset of profuse watery diarrhea and occasional fecal incontinence for six weeks. She doesn’t have rectal bleeding. She is a runner. She has been using naproxen for tendonitis.
PMH: Neg., Meds – naproxen only
PE: unremarkable, Hemoccult® negative stool
Labs: CBC, CMP, TSH - negative. Stools studies all negative, including: fecal leukocytes, qualitative stool for fecal fat, culture, Crypto. and Giardia stool antigens, C. dif.

21. The next best test is:
Magnetic resonance enterography (small bowel imaging)
Stool osmotic gap
Stool for ova and parasites (warm purged stool is available in your lab)
Colonoscopy with random biopsies
Empiric course of Cipro

23. 55 year old female presents with abrupt onset of profuse watery diarrhea and occasional fecal incontinence for six weeks. She doesn’t have rectal bleeding. She is a runner. She has been using naproxen for tendonitis.
PMH: Neg., Meds – naproxen only
PE: unremarkable, Hemoccult negative stool
Labs: CBC, CMP, TSH - negative. Stools studies all negative, including: fecal leukocytes, qualitative stool for fecal fat, culture, Crypto. and Giardia stool antigens, C. dif.

24. Enterohemorrhagic Escherichia coli (EIEC)
Causes acute hemorrhagic colitis
Mainly E. coli O157:H7
Prevalence
15% to 36% of hemorrhagic colitis
Epidemiology
Most often caused by eating hamburger
Cattle are the most important reservoir

25. Enterohemorrhagic Escherichia coli (cont.)
Clinical findings
Bloody diarrhea (95% of patients), nonbloody diarrhea, hemolytic-uremic syndrome (HHS), and thrombotic thrombocytopenic purpura (TTP)
HUS
Acute renal failure, microangiopathic hemolytic anemia, and thrombocytopenia

26. Enterohemorrhagic Escherichia coli (cont.)
Treatment
No studies to support efficacy of antibiotic treatment
Some data to support an association between antibiotic use and HUS
Routine use of antibiotics is not recommended
Follow for development of HUS

27. Malabsorption
Challenge is to recognize the subtle presentation
Bloating
Change in bowel habits
Nutrient deficiencies
Examples: B12, iron, calcium, magnesium

28. Pathophysiology
Solubilization
Digestion
Liberation of substrates
B12 bound to foods
Chemical changes
Changing the charge of iron
Mucosal absorption
Active & passive

29. Diseases causing malabsorption
Note: Causes are extensive, following is only a partial list, includes only the most common causes
Gastric diseases
Gastric bypass
Pancreatic diseases
Pancreatic insufficiency
Pancreatic tumors
Discuss supplements and monitoring in Roux-en-Y gastric bypass patients.

30. Diseases causing malabsorption (cont.)
Intestinal diseases
Celiac disease
Crohn’s disease
Infections
Giardia lamblia
AIDS
Whipple’s disease
Small bowel bacterial overgrowth
Endocrine
Hyperthyroidism
Systemic diseases
Scleroderma

31. Fecal elastase-1 
The most sensitive and specific indirect test of pancreatic function.
An enzymatic product of pancreatic secretion
Remains relatively stable during transport through the gastrointestinal tract.
Levels
<200 mcg/g is considered abnormal
Between 200 mcg/g and 250 mcg/g may be considered borderline.

32. Fecal elastase-1 
Sensitivity
Mild: 63%
Moderate: 100%
Severe: 100%
Specificity 93%
Dilution can decrease the level
Seen in watery diarrhea