Diarrhea and Malabsorption

Yinghong Wang

RAPID BOARD REVIEW—KEY POINTS TO REMEMBER

Diarrhea

Clinical clues
- Acute diarrhea (<4 weeks) is generally infectious in etiology.
- Presence of blood is a useful clue suggesting invasive infections, inflammation, ischemia, or neoplasm.
- Large-volume diarrhea suggests small bowel or proximal colonic disease.
- Small-volume, frequent stools suggest left colon or rectal disease.
- In the history, do not forget to ask about the intake of “sugar-free” foods (nonabsorbed carbohydrates).
- Oral ulcers and pyoderma gangrenosum suggests inflammatory bowel disease.
- Dermatitis herpetiformis is associated with celiac disease.
Categorize diarrhea as watery diarrhea (secretory and osmotic), inflammatory diarrhea, and fatty diarrhea
Osmotic diarrhea tends to stop during fasting and is associated with an osmotic gap >50 mOsm.
Secretory diarrhea persists with fasting and has osmotic gap <50 mOsm. It can be caused by underlying mucosal disease, bacterial toxins, stimulant use, and neuroendocrine tumors.
Inflammatory diarrhea is usually associated with bleeding, fecal leukocytes, fever, and abdominal pain.
Functional diarrhea is a diagnosis of exclusion.
Foodborne illness with Escherichia coli is the most common cause of traveler’s diarrhea.

Malabsorption

Diarrhea is almost universally present in malabsorption.
Steatorrhea can be due to pancreatic insufficiency, decreased luminal bile salt concentration, mucosal diseases (celiac disease, Whipple’s disease, inflammatory bowel disease), small bowel bacterial overgrowth (commonly due to diabetes and previous bowel surgeries), short bowel syndrome.
Workup for malabsorption can include fecal fat analysis, tests of pancreatic exocrine function, radiographic studies, breath tests, and endoscopic and histologic testing.

Specific Disorders

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