Chronic Diarrhea

Background

• Chronic diarrhea is increased volume or frequency (> 3 stools/day) of bowel movements and decreased consistency of stool lasting > 4 weeks.
• Categorizing chronic diarrhea as watery, inflammatory, or fatty (steatorrhea) helps guide diagnostic evaluation targeted to suspected etiologies.

Evaluation

• Assess for "red flag" features such as anemia, fever, significant weight loss, gross blood in stool, or nocturnal diarrhea.
• Conduct thorough history and physical examination, asking about diarrhea characteristics, additional symptoms, diet review, and recent travel history, to guide testing.
  • Perform medication review.
  • Consider a trial of food elimination with symptom diary if diarrhea is suspected to be triggered by certain foods (in particular, sugar alcohols, lactose, or fructose).
• Consider tests based on patient history or clinical presentation:
  • blood tests
    • perform serum IgA tissue transglutaminase (tTG) to assess for celiac disease (Strong recommendation)
    • consider complete blood count and metabolic profile to evaluate fluid and electrolyte balance and nutritional sufficiency
  • stool assessment
    • in patients with chronic watery diarrhea
      • test for Giardia using antigen test or polymerase chain reaction (Strong recommendation); testing for ova and parasites other than Giardia is not suggested unless patient reports recent travel to high-risk areas (Weak recommendation)
      • consider assessing fecal calprotectin or fecal lactoferrin to screen for inflammatory bowel disease (Weak recommendation)
      • consider testing for bile acid diarrhea (commonly 48-hour stool collection) (Weak recommendation)
    • if steatorrhea is suspected due to large-volume, pale, oily stools, consider Sudan stain on spot specimen or 48- to 72-hour timed stool collection to measure stool fat
    • consider elastase and chymotrypsin to screen for pancreatic insufficiency (Weak recommendation)
    • if there is watery diarrhea and differential remains broad, consider checking stool sodium and potassium levels to estimate fecal osmotic gap (290 mOsm/kg - 2 × [stool sodium + stool potassium]) to differentiate osmotic from secretory diarrhea
• Imaging can be useful in select patients.
  • For suspected inflammatory bowel disease, consider computed tomography (CT) or magnetic resonance (MR) enterography.
  • In patients with steatorrhea, consider abdominal CT or MR scanning with thin cuts through pancreas to assess for chronic pancreatitis or pancreatic malignancy.
• Consider lower gastrointestinal endoscopy with mucosal biopsy in patients with unexplained inflammatory or secretory diarrhea.

Management

• Consider therapeutic trials for disorders without definitive diagnostic tests or for patients without alarm features.
• Although dehydration and electrolyte imbalances are uncommon with chronic diarrhea, replace lost fluids and electrolytes if indicated.
• Consider empiric antidiarrheal therapy (such as diphenoxylate, loperamide, bismuth subsalicylate, fiber supplements or soluble fiber, or opiates) to manage symptoms in patients before diagnosis is established or if cause-specific treatment is not available.
• Antibiotic therapy is not useful as a nonspecific therapy in patients with chronic diarrhea. Consider antibiotic therapy only if there is a high likelihood of infection, such as high prevalence in the community.
• Consider probiotics in patients with diarrhea-predominant irritable bowel syndrome but not as nonspecific therapy in patients with chronic diarrhea.
• Consider empiric trial of bile acid binding resins if bile acid malabsorption is suspected.