I. Definitions & pathophysiology

  1. > 200g/stool/d in adults (avg. for adult man is 102-195g, woman is 31-81g)
  2. 2 mechanisms; sometimes both are at work
  1. Increased fluid secretion into colonic lumen ("secretory")
  1. Can be due to hormonal factors, enterotoxins, etc.
  2. Exudative diarrhea also falls under this heading (blood, fluid, mucus, etc.)
  3. Us. get large stool volumes (> 500ml/d) that don't decrease w/fasting
  1. Decreased absorption
  1. Osmotic diarrhea e.g. due to laxatives, carbohydrates, sorbitol
  2. Change in bowel motility
  3. Stool volumes smalled than w/secretory; often decreases w/fasting

II. Differential Dx

  1. Dietary factors: caffeine, sorbital (an artificial sweetener), lactose
  2. Drugs:
  1. EtOH
  2. Digitalis
  3. Narcotic withdrawal
  4. Guanethidine
  5. Laxative overuse
  6. Lactulose
  7. Antibiotics
  8. Loop diuretics
  9. Bronchodilators
  10. Propranolol
  11. Mg-containing antacids
  12. Theophylline
  13. Colchicine
  14. Levothyroxine (if excessive dose)
  15. Quinidine
  1. Idiopathic secretory diarrhea ("collagenous" or "microscopic" colitis)
  2. Infectious Enteritis
  3. Lymphocytic colitis (macroscopically normal mucosa, microscopic lymphocytic inflammation; causes chronic diarrhea; may overlap with other clinical entities; may be drug-induced).
  4. Inflammatory Bowel Disease
  5. Irritable Bowel Syndrome
  6. Malabsorptive syndromes
  1. Bacterial overgrowth
  2. Bile salt deficiency
  3. Pancreatic insufficiency
  4. Smal bowel disease, e.g. Celiac Disease, Whipple's disease
  1. Mechanical factors (fecal impaction, postsurgical syndromes)
  2. Metabolic disorders
  1. Hypothyroidism
  2. Diabetes
  3. Addison's
  1. Tumors
  1. Colon Ca (or adenoma)
  2. Endocrine tumors, e.g. carcinoid, gastrinoma, pheo
  3. Intestinal lymphoma
  4. Medullary carcinoma of the thyroid (?)
  5. Pancreatic carcinoma
  1. Mesenteric Ischemia
  2. Diverticulitis
  3. Radiation injury

III. Evaluation

  1. Hx:
  1. Relation to certain foods may indicate malabsorption
  1. Lactose intolerance-bloating, flatus, frothy stools after dairy intake
  2. Caffeine, sorbital (sugar substitute), EtOH can cause diarrhea
  1. Drugs (as above)
  2. Morning episodes more likely to be functional; at night or throughout the day more likely to be organic
  3. Diarrhea alt. w/constipation, long duration suggests functional
  4. Greasy, foul-smelling, difficult to flush suggests malabsorption
  5. Pus or blood suggest inflammation or Ca
  6. Mucus suggests inflammation
  7. Small volume, urgency & cramping relieved by defecation suggests distal rectal process
  8. Associated flushing can suggest carcinoid or pheo
  9. Associated illnesses
  1. HIV (opportunistic infections, e.g. amebae, giardia, isospora, crytosporidium)
  2. Part h/o pelvic or abdominal irradiation can produce diarrhea lasting months to years
  3. Past h/o intestinal surgery (dumping syndrome)
  1. Travel hx
  1. Px
  1. Decreased weight suggests malabsorption, inflammatory bowel dis., Ca, hyperthyroidism
  2. Hypotension, resting or orthostatic can suggest autonomic dysfunction or Addison's
  3. Thyroid exam for hyperthyroidism
  4. Lymph nodes for HIV or lymphoma
  5. Abd. for masses (Ca, Crohn's)
  6. Rectal exam for fistulae or abscesses
  7. Ext. for edema (malabsorption), synovitis (inflammatory bowel dis.)
  1. Skin for erythema nodosum or pyoderma gangrenosum (inflammatory bowel dis.), hyperpigmentation (Addison's; celiac disease, Whipple's)
  1. Lab evaluation
  1. Rarely necessary; tailor to clinical situation; may engage in trial of tx for IBS in a young healthy pt before doing extensive w/u
  2. Stool exam for:
  1. Fecal leukocytes (inflammatory bowel dis., infection)
  2. Blood (inflammatory bowel dis., Ca)
  3. O & P (if suspect, do 2-3x, 2-3d apart)
  4. Sudan stain for fat (malabsorption)
  5. Bacterial culture
  6. Clostridium dificile toxin
  1. CBC to screen for anemia if gross or occult blood in stool and to detect high WBC to suggest inflammatory bowel dis. or infection; eosinophilia may indicate parasitic disease
  2. ESR to screen for inflammatory bowel dis. or infection
  3. Electrolytes if concerned about fluid/electrolyte status
  4. Albumin, Ca if suspect malabsorption
  5. TSH if suspect hyperthyroidism
  6. Gastrin if has PUD and suspect Zollinger-Ellison
  7. Consider serologic testing for Celiac Disease--see link for details
  8. Urine for 5-hydroxyindoleacetic acid or vanillylmandelic acid if suspect carcinoid or pheo, respectively
  1. Sigmoidoscopy a useful early test if initial w/u doesn't reveal clear dx.
  2. Radiologic studies-rarely useful
  1. Abd. plain films-may see pancreatic calcifications indicating pancreatic insufficiency from chronic or recurrent pancreatitis
  2. UGI w/SBFT may help dx Crohn's
  3. Barium enema may help dx inflammatory bowel dis. or Ca
  4. Abdominal CT to evaluate mass

IV. Treatment

  1. Tailored to specific underlying condition
  2. Can use intestinal motility agents for symptomatic relief, e.g. Lomotil (diphenoxylate with atropine) or Imodium (loperamide)
  3. In a randomized trial in 105 young adults with travelers' diarrhea randomized to diet ad lib vs. advice re: "bland" diet with clear liquids and crackers, bread, or tortillas, there were no sig. diffs. in intensity or duration of sx (Clin. Inf. Dis. 39:468, 2004--JW)
  4. C. dificile colitis
    1. Traditionally treated with orally-active antibiotics, e.g. vancomycin, metronidazole
    2. Fecal transplantation for C. difile colitis
      1. In a study in 70 adults s/p multiple courses of antibiotics for clostridium dificile infection, who underwent stool transplantation (involving bowel preparation with oral polyethylene glycol then cecal infusion of stool via colonoscope), at 3mos, 66 of the pts had complete resolution of symptoms.  Over the year after transplantation, four pts relapsed.  No complications of the treatment were noted. (Gastroent 142:490, 2012-JW)
    3. Proton Pump Inhibitors and risk of recurrent C. dificile colitis
      1. In a cohort study in 1,100 pts with C. dificile infection, pts who had received PPIs had sig. higher risk of recurrence (25% vs. 18%) (Arch. Int. Med. 170:772, 2010-JW)
      2. In a cohort study of 100,000 hospital admissions over 5 years, incidence of nosocomial clostridium dificile infection was sig. higher among pts who received more-than-daily PPI therapy (1.4% vs. 0.3%) (Arch. Int. Med. 170:784, 2010-JW)