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Source: Fabel PH, Shealy KM. Diarrhea, constipation, and irritable bowel syndrome. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds., Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. Accessed March 14, 2017.


  • Self-limited increase in frequency and decrease in consistency of fecal discharge primarily due to viral, bacterial, or protozoal infection.


  • Most common bacterial causes: Shigella, Salmonella, Campylobacter, Staphylococcus, and Escherichia coli

  • Most common viral causes: Norwalk and rotavirus.

  • Medications (Table 1)

TABLE 1.Drugs Causing Diarrhea


  • Imbalance in absorption and secretion of water and electrolytes due to.

    • Change in active ion transport by decreased sodium absorption or increased chloride secretion (secretory diarrhea)

    • Change in intestinal motility caused by.

      • Reduced contact time in small intestine.

      • Premature emptying of colon.

      • Bacterial overgrowth.

    • Increase in luminal osmolarity.

    • Increase in tissue hydrostatic pressure.


  • Initiate isolation techniques in daycare centers and nursing homes to prevent transmission of viral illness.

  • Practice strict food handling, sanitation, water, and other environmental hygiene practices to prevent transmission of bacterial, parasitic, and protozoal infections.

  • Treat drinking water and limit consumption of fresh vegetables; in addition, prophylactic antibiotics and bismuth subsalicylate may be indicated when traveling.



  • Acute diarrheal episodes subside within 72 hours of onset.

  • Chronic diarrhea involves frequent attacks over extended periods of time.

  • Abrupt onset of.

    • Nausea.

    • Vomiting.

    • Abdominal pain.

    • Headache.

    • Fever.

    • Chills.

    • Malaise.

  • Frequent, nonbloody bowel movements over 12–60 hours.

  • Pain described as gripping or aching localized to.

    • Hypogastric region.

    • Left or right lower quadrant.

    • Sacral region.

  • Chronic diarrhea associated with.

    • Weight loss.

    • Anorexia.

    • Chronic weakness.

  • Physical exam demonstrates hyperperistalsis with borborygmi and generalized or local tenderness.



  • Stool analysis for microorganisms, blood, mucus, fat, osmolality, pH, electrolyte, and mineral concentration.

  • Stool cultures.

  • Stool test kits for detecting viruses, particularly rotavirus.

  • Antibody serologic testing is nonspecific and not practical.


  • Radiographic studies helpful in neoplastic and inflammatory conditions.


  • Assess for presence of colitis or cancer ...

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