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INTRODUCTION

  • Diarrhea is an increased frequency and decreased consistency of fecal discharge as compared with an individual’s normal bowel pattern. Diarrhea can be thought of as both a symptom and a sign of a systemic disease.

  • Acute diarrhea is commonly defined as shorter than 14 days’ duration, persistent diarrhea as longer than 14 days’ duration, and chronic diarrhea as longer than 30 days’ duration. Most cases of acute diarrhea are caused by infections with viruses, bacteria, or protozoa, and are generally self-limited.

PATHOPHYSIOLOGY

  • Although viruses are more commonly associated with acute gastroenteritis, bacteria are responsible for more cases of acute diarrhea. Common causative bacterial organisms include Shigella, Salmonella, Campylobacter, Staphylococcus, and Escherichia coli. Acute viral infections are attributed mostly to the Norwalk and rotavirus groups.

  • Diarrhea is an imbalance in absorption and secretion of water and electrolytes. It may be associated with a specific disease of the gastrointestinal (GI) tract or with a disease outside the GI tract.

  • Four general pathophysiologic mechanisms disrupt water and electrolyte balance, leading to diarrhea: (1) a change in active ion transport by either decreased sodium absorption or increased chloride secretion, (2) a change in intestinal motility, (3) an increase in luminal osmolarity, and (4) an increase in tissue hydrostatic pressure. These mechanisms have been related to four broad clinical diarrheal groups: secretory, osmotic, exudative, and altered intestinal transit.

  • Secretory diarrhea occurs when a stimulating substance (eg, vasoactive intestinal peptide [VIP] from a pancreatic tumor, unabsorbed dietary fat in steatorrhea, laxatives, hormones [such as secretion], bacterial toxins, and excessive bile salts) increases secretion or decreases absorption of large amounts of water and electrolytes.

  • Inflammatory diseases of the GI tract can cause exudative diarrhea by discharge of mucus, proteins, or blood into the gut. With altered intestinal transit, intestinal motility is altered by reduced contact time in the small intestine, premature emptying of the colon, or bacterial overgrowth.

CLINICAL PRESENTATION

  • Acute diarrhea is usually self-limiting and subsides within 72 hours of onset, whereas chronic diarrhea involves frequent attacks over extended time periods. However, infants, young children, the elderly, and debilitated persons are at risk for morbid and mortal events in prolonged or voluminous diarrhea.

  • Signs and symptoms include:

    • ✔ Abrupt onset of nausea, vomiting, abdominal pain, headache, fever, chills, and malaise

    • ✔ Bowel movements are frequent and never bloody, and diarrhea lasts 12–60 hours

    • ✔ Intermittent periumbilical or lower right quadrant pain with cramps and audible bowel sounds is characteristic of small intestinal disease

    • ✔ When pain is present in large intestinal diarrhea, it is a gripping, aching sensation with tenesmus (straining, ineffective, and painful stooling)

    • ✔ In chronic diarrhea, a history of previous bouts, weight loss, anorexia, and chronic weakness are important findings

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

  • Laboratory tests:

    • ✔ Stool analysis studies include examination for microorganisms, blood, ...

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