Diarrhea : Definition, Diagnosis, Cause, And Treatment

Wednesday, March 5th 2014. | Disease


Diarrhea is an increased frequency and decreased consistency of fecal discharge as compared with an individual’s normal bowel pattern. Frequency and consistency are variable within and between individuals. For example, some individuals defecate as many as 3 times a day, while others defecate only 2 or 3 times per week.
Pathophysiology of Diarrhea :
Diarrhea is an imbalance in absorption and secretion of water and electrolytes. Diarrhea may be associated with a specific disease of the gastrointestinal tract or with a disease outside the gastrointestinal tract.
Four general pathophysiologic mechanisms disrupt water and electrolyte balance, leading to diarrhea. These four mechanisms are the basis of diagnosis and therapy. They are (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 (e.g., vasoactive intestinal peptide [VIP], laxatives, or bacterial toxin) increases secretion or decreases absorption of large amounts of water and electrolytes.
  • Poorly absorbed substances retain intestinal fluids, resulting in osmotic diarrhea.
  • Inflammatory diseases of the gastrointestinal tract can cause exudative diarrhea by discharge of mucus, proteins, or blood into the gut.
  • Intestinal motility can be altered by reduced contact time in the small intestine, premature emptying of the colon, and by bacterial overgrowth.
Treatment for Diarrhea :
Most clinicians recommend stopping solid foods for 24 hours and avoiding dairy products.
Recommendations for treating acute diarrhea. Follow these steps: (1) Perform a complete history and physical examination. (2) Is the diarrhea acute or chronic? If chronic diarrhea. (3) If acute diarrhea, check for fever and/or systemic signs and symptoms (i.e., toxic patient). If systemic illness (fever, anorexia, or volume depletion), check for an infectious source. If positive for infectious diarrhea, use appropriate antibiotic/anthelmintic drug and symptomatic therapy. If negative for infectious cause, use only symtomatic treatment. (4) If no systemic findings, then use symptomatic therapy based on severity of volume depletion, oral or parenteral fluid/electrolytes, antidiarrheal agents, and diet.
When nausea or vomiting is mild, a digestible low-residue diet is administered for 24 hours.
If vomiting is present and is uncontrollable with antiemetics, nothing is taken by mouth. As bowel movements decrease, a bland diet is begun. Feeding should continue in children with acute bacterial diarrhea.
Pharmacology for Diarrhea : 
  1. Loperamide is often recommended for managing acute and chronic diarrhea. Diarrhea lasting 48 hours beyond initiating loperamide warrants medical attention.
  2. Adsorbents (such as kaolin-pectin) are used for symptomatic relief (see Table 22-4). Adsorbents are nonspecific in their action; they adsorb nutrients, toxins, drugs, and digestive juices. Coadministration with other drugs reduces their bioavailability.
  3. Bismuth subsalicylate is often used for treatment or prevention of diarrhea (traveler’s diarrhea) and has antisecretory, anti-inflammatory, and antibacterial effects.
  4. Lactobacillus preparation is intended to replace colonic microflora. This supposedly restores intestinal functions and suppresses the growth of pathogenic microorganisms. However, a dairy product diet containing 200 to 400 g of lactose or dextrin is equally effective in recolonization.
  5. Anticholinergic drugs, such as atropine, block vagal tone and prolong gut transit time. Their value in controlling diarrhea is questionable and limited by side effects.
  6. Octreotide, a synthetic octapeptide analog of endogenous somatostatin, is prescribed for the symptomatic treatment of carcinoid tumors and VIP-secreting tumors (VIPomas). Octreotide is used in selected patients with carcinoid syndrome. Octreotide blocks the release of serotonin and other active peptides and is effective in controlling diarrhea and flushing. Dosage range for managing diarrhea associated with carcinoid tumors is 100 to 600 mcg/day in two to four divided doses subcutaneously. Octreotide is associated with an adverse effects such as cholelithiasis, nausea, diarrhea, and abdominal pain.

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