Chapter 040. Diarrhea and Constipation (Part 7)

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ACUTE DIARRHEA: TREATMENT Fluid and electrolyte replacement are of central importance to all forms of acute diarrhea. Fluid replacement alone may suffice for mild cases. Oral sugarelectrolyte solutions (sport drinks or designed formulations) should be instituted promptly with severe diarrhea to limit dehydration, which is the major cause of death. Profoundly dehydrated patients, especially infants and the elderly, require IV rehydration. In moderately severe nonfebrile and nonbloody diarrhea, antimotility and antisecretory agents such as loperamide can be useful adjuncts to control symptoms. Such agents should be avoided with febrile dysentery, which may be exacerbated or prolonged by them. Bismuth subsalicylate may...

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Chapter 040. Diarrhea and Constipation (Part 7) ACUTE DIARRHEA: TREATMENT Fluid and electrolyte replacement are of central importance to all forms of acute diarrhea. Fluid replacement alone may suffice for mild cases. Oral sugar- electrolyte solutions (sport drinks or designed formulations) should be instituted promptly with severe diarrhea to limit dehydration, which is the major cause of death. Profoundly dehydrated patients, especially infants and the elderly, require IV rehydration. In moderately severe nonfebrile and nonbloody diarrhea, antimotility and antisecretory agents such as loperamide can be useful adjuncts to control symptoms. Such agents should be avoided with febrile dysentery, which may be
exacerbated or prolonged by them. Bismuth subsalicylate may reduce symptoms of vomiting and diarrhea but should not be used to treat immunocompromised patients or those with renal impairment because of the risk of bismuth encephalopathy. Judicious use of antibiotics is appropriate in selected instances of acute diarrhea and may reduce its severity and duration (Fig. 40-2). Many physicians treat moderately to severely ill patients with febrile dysentery empirically without diagnostic evaluation using a quinolone, such as ciprofloxacin (500 mg bid for 3– 5 d). Empirical treatment can also be considered for suspected giardiasis with metronidazole (250 mg qid for 7 d). Selection of antibiotics and dosage regimens are otherwise dictated by specific pathogens, geographic patterns of resistance, and conditions found (Chaps. 122, 143, 146, 147, 148, 149, 150, 151, and 152). Antibiotic coverage is indicated whether or not a causative organism is discovered in patients who are immunocompromised, have mechanical heart valves or recent vascular grafts, or are elderly. Antibiotic prophylaxis is indicated for certain patients traveling to high-risk countries in whom the likelihood or seriousness of acquired diarrhea would be especially high, including those with immunocompromise, IBD, hemochromatosis, or gastric achlorhydria. Use of trimethoprim/sulfamethoxazole, ciprofloxacin, or rifaximin may reduce bacterial diarrhea in such travelers by 90%, though rifaximin may not be suitable for invasive disease. Finally, physicians should be vigilant to identify if an outbreak
of diarrheal illness is occurring and to alert the public health authorities promptly. This may reduce the ultimate size of the affected population. Chronic Diarrhea Diarrhea lasting >4 weeks warrants evaluation to exclude serious underlying pathology. In contrast to acute diarrhea, most of the causes of chronic diarrhea are noninfectious. The classification of chronic diarrhea by pathophysiologic mechanism facilitates a rational approach to management, though many diseases cause diarrhea by more than one mechanism (Table 40-3). Table 40-3 Major Causes of Chronic Diarrhea According to Predominant Pathophysiologic Mechanism
Secretory causes Inflammatory causes Exogenous stimulant laxatives Idiopathic inflammatory bowel disease (Crohn's, chronic ulcerative Chronic ethanol ingestion colitis) Other drugs and toxins Lymphocytic and collagenous Endogenous laxatives colitis (dihydroxy bile acids) Immune-related mucosal disease Idiopathic secretory diarrhea (1° or 2° immunodeficiencies, food allergy, eosinophilic gastroenteritis, Certain bacterial infections graft-vs-host disease) Bowel resection, disease, or Infections (invasive bacteria, fistula (absorption) viruses, and parasites, Brainerd diarrhea) Partial bowel obstruction or Radiation injury fecal impaction Gastrointestinal malignancies Hormone-producing tumors (carcinoid, VIPoma, medullary cancer Dysmotile causes of thyroid, mastocytosis, gastrinoma, Irritable bowel syndrome colorectal villous adenoma)
Addison's disease (including post-infectious IBS) Congenital electrolyte Visceral neuromyopathies absorption defects Hyperthyroidism Osmotic causes Drugs (prokinetic agents) Osmotic laxatives (Mg2+, PO4–3, Postvagotomy –2 SO4 ) Factitial causes Lactase and other disaccharide deficiencies Munchausen Nonabsorbable carbohydrates Eating disorders (sorbitol, lactulose, polyethylene Iatrogenic causes glycol) Cholecystectomy Steatorrheal causes Ileal resection Intraluminal maldigestion (pancreatic exocrine insufficiency, Bariatric surgery bacterial overgrowth, bariatric surgery, Vagotomy, fundoplication liver disease) Mucosal malabsorption (celiac
sprue, Whipple's disease, infections, abetalipoproteinemia, ischemia) Post-mucosal obstruction (1° or 2° lymphatic obstruction) [newpage]