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Emergency And Acute Medicine – Adult Diarrhea
Basics
Description Diarrhea is defined as frequent bowel movements (>3/day) that are loose and watery, most commonly due to infectious agents or toxin exposure.
Etiology
Viruses Account for 50–70% of cases.
Invasive bacteria
Campylobacter: Contaminated food or water, wilderness water, birds, animals; most common bacterial cause; gross or occult blood in 60–90%.
Salmonella: Contaminated water, eggs, poultry, dairy; Salmonella typhi causes typhoid fever with sustained fever, abdominal pain, rose spots, splenomegaly, and bradycardia.
Shigella: Fecal–oral transmission.
Vibrio parahaemolyticus: Raw or undercooked seafood.
Yersinia: Contaminated pork, water, milk; may mimic appendicitis or present as mesenteric adenitis.
Bacterial toxin–mediated
Escherichia coli: Major cause of traveler’s diarrhea; fecal contamination of food or water.
Staphylococcus aureus: Most common toxin-related illness; symptoms 1–6 hr after ingestion.
Bacillus cereus: Classically from reheated fried rice; symptoms within 1–36 hr.
Clostridium difficile: Antibiotic-associated enteritis and pseudomembranous colitis; onset within 10 days of antibiotic exposure.
Aeromonas hydrophila: Aquatic exposure; typically affects children <3 yr; fecal leukocytes absent.< />pan>
Cholera (Vibrio cholerae): Enterotoxin-mediated; profuse “rice-water” stools.
Protozoa
Giardia lamblia: Most common parasitic cause in North America; associated with travel, daycare, institutions, men who have sex with men, and untreated mountain water.
Cryptosporidium parvum: Common in patients with AIDS.
Entamoeba histolytica: May cause extraintestinal disease, including hepatic amebic abscess.
Pediatric considerations Most cases are viral and self-limited; rotavirus accounts for ~50%. Shigella may be associated with seizures. Assessment should focus on hydration status.
Diagnosis
Signs And Symptoms
History Loose or watery stools, bloody stools with mucus, abdominal cramps, tenesmus, flatulence, fever, headache, myalgias, nausea, vomiting, dehydration, lethargy, or stupor.
Physical exam Dry mucous membranes, abdominal tenderness, perianal inflammation, fissures, or fistulae.
Essential Workup Digital rectal exam for gross or occult blood. Fecal leukocytes suggest invasive bacterial infection and are absent in viral, protozoal, or toxin-mediated diarrhea.
Diagnosis Tests And Interpretation
Lab
CBC for significant blood loss or systemic toxicity.
Electrolytes, glucose, BUN, creatinine for lethargy, dehydration, toxicity, altered mental status, diuretic use, or chronic liver/renal disease.
Stool culture if fecal leukocytes present or in immunocompromised patients, travelers, men who have sex with men, food handlers, healthcare workers, daycare workers, or institutionalized patients.
Blood cultures if bacteremia suspected, patient requires admission, or is immunocompromised, elderly, or an infant.
Imaging Abdominal radiographs only if obstruction or toxic megacolon is suspected.
Differential Diagnosis Ulcerative colitis, Crohn disease, mesenteric ischemia, diverticulitis, anal fissures, hemorrhoids, irritable bowel syndrome, food allergies, malrotation with volvulus, Meckel diverticulum, intussusception, appendicitis, drugs and toxins (mannitol, sorbitol, magnesium antacids, quinidine, colchicine), mushrooms, mercury poisoning.
Treatment
Prehospital Establish IV access if severe dehydration; avoid exposure to contaminated body fluids.
Initial stabilization and therapy Assess airway, breathing, circulation. Begin IV 0.9% normal saline for severe dehydration.
Emergency department treatment and procedures
Oral rehydration for mild dehydration (oral rehydration solutions).
IV fluids for hypotension, persistent vomiting, obtundation, metabolic acidosis, or severe electrolyte abnormalities.
Bismuth subsalicylate for symptomatic relief.
Kaolin-pectin reduces stool liquidity but does not alter disease course.
Antimotility agents (loperamide, diphenoxylate) may be used cautiously in noninfectious diarrhea; avoid prolonged use in infectious diarrhea due to risk of toxic megacolon and bacteremia.
Targeted antibiotics for confirmed or strongly suspected bacterial or protozoal infections.
Medication
Ampicillin, TMP-SMX, ceftriaxone, ciprofloxacin, doxycycline, erythromycin, iodoquinol, metronidazole, quinacrine, tetracycline, or oral vancomycin as indicated by organism and patient factors.
Follow-Up Disposition
Admission criteria Hypotension refractory to fluids, significant bleeding, sepsis or toxicity, intractable vomiting or abdominal pain, severe electrolyte imbalance, metabolic acidosis, altered mental status, or children with >10–15% dehydration.
Discharge criteria Mild disease with adequate oral intake or dehydration responsive to IV fluids.
Issues for referral Prolonged or recurrent diarrhea may require gastroenterology evaluation.
Follow-Up Recommendations Most cases are self-limited; routine follow-up is optional unless symptoms persist.
Pearls And Pitfalls Avoid prolonged antimotility therapy in infectious diarrhea. TMP-SMX, ciprofloxacin, doxycycline, and tetracycline are contraindicated in pregnancy; metronidazole may be used in the third trimester. Healthcare workers and food handlers with infectious diarrhea may require public health clearance before returning to work. Clostridioides difficile infection is increasingly common, particularly in nursing home populations.
Basics
Description Diarrhea is defined as frequent bowel movements (>3/day) that are loose and watery, most commonly due to infectious agents or toxin exposure.
Etiology
Viruses Account for 50–70% of cases.
Invasive bacteria
Campylobacter: Contaminated food or water, wilderness water, birds, animals; most common bacterial cause; gross or occult blood in 60–90%.
Salmonella: Contaminated water, eggs, poultry, dairy; Salmonella typhi causes typhoid fever with sustained fever, abdominal pain, rose spots, splenomegaly, and bradycardia.
Shigella: Fecal–oral transmission.
Vibrio parahaemolyticus: Raw or undercooked seafood.
Yersinia: Contaminated pork, water, milk; may mimic appendicitis or present as mesenteric adenitis.
Bacterial toxin–mediated
Escherichia coli: Major cause of traveler’s diarrhea; fecal contamination of food or water.
Staphylococcus aureus: Most common toxin-related illness; symptoms 1–6 hr after ingestion.
Bacillus cereus: Classically from reheated fried rice; symptoms within 1–36 hr.
Clostridium difficile: Antibiotic-associated enteritis and pseudomembranous colitis; onset within 10 days of antibiotic exposure.
Aeromonas hydrophila: Aquatic exposure; typically affects children <3 yr; fecal leukocytes absent.< />pan>
Cholera (Vibrio cholerae): Enterotoxin-mediated; profuse “rice-water” stools.
Protozoa
Giardia lamblia: Most common parasitic cause in North America; associated with travel, daycare, institutions, men who have sex with men, and untreated mountain water.
Cryptosporidium parvum: Common in patients with AIDS.
Entamoeba histolytica: May cause extraintestinal disease, including hepatic amebic abscess.
Pediatric considerations Most cases are viral and self-limited; rotavirus accounts for ~50%. Shigella may be associated with seizures. Assessment should focus on hydration status.
Diagnosis
Signs And Symptoms
History Loose or watery stools, bloody stools with mucus, abdominal cramps, tenesmus, flatulence, fever, headache, myalgias, nausea, vomiting, dehydration, lethargy, or stupor.
Physical exam Dry mucous membranes, abdominal tenderness, perianal inflammation, fissures, or fistulae.
Essential Workup Digital rectal exam for gross or occult blood. Fecal leukocytes suggest invasive bacterial infection and are absent in viral, protozoal, or toxin-mediated diarrhea.
Diagnosis Tests And Interpretation
Lab
CBC for significant blood loss or systemic toxicity.
Electrolytes, glucose, BUN, creatinine for lethargy, dehydration, toxicity, altered mental status, diuretic use, or chronic liver/renal disease.
Stool culture if fecal leukocytes present or in immunocompromised patients, travelers, men who have sex with men, food handlers, healthcare workers, daycare workers, or institutionalized patients.
Blood cultures if bacteremia suspected, patient requires admission, or is immunocompromised, elderly, or an infant.
Imaging Abdominal radiographs only if obstruction or toxic megacolon is suspected.
Differential Diagnosis Ulcerative colitis, Crohn disease, mesenteric ischemia, diverticulitis, anal fissures, hemorrhoids, irritable bowel syndrome, food allergies, malrotation with volvulus, Meckel diverticulum, intussusception, appendicitis, drugs and toxins (mannitol, sorbitol, magnesium antacids, quinidine, colchicine), mushrooms, mercury poisoning.
Treatment
Prehospital Establish IV access if severe dehydration; avoid exposure to contaminated body fluids.
Initial stabilization and therapy Assess airway, breathing, circulation. Begin IV 0.9% normal saline for severe dehydration.
Emergency department treatment and procedures
Oral rehydration for mild dehydration (oral rehydration solutions).
IV fluids for hypotension, persistent vomiting, obtundation, metabolic acidosis, or severe electrolyte abnormalities.
Bismuth subsalicylate for symptomatic relief.
Kaolin-pectin reduces stool liquidity but does not alter disease course.
Antimotility agents (loperamide, diphenoxylate) may be used cautiously in noninfectious diarrhea; avoid prolonged use in infectious diarrhea due to risk of toxic megacolon and bacteremia.
Targeted antibiotics for confirmed or strongly suspected bacterial or protozoal infections.
Medication
Ampicillin, TMP-SMX, ceftriaxone, ciprofloxacin, doxycycline, erythromycin, iodoquinol, metronidazole, quinacrine, tetracycline, or oral vancomycin as indicated by organism and patient factors.
Follow-Up Disposition
Admission criteria Hypotension refractory to fluids, significant bleeding, sepsis or toxicity, intractable vomiting or abdominal pain, severe electrolyte imbalance, metabolic acidosis, altered mental status, or children with >10–15% dehydration.
Discharge criteria Mild disease with adequate oral intake or dehydration responsive to IV fluids.
Issues for referral Prolonged or recurrent diarrhea may require gastroenterology evaluation.
Follow-Up Recommendations Most cases are self-limited; routine follow-up is optional unless symptoms persist.
Pearls And Pitfalls Avoid prolonged antimotility therapy in infectious diarrhea. TMP-SMX, ciprofloxacin, doxycycline, and tetracycline are contraindicated in pregnancy; metronidazole may be used in the third trimester. Healthcare workers and food handlers with infectious diarrhea may require public health clearance before returning to work. Clostridioides difficile infection is increasingly common, particularly in nursing home populations.
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