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Emergency And Acute Medicine - Gastroenteritis
Basic Overview
Gastroenteritis is an inflammatory condition of the stomach and intestines characterized by diarrhea and vomiting, most commonly caused by infectious agents or exposure to toxins.
Causes And Risk Factors
Infectious causes account for most cases. Viruses are responsible for approximately 50–70% of cases, with norovirus increasingly common among travelers, particularly those returning from Mexico and India. Invasive bacterial causes include Campylobacter, the most common bacterial pathogen, typically acquired from contaminated food, water, or animal exposure and often associated with gross or occult blood in stool. Salmonella is linked to contaminated water, eggs, poultry, or dairy products, with Salmonella typhi causing typhoid fever characterized by persistent fever, abdominal pain, rose spots, splenomegaly, and relative bradycardia. Shigella spreads via the fecal–oral route, while Vibrio parahaemolyticus is associated with raw or undercooked seafood. Yersinia infections arise from contaminated pork, water, or milk and may mimic appendicitis due to mesenteric adenitis. Food-borne toxin-mediated illnesses include Staphylococcus aureus, with symptoms appearing within 1–6 hours, and Bacillus cereus, classically associated with reheated rice, with symptoms developing within 1–36 hours. Cholera causes profuse watery diarrhea described as rice-water stools. Ciguatera poisoning follows fish ingestion and presents with neurologic symptoms such as paresthesias and hypotension. Scombroid poisoning results from spoiled fish and causes flushing, headache, and burning sensations, usually resolving within hours. Protozoal causes include Giardia lamblia, particularly in travelers, campers drinking untreated water, daycare children, and men who have sex with men. Noninfectious causes include heavy metals, organic chemicals, pesticides, radioactive substances, and adverse reactions to food additives. In pediatric patients, most cases are viral and self-limited, with rotavirus being common; Shigella infections may be associated with seizures.
Clinical Features And Presentation
Patients commonly present with nausea, vomiting, diarrhea, abdominal cramps, fever, malaise, myalgias, headache, and anorexia. Bloody or mucous stools suggest invasive disease. Severe cases may involve hypotension, lethargy, and dehydration.
Physical Examination Findings
Findings may include dry mucous membranes, tachycardia, abdominal tenderness, and perianal irritation such as fissures or fistulas, reflecting dehydration or inflammatory diarrhea.
Initial Evaluation And Assessment
Evaluation should include a digital rectal examination to assess for gross or occult blood. Stool leukocyte testing may help differentiate invasive bacterial infections, where leukocytes are present, from viral, protozoal, or toxin-mediated illnesses.
Laboratory And Imaging Evaluation
CBC is indicated in cases of significant blood loss or systemic toxicity. Electrolytes, glucose, BUN, and creatinine should be obtained in patients with lethargy, dehydration, toxicity, altered mental status, or underlying renal or liver disease. Stool cultures are indicated when fecal leukocytes are present, in immunocompromised patients, travelers, food handlers, and healthcare or daycare workers. Blood cultures are reserved for suspected bacteremia, severe systemic illness, or high-risk populations such as the elderly, infants, and immunocompromised patients. Imaging has limited value and is reserved for suspected obstruction or toxic megacolon. In children, laboratory testing is usually unnecessary unless toxicity or immunocompromise is present.
Differential Diagnosis Considerations
Conditions to consider include gastritis, peptic ulcer disease, food allergies, appendicitis, irritable bowel syndrome, inflammatory bowel disease, malrotation with volvulus, Meckel diverticulum, medication-induced diarrhea, and toxin exposures.
Prehospital Management
Establish IV access in patients with severe dehydration and minimize exposure to contaminated body fluids or clothing.
Stabilization And Early Treatment
Management focuses on airway, breathing, and circulation. Severely dehydrated patients require IV fluid resuscitation with 0.9% normal saline.
Emergency Department Care
Oral rehydration with electrolyte solutions is appropriate for mild dehydration. IV fluids are indicated for hypotension, persistent vomiting, altered mental status, metabolic derangements, or severe dehydration, using weight-appropriate boluses followed by maintenance fluids. Bismuth subsalicylate provides symptomatic relief and has antisecretory effects. Antimotility agents may be used cautiously in noninfectious diarrhea but should be avoided or limited in infectious cases due to the risk of prolonged illness or toxic megacolon. Antibiotics are reserved for specific pathogens such as Campylobacter, Salmonella, Shigella, Vibrio, Clostridium difficile, Escherichia coli, and Giardia. Antiemetics such as ondansetron, prochlorperazine, or promethazine may be used for symptom control.
Medication Options
Treatment may include antibiotics tailored to the identified pathogen, antiemetics, and supportive medications for hydration and symptom relief. Drug selection should consider age, pregnancy status, and comorbid conditions.
Disposition And Follow-Up
Admission is required for patients with refractory hypotension, significant bleeding, sepsis, intractable symptoms, severe electrolyte disturbances, metabolic acidosis, altered mental status, or severe dehydration, particularly in children. Patients with mild disease or dehydration responsive to fluids may be discharged.
Follow-Up Guidance
Most cases are self-limited and do not require routine follow-up. Patients with prolonged or recurrent symptoms may benefit from gastroenterology referral.
Key Clinical Insights And Pitfalls
Viruses cause the majority of gastroenteritis cases. Antimotility agents should be avoided in infectious diarrhea. Several commonly used antibiotics are contraindicated in pregnancy. Early recognition of dehydration and judicious use of antibiotics are critical to optimal management.
Basic Overview
Gastroenteritis is an inflammatory condition of the stomach and intestines characterized by diarrhea and vomiting, most commonly caused by infectious agents or exposure to toxins.
Causes And Risk Factors
Infectious causes account for most cases. Viruses are responsible for approximately 50–70% of cases, with norovirus increasingly common among travelers, particularly those returning from Mexico and India. Invasive bacterial causes include Campylobacter, the most common bacterial pathogen, typically acquired from contaminated food, water, or animal exposure and often associated with gross or occult blood in stool. Salmonella is linked to contaminated water, eggs, poultry, or dairy products, with Salmonella typhi causing typhoid fever characterized by persistent fever, abdominal pain, rose spots, splenomegaly, and relative bradycardia. Shigella spreads via the fecal–oral route, while Vibrio parahaemolyticus is associated with raw or undercooked seafood. Yersinia infections arise from contaminated pork, water, or milk and may mimic appendicitis due to mesenteric adenitis. Food-borne toxin-mediated illnesses include Staphylococcus aureus, with symptoms appearing within 1–6 hours, and Bacillus cereus, classically associated with reheated rice, with symptoms developing within 1–36 hours. Cholera causes profuse watery diarrhea described as rice-water stools. Ciguatera poisoning follows fish ingestion and presents with neurologic symptoms such as paresthesias and hypotension. Scombroid poisoning results from spoiled fish and causes flushing, headache, and burning sensations, usually resolving within hours. Protozoal causes include Giardia lamblia, particularly in travelers, campers drinking untreated water, daycare children, and men who have sex with men. Noninfectious causes include heavy metals, organic chemicals, pesticides, radioactive substances, and adverse reactions to food additives. In pediatric patients, most cases are viral and self-limited, with rotavirus being common; Shigella infections may be associated with seizures.
Clinical Features And Presentation
Patients commonly present with nausea, vomiting, diarrhea, abdominal cramps, fever, malaise, myalgias, headache, and anorexia. Bloody or mucous stools suggest invasive disease. Severe cases may involve hypotension, lethargy, and dehydration.
Physical Examination Findings
Findings may include dry mucous membranes, tachycardia, abdominal tenderness, and perianal irritation such as fissures or fistulas, reflecting dehydration or inflammatory diarrhea.
Initial Evaluation And Assessment
Evaluation should include a digital rectal examination to assess for gross or occult blood. Stool leukocyte testing may help differentiate invasive bacterial infections, where leukocytes are present, from viral, protozoal, or toxin-mediated illnesses.
Laboratory And Imaging Evaluation
CBC is indicated in cases of significant blood loss or systemic toxicity. Electrolytes, glucose, BUN, and creatinine should be obtained in patients with lethargy, dehydration, toxicity, altered mental status, or underlying renal or liver disease. Stool cultures are indicated when fecal leukocytes are present, in immunocompromised patients, travelers, food handlers, and healthcare or daycare workers. Blood cultures are reserved for suspected bacteremia, severe systemic illness, or high-risk populations such as the elderly, infants, and immunocompromised patients. Imaging has limited value and is reserved for suspected obstruction or toxic megacolon. In children, laboratory testing is usually unnecessary unless toxicity or immunocompromise is present.
Differential Diagnosis Considerations
Conditions to consider include gastritis, peptic ulcer disease, food allergies, appendicitis, irritable bowel syndrome, inflammatory bowel disease, malrotation with volvulus, Meckel diverticulum, medication-induced diarrhea, and toxin exposures.
Prehospital Management
Establish IV access in patients with severe dehydration and minimize exposure to contaminated body fluids or clothing.
Stabilization And Early Treatment
Management focuses on airway, breathing, and circulation. Severely dehydrated patients require IV fluid resuscitation with 0.9% normal saline.
Emergency Department Care
Oral rehydration with electrolyte solutions is appropriate for mild dehydration. IV fluids are indicated for hypotension, persistent vomiting, altered mental status, metabolic derangements, or severe dehydration, using weight-appropriate boluses followed by maintenance fluids. Bismuth subsalicylate provides symptomatic relief and has antisecretory effects. Antimotility agents may be used cautiously in noninfectious diarrhea but should be avoided or limited in infectious cases due to the risk of prolonged illness or toxic megacolon. Antibiotics are reserved for specific pathogens such as Campylobacter, Salmonella, Shigella, Vibrio, Clostridium difficile, Escherichia coli, and Giardia. Antiemetics such as ondansetron, prochlorperazine, or promethazine may be used for symptom control.
Medication Options
Treatment may include antibiotics tailored to the identified pathogen, antiemetics, and supportive medications for hydration and symptom relief. Drug selection should consider age, pregnancy status, and comorbid conditions.
Disposition And Follow-Up
Admission is required for patients with refractory hypotension, significant bleeding, sepsis, intractable symptoms, severe electrolyte disturbances, metabolic acidosis, altered mental status, or severe dehydration, particularly in children. Patients with mild disease or dehydration responsive to fluids may be discharged.
Follow-Up Guidance
Most cases are self-limited and do not require routine follow-up. Patients with prolonged or recurrent symptoms may benefit from gastroenterology referral.
Key Clinical Insights And Pitfalls
Viruses cause the majority of gastroenteritis cases. Antimotility agents should be avoided in infectious diarrhea. Several commonly used antibiotics are contraindicated in pregnancy. Early recognition of dehydration and judicious use of antibiotics are critical to optimal management.
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