Gastroenteritis resident survival guide
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Acute gastroenteritis and diarrhea are among the leading reasons for seeking medical care. Approximately 48 million cases occur annually in the United States, resulting in a cost of about $150 million to the U.S. health care system. Gastroenteritis is defined as inflammation of the stomach or intestinal mucosa. Patients with gastroenteritis typically present with acute diarrhea, fever, nausea and vomiting, anorexia, and crampy abdominal pain; the disease is defined as the passage of loose stool for at least 3 times per day for less than 14 days. It may be caused by viruses, bacteria, or parasites. Most cases of acute gastroenteritis are caused by viruses. Among the different viral causes, norovirus is the most common etiology for adults. Other common viral causes include rotavirus, adenovirus, and astrovirus. Common bacterial causes of gastroenteritis include Escherichia coli sp, Salmonella sp, Yersinia enterocolitica, and Vibrio sp, which can cause watery diarrhea, and Shigella sp and Campylobacter sp, which can cause dysenteric diarrhea. Parasites may also cause gastroenteritis, especially in developing countries. Giardia lamblia and Entamoeba histolytica are the most common parasitic causes of gastroenteritis. The first step in the management of these patients is to evaluate the hydration status and vital signs. Once the patient is stabilized, proceed to diagnostic evaluation. Practices that decrease the risk of acquiring infection include using safe water and food, avoiding unsafe foods during traveling, and hand-washing.
Classification based on etiology
- Viral gastroenteritis
- Bacterial gastroenteritis
- Parasitic gastroenteritis
Classification based on anatomical site involvement
- Characterized by watery, voluminous diarrhea that never presents with gross blood.
- Characterized by small volume mucousy and/or bloody diarrhea.
Classification based on pathology
- Characterized by WBC presence in stool
- WBC is not find in the stool
Life threatening causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. Some pathogens, such as Vibrio cholerae and Vibrio parahemolyticus can cause death due to severe dehydration and electrolyte imbalances.
Common causes and less common causes
Abbreviations: ETEC: Enterotoxigenic Escherichia coli, EPEC: Enteropathogenic Escherichia coli, EHEC: Enterohemorrhagic Escherichia coli, EAEC: Enteroaggregative Escherichia coli, EIEC: Enteroinvasive Escherichia coli, SARS: severe acute respiratory syndrome
|Common||Less Common||Common||Less Common||Helminthic||Protozoal|
|Gram Positive||Gram Negative||Gram Positive||Gram Negative||•Trichinella spiralis|
|•Giardia lamblia |
|Dysenteric diarreha||Watery diarrhea||• Bacillus cereus |
|•Bacteroides fragilis |
|•Shigella sp., •Campylobacter sp.||•Escherichia coli |
(ETEC, EPEC, EHEC, EAEC, EIEC)
§ EHEC, EIEC, EPEC and EAEC may cause bloody diarrhea, but they are classically associated with watery diarrhea.
† Either Salmonella and Yersinia can cause dysentery.
‡ Entamoeba histolytica may cause dysentery
FIRE: Focused Initial Rapid Evaluation
A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients with gastroenteritis are hemodynamically stable before starting diagnostic evaluation. Shown below is an algorithm depicting the initial management of acute diarrhea is based on the 2001 IDSA practice guidelines for the management of infectious diarrhea.
- Severe: Total disability due to diarrhea;
- Moderate: Able to function but with forced change in activities due to illness;
- Mild: No change in activities
- Diagnosis is based on clinical presentation which include, history of diarrhea (passage of more than 3 unformed stool in 24 h) in addition to enteric symptoms such as, nausea, vomiting, cramping abdominal pain, tenesmus, fecal urgency and moderate to severe flatulence.
- Stool diagnostic studies are not required except for some indications which are,
- Stool diagnostic tools include: bacterial culture, microscopy with and without stains or immunofluorescence and stool antigen tests for detection of protozoa, and for detecting viral agents, electron microscopy, or antigen-based tests.
- Novel molecular diagnostic tests are available now. They are faster, providing results in hours rather than days and also more applicable in outpatient setting.
- The most useful available FDA approved tests are:
- Luminex that can detect 15 different type of bacteria, viruses or parasites in less than 5 hours.
- Biofire Diagnostics that can detect 22 different type of bacteria, viruses or parasites in less than 2 hours.
- Rehydration with a balanced sodium-glucose solution is the first step for treatment. Oral rehydration solution (ORS) has reduced infant mortality in developing countries by at least 50%. ORS has no effect on disease course however, it's valuable to treat dehydration.
- For infants and the elderly with severe travelers diarrhea (TD) and in anyone who develops profuse cholera-like watery diarrhea, balanced ORS and medical evaluation are advised.
- For most otherwise healthy adults with TD, formal ORS is not needed as they can keep up with fluid losses by taking in salty soups, fruit juices, and carbohydrates to compensate.
- In severe diarrhea, a balanced ORS can usually be found at a local pharmacy with sodium of 60–75 mEq/l and glucose of 75–90 mmol/l for replacing salt and water. 
- Bismuth subsalicylates (BSSs) can be administered to control rates of passage of stool and may help travelers function better during bouts of mild to moderate illness. The recommended dose of BSS for therapy of acute diarrhea is 30 ml (525 mg) of liquid formulation or two tablets (263 mg per tablet) chewed well each 30–60 min not to exceed eight doses in 24 h. The drug will cause black stools and black tongues.
- In patients receiving antibiotics for TD, adjunctive loperamide therapy can be administered to decrease duration of diarrhea and increase chance for a cure. The recommended dose of loperamide for therapy for adults with diarrhea is 4 mg initially followed by 2 mg after subsequently passed watery stools not to exceed 8 mg per day. Loperamide is not given for more than 48 h. The most valuable use of loperamide in the self-treatment of TD is as a combination drug with antibacterial drugs where the antimotility drug quickly reduces the number of diarrhea stools passed while the antibiotic cures the enteric infection. 
- Empiric anti-microbial therapy for routine acute diarrheal infection, except in cases of TD where the likelihood of bacterial pathogens is high enough to justify the potential side effects of antibiotics.
- Use of antibiotics for community-acquired diarrhea should be discouraged as epidemiological studies suggest that most community-acquired diarrhea is viral in origin (norovirus, rotavirus, and adenovirus) and is not shortened by the use of antibiotics.
- Antibiotics shorten the overall duration of moderate-to-severe TD to a little over 24 h and are recommended in TD. The following table summarizes the recommended antibiotics for TD.
†: If symptoms are not resolved after 24 h, complete a 3-day course of antibiotics.
‡: Preferred regimen for dysentery or febrile diarrhea.
¶: Do not use if clinical suspicion for Campylobacter , Salmonella , Shigella , or other causes of invasive diarrhea.
- First, evaluate the hydration status of the patient. If the patient is hypovolumic, consider rehydration.
- If the patient is able to drink, start ORS otherwise, consider IV rehydration with isotonic fluids.
- As soon as the vital signs are stabilized, proceed to diagnosis and possible medication.
- Prescribe antidiarrheal agents such as, loperamide if the patient is afebrile and does not have a history of bloody diarrhea.
- Consider short-term antibiotic therapy in moderate to severe travelers diarrhea.
- Avoid antidiarrheal agents in bloody diarrhea (dysentery).
- Don't prescribe probiotics or prebiotics for the treatment of acute diarrhea.
- Don't prescribe antibiotics for community-acquired diarrhea, because they are mostly viral.
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