What is the recommended approach to assess and manage acute gastroenteritis, including severity assessment, rehydration, diet, antiemetics, antidiarrheals, antibiotics, and indications for laboratory testing?

Approach to Acute Gastroenteritis

The cornerstone of managing acute gastroenteritis is immediate assessment of dehydration severity followed by oral rehydration solution (ORS) as first-line therapy for mild-to-moderate dehydration, with early refeeding and avoidance of antidiarrheal agents in children. 1

Initial Clinical Assessment

Obtain accurate body weight and assess dehydration severity using specific clinical signs:

Mild Dehydration (3-5% fluid deficit):

• Increased thirst 1
• Slightly dry mucous membranes 1

Moderate Dehydration (6-9% fluid deficit):

• Loss of skin turgor with tenting when pinched 1
• Dry mucous membranes 1
• Decreased urine output 1

Severe Dehydration (≥10% fluid deficit):

• Severe lethargy or altered consciousness 1
• Prolonged skin tenting >2 seconds 1
• Cool, poorly perfused extremities 1
• Decreased capillary refill 1
• Rapid, deep breathing (acidosis) 1

The most reliable predictors of significant dehydration are prolonged skin retraction time, abnormal capillary refill, and rapid deep breathing—more so than sunken fontanelle or absent tears. 1, 2

Rule Out Alternative Diagnoses

Fever, vomiting, and loose stools can indicate non-gastrointestinal illnesses including meningitis, bacterial sepsis, pneumonia, otitis media, or urinary tract infection—particularly in infants and young children. 1 Perform a complete physical examination including auscultation for adequate bowel sounds before initiating oral therapy. 1

Laboratory Testing Indications

Laboratory studies are rarely needed for routine acute gastroenteritis. 1

Order serum electrolytes when:

• Clinical signs suggest abnormal sodium or potassium concentrations 1
• Severe dehydration is present 1

Order stool cultures when:

• Bloody diarrhea (dysentery) is present 1
• White blood cells visible on methylene blue stain 1
• Recent antibiotic use (suspect Clostridium difficile) 1
• Exposure to day care centers with Giardia or Shigella outbreaks 1
• Recent foreign travel 1
• Immunodeficiency 1

Order blood cultures when:

• Infants <3 months of age 1
• Signs of septicemia or enteric fever 1
• Immunocompromised status 1
• Travel to enteric fever-endemic areas with unexplained fever 1

For suspected Shiga toxin-producing organisms, use diagnostic approaches that detect Shiga toxin or its genes and distinguish E. coli O157:H7 from other STEC. 1

Rehydration Strategy

Mild Dehydration (3-5% deficit):

• Administer ORS containing 50-90 mEq/L sodium 1
• Give 50 mL/kg over 2-4 hours 1
• Start with small volumes (one teaspoon) using spoon, syringe, or medicine dropper 1
• Gradually increase amount as tolerated 1
• Reassess hydration status after 2-4 hours 1

Moderate Dehydration (6-9% deficit):

• Administer ORS 100 mL/kg over 2-4 hours 1
• Use same small-volume technique as mild dehydration 1
• If oral intake fails, consider nasogastric ORS administration 1

Severe Dehydration (≥10% deficit or shock):

• Initiate intravenous isotonic fluids immediately (lactated Ringer's or normal saline) 1
• Give 20 mL/kg boluses until pulse, perfusion, and mental status normalize 1
• May require two IV lines or alternate access (venous cutdown, femoral vein, intraosseous) 1
• Once consciousness returns and no aspiration risk or ileus, transition remaining deficit to ORS 1

Reduced osmolarity ORS is recommended as first-line therapy for mild-to-moderate dehydration from any cause. 1

Replace Ongoing Losses:

• Continue ORS to replace ongoing stool and vomit losses throughout rehydration and maintenance phases 1

Nutritional Management

Resume age-appropriate usual diet immediately during or after rehydration is completed. 1

Infants:

• Continue breastfeeding throughout the diarrheal episode 1
• Continue regular formula (do not dilute) 1

Children:

• Offer starches (rice, potatoes, noodles, crackers, bananas), cereals (rice, wheat, oat), soup, yogurt, vegetables, and fresh fruits 3
• Avoid high-fat foods that delay gastric emptying 3
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice, Jell-O, presweetened cereals) 3

Early refeeding reduces illness severity and duration rather than prolonging symptoms. 3

Antiemetic Use

Ondansetron may be given to children >4 years of age to facilitate oral rehydration when vomiting is significant. 1

• Reduces vomiting episodes 2, 4
• Improves oral intake success 2, 4
• Decreases need for IV rehydration 2, 4
• Reduces ED length of stay 2
• Few serious side effects reported 2, 4

For younger children with vomiting, administer small ORS volumes (5-10 mL) every 1-2 minutes, gradually increasing as tolerated. 3

Medications to AVOID

Antimotility Agents (Loperamide):

Do NOT give to children <18 years of age with acute diarrhea. 1

• Serious side effects include ileus, drowsiness, and potentially fatal abdominal distention 1
• Six deaths reported in one series 1
• Does not reduce diarrhea volume or duration 1

In adults, loperamide may be given for acute watery diarrhea but must be avoided in inflammatory diarrhea or fever (risk of toxic megacolon). 1

Other Antidiarrheal Agents:

Avoid adsorbents (kaolin-pectin), antisecretory drugs, and toxin binders (cholestyramine). 1

• No demonstrated effectiveness in reducing diarrhea volume or duration 1
• May increase electrolyte losses 1
• Shift therapeutic focus away from appropriate fluid and nutritional therapy 1
• Unnecessarily increase economic costs 1

Antibiotic Indications

Most acute gastroenteritis is viral and does not require antimicrobial therapy. 1

Consider antibiotics when:

• Bloody diarrhea with fever and systemic toxicity 1
• Stool culture identifies treatable bacterial pathogen 1
• Suspected Clostridium difficile (recent antibiotic use) 1
• Confirmed Giardia or Shigella in high-risk settings 1
• Immunocompromised patients 1
• Asymptomatic Salmonella typhi carriers to reduce transmission 1

Watery diarrhea and vomiting in a child <2 years most likely represents viral gastroenteritis and does not require antimicrobial therapy. 1

Common Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing 3
• Do not use inappropriate fluids (apple juice, sports drinks) as primary rehydration for moderate-to-severe dehydration 3
• Do not restrict diet unnecessarily during or after rehydration 3
• Do not rely exclusively on "BRAT diet" for prolonged periods (inadequate energy and protein) 3
• Do not use diluted formulas for extended periods (inadequate nutrition) 3
• Do not give antimotility agents to children 1

Indications for Hospitalization

• Severe dehydration (≥10% deficit) or shock 3
• Failure of oral rehydration therapy after antiemetic trial 3
• Altered mental status 3
• Ileus (absent bowel sounds) 3
• Persistent vomiting preventing adequate oral intake 3

Infection Control

Practice hand hygiene after toilet use, diaper changes, before food preparation, before eating, after handling garbage or soiled laundry, and after animal contact. 1

Use gloves and gowns when caring for patients with diarrhea; hand hygiene with soap and water or alcohol-based sanitizers is essential. 1

Patients in high-risk settings (healthcare, childcare, eldercare, food service) should follow local public health guidance for return to work/school. 1