Last reviewed: March 2026
Contents
MDM Templates
Gastroenteritis — Mild Dehydration
Child presents with vomiting and/or diarrhea. Well appearing with moist mucous membranes, brisk capillary refill, and adequate urine output. Tolerating oral intake. No bilious vomiting, bloody stool, or abdominal distention.
Presentation consistent with viral gastroenteritis with mild dehydration. Not consistent with intussusception, volvulus, appendicitis, pyloric stenosis, or other surgical pathology. No peritoneal signs, no significant abdominal tenderness.[1]
Plan: Ondansetron 0.15 mg/kg ODT (single dose) to facilitate oral rehydration. ORT with Pedialyte in frequent small volumes. Discharge with PCP follow-up in 24-48 hours. Return for bilious vomiting, bloody stool, persistent vomiting despite ondansetron, signs of worsening dehydration, or fever >39.5°C.
Gastroenteritis — Moderate-Severe Dehydration
Child presents with vomiting and/or diarrhea with clinical signs of moderate to severe dehydration — delayed capillary refill, dry mucous membranes, decreased skin turgor, reduced urine output, and inability to tolerate oral intake. Sunken fontanelle in infant.
Degree of dehydration warrants IV fluid resuscitation. Not consistent with surgical pathology — no bilious vomiting, peritoneal signs, or abdominal distention. Differential includes viral gastroenteritis, bacterial enteritis, and less commonly HUS or DKA.[1]
Plan: NS or LR 20 mL/kg bolus over 15-30 minutes, reassess. Ondansetron once IV access established. Electrolytes, BUN, creatinine obtained. Transition to ORT once tolerating oral intake.
If severe dehydration with shock (altered mental status, poor perfusion): Aggressive fluid resuscitation. Admit for IV rehydration, electrolyte monitoring, and serial reassessment.
Vomiting — Surgical Concern
Child presents with vomiting that is bilious in character. Bilious vomiting mandates evaluation for surgical obstruction until proven otherwise. Additional concerning features include abdominal distention, peritoneal signs, and hemodynamic instability.
Presentation raises concern for volvulus (midgut malrotation), intussusception, appendicitis, or other obstructive pathology. Not consistent with simple viral gastroenteritis given bilious character and exam findings. Pyloric stenosis considered in 3-6 week old with projectile non-bilious vomiting.[1]
Plan: NPO. Two large-bore IVs, labs including CBC and BMP, type and screen. Imaging as directed by clinical scenario (ultrasound for intussusception or pyloric stenosis, CT for appendicitis/volvulus in older child, upper GI series for malrotation). Pediatric surgery consulted. Admit for evaluation and definitive management.
Clinical Education
Dehydration Assessment
| Severity | Fluid Loss | Key Findings |
| Mild | <5% | Normal mental status, slightly dry mucous membranes, cap refill <2 sec |
| Moderate | 5-10% | Slightly altered, dry membranes, decreased turgor, cap refill 2-3 sec, sunken fontanelle |
| Severe | >10% | Altered mental status, tenting, cap refill >3 sec, minimal/absent urine output |
The combination of clinical signs is more reliable than any single finding. Sunken fontanelle in infants <18 months is a sensitive marker. Oliguria (<0.5 mL/kg/hour) is concerning.[1]
Oral Rehydration Therapy
ORT is first-line for mild-moderate dehydration and is as effective as IV rehydration for the vast majority of pediatric gastroenteritis. Pedialyte or WHO ORS solution (sodium 75 mEq/L, glucose 75 mmol/L) given in frequent small volumes — 5-10 mL every few minutes by syringe or small cup. This approach reduces vomiting compared to large boluses.[1]
Continue breastfeeding. Formula-fed infants may continue formula after initial rehydration. Avoid sports drinks and juices (high sugar, low sodium, worsen osmotic diarrhea). Rehydrate over 3-4 hours, then continue maintenance plus ongoing losses.
Ondansetron
Single-dose ondansetron (0.15 mg/kg ODT, max 4 mg) significantly reduces vomiting and facilitates successful ORT. Safe in children ≥6 months. Reduces ED revisits, hospital admissions, and need for IV rehydration. The value is in “unblocking” the ability to take oral fluids, not treating the underlying gastroenteritis.[2]
Ondansetron does not mask surgical disease. Should not be withheld when concerning features are absent. A child who vomits once after ondansetron is still more likely to tolerate subsequent small sips.
Red Flags
Bilious vomiting is a surgical emergency until proven otherwise. Green or yellow-green vomiting mandates urgent imaging to exclude volvulus, malrotation, and other obstruction. Do not discharge a child with bilious vomiting on the assumption of gastroenteritis.[1]
Projectile non-bilious vomiting in a 3-6 week old infant strongly suggests hypertrophic pyloric stenosis. Ultrasound is diagnostic.
Bloody diarrhea warrants consideration of: intussusception (6-36 months, “currant jelly” stools), HUS (hematuria + thrombocytopenia + AKI following bloody diarrhea), and bacterial enteroinvasive pathogens (Salmonella, Shigella, Campylobacter, enteroinvasive E. coli).
Altered mental status, severe pain with peritoneal signs, or fever out of proportion should raise concern for appendicitis, perforation, or sepsis.
Foodborne Illness Pearls
Onset timing and food history guide the differential. Vomiting within 1-6 hours: S. aureus (mayo-based foods left out) or B. cereus (reheated fried rice). Diarrhea at 6-72 hours: Salmonella, Shigella (bloody diarrhea, highly contagious person-to-person), Campylobacter. C. difficile if recent antibiotics — send toxin/NAAT testing and avoid antimotility agents.[3]
Disposition
Admit: Severe dehydration with shock. Inability to tolerate oral intake despite ondansetron. Altered mental status. Suspected surgical pathology. Electrolyte derangements requiring correction. Inadequate home support for monitoring.
Discharge: Mild-moderate dehydration responding to ORT. Tolerating oral intake after ondansetron. Well appearing with adequate urine output. Reliable follow-up in 24-48 hours. Return for persistent vomiting, bloody stool, bilious vomiting, signs of dehydration, or high fever.
References
- King CK, Glass R, Bresee JS, Duggan C. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. 2003;52(RR-16):1-16. PubMed
- Freedman SB, Adler M, Seshadri R, Powell EC. Oral ondansetron for gastroenteritis in a pediatric emergency department. N Engl J Med. 2006;354(16):1698-1705. PubMed
- Churgay CA, Aftab Z. Gastroenteritis in children: Part I. Diagnosis. Am Fam Physician. 2012;85(11):1059-1062. PubMed
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