What is the differential diagnosis for a child presenting with acute gastroenteritis?

Differential Diagnosis for Pediatric Acute Gastroenteritis

Primary Differential Considerations

When a child presents with vomiting and diarrhea, the differential diagnosis must systematically exclude serious non-gastroenteritis conditions before attributing symptoms to viral gastroenteritis. 1, 2

Infectious Causes

Viral Gastroenteritis (Most Common)

• Accounts for approximately 70% of acute gastroenteritis cases in children 3
• Rotavirus, norovirus, and adenovirus are the predominant pathogens 4
• Typically presents with watery diarrhea, vomiting, low-grade fever, and abdominal pain 5
• Self-limited course lasting 3-7 days 4

Bacterial Gastroenteritis

• Consider when bloody diarrhea, high fever (>39°C), and systemic toxicity are present 1, 2
• Key pathogens include Salmonella, Shigella, Campylobacter, and enterohemorrhagic E. coli 1, 2
• Stool culture is specifically indicated for dysentery (bloody diarrhea) 2
• Risk factors include recent antibiotic use, foreign travel, exposure to contaminated food/water, or immunodeficiency 1

Parasitic Infections

• Giardia and Cryptosporidium should be considered with prolonged diarrhea (>7 days) 6
• More common in developing countries or after travel 6

Critical Non-Gastroenteritis Diagnoses to Exclude

Urinary Tract Infection/Pyelonephritis

• Vomiting and abdominal pain can be the primary presentation in young children 1
• Obtain urinalysis with microscopy and urine culture when urinary symptoms present (reduced volume, increased frequency) 1
• Particularly important in infants and young children who may not localize symptoms 1

Surgical Emergencies

• Intussusception: Intermittent severe abdominal pain, "currant jelly" stools, palpable abdominal mass 2
• Appendicitis: Persistent right lower quadrant pain, fever, anorexia, rebound tenderness 2
• Malrotation with volvulus: Bilious vomiting, severe abdominal pain, bloody stools, signs of shock 2
• Severe abdominal pain disproportionate to examination findings mandates surgical evaluation 1

Metabolic and Endocrine Disorders

• Diabetic ketoacidosis: Vomiting, abdominal pain, rapid deep breathing (Kussmaul respirations), altered mental status 1
• Inborn errors of metabolism: Consider in infants with recurrent vomiting, lethargy, and failure to thrive 6
• Adrenal insufficiency: Vomiting, dehydration, hypotension, hyponatremia 6

Central Nervous System Pathology

• Meningitis/encephalitis: Vomiting with fever, altered mental status, nuchal rigidity, bulging fontanelle in infants 1
• Increased intracranial pressure: Projectile vomiting, headache, altered consciousness 6

Toxic Ingestions

• Food poisoning from preformed toxins (Staphylococcus aureus, Bacillus cereus) presents with rapid onset vomiting within 1-6 hours 3
• Accidental ingestion of medications or household products 6

Age-Specific Considerations

Infants <3 Months

• Lower threshold for serious bacterial infection including sepsis 1
• Consider pyloric stenosis (projectile non-bilious vomiting, palpable "olive" mass) 6
• Necrotizing enterocolitis in premature infants 6
• Blood culture indicated if febrile or toxic-appearing 1

Immunocompromised Children

• Broader differential including opportunistic infections 1
• Lower threshold for admission and aggressive management 1
• Consider cytomegalovirus, cryptosporidium, and other atypical pathogens 1

Clinical Approach to Narrowing the Differential

Red Flags Requiring Immediate Alternative Diagnosis Consideration:

• Bilious vomiting (suggests obstruction) 2
• Severe abdominal pain out of proportion to examination 1, 2
• Altered mental status beyond expected dehydration 1, 2
• Absent bowel sounds (contraindication to oral rehydration) 1, 2
• Bloody diarrhea with fever and systemic toxicity 1, 2
• Age <3 months with fever 1
• Signs of shock or severe dehydration (≥10% fluid deficit) 1, 2

Historical Features Supporting Viral Gastroenteritis:

• Acute onset of watery diarrhea and vomiting 5, 4
• Known sick contacts or community outbreak 4
• No recent antibiotic use or foreign travel 1
• Absence of bloody stools 5
• Self-limited course with gradual improvement 4

Physical Examination Priorities:

• Assess hydration status using skin turgor, capillary refill, respiratory pattern, and mental status 1, 2, 7
• Auscultate for bowel sounds before initiating oral therapy 2
• Palpate abdomen for focal tenderness, masses, or peritoneal signs 2
• Check for nuchal rigidity and fontanelle tension in infants 1

Common Pitfalls to Avoid

• Do not assume viral gastroenteritis without excluding urinary tract infection, especially in young children with vomiting and abdominal pain 1
• Do not miss surgical emergencies by attributing all vomiting and diarrhea to gastroenteritis without careful abdominal examination 2
• Do not overlook diabetic ketoacidosis in children with vomiting, abdominal pain, and rapid deep breathing 1
• Recognize that bloody diarrhea requires stool culture and consideration of bacterial pathogens before attributing to viral causes 2