What is the differential diagnosis for intermittent abdominal pain in a 15-year-old boy?

Differential Diagnosis for Intermittent Abdominal Pain in a 15-Year-Old Boy

In a 15-year-old boy with 2 days of intermittent abdominal pain, the differential diagnosis must prioritize life-threatening surgical emergencies first, followed by common benign causes, with acute appendicitis being the most likely diagnosis in this age group. 1

Life-Threatening Causes to Rule Out Immediately

Surgical Emergencies Requiring Urgent Intervention

• Acute appendicitis is the most common surgical emergency causing acute abdominal pain in adolescents and must be excluded first 1

  • Classically presents with periumbilical pain migrating to right lower quadrant 1
  • Accounts for nearly 50% of emergency presentations with right lower quadrant pain 1

• Midgut volvulus, though rare in adolescents, can present with intermittent pain and carries catastrophic outcomes if missed 2, 3

  • CT shows characteristic "swirling" mesenteric vessels 2
  • Can be mistaken for gastroenteritis with disastrous results 3
  • Requires immediate surgical intervention to prevent bowel necrosis 3

• Sigmoid volvulus should be considered despite being uncommon in this age group 2

  • Presents with intermittent suprapubic pain 2
  • CT demonstrates swirling mesenteric vessels with dilated sigmoid colon 2

• Bowel obstruction from various causes must be evaluated 4

  • Adhesions (though less likely without prior abdominal surgery) 4
  • Hernias at umbilical, inguinal, or femoral sites require careful examination 4
  • Pain is classically colicky due to increased peristalsis attempting to overcome obstruction 4

• Mesenteric ischemia, while exponentially more common in elderly patients, can occur in adolescents with predisposing conditions 5, 6

  • Presents with pain out of proportion to physical examination findings 5, 6
  • Mortality rate of 30-90% if not diagnosed early 5, 6
  • In patients ≥75 years, more prevalent than appendicitis, but extremely rare at age 15 6

Common Non-Surgical Causes

Infectious and Inflammatory Conditions

• Gastroenteritis is the most common benign cause in mild cases 7

  • Often accompanied by nausea, vomiting, and diarrhea 7
  • Can mimic more serious conditions like midgut volvulus 3

• Mesenteric lymphadenitis presents with abdominal pain and may mimic appendicitis 1

• Constipation is a frequent cause of intermittent abdominal pain in adolescents 7

Other Considerations

• Lower lobe pneumonia should be considered when abdominal findings are minimal despite moderate-severe pain 7

• Ureteropelvic junction obstruction can cause episodic abdominal pain and may be detected by ultrasound 8

• Functional abdominal pain is the most common cause of chronic intermittent pain but is a diagnosis of exclusion 9

  • Absence of alarm symptoms (weight loss, GI bleeding, persistent fever, chronic severe diarrhea, significant vomiting) suggests functional etiology 9

Critical Diagnostic Approach

Immediate Assessment Priorities

• Evaluate for hemodynamic instability indicating shock from perforation, ischemia, or severe dehydration 7

  • Check vital signs: tachycardia, tachypnea, hypotension, altered mental status 4
  • Assess for peritoneal signs suggesting perforation or ischemia 4

• Examine all hernia orifices (umbilical, inguinal, femoral) and any surgical scars 4

• Perform digital rectal examination to detect blood or masses 4

Laboratory Testing

• Complete blood count (leukocytosis >14,000 suggests infection or ischemia) 4, 6
• Serum lactate (>2 mmol/L associated with irreversible intestinal ischemia) 6
• Renal function and electrolytes 4

Imaging Strategy

• Ultrasound is the first-line imaging for adolescents with moderate-severe pain and localizing findings 7

  • Sensitivity 85.7-100% and specificity 94.8-100% for appendicitis in this age group 1
  • Avoids radiation exposure 1

• CT abdomen/pelvis with contrast should be obtained if:

  • Ultrasound is non-diagnostic 1
  • Clinical suspicion for volvulus, bowel obstruction, or mesenteric ischemia 4, 2
  • Patient appears critically ill 7

• Plain radiographs have limited utility and should not delay definitive imaging 4, 5

Common Pitfalls to Avoid

• Anchoring bias: Do not dismiss rare but catastrophic diagnoses like midgut volvulus simply because they are uncommon in adolescents 2
• Mistaking volvulus for gastroenteritis: Intermittent symptoms can lead to delayed diagnosis with fatal outcomes 3
• Relying solely on ultrasound: While excellent for appendicitis, US may miss volvulus and other critical diagnoses requiring CT 2
• Delaying surgical consultation: Any patient with peritoneal signs, hemodynamic instability, or concerning imaging requires immediate surgical evaluation 7