What are the differential diagnoses for a 15‑year‑old adolescent with post‑prandial abdominal pain?

Differential Diagnoses for Post-Prandial Abdominal Pain in a 15-Year-Old

In a 15-year-old with pain after eating, the most critical differentials to consider are inflammatory bowel disease (particularly ulcerative colitis or Crohn's disease), peptic ulcer disease, functional dyspepsia, and gastroesophageal reflux disease, with IBD being especially important given that 10-15% of cases present before age 18 and can have serious consequences on growth and development. 1

High-Priority Organic Causes

Inflammatory Bowel Disease

• IBD is an essential consideration in adolescents with post-prandial abdominal pain, as pediatric-onset IBD has distinct phenotypic differences from adult-onset disease that may delay diagnosis and treatment. 1
• Children with ulcerative colitis more commonly present with extensive colitis (42-90%) compared to adults, and may show atypical features including patchy inflammation and rectal sparing in up to 30% of cases. 1
• Crohn's disease should remain in the differential even with periappendiceal inflammation alone, though this finding is frequently seen in UC and should not be regarded as supportive evidence for CD. 1
• The gold standard for diagnosis remains endoscopic evaluation of upper and lower gastrointestinal tracts with mucosal biopsies. 1

Peptic Ulcer Disease

• Duodenal ulcers account for approximately 14.8% of endoscopic findings in adolescents presenting with epigastric pain. 2
• In older children and adolescents, duodenal ulcers have a relapsing course increasingly related to chronic active antral gastritis and Helicobacter pylori infection. 3
• Among children with recurrent abdominal pain undergoing endoscopy, 22% were infected with H. pylori, and all three children with duodenal ulcers were H. pylori positive. 4
• Peptic ulcer disease represents approximately 10% of upper gastrointestinal symptoms in the general dyspeptic population. 1

Gastroesophageal Reflux Disease

• GERD presents with epigastric pain often accompanied by heartburn and regurgitation, though abdominal pain is a relatively common but less well-recognized mode of presentation in children. 5, 6
• Esophagitis was found in 8 children with gastritis among those undergoing endoscopy for recurrent abdominal pain, all of whom had documented gastroesophageal reflux. 4
• More than 50% of patients with GERD will not have evidence of esophagitis at endoscopy, making it difficult to distinguish from functional dyspepsia. 1

Gastritis and Duodenitis

• Gastritis was found in 58.5% of children undergoing endoscopy for recurrent abdominal pain, with 37.5% testing positive for H. pylori. 4
• Gastritis (12.6%) and duodenitis (4.4%) are commonly seen in adolescents and must be included in the differential diagnosis. 2

Functional Disorders

Functional Dyspepsia

• Most patients with dyspepsia undergoing endoscopy are found to have functional dyspepsia, representing the majority of cases when organic pathology is excluded. 1
• Rome IV criteria define functional dyspepsia as one or more of: bothersome epigastric pain, epigastric burning, postprandial fullness, or early satiation, with symptom onset at least 6 months prior and no structural disease on endoscopy. 1
• Postprandial distress syndrome specifically requires bothersome postprandial fullness or early satiation at least 3 days per week. 1
• However, persistent vomiting likely suggests another disorder and should not be attributed to functional dyspepsia. 1, 5

Critical Red Flags Requiring Urgent Investigation

Alarm Features

• Weight loss, anemia, dysphagia, or persistent vomiting mandate urgent endoscopy regardless of age. 5, 7
• The presence of epigastric tenderness on examination suggests organic pathology rather than functional disease and warrants consideration of earlier endoscopy. 5
• Bilious or fecaloid vomiting indicates mechanical obstruction and requires immediate nasogastric decompression and NPO status. 7

Life-Threatening Conditions to Exclude

• In patients with severe postprandial pain and vomiting, immediate CT abdomen/pelvis with IV contrast is recommended to rule out mesenteric ischemia, intestinal obstruction, or biliary/pancreatic pathology. 7
• The classic triad of postprandial pain 30-60 minutes after eating, weight loss, and food avoidance suggests chronic mesenteric ischemia. 7
• Acute pancreatitis should be excluded with serum amylase (≥4x normal) or lipase (≥2x normal), which have 80-90% sensitivity and specificity. 5

Diagnostic Approach

Initial Assessment

• Evaluate timing of pain relative to meals, severity, and associated symptoms including nausea, vomiting, hematemesis, heartburn, and regurgitation. 5
• Check for alarm symptoms: weight loss, anemia, dysphagia, persistent vomiting. 5
• Assess vital signs for tachycardia ≥110 bpm, fever ≥38°C, or hypotension, which predict serious complications. 5, 7

Laboratory Testing

• Order complete blood count, electrolytes, glucose, liver function tests, and serum lipase immediately. 5, 7
• Test for H. pylori using 13C-urea breath test or stool antigen test if peptic ulcer disease is suspected. 1

Imaging Strategy

• CT abdomen/pelvis with IV contrast is the definitive study to identify obstruction, ischemia, and surgical causes, changing diagnosis in 49% of cases. 7
• Upper GI fluoroscopy can detect ulcers, gastritis, and hiatal hernias but is less sensitive than endoscopy. 5

Endoscopy Indications

• Endoscopy is warranted for persistent symptoms beyond 8 weeks with epigastric tenderness, regardless of age. 5
• In adolescents with treatment-resistant symptoms, nausea/vomiting, or alarm features, endoscopy should not be delayed. 5, 8

Common Pitfalls to Avoid

• Do not assume functional dyspepsia without first excluding organic causes with appropriate imaging and/or endoscopy, especially in adolescents where IBD prevalence is significant. 1, 7
• Do not delay endoscopy in patients with alarm features such as persistent vomiting, weight loss, or anemia. 5
• Do not rely on negative plain radiography to exclude serious pathology. 7
• Do not dismiss new-onset symptoms in adolescents as functional without proper investigation, as organic pathology is more common than previously thought. 4