In a 12-year-old with a one-year history of recurrent epigastric pain, occasional vomiting, and stool containing blood and mucus with a positive fecal occult blood test, what is the most likely diagnosis?

Inflammatory Bowel Disease (C)

The diagnosis is inflammatory bowel disease (IBD), specifically because the combination of blood AND mucus in stool with a positive fecal occult blood test is pathognomonic for mucosal inflammation and definitively excludes functional disorders like abdominal migraine and irritable bowel syndrome. 1

Why IBD is the Correct Diagnosis

Blood and Mucus Together Rule Out Functional Disorders

• The presence of both blood and mucus in stool with positive fecal occult blood testing indicates mucosal inflammation and cannot occur in functional disorders 1
• Irritable bowel syndrome diagnostic criteria explicitly require the ABSENCE of rectal bleeding—any detectable blood in stool completely rules out IBS 1, 2
• Abdominal migraine does not cause bloody stools or positive fecal occult blood tests, making it incompatible with this presentation 1

The Clinical Pattern Fits Pediatric IBD Perfectly

• Up to 75% of children with IBD demonstrate upper gastrointestinal inflammation, which explains this patient's epigastric pain and vomiting 1
• Children aged 10-15 years (this patient is 12) account for a large share of new IBD diagnoses, with approximately 10-15% of all IBD patients diagnosed before age 18 1
• The one-year duration of recurrent symptoms is consistent with chronic inflammatory disease rather than acute infectious processes 3

Why Not the Other Options

Peptic ulcer disease and gastritis (Option D):

• While peptic ulcer disease can cause epigastric pain and vomiting, it does NOT typically produce blood and mucus together in stool 1
• Peptic ulcers may cause melena (black tarry stools) from upper GI bleeding, but the combination of blood, mucus, and positive fecal occult blood points to colonic inflammation, not isolated upper GI pathology 1

Abdominal migraine (Option A):

• Abdominal migraine is a functional disorder that does not cause mucosal inflammation or bloody stools 1
• The positive fecal occult blood test definitively excludes this diagnosis 1

Irritable bowel syndrome (Option B):

• IBS diagnostic criteria mandate the absence of rectal bleeding—this patient has documented blood in stool 1, 2
• IBS does not cause positive fecal occult blood tests or mucus with blood 1

Critical Diagnostic Pitfalls to Avoid

• Never attribute pediatric rectal bleeding to hemorrhoids without thorough evaluation—blood in stool mandates full diagnostic work-up 1, 4
• Do not delay endoscopy in children with these findings; early diagnosis is essential to prevent adverse effects on growth and development 1
• Children younger than 12 years may exhibit atypical endoscopic patterns, including rectal sparing in roughly 30% of cases, which can make diagnosis more challenging 1

Recommended Next Steps

• The gold standard for diagnosing pediatric IBD is combined upper and lower gastrointestinal endoscopy with systematic mucosal biopsies from the esophagus, stomach, duodenum, terminal ileum, and multiple colonic sites 1
• Fecal calprotectin is the single most useful non-invasive screening test to differentiate IBD from functional disorders in children 4
• Complete blood count, inflammatory markers (ESR, CRP), and comprehensive stool studies should be obtained 4
• Small-bowel imaging such as MR enterography is recommended because children have higher prevalence of small-bowel involvement compared with adults 1, 5