Inflammatory Bowel Disease (C)
The diagnosis is inflammatory bowel disease (IBD), specifically because the presence of blood and mucus in stool with a positive fecal occult blood test indicates colonic inflammation, which definitively excludes functional disorders and points to organic pathology requiring immediate investigation. 1
Why IBD is the Correct Diagnosis
The British Society of Gastroenterology explicitly states that blood in stool is a clear alarm feature that rules out IBS diagnosis, and the combination of blood and mucus in stool suggests inflammatory pathology rather than functional disorders like IBS or abdominal migraine. 1
Key Distinguishing Features Present in This Case:
- Blood and mucus in stool: This combination specifically points to colonic inflammation, not upper GI pathology. 1
- Positive fecal occult blood test: Confirms the presence of gastrointestinal bleeding requiring organic disease investigation. 1
- Recurrent symptoms over 1 year: IBD commonly presents with chronic, recurrent symptoms in pediatric patients. 2
- Age 12 years: IBD frequently presents in adolescence and young adulthood. 3
Why Other Options Are Incorrect
Abdominal Migraine (A) - Excluded
- Abdominal migraine is a functional disorder that does not cause blood or mucus in stool. 1
- The presence of alarm features (blood in stool) mandates investigation for organic disease, not functional disorders. 1
Irritable Bowel Syndrome (B) - Excluded
- The American Gastroenterological Association states that IBS diagnosis requires absence of alarm symptoms, and blood in stool is explicitly an alarm feature. 4
- IBS is a functional bowel disorder that presumes the absence of structural or biochemical explanation for symptoms. 4
- While IBS can present with mucus passage, it does not cause blood in stool or positive fecal occult blood tests. 4
Peptic Ulcer Disease (D) - Excluded
- PUD causes epigastric pain and vomiting but does not typically produce blood and mucus in stool. 1, 5
- PUD bleeding manifests as hematemesis (upper GI bleeding) or melena (black, tarry stools), not bloody stool with mucus. 5
- The combination of mucus and blood points to colonic inflammation, not upper GI ulceration. 1
Clinical Presentation of IBD in This Patient
The most common presenting symptoms in IBD include:
- In Crohn's disease: Tiredness/fatigue (80.6%) and abdominal pain (80.4%). 2
- In ulcerative colitis: Passage of blood with bowel movements (86.6%) and loose/watery bowel movements (86.5%). 2
This patient's presentation with epigastric pain, vomiting, and bloody/mucoid stools is consistent with IBD, particularly given the chronic nature (1 year duration). 2, 3
Next Steps in Management
Immediate diagnostic workup required:
- Fecal calprotectin or lactoferrin testing (highly sensitive for intestinal inflammation). 1
- Complete blood count to assess for anemia. 4
- Erythrocyte sedimentation rate (particularly important in younger patients). 4
- Colonoscopy with biopsy to confirm diagnosis and determine disease extent. 4
Critical pitfall to avoid: Do not dismiss bloody stools as a functional disorder or delay endoscopic evaluation in a pediatric patient with alarm features. 1