Intestinal Disorders, Malabsorption, and Mucosal Disease
Scope
Covers celiac disease, inflammatory bowel disease overlap, short bowel syndrome, carbohydrate malabsorption, and infectious enteritis.
Concepts to master
- Celiac disease: IgA tissue transglutaminase with total IgA; duodenal biopsy showing villous atrophy and crypt hyperplasia; strict gluten-free diet.
- Malabsorption physiology: fat malabsorption causes steatorrhea and fat-soluble vitamin deficiency; carbohydrate malabsorption causes osmotic diarrhea and bloating.
- Short bowel syndrome: depends on residual bowel length and ileocecal valve; manage with parenteral nutrition, weaning, and monitoring for bacterial overgrowth.
- Infectious enteritis: viral (rotavirus, norovirus) self-limited; bacterial (Campylobacter, Salmonella, Shigella, E. coli) may need antibiotics; C. difficile in antibiotic-exposed children.
Traps
Candidates forget to check total IgA when interpreting tTG-IgA deficiency causes false negatives. Another trap: diagnosing celiac without biopsy in ambiguous cases, or starting gluten-free diet before testing. Beware attributing chronic diarrhea to infection when growth failure suggests malabsorption.
Worked example
A 6-year-old with chronic diarrhea, bloating, iron deficiency, and growth failure: check tTG-IgA and total IgA; if positive, confirm with duodenal biopsy before diet.
Rule of thumb
Chronic diarrhea plus growth failure = malabsorption workup; always pair tTG with total IgA.