Digestive System Diseases: Classification by Etiology with Examples

Digestive diseases are categorized by underlying mechanism. Accurate classification guides diagnostic approach and treatment.

1. Infectious and Inflammatory

• Bacterial: H. pylori (gastritis, ulcer, cancer), Salmonella, Shigella, Campylobacter, C. difficile (enterocolitis), E. coli (traveler's diarrhea, HUS)
• Viral: Norovirus, rotavirus, hepatitis A/E (enteric), hepatitis B/C/D (blood-borne → liver)
• Parasitic: Giardia, Cryptosporidium, Entamoeba, Ascaris, Strongyloides
• Fungal: Candida esophagitis (immunocompromised)

2. Functional Disorders (Disorders of Gut-Brain Interaction - DGBI)

• IBS: Abdominal pain + altered bowel habits (Rome IV criteria); subtypes IBS-C, D, M, U
• Functional dyspepsia: Epigastric pain/bloating without structural cause
• Functional constipation/diarrhea: Symptom-based, no alarm features
• Cyclic vomiting syndrome, rumination syndrome

3. Structural and Mechanical

• Hernias: Inguinal, femoral, umbilical, incisional, hiatal
• Diverticular disease: Diverticulosis → diverticulitis
• Strictures/adhesions: Post-surgical, inflammatory, radiation
• Volvulus, intussusception, malrotation
• Polyps: Adenomatous (premalignant), hyperplastic, serrated

4. Inflammatory Bowel Disease (IBD) — Immune-Mediated

• Crohn's disease: Transmural, skip lesions, any GI segment; fistulae, strictures
• Ulcerative colitis: Mucosal, continuous from rectum; bloody diarrhea
• Distinct from functional disorders — structural damage, biomarkers elevated

5. Malignant Neoplasms

• Esophageal (SCC, adenocarcinoma), gastric, small bowel, colorectal, anal
• Hepatocellular carcinoma, cholangiocarcinoma, pancreatic adenocarcinoma
• GIST, neuroendocrine tumors, lymphoma

6. Vascular

• Mesenteric ischemia (acute/chronic)
• Hemorrhoids, angiodysplasia

7. Metabolic/Storage

• Hemochromatosis, Wilson disease, α1-antitrypsin deficiency

8. Congenital/Developmental

• Biliary atresia, Hirschsprung disease, intestinal atresia, annular pancreas

Many conditions span categories (e.g., IBD has immune + structural features). Clinical presentation guides targeted workup.