Coeliac Disease

•    Autoimmune reaction to gluten (gliadin) in genetically susceptible individuals (HLA-DQ2/DQ8)

•    Features: diarrhoea, weight loss, iron deficiency anaemia, fatigue

•    Associated conditions: dermatitis herpetiformis, autoimmune thyroid disease, T1DM

•    Diagnosis:

o    First-line: ↑ anti-tTG IgA

o    Confirm with duodenal biopsy: villous atrophy, crypt hyperplasia, intraepithelial lymphocytes

•    Treatment: lifelong gluten-free diet

•    Complications: osteoporosis, small bowel lymphoma, hyposplenism

Tropical Sprue

•    Occurs in residents/travellers to tropical regions

•    Features: chronic diarrhoea, malabsorption, megaloblastic anaemia (↓ folate/B12)

•    Diagnosis: exclusion of other causes; biopsy resembles coeliac disease

•    Treatment: tetracycline + folate for 3–6 months

Whipple’s Disease

•    Infection with Tropheryma whipplei

•    Features: steatorrhoea, arthralgia, lymphadenopathy, neurological symptoms

•    Diagnosis:

o    Small bowel biopsy: PAS-positive foamy macrophages

o    Confirm with PCR

•    Treatment: IV ceftriaxone → long-term co-trimoxazole

Carcinoid Syndrome

•    Caused by metastatic serotonin-secreting neuroendocrine tumours (often ileal)

•    Features: flushing, diarrhoea, wheeze, tricuspid regurgitation

•    Diagnosis:

o    ↑ 5-HIAA in 24h urine

o    CT/MRI ± octreotide scan for localisation

•    Treatment: somatostatin analogues (e.g. octreotide), surgical resection

Angiodysplasia

•    Dilated submucosal vessels (AVMs), most commonly in right colon

•    Features: painless GI bleeding (iron deficiency, melaena, or haematochezia)

•    May be associated with aortic stenosis (Heyde’s syndrome)

•    Diagnosis: colonoscopy, CT angiography, capsule endoscopy

•    Treatment: endoscopic coagulation; surgery or embolisation if persistent

Short Bowel Syndrome

•    Occurs after extensive small bowel resection

•    Features: diarrhoea, malabsorption, nutritional deficiencies

•    Risk of B12 and bile salt malabsorption if ileum is resected

•    Management:

o    Nutritional support (oral supplements or TPN)

o    Anti-diarrhoeals (e.g. loperamide)

o    Vitamin/mineral replacement

Small Bowel Obstruction

•    Most common causes: adhesions > hernias

•    Features: colicky abdominal pain, vomiting, abdominal distension, obstipation

•    Signs: tinkling/high-pitched bowel sounds or absent sounds (late)

•    Diagnosis:

o    AXR: dilated loops, air–fluid levels

o    CT: more sensitive; identifies cause/complications

•    Management:

o    Conservative: NBM, NG tube, IV fluids

o    Surgical: if strangulation, peritonitis, or failure to improve

Lactose Intolerance

•    Lactase deficiency → osmotic diarrhoea after dairy

•    Features: bloating, flatulence, diarrhoea

•    Diagnosis: hydrogen breath test

•    Treatment: lactose-free diet

Small Intestinal Bacterial Overgrowth (SIBO)

•    Excess bacteria in small intestine → malabsorption

•    Causes: altered anatomy (e.g. blind loops), motility disorders (e.g. scleroderma)

•    Features: bloating, diarrhoea, weight loss, B12 deficiency

•    Diagnosis: hydrogen/methane breath test

•    Treatment: antibiotics (e.g. rifaximin)