Crohn’s Disease

•    Chronic inflammatory bowel disease affecting mouth to anus

•    Features:

o    Skip lesions

o    Transmural inflammation

o    Fistulae, strictures, abscesses

o    Non-caseating granulomas (on histology)

•    Extra-intestinal: arthritis, uveitis, erythema nodosum

•    Investigations: colonoscopy with biopsy, faecal calprotectin, MRI enterography

•    Treatment: steroids, immunomodulators (azathioprine), biologics (anti-TNF), surgery for complications

Ulcerative Colitis (UC)

•    Chronic inflammatory disease of colon only

•    Features:

o    Starts at rectum, spreads proximally in continuous fashion

o    Inflammation limited to mucosa

o    Bloody diarrhoea, urgency, tenesmus

•    ↑ Risk of colorectal cancer (screen after 8–10 years)

•    Histology: crypt abscesses, no granulomas

•    Treatment: aminosalicylates (mesalazine), steroids, biologics, surgery (curative)

Complications of IBD

•    Toxic megacolon: colonic dilatation + systemic toxicity → surgical emergency

•    Colorectal cancer

•    Extra-intestinal:

o    Musculoskeletal: arthritis (seronegative), ankylosing spondylitis

o    Ocular: uveitis, episcleritis

o    Hepatic: primary sclerosing cholangitis (esp. in UC)

o    Dermatologic: erythema nodosum, pyoderma gangrenosum

Pseudomembranous Colitis

•    Caused by Clostridioides difficile overgrowth post-antibiotics

•    Features: diarrhoea, fever, leukocytosis ± toxic megacolon

•    Diagnosis: stool C. difficile toxin assay (or PCR)

•    Treatment:

o    Oral vancomycin or fidaxomicin

o    Avoid anti-motility agents

o    Recurrent cases: faecal microbiota transplant

Colorectal Polyps

•    Adenomatous polyps (esp. villous type) have malignant potential

•    Surveillance colonoscopy based on polyp number, size, histology

•    Hyperplastic polyps: benign

Familial Adenomatous Polyposis (FAP)

•    Autosomal dominant APC gene mutation

•    Hundreds to thousands of polyps in colon by adolescence

•    100% risk of colorectal cancer if untreated

•    Management: regular screening from childhood, prophylactic colectomy

Hereditary Non-Polyposis Colorectal Cancer (HNPCC / Lynch Syndrome)

•    Autosomal dominant; DNA mismatch repair defect

•    Cancers: colorectal, endometrial, ovarian, gastric, urinary tract

•    Right-sided CRC common and often at young age

•    Amsterdam criteria and genetic testing for diagnosis

•    Management: regular screening, consider prophylactic surgery

Peutz–Jeghers Syndrome

•    Autosomal dominant; hamartomatous polyps in GI tract

•    Mucocutaneous pigmentation (lips, buccal mucosa, hands)

•    ↑ Risk of GI and non-GI malignancies (e.g. pancreas, breast, ovary)

Colorectal Cancer

•    Left-sided:

o    Obstructive symptoms, change in bowel habit, rectal bleeding

•    Right-sided:

o    Iron deficiency anaemia, weight loss, occult bleeding

•    Risk factors: age, IBD, polyps, FHx, FAP, HNPCC

•    Diagnosis: colonoscopy + biopsy

•    Staging: CT CAP ± MRI pelvis (rectal cancer)

•    Treatment: surgical resection ± chemo/radiotherapy

Irritable Bowel Syndrome (IBS)

•    Functional bowel disorder, no structural abnormality

•    Features: abdominal pain, bloating, altered bowel habit (constipation/diarrhoea)

•    Diagnosis of exclusion; Rome IV criteria used

•    Triggered by stress, diet

•    Treatment: reassurance, dietary modification (e.g. low FODMAP), antispasmodics, SSRIs or TCAs for severe symptoms

Diverticular Disease

•    Outpouchings of colonic mucosa; common in sigmoid colon

•    Diverticulosis: often asymptomatic; associated with low-fibre diet

•    Diverticulitis:

o    Features: LLQ pain, fever, leukocytosis, altered bowel habit

o    Diagnosis: CT abdomen (do not scope acutely)

o    Treatment: oral/IV antibiotics, bowel rest; surgery if recurrent/complicated (abscess, perforation)