Write a short note on inflammatory bowel disease.

Definition

Inflammatory bowel disease (IBD) comprises two chronic relapsing-remitting inflammatory disorders of the gastrointestinal tract — ulcerative colitis (UC) and Crohn's disease (CD) — arising from a dysregulated mucosal immune response to gut microbiota in a genetically susceptible host. Incidence is rising rapidly in India with urbanisation and dietary change.

ULCERATIVE COLITIS versus CROHN'S DISEASE

Clinical Features

Ulcerative colitis: bloody diarrhoea with mucus, urgency, tenesmus, lower abdominal cramping relieved by defecation, and nocturnal symptoms. Severity is graded by the Truelove and Witts criteria (stool frequency, blood, fever, tachycardia, anaemia and ESR). Proctitis may present only with rectal bleeding and urgency.

Crohn's disease: abdominal pain (often right iliac fossa, mimicking appendicitis), chronic diarrhoea (often without blood), weight loss and failure to thrive, fever, a right iliac fossa mass, and perianal disease — which may precede intestinal symptoms by years. Obstructive symptoms from strictures; oral aphthous ulceration.

Extraintestinal manifestations (in up to 30%) — a favourite examination area:

Complications

Ulcerative colitis: TOXIC MEGACOLON (transverse colon diameter > 6 cm with systemic toxicity — a surgical emergency), perforation, massive haemorrhage, stricture, and colorectal carcinoma (risk related to duration and extent; requires surveillance colonoscopy).

Crohn's disease: strictures with obstruction, fistulae (enteroenteric, enterovesical, enterocutaneous, perianal), abscess, perforation, malabsorption with B12 deficiency (terminal ileal disease), gallstones and oxalate renal stones, short bowel syndrome after repeated resections, and malignancy.

Investigations

• Bloods: CBC (anaemia, thrombocytosis), raised CRP and ESR, low albumin, iron studies, B12 and folate, and liver function (raised ALP suggests primary sclerosing cholangitis).
• Faecal calprotectin — a sensitive marker of intestinal inflammation; valuable for distinguishing IBD from irritable bowel syndrome and for monitoring disease activity non-invasively.
• Stool studies — mandatory before immunosuppression: culture, ova and parasites, *C. difficile* toxin, and amoebic testing, since infection both mimics and complicates IBD.
• Ileocolonoscopy with multiple biopsies — the diagnostic cornerstone, defining extent and obtaining histology.
• Upper GI endoscopy for suspected upper tract Crohn's disease.
• Cross-sectional imaging: MR enterography (preferred, avoiding radiation in a young population needing repeated imaging), CT enterography, and MRI pelvis for perianal fistulae.
• Plain abdominal X-ray in acute severe colitis — for toxic megacolon and to assess extent.
• Exclude intestinal tuberculosis (see the danger box) and, where relevant, screen for latent TB and hepatitis B before biologic therapy.

Management

Principles: induce remission, then maintain it, with treatment matched to disease severity, extent and behaviour; the modern goal is mucosal healing, not merely symptom control.

Ulcerative colitis:

• Mild to moderate: 5-aminosalicylates (mesalazine) — oral for extensive disease, topical (suppository or enema) for proctitis and left-sided disease, and combined for best effect. These are also the maintenance agents.
• Moderate to severe: corticosteroids to induce remission (never for maintenance), with thiopurines (azathioprine, mercaptopurine) as steroid-sparing maintenance.
• Refractory or steroid-dependent: biologics — anti-TNF (infliximab, adalimumab), vedolizumab (gut-selective anti-integrin), ustekinumab — and JAK inhibitors (tofacitinib).
• Acute severe colitis — a medical emergency: admit, intravenous corticosteroids, fluids, thromboprophylaxis, exclude infection and toxic megacolon, and assess response at day 3 using stool frequency and CRP; if there is no response, proceed to rescue therapy (infliximab or ciclosporin) or colectomy. Involve surgeons early rather than late.
• Surgery: proctocolectomy is CURATIVE — indicated for failed medical therapy, toxic megacolon, perforation, haemorrhage and dysplasia.

Crohn's disease:

• Induction: corticosteroids (or budesonide for ileocaecal disease, with fewer systemic effects); exclusive enteral nutrition — highly effective and the preferred first-line in children.
• Maintenance: thiopurines, methotrexate; biologics — anti-TNF, ustekinumab, vedolizumab, risankizumab. 5-ASAs have little role in Crohn's disease.
• Perianal and fistulising disease: anti-TNF therapy with antibiotics (metronidazole, ciprofloxacin) and surgical drainage or seton placement.
• STOP SMOKING — the single most effective non-pharmacological intervention in Crohn's disease.
• Surgery for strictures (resection or stricturoplasty), abscess, fistula and obstruction — conservative resection, since disease recurs and repeated resections risk short bowel syndrome.

General care for both: nutritional assessment and correction of deficiencies (iron, B12, vitamin D, calcium), bone protection, vaccination before immunosuppression (live vaccines contraindicated afterwards), screening for latent TB and hepatitis B before biologics, colonoscopic surveillance for dysplasia, psychological support, and pregnancy planning (most drugs are compatible; methotrexate is absolutely contraindicated).