Ulcerative colitis

Definition
Ulcerative colitis is a chronic idiopathic inflammatory bowel disease (IBD) characterised by continuous mucosal inflammation of the colon starting at the rectum and extending proximally in a continuous fashion. It affects only the large intestine and involves the mucosa and submucosa.

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Causes and Risk Factors

• Exact cause unknown; likely multifactorial involving:

  • Genetic predisposition

  • Dysregulated immune response to gut microbiota

  • Environmental triggers

• Risk factors:

  • Family history of IBD

  • Caucasian ethnicity, especially Ashkenazi Jewish heritage

  • Higher incidence in developed countries

  • Possible association with low-fibre/high-fat diet and NSAID use

  • Former smoking (protective effect of current smoking observed in UC)

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Pathophysiology

• Abnormal immune activation in genetically susceptible individuals → chronic inflammation of colonic mucosa

• Continuous inflammation from rectum proximally, no skip lesions (unlike Crohn’s disease)

• Ulceration, loss of mucosal integrity, crypt abscesses, and bleeding

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Classification (by extent)

• Proctitis – rectum only

• Proctosigmoiditis – rectum and sigmoid colon

• Left-sided colitis – up to the splenic flexure

• Extensive colitis – beyond the splenic flexure

• Pancolitis – entire colon

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Clinical Features

• Bloody diarrhoea (hallmark)

• Urgency and tenesmus

• Abdominal pain (often left lower quadrant)

• Fatigue, weight loss in more severe cases

• Fever in severe disease

• Extraintestinal manifestations (can precede bowel symptoms):

  • Musculoskeletal: arthritis, ankylosing spondylitis

  • Dermatologic: erythema nodosum, pyoderma gangrenosum

  • Ocular: uveitis, episcleritis

  • Hepatobiliary: primary sclerosing cholangitis (PSC)

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Complications

• Severe acute colitis → toxic megacolon (life-threatening colonic dilatation)

• Massive haemorrhage

• Perforation (rare but severe)

• Increased risk of colorectal cancer (especially in pancolitis, long duration >8–10 years)

• Strictures (less common than in Crohn’s disease)

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Diagnosis

• History and examination: chronic bloody diarrhoea, systemic features, extraintestinal signs

• Blood tests: anaemia, elevated ESR/CRP, low albumin, pANCA positivity (non-specific)

• Stool tests: exclude infection (e.g., C. difficile, ova, and parasites)

• Colonoscopy with biopsy (gold standard): continuous mucosal inflammation starting at rectum, friable mucosa, ulcerations

• Histology: crypt abscesses, mucosal/submucosal inflammation, no granulomas

• Imaging (if colonoscopy contraindicated): CT or MRI for complications (e.g., toxic megacolon)

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Treatment

1. Induction of remission (based on severity and extent)

• Mild to moderate proctitis/proctosigmoiditis:

  • Topical mesalazine (5-ASA) suppositories or enemas

  • Oral mesalazine if not responding to topical

• Left-sided or extensive disease:

  • Oral mesalazine ± topical 5-ASA

  • If inadequate, add oral corticosteroids (prednisolone) or budesonide MMX

• Severe colitis:

  • Hospital admission, IV corticosteroids

  • If no improvement in 3–5 days → IV ciclosporin or infliximab

2. Maintenance of remission

• Mesalazine (oral and/or topical) long term

• Immunomodulators (azathioprine, 6-mercaptopurine) if steroid-dependent or frequently relapsing

• Biologics (anti-TNF: infliximab, adalimumab; anti-integrin: vedolizumab; anti-IL12/23: ustekinumab) for refractory disease

3. Surgery

• Indications: refractory disease, severe complications, dysplasia/cancer

• Procedure: proctocolectomy with ileal pouch–anal anastomosis or permanent ileostomy

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Lifestyle and Supportive Measures

• Balanced diet; avoid known triggers during flares

• Iron, folate, vitamin D, calcium supplementation if deficient

• Vaccinations (especially before immunosuppression)

• Colorectal cancer surveillance colonoscopy:

• Start 8 years after diagnosis (if >30% colon involved)

• Repeat every 1–3 years depending on risk