Ulcerative Colitis — Causes, Symptoms, Biologic Therapy & Surgery Guide — Symptoms, Causes & Treatment | MyMedicPlus

Ulcerative colitis (UC) is a chronic, relapsing-remitting inflammatory bowel disease (IBD) characterised by diffuse mucosal inflammation of the colon and rectum. Unlike Crohn's disease (which can affect the entire GI tract with transmural inflammation and skip lesions), UC affects only the colon and rectum, with inflammation confined to the mucosal layer; it extends continuously from the rectum proximally to a variable extent — proctitis (rectum only — 30-40%); left-sided colitis (to the splenic flexure — 30-40%); and extensive colitis or pancolitis (beyond the splenic flexure or throughout the entire colon — 20-30%). UC is characterised pathologically by goblet cell depletion, crypt architectural distortion, crypt abscesses, and diffuse mucosal ulceration. The disease follows a relapsing-remitting course in the majority of patients — approximately 50% of patients have a relapse in any given year. UC affects approximately 2.5 million people in Europe and North America, with incidence rates of 10-20 per 100,000 per year; it is more common in high-income industrialised countries and incidence is rising in newly industrialising countries as they adopt a more Westernised lifestyle. Peak onset is bimodal — ages 15-30 and 50-70. There is no medical cure for UC; however, colectomy (surgical removal of the colon) is curative. The goal of modern UC management is mucosal healing (endoscopic remission) rather than merely symptomatic control, as mucosal healing reduces hospitalisation, colectomy rates, and colorectal cancer risk.

The aetiology of UC is multifactorial — a combination of genetic susceptibility, dysregulated immune response to commensal gut microbiota, and environmental factors. Genetic factors: UC is 10-15 times more common in first-degree relatives of affected individuals; concordance in identical twins is approximately 15% (lower than Crohn's — 50% — suggesting greater environmental influence in UC). Over 200 genetic loci are associated with IBD; the HLA-DRB1 locus is the strongest genetic risk for UC specifically. Immune dysregulation: UC is characterised by a Th2-dominant mucosal immune response with IL-5, IL-13, and TGF-beta signalling; upregulation of TNF-alpha and IL-6 drives mucosal inflammation. Natural killer T (NKT) cells and altered regulatory T-cell function contribute to loss of mucosal tolerance to commensal bacteria. Gut microbiome: patients with UC have reduced microbial diversity and loss of protective commensal species (Faecobacterium prausnitzii — a key butyrate producer with anti-inflammatory properties); faecal microbiota transplantation (FMT) can induce remission in some patients. Environmental factors: non-steroidal anti-inflammatory drugs (NSAIDs) and aspirin can trigger or worsen UC flares; antibiotics alter gut flora and may precipitate the first episode; high-fat, low-fibre Western diet; psychological stress (exacerbates but does not cause UC — the gut-brain axis is important); urban living and high socioeconomic status (hygiene hypothesis). Protective factors: appendicectomy (particularly before age 20) reduces UC risk by approximately 70% — the mechanism is unclear but may involve regulatory T-cell induction; smoking (paradoxically protective in UC — former smokers who quit have higher UC risk; transdermal nicotine patches have modest therapeutic benefit in UC; opposite of Crohn's where smoking worsens disease); breastfeeding.

The cardinal symptoms of UC are bloody diarrhoea, rectal urgency, and tenesmus (a persistent feeling of incomplete defecation). The frequency and severity of symptoms correlate with the extent and severity of colonic inflammation. Mild UC: fewer than four stools per day (with or without blood); no systemic disturbance; normal or mildly raised CRP. Moderate UC: 4-6 stools per day with blood; mild systemic symptoms (low-grade fever, anaemia, elevated CRP). Severe UC (Truelove and Witts criteria): six or more bloody stools per day; plus one or more of: fever (above 37.8 degrees Celsius); tachycardia (above 90 bpm); anaemia (haemoglobin below 10.5 g/dL); elevated ESR above 30 mm/hour. Severe UC requires hospital admission for IV corticosteroids. GI symptoms: bloody diarrhoea (blood mixed through the stool — distinguishes from haemorrhoids where blood is separate); rectal urgency and frequency (up to 20 times daily in severe flare); nocturnal diarrhoea (waking from sleep to defecate — distinguishes IBD from functional bowel disease which is not nocturnal); abdominal cramping (usually lower, particularly before defecation); and tenesmus (urge to defecate with little stool produced from rectal inflammation). Systemic symptoms during flares: fatigue, anorexia, weight loss, low-grade fever. Anaemia (iron deficiency from chronic blood loss — the most common systemic complication). Extra-intestinal manifestations (EIM — approximately 25% of UC patients): joints (peripheral arthritis, sacroiliitis — flares with colonic disease activity); eyes (episcleritis, uveitis); skin (erythema nodosum, pyoderma gangrenosum); liver (primary sclerosing cholangitis — PSC — in 2-5% of UC; increases colorectal cancer risk significantly).

Diagnosis of UC requires clinical assessment combined with endoscopic and histological confirmation. Stool tests: stool cultures and Clostridium difficile PCR (to exclude infective colitis mimicking UC — particularly important in first presentations and flares); faecal calprotectin (a marker of colonic mucosal inflammation — elevated in IBD, above 250 micrograms/g is highly sensitive for active IBD and helps distinguish from irritable bowel syndrome; used to monitor disease activity and predict relapse). Blood tests: full blood count (anaemia, thrombocytosis in active inflammation, leucocytosis); CRP and ESR (reflect inflammatory activity — correlate with disease severity); albumin (low in severe or chronic active UC — marker of malnutrition and disease severity); LFTs and renal function (baseline and monitoring); vitamin B12, folate, iron studies (nutritional deficiencies). Flexible sigmoidoscopy or colonoscopy: the cornerstone of UC diagnosis — reveals continuous mucosal inflammation with loss of vascular pattern, granularity, friability (bleeds on contact — positive 'contact bleeding'), mucosal oedema, ulceration, and pseudopolyps in chronic disease; biopsy from multiple sites provides histological confirmation — crypt distortion, goblet cell depletion, and basal plasmacytosis are diagnostic of UC. Colonoscopy with biopsies also assesses disease extent and excludes dysplasia. MRI abdomen: used to assess disease extent and exclude complications; avoids radiation; colonic MRI less sensitive than colonoscopy for mucosal detail. CT abdomen (with or without contrast): useful for acute severe UC to exclude toxic megacolon (colonic diameter above 5.5 cm on plain film or CT — a surgical emergency); exclude complications (perforation, abscess). Capsule endoscopy: used to assess small bowel in suspected Crohn's disease. Colonoscopic surveillance for dysplasia: begins 10 years after disease onset for pancolitis and 15-20 years for left-sided colitis — dye-spray (chromoendoscopy) or virtual chromoendoscopy improves dysplasia detection.

Treatment strategy in UC follows a step-up approach based on disease severity, extent, and steroid dependency. Induction of remission in mild-moderate UC: 5-aminosalicylic acid compounds (aminosalicylates — 5-ASA): mesalazine (Pentasa, Asacol, Mezavant) is the first-line induction and maintenance treatment for mild-moderate UC — oral 2.4-4.8 g daily combined with rectal mesalazine suppository or enema achieves remission in 50-70% of mild-moderate UC; sulfasalazine is an alternative in those who also have arthritis (sulfapyridine moiety treats arthritis). Rectal mesalazine (suppository for proctitis, enema for left-sided colitis) is more effective than oral alone. Induction of remission in moderate-severe UC: oral prednisolone 40-60 mg daily for 4-8 weeks (tapered over 8-12 weeks); IV hydrocortisone 100 mg four times daily for hospitalised severe UC (Truelove-Witts criteria); if IV steroids fail after 3-5 days — rescue therapy with IV ciclosporin (2-4 mg/kg/day) or infliximab (5 mg/kg infusion) achieves colectomy avoidance in 60-70% in the short term. Maintenance therapy: azathioprine (2-2.5 mg/kg/day) or 6-mercaptopurine (1.5 mg/kg/day) — thiopurine immunomodulators; check TPMT enzyme activity before starting; effective for steroid-sparing maintenance. Biologic therapies (for moderate-severe UC failing or dependent on steroids): anti-TNF agents — infliximab (5 mg/kg IV at 0, 2, 6 weeks then 8-weekly) and adalimumab (160 mg SC then 80 mg then 40 mg biweekly); vedolizumab (anti-integrin — gut-selective; 300 mg IV at 0, 2, 6 weeks then 8-weekly; preferred for older patients and those with prior serious infections); ustekinumab (anti-IL-12/23 — 130 mg IV then 90 mg SC 8-weekly); small molecule oral therapies: tofacitinib (JAK inhibitor — 10 mg twice daily for 8 weeks then 5 mg twice daily maintenance), ozanimod (S1P modulator). Surgery (colectomy): total colectomy with ileal pouch-anal anastomosis (IPAA — 'J-pouch') is the curative surgery for UC; indicated for medically refractory disease, colorectal dysplasia or cancer, toxic megacolon, perforation, or severe haemorrhage. IPAA allows normal defecation (4-8 times daily) without a permanent stoma in most patients; pouchitis (inflammation of the ileal pouch) occurs in 50% and is treated with metronidazole or ciprofloxacin.

Toxic megacolon: the most acute life-threatening complication — severe transmural inflammation causes dilatation of the colon (transverse colon diameter above 5.5 cm on plain abdominal X-ray) with systemic toxicity (fever above 38 degrees, tachycardia above 120, leucocytosis, anaemia, hypoalbuminaemia); risk of perforation with peritonitis and sepsis; requires intensive care, IV fluids, IV corticosteroids, and emergency colectomy if no improvement within 24-48 hours. Colorectal cancer (CRC): UC increases CRC risk proportional to disease extent and duration — pancolitis of 10 years duration confers approximately 2-fold increased CRC risk compared to the general population; risk increases further with primary sclerosing cholangitis (PSC) co-existing. Regular colonoscopic surveillance with dye-spray chromoendoscopy and targeted biopsies is essential from 10 years after pancolitis onset. Achieving mucosal healing reduces CRC risk. Primary sclerosing cholangitis (PSC): present in 2-5% of UC patients — causes progressive biliary fibrosis leading to cirrhosis, liver failure, and cholangiocarcinoma; PSC requires liver transplantation in advanced cases. Nutritional complications: iron deficiency anaemia from chronic blood loss; folate deficiency; vitamin D deficiency; osteoporosis from corticosteroid use. Treatment complications: thiopurine-related leucopenia (monitor FBC monthly for 3 months); thiopurine-related lymphoma risk (marginally elevated); anti-TNF-related infections (TB reactivation — screen with IGRA before starting; PCP — prophylaxis if co-administered with corticosteroids); JAK inhibitor-related thromboembolism and herpes zoster reactivation. Pouchitis: occurs in 50% of patients after IPAA — most respond to antibiotics; chronic antibiotic-refractory pouchitis may require biologic therapy.

Medication adherence is the most critical factor in preventing UC relapse — studies show that non-adherence to maintenance 5-ASA treatment increases relapse risk 5-fold; adherence to maintenance therapy (mesalazine, azathioprine, or biologics) keeps most patients in long-term remission. Dietary management: while no specific diet prevents UC, a Mediterranean-style anti-inflammatory diet (high in fruit, vegetables, wholegrains, fish, and olive oil; low in red meat, processed foods, and alcohol) reduces inflammatory burden and may support remission. Identify and avoid personal dietary triggers during flares — lactose intolerance is common in active IBD; low-residue diet during acute flare reduces bowel frequency. Smoking cessation advice in non-smokers: all newly diagnosed UC patients should be advised not to start smoking (despite its paradoxical anti-inflammatory effect in UC — the overall health harms of smoking dramatically outweigh any marginal UC benefit). Psychological wellbeing: IBD has a bidirectional relationship with psychological health — stress, anxiety, and depression worsen disease activity and quality of life in UC; cognitive behavioural therapy (CBT) and mindfulness-based interventions improve coping and may reduce relapse rates; IBD nursing teams and patient organisations (Crohn's and Colitis UK) provide important psychological support. Vaccination: all UC patients should be up to date with vaccinations — particularly annual influenza, pneumococcal, and meningococcal C vaccination (immunosuppressed patients cannot receive live vaccines such as BCG, MMR, or yellow fever). Regular cancer surveillance (colonoscopy) from 10 years after disease onset as per BSG guidelines.

Go to A&E immediately for: sudden severe abdominal pain with distension in a known UC patient — possible toxic megacolon or perforation (surgical emergency); blood transfusion-requiring haematochezia (life-threatening GI haemorrhage); fever above 38.5 degrees with severe abdominal pain and diarrhoea (possible colonic perforation or fulminant colitis with sepsis); and severe UC flare not improving after 48 hours of oral prednisolone. See a GP or gastroenterologist urgently for: bloody diarrhoea persisting for more than 2 weeks — to exclude new UC diagnosis or flare; any new or worsening UC symptoms in a patient on maintenance therapy — disease breakthrough requiring treatment escalation; inability to maintain adequate oral hydration due to frequent diarrhoea (dehydration risk); and symptoms of obstruction (abdominal distension, severe cramping, vomiting) in a patient with known UC. Any first presentation of bloody diarrhoea in an adult requires prompt investigation including stool culture, faecal calprotectin, and flexible sigmoidoscopy or colonoscopy to exclude UC, Crohn's disease, and colorectal cancer.