Ulcerative colitis and Crohn disease

Overview

Inflammatory bowel disease (IBD) means chronic, relapsing inflammation of the gut. The two main forms are ulcerative colitis (UC) and Crohn disease (CD). A small group with colitis that cannot be classed as either is called IBD unclassified (indeterminate colitis).

IBD usually starts in young adults (peak about 20–40 years). It is less common in Pakistan than in the West but is being diagnosed more often. Here the key practical point is that intestinal TB, amoebic colitis and infective diarrhoea must always be excluded first.

Aetiology

IBD results from an abnormal immune response to gut bacteria in a genetically susceptible person, triggered by environmental factors.

• Genetics: family history is the strongest risk factor. NOD2 (CARD15) gene variants are linked to ileal Crohn disease; HLA-B27 to sacroiliitis.
• Smoking: increases the risk and severity of Crohn disease but is protective against UC (UC often appears after stopping smoking).
• Appendicectomy at a young age appears to protect against UC.
• NSAIDs can trigger onset or flares. Breast-feeding may protect.
• Immune mechanism: excess Th1/Th17 activity and TNF-α, which is why anti-TNF drugs work.

Pathology: UC versus Crohn

Extent of UC (Montreal)

• E1 Proctitis: rectum only.
• E2 Left-sided (distal) colitis: up to the splenic flexure.
• E3 Extensive colitis / pancolitis: beyond the splenic flexure.

Clinical features

Ulcerative colitis

• Bloody diarrhoea with mucus; urgency, tenesmus, nocturnal stools.
• Proctitis: fresh blood and mucus, frequent small stools, often formed; few systemic symptoms.
• Extensive colitis: many liquid bloody stools a day, cramps, fever, weight loss, anaemia.
• Course of relapses and remissions.
• Examination: often little; blood on rectal examination; tachycardia and fever mean a severe attack.

Crohn disease

• Diarrhoea, abdominal pain and weight loss (the main triad); fatigue, fever, anorexia.
• Small bowel disease: colicky pain from subacute obstruction, right iliac fossa pain or mass, malabsorption and steatorrhoea; may mimic appendicitis.
• Colonic disease: bloody diarrhoea, like UC.
• Perianal disease (in about a quarter it is the first sign): fissures, fistulas, abscesses, skin tags.
• Mouth ulcers.
• Children: growth failure and delayed puberty.
• Progression over time from inflammatory to stricturing and penetrating (fistulising) disease.

Extra-intestinal manifestations

Investigations

Blood tests

• Anaemia, raised platelets, ESR and CRP (CRP rises more in Crohn), low albumin in severe disease.
• Iron studies, B12 and folate, liver tests (PSC).
• pANCA (UC) and ASCA (CD) are supportive only.

Stool tests

• Stool culture and C. difficile toxin in every flare; stool microscopy for amoebae (very important in Pakistan).
• Faecal calprotectin: raised in active gut inflammation; helps separate IBD from IBS and is used to monitor disease.

Endoscopy and biopsy

• Ileocolonoscopy with multiple biopsies is the key diagnostic test for both.
  • UC: continuous inflammation from the rectum, loss of vascular pattern, friability, ulcers, pseudopolyps.
  • CD: patchy aphthous or deep ulcers, cobblestoning, ileal involvement, rectal sparing.
• In a severe attack, do only a limited unprepared flexible sigmoidoscopy; full colonoscopy risks perforation.
• Upper GI endoscopy if symptoms suggest proximal Crohn disease.

Imaging

• Plain abdominal X-ray in acute severe colitis: colonic dilatation (toxic megacolon), mucosal islands, thumbprinting.
• MR enterography (or CT, barium follow-through, small bowel ultrasound) for small bowel Crohn: thick ileum, strictures with dilatation above, fistulas, abscesses. The narrowed terminal ileum may show the "string sign" of Kantor.
• Barium enema in long-standing UC: loss of haustra and a narrow, smooth "lead-pipe" colon; collar-stud ulcers in active disease.
• Pelvic MRI for perianal fistulas; capsule endoscopy when small bowel imaging is normal but suspicion remains.

Acute severe ulcerative colitis

Truelove and Witts criteria

Severe = more than 6 bloody stools a day plus at least one sign of systemic illness:

• Temperature over 37.5 °C
• Pulse over 90/min
• Haemoglobin under 100 g/L
• ESR over 30 mm/h (or raised CRP)

Low albumin (under 30 g/L) is an additional marker of severity.

Management

• Admit under joint medical and surgical care.
• Exclude infection: stool culture, C. difficile, amoebae; biopsy for CMV if refractory.
• IV hydrocortisone 100 mg four times daily (6-hourly).
• IV fluids, correct potassium and anaemia (transfuse if needed), nutritional support.
• Prophylactic low molecular weight heparin: IBD carries a high clot risk, even with rectal bleeding.
• Stop anticholinergics, opioids, antidiarrhoeals and NSAIDs (they can precipitate toxic megacolon).
• Daily stool chart, pulse, temperature, CRP, FBC, electrolytes; daily abdominal X-ray if not improving.
• Day 3 review: if CRP over 45 mg/L or more than 8 stools a day, start rescue therapy with IV ciclosporin or infliximab, or proceed to colectomy.
• If no response to rescue treatment: subtotal colectomy with end ileostomy, leaving the rectum.

Toxic megacolon

• Colon dilated to more than 6 cm (usually the transverse colon) on plain X-ray, with systemic toxicity.
• Risk of perforation, which has a high mortality; steroids can mask the signs.
• A falling stool frequency with increasing distension is a danger sign, not improvement.
• Needs urgent surgery if it does not resolve quickly on intensive treatment.

Drug treatment

Main drug groups

Ulcerative colitis by extent

• Proctitis: rectal 5-ASA (suppositories) first; add oral 5-ASA; steroids if no response.
• Left-sided colitis: 5-ASA enemas plus oral 5-ASA; oral prednisolone if not settling.
• Extensive colitis: oral 5-ASA (plus rectal); oral prednisolone for moderate flares.
• Maintenance: 5-ASA for most; azathioprine after a severe attack or frequent steroid use; biologics for refractory disease.

Crohn disease

• Stop smoking: the single most useful step.
• Induction: oral prednisolone (or IV for severe); budesonide for mild–moderate ileocaecal disease; exclusive enteral nutrition (first-line in children).
• Maintenance: azathioprine/mercaptopurine or methotrexate; anti-TNF for poor-prognosis, refractory or fistulising disease, often combined with a thiopurine.
• Perianal disease: drain sepsis (seton), antibiotics, then thiopurine and/or anti-TNF.
• Treat deficiencies: iron, B12 injections after ileal resection, vitamin D.

Surgery

Ulcerative colitis (surgery is curative)

Indications: acute severe colitis failing medical treatment, toxic megacolon, perforation, massive haemorrhage; chronic disease with poor control or steroid dependence; dysplasia or cancer on surveillance; growth failure in children.

• Emergency: subtotal colectomy with end ileostomy, keeping the rectum.
• Elective: restorative proctocolectomy with ileal pouch–anal anastomosis (IPAA), or panproctocolectomy with permanent ileostomy.
• Pouchitis affects about a third of pouch patients; treat with metronidazole and/or ciprofloxacin.

Crohn disease (surgery is not curative)

Indications: obstruction from strictures, fistulas, abscesses, perforation, bleeding, failed medical treatment, growth failure.

• Keep resections short (risk of short bowel syndrome); use strictureplasty for short strictures.
• Recurrence after surgery is common, usually at the anastomosis; stop smoking.
• An ileal pouch is not advised in Crohn disease because of high pouch failure.

Complications and prognosis

• Toxic megacolon, perforation, haemorrhage (UC).
• Strictures, fistulas, abscesses, malabsorption, short bowel (CD).
• Bowel (colon and rectal) cancer risk in long-standing extensive UC and extensive Crohn colitis; higher with longer duration, greater extent, PSC, ongoing inflammation and a family history. Regular colonoscopic surveillance is advised for extensive colitis lasting more than about 10 years.
• Small bowel adenocarcinoma and lymphoma (rare, CD).
• Venous thromboembolism.
• Most patients have a normal life expectancy with good care; about a third of UC patients have only one attack.

Quick revision

• UC: rectum always, continuous, mucosal, bloody diarrhoea, crypt abscesses, pANCA.
• CD: mouth to anus, skip lesions, transmural, granulomas, fistulas, perianal disease, ASCA.
• Smoking protects in UC, harms in CD.
• PSC goes with UC; gallstones and oxalate stones with ileal CD.
• Severe UC: more than 6 bloody stools/day plus fever, tachycardia, anaemia or high ESR.
• Treat severe UC: IV hydrocortisone, LMWH, exclude infection; day 3 rescue or colectomy.
• Toxic megacolon: over 6 cm, risk of perforation.
• 5-ASA first-line in mild–moderate UC; steroids induce, do not maintain.
• TPMT before azathioprine; TB screen before anti-TNF.
• UC surgery is curative; Crohn surgery is not.

Written by The House Job from standard references (Kumar and Clark's Clinical Medicine; Bailey & Love's Short Practice of Surgery).

FAQ