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Ulcerative Colitis

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Last updated: February 13, 2022
Revisions: 33

Last updated: February 13, 2022
Revisions: 33

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Ulcerative colitis (UC) is the most common form of inflammatory bowel disease, the other major type being Crohn’s disease (CD)

It is most prevalent among the Caucasian population, with the presentation following a bimodal distribution between 15-25yrs for most cases and a smaller peak of incidence between 55-65yrs. Prevalence in the UK is approximately 0.2%, with males and females affected equally.

The disease typically follows a remitting and relapsing course. A severe fulminant exacerbation may be life-threatening, resulting in severe systemic upset, toxic megacolon, colonic perforation, and even death.

Fig. 1 – Histology of Bowel Segment in UC, showing non-granulomatous inflammation with crypt abscess (circled) formation

Figure 1 – Histology of Bowel Segment in UC, showing non-granulomatous inflammation with crypt abscess (circled) formation


Although the exact aetiology of ulcerative colitis is unknown, current theories suggest it develops as an interaction between genetic factors and environmental triggers*.

It is characterised by diffuse continual mucosal inflammation of the large bowel, beginning in the rectum and spreading proximally, potentially affecting the entire large bowel. A portion of the distal ileum can become affected in a small proportion of cases, termed ‘backwash ileitis’ (if the ileocaecal valve is not competent).

Histological changes include non-granulomatous inflammation of the mucosa and submucosa, crypt abscesses (Fig. 1), and goblet cell hypoplasia. Repeated cycles of ulceration and healing may lead to raised areas of inflamed tissue termed ‘pseudopolyps’.

*Smoking is protective against UC, whilst a positive family history of inflammatory bowel disease is a strong risk factor

Ulcerative Colitis Crohn’s Disease
Site Involvement Large bowel Entire GI tract
Inflammation Mucosa only Transmural
Microscopic Changes Crypt abscess formation
Reduced goblet cells
Granulomatous (non-caseating)
Macroscopic Changes Continuous inflammation (proximal from rectum)
Pseudopolyps and ulcers may form
Discontinuous inflammation (‘skip lesions’)
Fissures and deep ulcers (‘cobblestone appearance’)
Fistula formation

Table 1 – Characteristic Features of Inflammatory Bowel Disease

Clinical Features

Ulcerative colitis is typically insidious in onset. The cardinal feature is bloody diarrhoea, with visible blood in stool reported in more than 90% of cases.

The most common manifestation of ulcerative colitis is proctitis, whereby the inflammation is confined to the rectum only. Patients may complain of PR bleeding and mucus discharge, increased frequency and urgency of defecation, and tenesmus.

Patients presenting with more widespread colonic involvement are more likely to experience bloody diarrhoea with clinical features of dehydration and electrolyte imbalance. Systemic symptoms also include malaise, anorexia, and low-grade pyrexia.

Unless there is a severe exacerbation, clinical examination is generally unremarkable. Fulminant colitis, toxic megacolon, or colonic perforation should be suspected if the patient complains of severe abdominal pain and on examination demonstrates systemic involvement or signs of peritonism.

Disease Grading

The severity of an exacerbation can be graded using the Truelove and Witt criteria (Table 2). The severity degree is based on the presence of any one of the criteria:

Criteria Mild Moderate Severe
Bowel movements per day <4 4-6 >6
Blood in stool Minimal Mild to severe Visible blood
Pyrexia No No Yes
Pulse >90 bpm No No Yes
Anaemia No No Yes
ESR (mm/hour) ≤30 30 >30

Table 2 – Truelove and Witt Criteria

Extra-Intestinal Manifestations

Ulcerative colitis, much like Crohn’s disease, is associated with certain extra-intestinal manifestations of the disease:

  • Musculoskeletal – enteropathic arthritis (typically affecting sacroiliac and other large joints) or nail clubbing
  • Skin – Erythema nodosum (tender red/purple subcutaneous nodules, typically on the shins, Fig. 2)
  • Eyes – Episcleritis, anterior uveitis, or iritis
  • Hepatobiliary – Primary sclerosing cholangitis* (chronic inflammation and fibrosis of the bile ducts)

*Around 70% of patients with PSC will have IBD, whilst around 5% of patients with IBD will have PSC

Fig 2 - Erythema nodosum is a relatively common extra-intestinal feature of ulcerative colitis.

Figure 2 – Erythema nodosum is a relatively common extra-intestinal feature of ulcerative colitis

Differential Diagnosis

The primary differential diagnosis for ulcerative colitis is Crohn’s disease, as this can present in a similar fashion, however patients with UC patients typically experience a more bloody diarrhoea.

Alternative forms of colitis include chronic infections (schistosomiasis, giardiasis, or abdominal tuberculosis), mesenteric ischaemia, or radiation colitis. Other differentials to consider include malignancy, irritable bowel syndrome, or coeliac disease.


Routine bloods* (FBC, U&Es, CRP, LFTs, and clotting) are required to examine for anaemia, low albumin (secondary to systemic illness), and evidence of inflammation (raised CRP and WCC).

NICE guidelines recommend that faecal calprotectin testing is carried out in patents with recent onset lower gastrointestinal symptoms (and to monitor disease severity following treatment); it is raised in inflammatory bowel disease, but unchanged in irritable bowel syndrome. A stool sample should be sent for microscopy and culture.

*Liver function tests may become deranged in patients on medical treatment and clotting can become deranged in severe attacks due to the large inflammatory response affecting the coagulation cascade


The definitive diagnosis for ulcerative colitis is via colonoscopy with biopsy*. Characteristic macroscopic findings are of continuous inflammation with possible ulcers and pseudopolyps visible. The Montreal score can be used for quantifying disease extent and the Mayo score for disease severity.

In acute exacerbations, plain film abdominal radiographs (AXR) or CT imaging can be used to assess for toxic megacolon (Fig. 3C) and/or the presence of a bowel perforation. AXR features of acute ulcerative colitis flares also include mural thickening and thumbprinting, indicating a severe inflammatory process in the bowel wall; in chronic cases of UC, a lead-pipe colon is often described (best seen on barium studies).

*Acute severe UC flare will need urgent flexible sigmoidoscopy for biopsy (including to exclude other causes of colitis, including CMV colitis)

Fig. 3 - (A) bowel fibrosis, secondary to chronic UC (B) active inflammation in patient with UC (C) AXR changes in active UC, showing toxic megacolon with lead-pipe colon ( seen in descending colon)

Figure 3 – (A) bowel fibrosis, secondary to chronic UC (B) active inflammation in patient with UC (C) AXR changes in active UC, showing toxic megacolon with lead-pipe colon (seen in descending colon)


Patients with suspected IBD should be referred to a gastroenterologist for confirmation of the diagnosis and initiation of treatment; those with acute severe disease should be admitted on an emergency basis.

Anti-motility drugs, such as loperamide, should be avoided in acute attacks, as these can precipitate toxic megacolon.

Inducing Remission

Any acute attacks will also warrant aggressive fluid resuscitation, nutritional support, and prophylactic heparin (due to the prothrombotic state of IBD flares).

The medical management to induce remission in UC typically requires use of intravenous corticosteroid therapy and immunosuppresive agents, such as ciclosporin or 5-ASA suppositories. Biological agents, such as infliximab, can be trialled as rescue therapy if then needed.

NICE guidelines suggest that a stepwise approach is adopted, dependent upon the clinical severity and location of the exacerbation.

Maintaining Remission

Once any acute event has been controlled, remission of the disease can be maintained using immunomodulators, typically 5-ASAs, such as mesalazine or sulfasalazine, or azathioprine.

Due to increased risk of colorectal malignancy, colonoscopic surveillance is offered to people who have had the disease for >10 years with >1 segment of bowel affected.

Patients should be referred to IBD-nurse specialists and patient-support groups. Enteral nutritional support should be considered in young patients with growth concerns, with close support from a nutritional team.

Surgical Management

Approximately 30% of patients with ulcerative colitis will at some point require surgery.

Indications for acute surgical treatment include disease refractory to medical management, toxic megacolon, or bowel perforation. Surgery will depend on patient and disease factors, however will typically require segmental bowel resection (typically needing a subtotal colectomy) and defunctioning stoma, as primary anastomosis during acute IBD flare is not advised.

For elective cases, total proctocolectomy is curative* (with the patient requiring an end ileostomy), yet many patients for disease control will often initially undergo a subtotal colectomy with ileo-rectal anastomosis (IRA) or panproctocolectomy with ileo-pouch  anal anastomosis (IPAA)


Patients with well-controlled UC can expect to have a similar life expectancy as those in the general population. However, the main complications of UC include:

  • Toxic megacolon, present with severe abdominal pain, abdominal distension, pyrexia, and systemic toxicity
    • Decompression of the bowel is required as soon as possible, due to high risk of perforation, and failure to respond to medical management is an indication for surgery
  • Colorectal carcinoma
  • Osteoporosis, requiring regular assessment for fracture risk and treated as necessary
  • Pouchitis, inflammation of an ileal pouch in those who have undergone an IPAA, with typical symptoms of abdominal pain and bloody diarrhoea; this can be treated with metronidazole and ciprofloxacin

Key Points

  • Ulcerative Colitis will only affect the large bowel and definitive diagnosis is made from colonoscopy with biopsy
  • Medical management of acute flares involves sequential escalation of treatment, from corticosteroids and immunosuppressors to biological therapies
  • Surgical input should be sought urgently in cases refractory to medical management, patients who have developed toxic megacolon, or suspected bowel perforation
  • Complications of the disease can be both intestinal and extra-intestinal manifestations