Definition
A chronic inflammatory disorder of unknown cause of the colonic mucosa, usually beginning in the rectum and extending proximally to a variable extent. Ulcerative colitis and Crohn’s disease together are referred to as idiopathic inflammatory bowel disease.
- Serological markers (ANCA and ASCA) are useful in making diagnosis.
- The majority of colitis is controlled by medical management – surgery is usually only required for poor control of symptoms or complications.
- Acute attacks require close scrutiny to avoid major complications.
- Long-term colitis carries a risk of colonic malignancy.
- Ileoanal pouch reconstruction offers good function in the majority of cases where surgery is required.
Epidemiology
Male : female 1:1.6, peak incidence 30–50 years. High incidence among relatives of patients (up to 40%) and among Europeans and people of Jewish descent.
Aetiology
- Uncertain but definite genetic linkage: increased prevalence (10%) in relatives, associated with HLA-B27 phenotype. Similar genes implicated in UC and Crohn’s disease.
- Autoimmune basis – autoantibodies against intestinal epithelial cells, ANCA, ASCA.
- Association with increased sulphide in GI tract, decreased vitamins A and E, NSAID use, milk consumption.
- Smoking ‘protects’ against relapse.
Pathology
Disease confined to colon, rectum always involved, may be ‘backwash’ ileitis.
Macroscopic
In simple disease, only the mucosa is involved with superficial ulceration, exudation and pseudopolyposis. In severe disease, the full thickness of the colon wall may become involved in inflammation.
Histological
Mucin depletion, crypt abscess formation, acute neutrophilic infiltrate in severe disease, inflammatory pseudopolyps and highly vascular granulation tissue. Epithelial dysplasia with long-standing disease. (Sub)mucosal atrophy and fibrosis in chronic, ‘burnt out’ disease.
Clinical Features
Disease distribution is ‘distal to proximal’; rectum almost always involved with (sequentially) sigmoid, left side, pan colon involvement. Rectum rarely spared. Caecum may have isolated ‘patch’ of inflammation.
Proctitis
- Mucus, pus and blood PR.
- Urgency and frequency (diarrhoea less prominent).
Left-Sided Colitis → Total Colitis
Symptoms of proctitis + increasing features of systemic upset, abdominal pain, anorexia, weight loss and anaemia with more extensive disease.
Extraintestinal Features
Percentage involved:
- Joints: arthritis (25%).
- Eye: uveitis (10%).
- Skin: erythema nodosum, pyoderma gangrenosum (10%).
- Liver: pericholangitis, fatty liver (3%), primary sclerosing cholangitis.
- Blood: thromboembolic disease (rare).
Severe/Fulminant Disease
- 6–20 bloody bowel motions per day/dehydration.
- Fever, anaemia, dehydration, electrolyte imbalance.
- Colonic dilatation/perforation – ‘toxic megacolon’/shock.
Investigations
- FBC: iron deficiency anaemia. WBC raised, ESR raised.
- Serological markers: ANCA and pANCA as with UC, ASCA more with Crohn’s disease.
- Stool culture + C. difficile toxin: exclude infective colitis before treatment.
- Plain abdominal radiograph: colonic dilatation or air under diaphragm indicating perforation in fulminant colitis.
- Double-contrast barium enema: loss of haustrations, shortened ‘lead pipe’ colon.
- Radionuclide studies useful in acute fulminant colitis.
- Sigmoidoscopy: inflamed friable mucosa, bleeds to touch.
- Colonoscopy: extent of disease at presentation, evaluation of response to treatment after exacerbations, screening of long-standing disease for dysplasia.
- Biopsy: typical histological features.
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