Between relapses, Ulcerative Colitis (UC) is usually symptomless. In relapse, the severity of diarrhoea and systemic upset depends on the extent of the disease and the depth of mucosal ulceration. Active sub-total or total UC, involving the large intestine from the rectum at least to the hepatic flexure, causes frequent bloody diarrhoea, often with fever, malaise, anorexia, weight loss, abdominal pain, anaemia and tachycardia. By contrast, active proctitis is characterised by rectal bleeding and mucous discharge - often with tenesmus - but the stool is usually well-formed and general health maintained. Rarely, patients may present initially with complications of UC, such as arthropathy and sclerosing cholangitis.
Severe attacks may be complicated by toxic megacolon (or colonic dilatation with less severe systemic upset), perforation and, rarely, massive haemorrhage. Patients who have had sub-total or total UC for over ten years are at increased risk of colonic carcinoma (cumulative risk 10-15% at 20 years).
Most commonly these affect the skin (erythema nodosum, pyoderma gangrenosum), eyes (uveitis, episcleritis), joints (large joint arthropathy, sacro-iliitis, ankylosing spondylitis), liver (sclerosing cholangitis, choangiocarcinoma) and vasculature (arterial and venous thrombosis).
To establish the diagnosis and disease extent
The diagnosis of DC is suggested by finding inflamed mucosa at sigmoidoscopy and confirmed by rectal biopsy. If the upper limit of inflammation is not visible then colonoscopy, with further biopsies, is usually preferred to barium enema to confirm the diagnosis and its extent, and to exclude Crohn's disease. Where relevant, irradiation, ischaemic and other types of colitis should also be excluded (see Table I). Stool microscopy and culture is essential to exclude specific infections.
To assess disease severity in relapse
Disease activity can be quantified clinically (stool frequency, rectal bleeding, fever, tachycardia, and abdominal tenderness and/or distension), and by laboratory tests (for anaemia, leucocytosis,thrombocytosis, hypoalbuminaemia, and raised ESR and C-reactive protein). Cautious sigmoidoscopy is safe, but colonoscopy and standard barium enema may cause colonic dilatation or perforation in very active disease. Alternative assessment measures include plain abdominal Xray, 'instant' barium enema (without bowel preparation), and radiolabelled leucocyte scanning.