Description
Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterised by relapsing and remitting mucosal inflammation, confined to the colon. It primarily affects the rectum and may extend in a continuous manner to involve other parts of the colon.
Pathogenesis
The pathogenesis of UC is not fully understood but it likely involves a dysregulated immune response to gut microbiota in genetically predisposed individuals. Environmental factors, such as diet and smoking, are also thought to play a role.
Epidemiology, Risk Factors & Associations
UC is most commonly diagnosed between the ages of 15 and 30, with a second peak in the 6th decade of life. Risk factors include a family history of the disease and environmental factors such as diet, oral contraceptive use, and appendectomy.
- Primary Sclerosing Cholangitis (PSC) (70-80% of cases): Majority of PSC patients develop inflammatory bowel disease, majority of which is ulcerative colitis. Leads to progressive liver disease.
- Ankylosing Spondylitis: Spinal inflammatory condition. Can present as chronic back pain and stiffness in UC patients.
- Colorectal Carcinoma: Risk increases with duration and extent of UC. Surveillance colonoscopies recommended for early detection.
- Coeliac Disease: 3x increased risk in UC patients. Presents with malabsorption symptoms, can complicate management of UC.
- Moyamoya Phenomenon: Rare but notable association. Characterised by progressive stenosis of cerebral arteries leading to development of a network of tiny vessels.
Clinical Features
Intestinal Manifestations
Patients with UC typically present with bloody diarrhoea, urgency, and lower abdominal pain. Other symptoms may include fatigue, weight loss, and fevers. The disease course can be variable, ranging from mild with infrequent flare-ups, to severe with continuous symptoms.
Extra-intestinal Manifestations
- Dermatologic conditions: Such as erythema nodosum, which presents as tender nodules usually on the shins, and pyoderma gangrenosum, a painful ulcerative skin condition.
- Ophthalmologic conditions: Including uveitis (inflammation of the uvea, the middle layer of the eye) and episcleritis (inflammation of the episclera, a thin layer of tissue covering the white part of the eye).
- Arthritic conditions: Arthritis can be peripheral (affecting the large joints of the arms and legs) or axial (affecting the spine and sacroiliac joints)
- Hepatobiliary disease: Primary sclerosing cholangitis, a rare disease of the bile ducts that can lead to liver damage.
- Thromboembolic events: People with UC have an increased risk of developing blood clots, particularly during flare-ups of their disease.
- Bone disease: Chronic inflammation and steroid use in UC can lead to osteoporosis, raising the risk of fractures.
- Mental health problems: Many people with UC experience mental health problems such as depression and anxiety.
Complications
Backwash Ileitis: This is a condition where inflammation extends into the terminal ileum, typically seen in severe cases of ulcerative colitis. It can complicate the clinical course and can make it difficult to distinguish ulcerative colitis from Crohn’s disease, as the latter can also affect the ileum.
Long-term complications of UC include colon cancer, toxic megacolon, and increased risk of thromboembolism. Extra-intestinal complications can affect the skin, eyes, joints, and liver.
Pathological Features
Histopathology
- UC is characterised by continuous mucosal (vs. transmural in Crohn’s disease) inflammation starting from the rectum. Key features include crypt abscesses, ulceration, and inflammatory cell infiltrates in the mucosa. Chronic changes include crypt architectural distortion.
Biochemistry
- May show elevated inflammatory markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Faecal calprotectin, a marker of intestinal inflammation, may also be elevated.
Radiological Features
General Features
- Continuity of disease (rectum to varying extents of colon), loss of haustral markings, mucosal ulceration, and pseudopolyps.
- May demonstrate associated colorectal carcinoma (sessile mural lesion or stricture)
Fluoroscopy
- Classically shows “lead pipe” appearance due to loss of haustral markings.
CT
- May show wall thickening, fat stranding, and loss of haustral folds.
- May demonstrate submucosal fat deposition in and around the rectum, possibly widening the presacral space (fat halo sign) – suggestive of chronic UC.
- Useful for detecting complications such as perforation.
MRI
- May show colonic wall thickening, increased enhancement, and pericolonic inflammation.
Differential Diagnosis
- Crohn’s disease: Can be differentiated by its transmural inflammation, skip lesions, and rectal sparing on imaging.
- Infectious colitis: May be similar clinically but history and stool culture can aid in differentiating.
- Ischaemic colitis: Typically presents in older patients, often with vascular disease, and is segmental on imaging.
Management
Management of UC involves a multidisciplinary approach and may include aminosalicylates, corticosteroids, and immunosuppressive agents for controlling inflammation, as well as surgery for those with severe or refractory disease. Surveillance colonoscopy for colorectal cancer screening is also important due to the increased risk.