Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that affects the colon and rectum. UC is the most common form of IBD and has an annual incidence of 1.2-20.3 cases per 100 000 persons, with a bimodal age distribution with peaks in the third and seventh decades of life. UC has a higher incidence in males, Ashkenazi Jews, and people of Northern European ancestry. Worldwide, the incidence of UC is increasing.

The pathophysiology has not been fully elucidated. There are hypothesized genetic, environmental, and immune factors that likely contribute to the development of UC. Most likely, the etiology is multifactorial.

Clinical manifestations include relapsing episodes of bloody diarrhea, abdominal pain, fever, malaise, and weight loss. Patients may be anemic.

UC is associated with extraintestinal manifestations. These include dermatologic conditions (ie, erythema nodosum, pyoderma gangrenosum, psoriasis), inflammatory arthritis, uveitis, and primary sclerosing cholangitis.

Although 83% of patients will suffer from at least one relapse during the first 10 years after initial onset, the prognosis for UC in general is good. Over half of patients report remission or only mild intestinal symptoms.

On endoscopy, UC almost always presents with continuous involvement of the rectum and/or colon. During the active phase of disease, the mucosa can appear erythematous and friable. Pseudopolyps and inflammatory polyps may also be present as a result of chronic inflammation.

Risk factors: UC is most common in developed countries. This is suggestive of environmental risk factors for the development of UC.

There are myriad genes associated with UC, but no identifiable genetic cause of UC.

Smoking cessation is a risk factor for the development of UC.

Timeline: The course of UC is unpredictable. The initial presentation can vary from mild / asymptomatic to severe (toxic hemorrhagic colitis). Some patients have a quiescent disease course, while others can have progressive worsening of bowel inflammation.

Pediatric patient considerations: The mean age at time of diagnosis of IBD among children is 10.3 years. Pediatric-onset disease has a worse course, with more extensive disease, a higher colectomy rate (30%-40% at 10 years compared with 20% in adult-onset disease), and more frequent hospitalizations.