This is the first of three pictorial essays whose purpose is to discuss the clinical, pathological, and imaging characteristics of colitis. Although colitis is a broad topic, it can be readily divided into three major types: ulcerative colitis, Crohn’s disease, and other colitities (indeterminate, psuedomembranous, infectious, ischemic, and radiation-induced). Although ulcerative colitis and Crohn's disease are by far the most well recognized processes, the other entities are equally important and, collectively, they are equally as common. There are overlapping as well as distinctive features that may be seen with this last group of colitities. It is, however, the features of ulcerative colitis and Crohn's disease that represent the quintessential paradigms of colitis with which we compare and contrast clinical aspects of the disease.

Clinical Picture
[Intro Slide]

• "First-degree burn"
• More common than Crohn's disease
• Peak 15 to 25 years; 55 to 65 years (smaller peak)
• Family history
• Symptoms include intermittent diarrhea, pain, bleeding
• Multiple extraintestinal manifestations

Extraintestinal Manifestations
[Fig 22] [Fig 23]

HEPATOBILIARY: fatty liver, hepatitis, carcinoma, primary sclerosing cholangitis, pericholangitis

MUSCULOSKELETAL: sacroiliitis, ankolosing spondilitis, peripheral arthritis

OCULAR/DERMATOLOGICAL: pyoderma gangrenosus, erythema nodosum, uveitis

RENAL: nephrolithiasis

THROMBOEMBOLIC COMPLICATIONS

Location
[Fig 4] [Fig 5] [Fig 6] [Fig 7] [Fig 8] [Fig 9] [Fig 10]

• Rectum involved in approximately 95 percent
• Rectum only involved in approximately 30 percent
• Left colon only involved in about 40 percent
• Pancolitis seen in 30 percent; one-third of whom have "backwash ileitis"

Distribution
[Fig 4] [Fig 5] [Fig 6] [Fig 7] [Fig 8] [Fig 9] [Fig 10]

• Diffuse
• Contiguous
• Confluent
• Circumferential
• Symmetrical
• Superficial

Histology (Three Phases)
[Fig 2] [Fig 3]

ACUTE: mucosal capillary congestion, hemorrhage; crypt abscess formation with lymphocytes and PMN’s in the lamina propria; one may see ulceration

RESOLVING: resolving congestion, replenished goblet cells and epithelial proliferation

REMISSION: mucosal atrophy; thickened muscularis mucosa?

Gross Pathology
[Fig 3] [Fig 4] [Fig 5] [Fig 12] [Fig 14] [Fig 17] [Fig 21]

• Congested, granular, and hemorrhagic mucosa
• Ulcerations extending to muscularis propria
• Polypoid tags and pseudopolyps (usually proximal and in the direction of the fecal stream) Shortening of the colon
• Loss of haustral folds

Radiology
[Fig 6] [Fig 7] [Fig 8] [Fig 9] [Fig 10] [Fig 12] [Fig 13]

• Granular pattern of the mucosa, mucosal stippling due to crypt abscesses, collar-button ulcers due to undermining of? the muscularis propria
• Inflammatory polyps representing an island of mucosa in a sea of ulceration
• Post-inflammatory pseudopolyps, which represent exuberant mucosal regeneration during remission
• Backwash ileitis with secondary patulous ileo-cecal valve
  Blunting and loss of haustra
• There is widening of the presacral space and narrowing of the rectal lumen due to proliferation and infiltration of the presacral fat
• There is mural thickening due to a thickening in the muscularis propria and lamina propria; fatty deposition may be seen in the submucosa (giving the so-called "target sign"); this is analogous to the fibro-fatty proliferation seen in the serosa in Crohn's disease
• There is dysplasia and carcinoma seen as nodular protrusions, irregular mucosa, strictures, or masses

Carcinoma: Risk Factors

• Ten years after onset
• 0.5% per year for 10 to 20 years; 0.9% per year thereafter
• Depends on extent and duration of disease

Carcinoma and Ulcerative Colitis
[Fig 15] [Fig 16] [Fig 17] [Fig 18]

• Mucin-producing
• High-grade infiltrating
• Rectum and sigmoid are the most common locations and disease is often multifocal
• Five-year survival is 89% in patients without symptoms and 19% in symptomatic patients (that is, when the disease is more advanced at the time of diagnosis)

Toxic Megacolon
[Fig 19] [Fig 20] [Fig 21]

• Seen in 4% to 10% of patients with ulcerative colitis
• Usually > 6 cm in transverse diameter but this is variable
• Perforation seen in up to 40%
• Mortality is between 5% and 30%
• The wall has the texture of "wet tissue paper"
• The thickening seen on radiographs actually represents serosal and omental edema rather than actual thickening of the bowel wall proper.

Treatment and Prognosis

Surgery is the a treatment of choice (colectomy). Only 15 to 25 percent require a complete colectomy; others with mild to moderate disease do not. The mortality is the highest in the first two years, usually in patients diagnosed over 40 years of age.

Surveillance includes colonoscopy each year beginning ten years after the disease onset; 25 to 30 random biopsies are taken looking for dysplasia; there is a complementary role for air contrast barium enema.