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For further information, see CMDT Part 15-35: Inflammatory Bowel Disease

Key Features

Essentials of Diagnosis

  • Bloody diarrhea

  • Lower abdominal cramps and fecal urgency

  • Anemia, low serum albumin

  • Negative stool studies for pathogens

  • Sigmoidoscopy is key to diagnosis

General Considerations

  • Idiopathic inflammatory condition that involves the mucosal surface of the colon, resulting in diffuse friability and erosions with bleeding

  • One-fourth of patients have disease confined to the rectosigmoid region (proctosigmoiditis); one-half have disease that extends to the splenic flexure (left-sided colitis); and one-fourth have disease that extends more proximally (extensive colitis)

  • In patients with distal colitis, the disease progresses with time to more extensive involvement in 25%

  • Most affected patients experience periods of symptomatic flare-ups, periods of mild activity, or remission

  • Approximately 15% may have an aggressive course with increased risk for hospitalization or surgery

  • Of patients hospitalized with severe colitis, colectomy is required in up to 30% for unresponsive or 'fulminant' disease


  • More common in nonsmokers and former smokers, severity may worsen in patients who stop smoking

  • Appendectomy before age 20 reduces risk

Clinical Findings

Symptoms and Signs

  • Bloody diarrhea

  • Cramps, abdominal pain

  • Fecal urgency, tenesmus, extraintestinal symptoms

  • Tenderness, evidence of peritoneal inflammation

  • Bright red blood on digital rectal examination

Mild disease

  • Fewer than 4–6 bowel movements per day

  • Rectal bleeding

  • Stools may be formed or loose

  • Left lower quadrant cramps, relieved by defecation

  • No significant abdominal pain or tenderness

  • Mild anemia and hypoalbuminemia

Moderate disease

  • Diarrhea more severe with frequent bleeding

  • Abdominal pain and tenderness (but not severe)

  • Mild fever, anemia, and hypoalbuminemia

Severe disease

  • > 6 bloody bowel movements per day

  • Signs of hypovolemia and impaired nutrition

  • Abdominal pain and tenderness

Fulminant disease

  • Rapid progression of symptoms and signs of severe toxicity (hypovolemia, hemorrhage requiring transfusion, and abdominal distention with tenderness) over 1–2 weeks

Toxic megacolon

  • Colonic dilation of > 6 cm on radiographs with signs of toxicity, occurring in < 2% of ulcerative colitis patients, heightens risk of perforation

Extracolonic manifestations

  • Occur in 50% of cases

  • Oral ulcers

  • Erythema nodosum, pyoderma gangrenosum

  • Episcleritis or uveitis

  • Spondylitis or sacroiliitis

  • Thromboembolic events

  • Oligoarticular or polyarticular nondeforming arthritis

  • Sclerosing cholangitis

Differential Diagnosis

  • Infectious colitis

    • Salmonella

    • Shigella

    • Campylobacter

    • Amebiasis

    • Clostridioides difficile

    • Enteroinvasive Escherichia coli

  • Ischemic colitis

  • Crohn disease

  • Diverticular disease

  • Colon cancer

  • Antibiotic-associated diarrhea or pseudomembranous colitis

  • Infectious proctitis: gonorrhea, chlamydia, herpes, syphilis

  • Radiation colitis or proctitis

  • Cytomegalovirus colitis in immunocompromised persons


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