Inflammatory bowel disease (IBD) represents a spectrum of chronic disorders affecting the gastrointestinal tract of which Crohn disease (CD) and ulcerative colitis (UC) are the major entities. In some cases referred to as indeterminate colitis (IC), a definite diagnosis of CD or UC following colectomy cannot be made. Recently, inflammatory bowel disease, type unclassified (IBDU), was coined to reflect clinical and endoscopic evidence for IBD of the colon with no small bowel involvement, no histological evidence in favor of CD or UC and no infection.

Epidemiology

• Incidence
  • UC - 1/1000
  • CD - 0.8/1000
• Age
  • Initial peak - 15-30 years of age
  • Second peak - 50-80 years
• Sex
  • Male to female is 1.8:1 in CD
  • Male to female is 1:1 in UC
• Ethnicity - highest incidence in Jews, lowest in Black, Hispanic

Risk Factors

• Genetics
  • CD - first-degree relatives have 4-20 times increased risk   

Pathophysiology

Clinical Presentation

• UC - diarrhea, rectal bleeding, abdominal pain
• CD - ileocolitis, abdominal pain, fever
• Extraintestinal manifestations
  • Erythema nodosum - 15% CD and 10% UC
  • Pyoderma gangrenosum - <1% CD and 5-10% UC
  • Arthritis - 10-15% of all IBD patients; large joints, often asymmetric
  • Ankylosing spondylitis - 10% of all IBD patients
  • Uveitis/iritis - 10% of all IBD patients
  • Hepatic steatosis - 50% of all IBD patients
  • Primary sclerosing cholangitis (PSC) - 1-5% of all IBD patients; however, 50-75% of all PSC patients have IBD
  • Ureteral obstruction and fistulae - <5% of all patients
  • Nephrolithiasis - 10-20% CD
• Complications
  • UC - massive hemorrhage, toxic megacolon, marked increased incidence of colon cancer
  • CD - fistulas, abscesses

Treatment

• Early treatment may delay complications
• Goal of treatment is remission
• Colorectal cancer screening is highly recommended because of an increased risk of colon cancer in UC

Diagnosis

• Diagnosis and classification can be made in most cases by:
  • History and physical examination
  • Endoscopy
  • Radiography
  • Histology
    • Biopsy
  • Serologic markers may be useful in supporting a diagnosis and classification of IBD, especially in indeterminate colitis
    • More than 20 serologic markers with variable clinical utilities exist
    • The most studied serologic markers include:
      • ANCA - usually atypical pANCA staining
      • ASCA IgG and IgA antibodies
• Subtypes differentiation as listed in the table below

• Predictive markers for disease activity include:
  • Fecal lactoferrin
    • Released during active IBC
    • May be useful as a marker in UC
  • Calprotectin
    • Released from neutrophils during acute IBC
    • Levels change with disease severity
    • May be useful in monitoring disease severity