Pharmacotherapy of Inflammatory Bowel Disease

Pharmacotherapy of Inflammatory Bowel Disease

1. Definition, spectrum & overview

• Inflammatory bowel disease (IBD) is a spectrum of remitting–relapsing, chronic, idiopathic inflammatory intestinal conditions causing diarrhoea, abdominal pain, bleeding, anaemia, and weight loss; conventionally divided into two major subtypes — ulcerative colitis (UC) and Crohn's disease (CD) (G&G 14e Ch.55, p.1111).
  • Ulcerative colitis — confluent mucosal (mucosa + submucosa) inflammation of the colon, starting at the anal verge and extending proximally in a continuous manner for a variable extent — proctitis, left-sided colitis, or pancolitis (G&G 14e Ch.55, p.1111; DiPiro 12e Ch.52, p.505).
  • Crohn's disease — transmural inflammation of any part of the GI tract (mouth to anus), most commonly adjacent to the ileocaecal valve; inflammation is not confluent, leaving "skip areas" of normal mucosa; the transmural nature predisposes to fibrosis, strictures, and fistulae (G&G 14e Ch.55, p.1111; DiPiro 12e Ch.52, pp.505–506).
• A minority of patients have features of both and cannot be cleanly categorised — termed indeterminate colitis (DiPiro 12e Ch.52, p.505; KDT 8e Ch.49, p.734).
• IBD is associated with extraintestinal manifestations (joints, skin, eyes — up to ~50% of patients) and, increasingly recognised, comorbid psychological manifestations (anxiety, depression) (G&G 14e Ch.55, p.1111; KDT 8e Ch.49, p.734).
• Primary sclerosing cholangitis (PSC) is a serious but infrequent extraintestinal manifestation (usually of UC) with inflammation/fibrostenosis of the intra- and extrahepatic biliary tree (G&G 14e Ch.55, p.1111; DiPiro 12e Ch.52, p.506).
• Chronic, severe IBD carries an increased risk of colorectal cancer (CRC) (G&G 14e Ch.55, p.1111; DiPiro 12e Ch.52, p.506).

Comparative pathology of UC vs CD (DiPiro 12e Ch.52, Table 52-1, p.505):

• Rectal involvement — common in UC, rare in CD; ileal involvement — very common in CD, rare in UC.
• Distribution — continuous in UC, discontinuous (skip lesions) in CD.
• Transmural involvement, strictures, fistulas, granulomas, linear clefts, cobblestone appearance — common/characteristic of CD, rare in UC.
• Crypt abscesses — very common in UC, rare in CD.
• Abdominal mass, internal/wall fistulas — present in CD, absent in UC.