Is Primary Biliary Cholangitis (PBC) more commonly associated with Ulcerative Colitis (UC) or Crohn's Disease (CD)?

Association Between Primary Biliary Cholangitis and Inflammatory Bowel Disease

Primary Biliary Cholangitis (PBC) is more commonly associated with Ulcerative Colitis than Crohn's Disease, though the overall association between PBC and IBD is rare compared to the well-established association between Primary Sclerosing Cholangitis (PSC) and IBD.

Understanding the Relationship Between PBC and IBD

Epidemiological Evidence

• Recent research indicates a causal relationship between IBD and PBC, with IBD potentially increasing the risk of developing PBC 1, 2
• In a two-sample Mendelian randomization study, both UC and CD were associated with an increased risk of PBC:
  • UC: OR 1.244 (95% CI: 1.057-1.430)
  • CD: OR 1.269 (95% CI: 1.159-1.379) 2
• However, the reverse causality was not observed - PBC did not increase the risk of developing IBD 2

Clinical Observations

• While PBC-IBD association is uncommon, case series have documented patients with both conditions:
  • In one series of 6 patients with PBC-associated IBD, 3 had Crohn's disease and 3 had ulcerative colitis 3
  • In all documented cases, PBC was diagnosed after IBD had been established 3

Contrast with Primary Sclerosing Cholangitis (PSC)

PSC-IBD Association

• PSC has a much stronger and well-established association with IBD, particularly with UC:
  • Among PSC patients with IBD, 86% had UC, 7% had CD, and 7% had indeterminate colitis 4
  • PSC patients with UC show distinctive features including extensive colitis with right-sided predominance, rectal sparing, and backwash ileitis 4

Diagnostic Considerations

• When evaluating cholestatic liver enzymes in IBD patients:
  • PSC should be the first consideration, especially in UC patients
  • However, PBC should also be considered when:
    • MRCP is repeatedly normal
    • Anti-mitochondrial antibodies (AMA) are positive (hallmark of PBC) 5
    • Patient has other autoimmune conditions

Clinical Implications

Screening and Diagnosis

• For IBD patients with abnormal liver function tests:
  • Test for anti-mitochondrial antibodies (AMA)
  • Perform MRCP to rule out PSC
  • Consider liver biopsy for definitive diagnosis of PBC

Treatment

• PBC associated with IBD typically responds well to ursodeoxycholic acid (UDCA) at 13 mg/kg/day 5
• Management of the underlying IBD should continue according to standard guidelines

Surveillance

• IBD patients with PBC require regular monitoring of liver function tests
• Unlike PSC, PBC does not significantly increase colorectal cancer risk beyond that associated with IBD itself

Conclusion

While PSC remains the most common hepatobiliary manifestation in IBD (particularly UC), clinicians should maintain awareness of the potential for PBC in IBD patients with unexplained cholestasis, especially when MRCP is normal and AMA testing is positive.