What is a typical feature of Primary Sclerosing Cholangitis (PSC) associated with Inflammatory Bowel Disease (IBD)?

Typical Features of PSC Associated with IBD

The most characteristic feature of Primary Sclerosing Cholangitis (PSC) associated with Inflammatory Bowel Disease (IBD) is extensive colitis with right-sided predominance, often accompanied by rectal sparing and backwash ileitis, despite a mild or quiescent clinical course. 1

Epidemiological Association

• PSC is strongly associated with IBD, with prevalence of IBD in PSC patients ranging from 60-80% in Western countries 1
• UC accounts for the majority (80%) of IBD cases in PSC, while approximately 10% have Crohn's disease and 10% have indeterminate colitis 1
• In most cases, IBD diagnosis precedes PSC diagnosis, sometimes by several years 1

Distinctive IBD Features in PSC Patients

Colonic Distribution and Presentation

• Extensive colitis: Pancolitis is present in 87% of PSC-IBD patients vs. 54% in UC-only patients 1
• Right-sided predominance of inflammatory activity 1
• Rectal sparing: Present in 52% of PSC-IBD patients vs. 6% in UC-only patients 1
• Backwash ileitis: Present in 51% of PSC-IBD patients vs. 7% in UC-only patients 1

Disease Activity and Course

• Mild or quiescent clinical course despite extensive endoscopic involvement 1
• Often subclinical with minimal symptoms even with active disease 1
• In a follow-up study, 44% of PSC-IBD patients reported disease activity only initially after IBD diagnosis, followed by a quiescent phase 1
• Colonoscopy typically reveals mild or inactive findings despite extensive disease 1

Crohn's Disease in PSC

• PSC-associated Crohn's disease typically manifests as extensive colitis 1
• Small bowel-only Crohn's disease is not associated with PSC 1
• CD colitis in PSC may not always have features strongly suggestive of CD 1

Increased Malignancy Risk

• Increased risk of colorectal neoplasia compared to IBD patients without PSC 1, 2
• Colorectal neoplasia in PSC-IBD has a predilection for the right colon (up to 76%) 1
• Annual surveillance colonoscopy is recommended from the time of PSC diagnosis 1
• Even patients with PSC alone (without IBD) have significantly elevated CRC risk compared to the general population 3

Post-Surgical Complications

• Increased risk of pouchitis in patients undergoing proctocolectomy with ileal pouch-anal anastomosis (IPAA) 1
• Increased risk of peristomal varices in patients with portal hypertension who undergo proctocolectomy with ileostomy 1

Diagnostic Considerations

• IBD in PSC can be diagnosed at any time during the course of PSC 1
• Due to the often mild or asymptomatic nature of IBD in PSC patients, colonoscopy with biopsies is recommended as part of routine work-up for all PSC patients 1
• Classification of IBD type may be difficult due to the atypical features (rectal sparing, backwash ileitis) 1

Clinical Implications

• The distinctive IBD phenotype in PSC requires vigilant colorectal cancer surveillance regardless of symptoms
• Full colonoscopy is necessary during surveillance due to right-sided predominance of neoplasia 1
• Despite the typically mild IBD course, these patients have higher colorectal cancer risk than those with IBD alone 1, 2

This unique constellation of features makes PSC-IBD a distinct clinical entity requiring specialized management and surveillance strategies focused on the increased risk of colorectal neoplasia despite the often deceptively mild clinical course.