Why Is Colorectal Cancer Risk So High in PSC-UC? The Microbiome–Bile Acid Axis Offers a Clue: Gut | September 2026

What Did the Study Find?

This study combined a large PSC-UC surveillance cohort with a novel experimental model to investigate why PSC-UC carries disproportionate colorectal neoplasia risk.

Compared with 8,839 UC-only patients, 251 patients with PSC-UC had greater inflammation and a distinctly right-sided dysplasia burden.

A novel PSC-IBD mouse model reproduced right-predominant colitis, dysplasia and progression to invasive cancer.

Germ-free mice were protected, indicating that live intestinal bacteria were required for disease expression.

Fecal microbiota transfer from affected mice reproduced severe colitis and dysplasia.

Dysbiosis was characterized by loss of bacterial 7α-dehydroxylation and near-absence of secondary bile acids DCA and LCA.

Direct DCA replacement caused hepatotoxicity, cautioning against simple bile-acid supplementation.

Why Does It Matter?

The study provides mechanistic evidence connecting dysbiosis, altered bile-acid metabolism, persistent inflammation and carcinogenesis in PSC-UC.

GastroAGI Takeaway

Mild-looking colitis does not mean low cancer risk in PSC-UC. These findings reinforce meticulous proximal-colon surveillance and control of microscopic inflammation. Microbiome restoration of bile-acid-transforming functions is an intriguing future chemoprevention strategy—but remains experimental, not ready for clinical practice.