Periductal Fibrosis and Cholangiocarcinoma-Related Outcomes in Liver Fluke-Endemic Regions: A Systematic Review and Meta-Analysis.

Background/Objectives: Periductal fibrosis (PDF) is a common hepatobiliary abnormality associated with chronic Opisthorchis viverrini infection and may represent an ultrasonographic marker of chronic biliary injury in liver fluke-endemic regions. This systematic review and meta-analysis evaluated the association between ultrasound-defined PDF and cholangiocarcinoma (CCA)-related outcomes and summarized the prevalence of overall PDF and advanced periductal fibrosis (APF) in endemic populations. Methods: PubMed, Embase, and Scopus were searched from database inception to April 2026, supplemented by manual screening of reference lists. Observational studies reporting PDF prevalence and/or the association between PDF and CCA-related outcomes were included. Pooled odds ratios (ORs) and prevalence estimates were calculated using random-effects models. Five studies met the inclusion criteria. Results: Three studies involving 758,686 participants were included in the pooled association analysis. Ultrasound-defined PDF was associated with higher odds of CCA-related outcomes, including confirmed CCA, incident CCA, and clinically suspected CCA, with a pooled OR of 2.77 (95% CI: 2.24-3.44; I2 = 0%). Because outcome definitions, effect measures, adjustment status, and PDF exposure categories varied across studies, this estimate should be interpreted as a summary association rather than as a precise estimate of confirmed CCA risk. Four studies involving 759,117 participants contributed to the overall PDF prevalence analysis, whereas three studies reported APF prevalence data. Prevalence estimates varied substantially across endemic settings, with extreme between-study heterogeneity. Conclusions: Overall, ultrasound-defined PDF may help identify individuals who warrant closer surveillance or further evaluation; however, it should not be interpreted as a definitive histopathological diagnosis or a proven causal precursor of CCA. Further prospective studies using standardized fibrosis definitions, blinded ultrasonographic assessment, confirmed or incident CCA outcomes, and adjustment for O. viverrini infection-related factors and other key confounders are needed to validate the role of PDF in CCA risk stratification.