Global patterns of disease progression in inflammatory bowel disease: a comprehensive synthesis of contemporary population-based cohorts.

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), follow heterogeneous clinical trajectories. Although therapeutic options have expanded substantially over the past two decades, the extent to which modern treatment modifies long-term structural outcomes remains uncertain. We performed a targeted review focusing on high-quality population-based inception cohorts and large registries that report long-term outcomes in adult- and pediatric-onset IBD. Outcomes of interest included phenotype or extent progression, surgery, extraintestinal manifestations (EIMs), and colorectal neoplasia. CD consistently emerged as the more structurally progressive condition. Approximately one third of adults' progress from inflammatory to stricturing or penetrating disease within 5 years, and around half do so over longer follow-up. Perianal disease develops in 10%-20% of patients, with higher rates in pediatric-onset CD. Despite declines in surgical rates in the biologic era, intestinal resection remains frequent. In UC, proximal extension is the dominant progression pattern, affecting roughly one third of patients with limited disease over the first decade; pediatric UC shows even higher extension rates. Colectomy risks have markedly decreased in contemporary cohorts, and colorectal cancer incidence has declined compared with historical estimates, reflecting improved inflammation control and surveillance. Across IBD, EIMs occur in approximately one quarter of patients and cluster with extensive colonic involvement and higher systemic inflammatory burden. Population-based evidence reveals that IBD remains progressive in a substantial subset of patients, with notable differences between CD and UC and between adult and pediatric disease. Declining surgical and colorectal cancer rates suggest a measurable therapeutic era effect, supporting the importance of early, sustained inflammation control. However, high-quality prospective disease-modification trials are still needed to further characterize how current strategies can durably alter the natural history of IBD.