Clinical Characteristics, Treatment Patterns, and Outcomes of Hospitalized Patients With Refractory Inflammatory Bowel Disease: A Multicenter Retrospective Cohort Study From China

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a chronic relapsing inflammatory disorder of the gastrointestinal tract. Although biologic agents and small-molecule therapies have substantially expanded treatment options, a subset of patients still experience persistent inflammation, repeated treatment failure, cumulative bowel damage, and poor clinical outcomes. Refractory IBD represents a clinically important high-risk disease state characterized by complex disease phenotypes, advanced therapeutic exposure, and an increased risk of hospitalization and surgery. However, real-world evidence regarding the clinical characteristics, treatment patterns, and outcomes of refractory IBD in Asian populations remains limited.

This study is a multicenter retrospective observational cohort study conducted at three tertiary referral centers in China: Shanghai Tenth People's Hospital, the First Affiliated Hospital of Zhejiang University School of Medicine, and the Second Affiliated Hospital of Soochow University. Consecutive hospitalized patients with an established diagnosis of CD or UC between January 1, 2020 and December 31, 2024 will be retrospectively identified from electronic medical records. Hospitalized patients are selected because they represent a clinically relevant population with active inflammation, complicated disease behavior, and substantial treatment burden.

Eligible patients are those with a confirmed diagnosis of CD or UC based on clinical, endoscopic, radiologic, and histopathologic findings. Patients will be excluded if they participated in clinical trials or received investigational drugs, had concomitant malignancy, severe immunodeficiency, other systemic autoimmune diseases, or were diagnosed with IBD-unclassified. For patients with multiple admissions during the study period, the first eligible admission will be used for baseline characterization, while subsequent treatment and outcome information will be collected longitudinally from medical records.

Refractory IBD will be defined according to the International Organization for the Study of Inflammatory Bowel Diseases consensus criteria. Patients will be classified as having refractory IBD if they meet at least one of the following criteria: failure of at least two biologic or small-molecule therapies with different mechanisms of action; recurrence after at least two surgeries in adult patients with CD; complex perianal disease; or chronic antibiotic-refractory pouchitis. Psychological factors will not be included because they cannot be consistently assessed in this retrospective study.

Data will be extracted from electronic medical records, including demographic characteristics, disease type and duration, Montreal classification, intestinal complications, extraintestinal manifestations, history of perianal fistula surgery, prior intestinal surgery, laboratory indices, exposure to biologic or small-molecule therapies, treatment sequence, treatment duration, reasons for treatment discontinuation or switching, and use of advanced combination therapy. Advanced therapy will be defined as treatment with biologics or small-molecule agents, including anti-tumor necrosis factor agents, vedolizumab, ustekinumab, tofacitinib, and upadacitinib. A new treatment line will be defined as initiation of a new biologic or small-molecule agent, either after switching from a previous agent or as part of an advanced combination regimen.