INFLAMMATORY bowel disease unclassified (IBD-U) remained a stable diagnosis for most patients during long term follow up, according to new data showing that nearly 90% retained their classification while demonstrating distinct treatment patterns and increased healthcare utilisation compared with ulcerative colitis and Crohn’s disease.
Long Term Stability of IBD Unclassified
IBD-U is diagnosed when it is not possible to determine whether a patient has ulcerative colitis or Crohn’s disease. Researchers analysed data from the Leeds IBD Steroid Study to better understand the long-term natural history and treatment patterns associated with IBD-U
The retrospective analysis included 153 patients with IBD-U who had contact with a tertiary IBD service between January 2016 and December 2017. Linked primary care and hospital electronic records were used, with follow up continuing until 2025. Among the cohort, 52% were male, the mean age was 46.6 years, and the mean disease duration was 13.1 years.
At the end of follow up, most patients remained classified as IBD-U. Data showed the following outcomes: 135 patients (88.2%) remained classified as IBD-U; 12 patients (7.8%) were reclassified as ulcerative colitis; six patients (3.9%) were reclassified as Crohn’s disease.
Distinct Treatment Patterns Observed
The study identified treatment patterns that differed from those seen in patients with ulcerative colitis and Crohn’s disease. Mesalazine use was lower among patients with IBD-U than among patients with ulcerative colitis: 85% vs 92% (p=0.0058). However, mesalazine use was substantially higher than in patients with Crohn’s disease, where 44% received the treatment (p<0.0001).
Biologic therapy use also differed across disease classifications. Patients with IBD-U were more likely to receive biologics than patients with ulcerative colitis: 21% versus 9.5% (p<0.0001). However, biologic use remained lower than in patients with Crohn’s disease, where 51% received these therapies (p<0.0001).
Increased Healthcare Utilisation
Researchers also found that steroid use and healthcare resource utilisation were higher among patients with IBD-U than among those with ulcerative colitis or Crohn’s disease. The findings suggest that IBD-U represents a clinically relevant and persistent phenotype rather than a temporary diagnostic category.
The authors concluded that the high degree of diagnostic stability, combined with distinct treatment requirements and greater healthcare utilisation, highlights the need to optimise treatment decisions and reduce the burden associated with ongoing diagnostic uncertainty in patients with IBD-U.
Reference
Latorre MA et al. Long-term classification stability and treatment patterns of inflammatory bowel disease unclassified: a longitudinal observational study. BMJ Open Gastroenterol. 2026;13(1):e002339.
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