Risk and characteristics of interstitial lung disease in patients with inflammatory bowel disease: A retrospective cohort study.

BACKGROUND: Inflammatory bowel disease (IBD) is a disorder with extraintestinal manifestations that may involve multiple organ systems. Interstitial lung disease (ILD) is an extraintestinal manifestation that remains underrecognized, and its prevalence, clinical characteristics, and risk factors in IBD are poorly defined. METHODS: We conducted a retrospective study of adults (≥18 years) with IBD who had at least 1 clinical encounter at our hospital between January 1, 2013, and December 31, 2023. IBD and ILD diagnoses were identified by using International Classification of Diseases, Ninth [or Tenth] Revision, Clinical Modification codes, and ILD diagnoses were confirmed by a thoracic radiologist. Demographic and clinical characteristics were abstracted from the electronic health record. Associations between patient characteristics and ILD were evaluated with 2 analyses: cross-sectional cohort and matched case-control. Risk of death was assessed by using a Cox proportional hazards model with ILD as a time-dependent covariate. RESULTS: Among 875 patients with IBD, 109 (12%) had ILD. Radiographic patterns of ILD most commonly showed nonspecific interstitial pneumonia (27%), indeterminate (26%), and usual interstitial pneumonia (24%). Pulmonary function testing most commonly showed restriction (59%) and impaired diffusing capacity (61%). The cohort analysis showed that higher BMI, bronchiectasis, history of smoking, and use of adalimumab or infliximab were independently associated with ILD. The case-control analysis confirmed these findings and identified older age as another significant factor. ILD was associated with a higher risk of death (hazard ratio, 3.78; 95% CI, 2.50-5.72; P<.001). CONCLUSION: ILD in patients with IBD was associated with various clinical characteristics and a higher risk of death. These findings highlight the need for early identification, routine respiratory assessment, and multidisciplinary management.