BACKGROUND: The corticosteroid-sparing effects of ileocaecal resection have not been thoroughly investigated in a population-based cohort. AIM: To investigate systemic corticosteroid use before and after primary ileocaecal resection in patients with Crohn's disease. METHODS: Through nationwide registries, we identified 1565 patients with Crohn's disease undergoing primary ileocaecal resection in Sweden 2006-2019. We stratified patients according to mean annual systemic corticosteroid (prednisolone equivalents) use in the last 5 years before surgery and compared Crohn's disease treatment after surgery. RESULTS: Some 19% (290/1565) of the patients had a mean annual corticosteroid use of ≥ 1000 mg up to 5 years pre-operatively, of whom 33% (97/290) had ≥ 2000 mg. Mean annual pre-operative CS use did not decrease during the study period (p = 0.35). Compared with patients with <
1000 mg/year pre-operative steroid use, patients with ≥ 1000 mg/year had more frequent previous bowel surgery (10% vs. 16%), exposure to biologics (29% vs. 38%), and immunomodulators (56% vs. 83%). Patients with a pre-operative mean annual corticosteroid use of ≥ 1000 mg had a mean annual reduction in corticosteroid use of 1354 mg after ileocaecal resection (1847 mg pre-operative versus 493 mg post-operative). During follow-up (median 6.8 years), exposure to biologics was similar among patients with different levels of pre-operative corticosteroid use. CONCLUSION: Our results suggest a significant corticosteroid-sparing effect of ileocaecal resection in Crohn's disease patients with high pre-operative use, indicating a beneficial outcome of earlier surgical intervention. Despite increasing use of biologics, pre-operative corticosteroid use was consistent over the study period.