BackgroundThe corticosteroid-sparing effects of ileocaecal resection have not been thoroughly investigated in a population-based cohort. AimTo investigate systemic corticosteroid use before and after primary ileocaecal resection in patients with Crohn's disease. MethodsThrough 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. ResultsSome 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. ConclusionOur 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.