Unplanned hospital readmissions after surgery are substantial drivers of expenditure and bed occupancy within the healthcare system. As a result, any targeted interventions that reduce readmission in this population can have a significant impact on patient well-being and the health budget.
We performed a large retrospective cohort study analysing data from patients from our institution who underwent major surgery between 1 May 2011 and 1 February 2022. We aimed primarily to study the epidemiology of patients who were readmitted within 90 days of discharge following an index procedure, as well as the reason(s) and risk factors for readmission. These complex, non-linear relationships were modelled with restricted cubic splines.
We identified 22,143 patients undergoing major surgery within the defined study period, of whom 1801 (12%) had an unplanned readmission. The most common reason for unplanned readmission across the entire cohort was wound complication, which was the primary cause identified in 232 (11%) readmissions. Ileus or small bowel obstruction was the primary cause of readmission identified following abdominal surgery, compared with pneumonia following thoracic surgery, mechanical injury following orthopaedic surgery and wound complication following cardiac surgery. A discharge haemoglobin concentration of < 100 g.l (p < 0.001), duration of hospital stay of 14-30 days (p < 0.001) and Charlson comorbidity index score ≥ 2 (p < 0.001) were associated with increased odds of unplanned readmission. No association was found with patient age or duration of surgery.
Our study identified the causes of readmission after major surgery from a range of surgical specialties. An improved understanding of the causes of and risk factors for unplanned readmissions will enable the development of targeted interventions that can minimise the burden of unplanned readmissions after major surgery on patients and the larger healthcare system.

© 2025 The Author(s). Anaesthesia published by John Wiley & Sons Ltd on behalf of Association of Anaesthetists.