Volume-outcome relationship for adrenalectomy: analysis of an administrative dataset for the Getting It Right First Time Programme

Lay summary Surgery for disease of the adrenal gland can be complex. In many cases the skill and experience of the surgeon and the wider surgical team is thought to be important in determining the success of the procedure. The relative rarity of adrenal surgery means that there is little evidence to support this view. This study looked at outcomes for all 4189 patients who underwent adrenal surgery in England over a 6-year period. There was evidence that outcomes were better for patents when the surgeon and hospital trust had performed a larger number of adrenal surgery procedures in the year prior to the procedure. This was, however, dependent on which patient outcomes were studied and the type of procedure. These findings will inform the ongoing debate as to whether adrenal surgery in England should only be performed in regional centres by experienced teams. Background A minimum volume threshold of at least six procedures per annum per surgeon has been set in UK and European guidelines for adrenal surgery. The aim of this study was to investigate outcomes for adrenal surgery in England relative to annual surgeon and hospital trust volume. Methods Data were extracted from the Hospital Episodes Statistics database for England. A 6-year period (January 2013 to December 2018 inclusive) for all adult admissions for unilateral adrenal surgery was used. The primary outcome measure was an emergency readmission within 30 days of discharge following surgery. Procedures were categorized as open or minimally invasive surgery for analysis. Multilevel modelling was used to adjust for hierarchy and potential confounders. Results Data for 4189 adrenalectomies were identified. Only one third of surgeons (who operated on just over a half of all patients) performed at least six procedures in the year prior to the index procedure. For open surgery, emergency readmission rates fell significantly from 15.2 to 6.4 per cent for surgeons and from 13.2 to 6.1 per cent for trusts between the lowest- and highest-volume categories. Significant, but less dramatic falls were also seen for minimally invasive surgery. Conclusion A volume-outcome effect was identified for adrenal surgery in England. Minimum volume thresholds should be set, although these may need to be more ambitious than the current threshold if outcomes are to be optimized. We provide evidence from 4,189 adrenalectomies conducted over a six-year period of a relationship between surgical volume and patient outcomes for adrenal surgery. Our study should help inform the ongoing debate regarding centralisation of adrenal surgery in England.