Epidemiological study of the relationship between volume and outcome after abdominal aortic aneurysm surgery in the UK from 2000 to 2005

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Abstract
The aim was to assess the relationship between hospital volume and outcome after abdominal aortic aneurysm (AAA) surgery in the UK. Hospital Episode Statistics (2000–2005) were classified as elective, urgent or ruptured AAA repair. Analysis was by modelling of mortality rate, complication rate and length of hospital stay with regard to the annual operative volume, after risk adjustment. There were 112 545 diagnoses, or repairs, of AAAs, of which 26 822 were infrarenal aneurysms. The mean mortality rate was 7·4, 23·6 and 41·8 per cent for elective, urgent and ruptured AAA repair respectively. Elective AAA repair undertaken at high-volume hospitals showed volume-related improvements in mortality (P < 0·001). Patients were discharged from hospital earlier (P < 0·001). The critical volume threshold was 32 elective AAA repairs per year. For urgent repair, patients at high-volume hospitals had a reduced mortality rate (P = 0·017) with an increased length of stay (P = 0·041). There was no relationship between volume and outcome for ruptured AAA repairs. Increased annual volumes were associated with significant reductions in mortality for elective and urgent AAA repair, but not for repair of ruptured AAAs.