Hospital volume and patient outcomes after cholecystectomy in Scotland: retrospective, national population based study
BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e3330 (Published 23 May 2012) Cite this as: BMJ 2012;344:e3330
- Ewen M Harrison, lecturer in surgery1,
- Stephen O’Neill, research fellow1,
- Thomas S Meurs, medical student2,
- Pang L Wong, medical student1,
- Mark Duxbury, clinician scientist and honorary consultant surgeon1,
- Simon Paterson-Brown, consultant surgeon and honorary senior lecturer1,
- Stephen J Wigmore, professor of transplantation surgery1,
- O James Garden, regius professor of clinical surgery1
- 1Department of Clinical Surgery, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh EH16 4SA, UK
- 2Department of Surgery, Leiden University Medical Centre, Leiden, Netherlands
- Correspondence to: E M Harrison mail{at}ewenharrison.com
- Accepted 8 April 2012
Abstract
Objectives To define associations between hospital volume and outcomes following cholecystectomy, after adjustment for case mix using a national database.
Design Retrospective, national population based study using multilevel modelling and simulation.
Setting Locally validated administrative dataset covering all NHS hospitals in Scotland.
Participants All patients undergoing cholecystectomy between 1 January 1998 and 31 December 2007.
Main outcome measures Mortality, 30 day reoperation rate, 30 day readmission rate, and length of stay.
Results We identified 59 918 patients who had a cholecystectomy in one of 37 hospitals: five hospitals had high volumes (>244 cholecystectomies/year), 10 had medium volumes (173-244), and 22 had low volumes (<173). Compared with low and medium volume hospitals, high volume hospitals performed more procedures non-electively (17.1% and 19.5% v 32.8%), completed more procedures laparoscopically (64.7% and 73.8% v 80.9%), and used more operative cholangiography (11.2% and 6.3% v 21.2%; χ2 test, all P<0.001). In a well performing multivariable analysis with bias correction for a low event rate, the odds ratio for death was greater in both the low volume (odds ratio 1.45, 95% confidence interval 1.06 to 2.00, P=0.022) and medium volume (1.52, 1.11 to 2.08, P=0.010) groups than in the high volume group. However, in simulation studies, absolute risk differences between volume groups were clinically negligible for patients with average risk (number needed to treat to harm, low v high volume, 3871, 1963 to 17 118), but were significant in patients with higher risk. In models accounting for the hierarchical structure of patients in hospitals, those in medium volume hospitals were more likely to undergo reoperation (odds ratio 1.74, 1.31 to 2.30, P<0.001) or be readmitted (1.17, 1.04 to 1.31, P=0.008) after cholecystectomy than those in high volume hospitals. Length of stay was shorter in high volume hospitals than in low (hazard ratio for discharge 0.78, 0.76 to 0.79, P<0.001) or medium volume hospitals (0.75, 0.74 to 0.77, P<0.001). These differences were also only of clinical significance in patients at higher risk.
Conclusions There is wide variation among hospitals in the management of gallstone disease and an association between higher hospital volume and better outcome after a cholecystectomy. The relative risk of death is lower in high volume centres, and although absolute risk differences between volume groups are significant for elderly patients and patients with comorbidity, they are clinically negligible for those at average risk.
Footnotes
We thank Harry Purser (head of health intelligence, NHS Lothian) and Colin Houston (Information Services Division of NHS Scotland) for providing access to the data and invaluable advice, and Olivia Swann for critically reviewing the manuscript.
Contributors: EMH is the guarantor and takes responsibility for the integrity and accuracy of these data and the final decision to submit for publication. EMH participated in the study design; data collection, processing, analysis, and interpretation; manuscript writing; and construction of tables and figures. SO’N participated in the systematic review, data interpretation, and manuscript writing. TM participated in the study design; data processing, analysis, and interpretation; and manuscript writing. PLW participated in data validation and manuscript writing. MD, SP-B, SJW, and OJG participated in the study design, data interpretation, and manuscript writing. The authors had full access to all data in the study.
Funding: The study was funded by the University of Edinburgh, which had no direct role in the study. The corresponding author had full independence from the funding source.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: support from the University of Edinburgh for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years; MD, SP-B, SJW, and OJG work as consultant surgeons in one of the institutions included in this study, constituting a non-financial interest that may be relevant to the submitted work.
Ethical approval: Study approval was granted by the National Services Scotland Privacy Advisory Committee. No ethical approval was required.
Patient consent: None required.
Data sharing: No additional data available.
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