title: Hierarchical multilevel analysis of increased caseload volume and postoperative outcome after elective colorectal surgery.
abstract: BACKGROUND
  The study aimed to explore the impact of surgeon and institution volume on outcome following colorectal surgery in England using multilevel hierarchical analysis.
  
  
  METHODS
  An observational study design was used. All patients undergoing primary elective colorectal resection between 2000 and 2008 were included from the Hospital Episode Statistics database. Consultant surgeons and hospitals were divided into tertiles (low, medium and high volume) according to their mean annual colorectal cancer resection caseload. Outcome measures examined were postoperative 30-day mortality, 28-day readmission and reoperation, and length of stay. Hierarchical multiple regression analysis adjusted for age, sex, co-morbidity, social deprivation, year of surgery, operation type and surgical approach.
  
  
  RESULTS
  A total of 109 261 elective cancer colorectal resections were included. High-volume consultant surgeons and hospitals were defined as performing more than 20·7 and 103·5 elective colorectal cancer procedures per year respectively. Consultant and hospital operative volumes increased throughout the study period. In hierarchical regression models, greater surgeon and institutional volume independently predicted only shorter length of hospital stay. No statistical association was observed between higher provider volume and postoperative mortality, 28-day reoperation or readmission rates.
  
  
  CONCLUSIONS
  Increasing elective colorectal cancer caseload alone may have marginal postoperative benefit.
authors.affiliation: Department of Surgery, Imperial College, St Mary's Hospital, London, UK.
authors.forename: E M
authors.initials: EM
authors.lastname: Burns
authors.forename: A
authors.initials: A
authors.lastname: Bottle
authors.forename: A M
authors.initials: AM
authors.lastname: Almoudaris
authors.forename: R
authors.initials: R
authors.lastname: Mamidanna
authors.forename: P
authors.initials: P
authors.lastname: Aylin
authors.forename: A
authors.initials: A
authors.lastname: Darzi
authors.forename: R J
authors.initials: RJ
authors.lastname: Nicholls
authors.forename: O D
authors.initials: OD
authors.lastname: Faiz
mesh_terms: D000369:Aged, 80 and over; D002983:Clinical Competence / Q000592:standards; D015179:Colorectal Neoplasms / Q000401:mortality / Q000601:surgery*; D003107:Colorectal Surgery / Q000401:mortality / Q000706:statistics & numerical data*; D003253:Consultants / Q000706:statistics & numerical data; D017558:Elective Surgical Procedures / Q000706:statistics & numerical data; D005260:Female; D006276:Health Facility Size / Q000706:statistics & numerical data; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D012044:Regression Analysis; D012086:Reoperation / Q000706:statistics & numerical data; D012737:Sex Factors; D016896:Treatment Outcome; D006113:United Kingdom; D016526:Workload / Q000706:statistics & numerical data*