title: The volume effect in liver surgery--a systematic review and meta-analysis.
abstract: BACKGROUND
  There is an inverse relationship between hospital and surgeon volume and mortality in many types of complex surgery. The aim of this paper is to investigate the volume effect on outcomes of liver surgery.
  
  
  METHODS
  A systematic review and meta-analysis was performed. A literature search was conducted using Medline and EMBASE from 1995 to 2012. A random effects model was used.
  
  
  RESULTS
  Seventeen studies were selected for detailed analysis. Definition of a high-volume institution varied from 2 to more than 33 procedures per year. The pooled odds ratio of mortality rate in low- vs high-volume centres was 2.0 [95 % confidence interval (CI), 1.6-2.4; P < 0.001]. Some studies divided centres into more than two groups and compared the highest and lowest volume groups. The pooled odds ratio of mortality rate for this comparison type was 3.2 (95 % CI, 1.7-5.8; P < 0.001). Funnel plots suggest possible publication bias. There was inadequate data to compare morbidity. Only two of seven studies demonstrated a shorter length of stay in the high-volume centres. There was no convincing volume effect on long-term survival.
  
  
  CONCLUSIONS
  This study suggests a strong relationship between volume and perioperative mortality. No difference in morbidity, length of stay or survival was demonstrated.
authors.affiliation: Department of Surgery, Westmead Hospital, University of Sydney, Westmead, Sydney, Australia, arthurr@arthurrichardson.com.au.
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Richardson
authors.forename: Tony C Y
authors.initials: TC
authors.lastname: Pang
authors.forename: Emma
authors.initials: E
authors.lastname: Johnston
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hollands
authors.forename: Vincent W T
authors.initials: VW
authors.lastname: Lam
authors.forename: Henry C C
authors.initials: HC
authors.lastname: Pleass
mesh_terms: D006498:Hepatectomy / Q000401:mortality*; D061847:Hospitals, High-Volume / Q000706:statistics & numerical data*; D061846:Hospitals, Low-Volume / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay; D016019:Survival Analysis