Table 2.

Keywords and query used for MEDLINE and Scopus

Database	Keywords and query
MEDLINE	Keywords: Volume, outcome, hospital, surgery, surgical, mortality, morbidity and cost Query: (“Volume-outcome” OR “Volume-mortality” OR (“hospital volume” AND (“outcome” OR “mortality” OR “morbidity” OR “cost”))) AND (“surgery” OR “surgical”) AND “hospital” NOT “surgeon” (TITLE)
Scopus	Keywords: Volume, outcome, hospital, surgery, surgical, mortality, morbidity, cost Query: TITLE-ABS-KEY ((“Volume-outcome” OR “Volume-mortality” OR (“hospital volume” AND (“outcome” OR “mortality” OR “morbidity” OR “cost”))) AND “surgery” AND “hospital”) AND NOT TITLE(“surgeon”) AND (LIMIT-TO (PUBSTAGE, “final”)) AND (LIMIT-TO(DOCTYPE, “ar”)) AND (LIMIT-TO (LANGUAGE, “English”))