Table 1.

ICD-9 codes used in this study

Calculus of gallbladder	574.00, 574.01, 574.10, 574.11, 574.20, 574.21
Cirrhosis	571.2, 571.5, 571.6
Laparoscopic cholecystectomy	51.23
<< conversion to open >>	V64.4, V64.41
Open cholecystectomy	51.22
Postoperative infection	998.1, 998.59, 682.2, 567.22
PRBCs blood transfusion	99.03, 99.04
Post-operative haemorrhage	998.1, 998.11, 998.12
Reoperation	54.12, 39.98
Liver failure	570, 572.2, 572.4
Ascites	789.5
Portal hypertension	456.0, 456.1, 456.20, 456.22, 572.3