1. University of the Witwatersrand; Department of Surgery; 7 York Road Johannesburg Gauteng South Africa 2193
2. Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital; Cochrane Hepato-Biliary Group; Blegdamsvej 9 Copenhagen Denmark DK-2100
3. University of Pretoria; Department of Surgery; Pretoria South Africa 0001