Ethical approval
Abdominal wall ultrasounds carried out systematically on post-operative day 30 were supported by the research fund of the Visceral Surgery Department of Lausanne University Hospital CHUV, Lausanne, Switzerland. The study was approved by the local ethics committee (CER-VD 31/07, DP-2007-CHV-UNIL) and was registered as a prospective randomized clinical trial on clinicaltrials.gov (NCT00478348).