Fig. 1

Flowchart of the patient selection process. “4177 unique patients with 8567 operations were assessed. Only the primary index operation was assessed thus 3021 concomitant secondary surgical operations were removed from the dataset (e.g. If a patient underwent a colonic resection and concomitant adhesiolysis, the adhesiolysis procedure was not assessed). 1369 subsequent operations not in relation to the primary operation were removed from the dataset (e.g. subsequent appendectomy years after a cholecystectomy). We thus had 4177 patients with one unique operation each. 487 patients were excluded due to the reasons given in Fig. 1. This left 3690 patients for analysis”