Wilhelm 2009.

Methods	Randomised clinical trial.
Participants	Country: Germany. Number randomised: 259. Post‐randomisation drop‐outs: 47 (18.1%). Revised sample size: 212. Mean age: 53 years. Females: 148 (69.8%). Inclusion criteria 1. Patients undergoing laparoscopic cholecystectomy for cholecystolithiasis.
Interventions	Participants were randomly assigned to 1 of 2 groups. Group 1: patient education (n = 114). Further details: multimedia DVD programme. Group 2: standard care (n = 98).
Outcomes	Patient satisfaction and patient knowledge.
Notes	Authors contacted in April 2013. They replied in April 2013. Reasons for post‐randomisation drop‐outs: did not return questionnaire (groups not stated).
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation	Low risk	Quote: "All patients were assigned randomly to either the DVD or the control group using a specifically built randomisation list and after having given informed consent concerning participating the study"; "We used a computer generated randomization list" (author replies). Comment: The information about the random list was generated was not stated.
Allocation concealment	Unclear risk	Comment: This information was not available.
Blinding of participants and personnel	High risk	Comment: It is impossible to blind the patients to the groups.
Blinding of outcome assessors	Low risk	Quote: "Those who assessed the patients' education level did not have any information concerning the allocation to the respective study arms" (author replies).
Incomplete outcome data addressed All outcomes	High risk	Comment: There were post‐randomisation drop‐outs.
Free of selective reporting	High risk	Comment: Important outcomes such as patient mortality and morbidity were not reported.
For‐profit bias	Low risk	Quote: "There was no funding of the study, the study was conducted as an internal project and in cooperation with the department of media sciences of the LMU Munich" (author replies).