We made clarifications to the types of participants according to the reviewer's suggestion (e.g. use of antibiotics and percutaneous drainage of appendiceal abscess were allowed for participants in both groups), and added a diagnosis definition.

The participant cohort among studies was heterogenous (appendiceal phlegmon versus appendiceal abscess), which were so dissimilar that the peer reviewer suggested they should not be combined in the same meta‐analysis. Thus, we analysed participants with appendiceal phlegmon and appendiceal abscess in separate comparisons instead of using subgroup analysis for all outcome measures to answer specific questions about particular patient groups.

Hospital costs are neither comparable nor reliable among included studies due to inflation and inter‐country economic differences. Thus, we did not include hospital costs as an outcome in the review stage.

We applied the GRADE approach for evaluating the quality of evidence for each outcome, which we had not stated in the protocol.

We updated the search strategies with the help of an information specialist and searched the reference lists of included studies and any relevant systematic reviews identified.

We added definitions for outcome measures.

We added 'unplanned bowel resection' as a morbidity outcome measure.

We employed a random‐effects model to obtain an overall weighted average of treatment effect, regardless of the number of studies.

We revised the interpretation of the I² statistic when we measured the statistical heterogeneity.

We conducted the systematic review according to the latest guidance in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2023).

We performed a posthoc sensitivity analysis by consecutively excluding every study from the meta‐analysis to explore the impact of individual studies on the statistical heterogeneity according to the peer reviewer's suggestion.

We applied the GRADE approach for evaluating the certainty of evidence for seven outcomes and presented these in the summary of findings tables: overall morbidity, wound infection, abdominal abscess, faecal fistula, mortality, total length of hospital stay, and time away from normal activities. This was not specified in the protocol and was different from the 2017 version where our SoF tables included overall morbidity, wound infection, faecal fistula, mortality, total length of hospital stay, time away from normal activities, quality of life, and pain.

We did not use some methods due to the small number of studies or lack of data (specifically, Peto OR for mortality, funnel plots for publication bias, subgroup analyses).