LAUSR

We read with great interest the article by Maita et al. regarding nonoperative treatment for nonperforated appendicitis in children: a systematic review and meta-analysis [1]. Without doubt, the authors have carried out a meaningful and thorough review. However, we would like to make some comments on this systematic review and meta-analysis. Firstly, one study [2] should be excluded from the metaanalysis (MA) because the purpose of this research is assessing ultrasound-based decision-making in the treatment of acute appendicitis in children, which led to an entirely different included population instead of uncomplicated or nonperforated appendicitis children, although patients with Grade I or Grade II in ultrasounds might have a partial crossover with the population in this MA. Secondly, some of the data were inconsistent with the original text. A total of 134 nonoperative management (NOM) appendicitis children in Koike et al. article [3] should be included instead of 125 successful NOM appendicitis children, other missing 9 appendicitis children consisted of 5 failure of NOM, 2 loss of US finding and 2 suspected appendicitis should be also included in the MA. In another study [4], efficacy data (19 success NOM in total of 25 acute simple appendicitis) should be included in analysis but was excluded by authors of MA. Moreover, the definition of recurrent appendicitis might not be suitable. In the MA, it was defined as appendectomy due to recurrent appendicitis or recurrent abdominal pain with normal appendix after discharged from the initial hospital stay, which neglected some patients who repeated episodes of appendicitis but continued to treat with conservative treatments. In another study [5], complications data should be two but not five as the definition of complication, which in original article says “The postoperative complication rate at 1 year in patients choosing surgery was 7.7% (5 of 65 patients), with 2 major complications (1 readmission, 1 reoperation)”. In addition, some small mistakes in Tables and Figures of this MA should be avoided because it affected the reading comfort of readers (such as completely wrong superscripts in Table 1, inverted locations of Figs. 4 and 5, many minor error in first author names and publication years, et al.). Lastly, some applications of methodology were inadequate or inappropriate. Statistically significant heterogeneity was noted in this MA for efficacy and recurrence meta-analysis (I2 value equal to 92% and 97%, respectively), which affected the stability and reliability of the results and conclusion, while no further analysis was conducted. So we suggest additional subgroup analyses, sensitivity analysis and detection for publication bias were essential for searching the sources of heterogeneity and stabilizing study results [6]. Based on what we have observed, an 8-week follow-up period in an included study [7] may be too short to obtain enough complications and recurrence data. Differentiated with appendicolith and non-appendicolith appendicitis children, redefined recurrence as recurrence for appendectomy This comment refers to the article available online at https ://doi. org/10.1007/s0038 3-019-04610 -1.