Introduction

Dear Editor,

We thank Malekiantaghi et al. for conducting a randomized controlled trial (RCT) evaluating abdominal massage as an adjunctive therapy for functional constipation.¹ While the study offers valuable clinical perspectives on non-pharmacological management, several methodological issues merit further consideration.

First, although food diaries were collected and uniform dietary recommendations were provided, no between-group comparisons of actual dietary fiber or fluid intake were reported. Dietary factors are key modifiable determinants of functional constipation; fiber and fluid intake may influence gastrointestinal transit and stool characteristics.^2,3 Should dietary composition or consumption patterns differ between groups during the intervention period, the observed differences may partly reflect dietary variation rather than massage effects. Future studies should therefore employ standardized dietary assessment tools, such as three-day dietary records or food-frequency questionnaires⁴, and incorporate dietary intake variables and measures of dietary adherence as covariates in analysis of covariance (ANCOVA) or multivariate regression models to minimize potential confounding.

Second, both groups received polyethylene glycol at 0.5 g/kg, with doses adjusted according to individual needs. While such flexibility reflects routine clinical practice, it may compromise internal validity and complicate the interpretation of treatment effects in an RCT context. Specifically, laxative dosing in both groups may have varied due to clinical judgment; however, the study did not report actual dosages administered, criteria or frequency of dose adjustments, or between-group comparisons of medication use. This introduces substantial bias risk, as differential dosing patterns—arising from clinician decision-making or varying responses to the intervention—may exist between groups. Consequently, observed outcome differences may partly reflect disparities in medication exposure rather than the effect of abdominal massage itself, with the direction of bias (overestimation or underestimation of the massage effects) remaining difficult to ascertain. A more rigorous approach would involve predefined dosing protocols, such as fixed-dose regimens where clinically appropriate or standardized titration algorithms. Additionally, detailed documentation of baseline dosages and subsequent modifications, along with analytical strategies that account for medication exposure (e.g., covariate adjustment or dose-stratified analyses), would improve comparability between groups.

Third, twelve massage sessions involved frequent interaction with therapists, whereas the medication-only control group had limited contact. This imbalance may bias outcomes through the Hawthorne effect⁵, leading to enhanced adherence in the intervention group. Furthermore, children with functional constipation often develop defecation anxiety due to prior painful defecation experiences, resulting in stool-withholding behaviors.⁶ Regular, non-threatening physical contact may foster a trusting clinician-patient relationship and alleviate children’s apprehension. Verbal reassurance during massage may also facilitate relaxation of pelvic floor muscles and reduce stool-withholding behaviors. These relational and behavioral mechanisms, prompted by the additional attention and contact provided by therapists, may contribute to symptom improvement independently of the physiological effects of massage. Incorporating attention-matched control conditions (e.g., sham-massage, light touch, or structured interaction) and standardizing therapist–participant interactions in future studies would ensure equivalence in attention, contact intensity, and communication across groups, thereby strengthening causal inference.

Fourth, “time until initiation of bowel movements” was prespecified but not reported; this is selective reporting that limits comprehensive assessment. Per “Consolidated Standards of Reporting Trials” (CONSORT)⁷, all predefined outcomes should be reported or justified, thereby improving transparency.

Author contribution

The authors confirm contribution to the paper as follows: Study conception and design: FYZ, LPY; analysis and interpretation of results: FYZ, LPY, QQF, JYZ; draft manuscript preparation: FYZ, JYZ; manuscript revision: FYZ, LPY, QQF, JYZ. All authors reviewed the results and approved the final version of the manuscript.

Source of funding

The authors declare the study received no funding.

Conflict of interest

The authors declare that there is no conflict of interest.