Abstract: One study from Australia including 46 children aged 8 to 18 years was eligible for inclusion. There were multiple reports identified, including one unpublished report, that focused on different outcomes of the same study. The study had unclear risk of selection bias, high risks of performance, detection and attrition biases, and low risks of reporting biases. We are very uncertain about the effects of TES on bowel movements, colonic transit, soiling symptoms and quality of life due to high risk of bias, indirectness and imprecision. For our outcomes of interest the 95% CI of most analysis results include potential benefit and no effect. There is insufficient evidence to determine the effect of TES on bowel movements and colonic transit. The study reported that 16/21 children in the TES group and 15/21 in the sham group had > 3 complete spontaneous bowel movements (CSBM) per week (RR 1.07, 95% CI 0.74 to 1.53; very low-quality evidence). Ten out of 14 children in the TES group had improved colonic transit compared to 1/7 in the sham group (RR 5.00, 95% CI 0.79 to 31.63; very low-quality evidence). Mean colonic transit rate, measured as the position of the geometric centre of the radioactive substance ingested along the intestinal tract, was higher in children who received TES compared to sham (MD 1.05, 95% CI 0.36 to 1.74; one study, 30 participants; very low-quality evidence). The radiological assessment of colonic transit outcomes means that these results might not translate to important improvement in clinical symptoms or increased bowel movements. There is insufficient evidence to determine the effect of TES on symptoms and quality of life (QoL) outcomes. Nine out of 13 children in the TES group had improved soiling-related symptoms compared to 4/12 sham participants (RR 2.08, 95% CI 0.86 to 5.00; very low-quality evidence). Four out of 8 TES participants reported an improvement in QoL compared to 1/8 sham participants (RR 4.00, 95% CI 0.56 to 28.40; very low-quality evidence). The effects of TES on self-perceived (MD 5.00, 95% CI -1.21 to 11.21; one study, 33 participants; very low-quality evidence) or parent-perceived QoL (MD -0.20, 95% CI -7.57 to 7.17, one study, 33 participants; very low-quality evidence) are uncertain. No adverse effects were reported in the included study. The results for the outcomes assessed in this review are uncertain. Thus no firm conclusions regarding the efficacy and safety of TES in children with chronic constipation can be drawn. Further randomized controlled trials assessing TES for the management of childhood constipation should be conducted. Future trials should include clear documentation of methodologies, especially measures to evaluate the effectiveness of blinding, and incorporate patient-important outcomes such as the number of patients with improved CSBM, improved clinical symptoms and quality of life.

Plain-language summary: We included a single study with 11 reports that focused on results for different outcomes. The participants of the included study were 46 children aged 8 to 18 years recruited from the clinic of a tertiary hospital in Melbourne, Australia who were diagnosed with long-term constipation either based on their symptoms and/or X-ray studies. The studies divided the patients into two groups, one receiving the actual TES , with electrodes placed on their belly and electrical current running, and the other receiving sham stimulation, with identical device administered but without the electrical current. The participants were followed-up for up to four years, although only outcome information up until the follow-up period of two months were available in this review. The study was funded by the Australian National Health and Medical Research Council and Murdoch Children's Research Institute Theme Investment Grants. There was not enough information on certain aspects of the trial methodologies from the reports gathered, although it was clear that the physiotherapists who administered the TES treatment or sham treatment were aware of which group the patients were allocated to. The knowledge of the participants' allocated group might have influenced the way the actual and sham therapies were administered, as well as the way some of the outcome data, such as symptoms of constipation and soiling and quality of life, might have been reported by the therapist as well as the patients and their carers. This raised concerns regarding the overall methodological quality of the study. The very low quality evidence for all of the results means that we are uncertain about the effects of TES when compared with sham stimulation. Overall, there were no differences between children who received TES and sham stimulation in the number of children with improved complete spontaneous bowel movements, improved bowel movements (as assessed by X-Ray with special contrast), improved symptoms related to soiling and quality of life. There were also no differences between the two groups in the average change in the quality of life scores after the therapy, as assessed by the children themselves as well as their parents. The only difference noted was in mean bowel transit rate, namely, distance travelled by the radioactive substance along the bowel, in which children who received TES had their radioactive substance slightly further down their bowel compared to children who received a sham stimulation. However, it was unclear whether such a difference in distance travelled in the bowel translated to any meaningful differences in defaecation and constipation-related symptoms. No side effects were reported in the study. Overall, this study included a small number of patients and we had concerns regarding the methods resulting in very low quality evidence for all the outcomes assessed. The results for the outcomes assessed in this review are uncertain. Thus no firm conclusions regarding the effectiveness and side effects of TES in children with chronic constipation can be drawn. Further studies assessing TES for the management of constipation are needed. We suggest that future research should provide clear documentation on specific methods in the conduct of the trials, and include outcomes that are important for patients, such as spontaneous or complete bowel movements or improvement in constipation-related symptoms along with assessments of quality of life.