Three-dimensional high-resolution anorectal manometry (3D HRAM) is a minimally invasive test allowing the assessment of lower gastrointestinal tract function. Nowadays, it is performed in left lateral or supine position (non-physiological) in accordance with the London Protocol. 3D HRAM can disclose pathological defecation model such as dyssynergic defecation (DD) that might be a cause of constipation in a significant percentage of patients.

3D HRAM in healthy adults in lying position shows up to 67%–87% abnormal results during the bear-down manoeuvre; it may result from the non-physiological position taken during the examination.

The aim of this study is to assess the influence of body position on parameters of the bear-down manoeuvre during 3D HRAM in children with constipation and healthy volunteers.

This is a prospective, case-control study. Study participants of 5–18 years old will be recruited and divided into two groups: (I) patients with functional constipation and non-retentive faecal incontinence diagnosed according to the Rome IV criteria and (II) healthy controls. Tests will be performed both in supine and sitting positions, successively using 3D HRAM. The order in which the examination will be performed will be in accordance with the randomisation list generated by computer.

The primary endpoint of the study is the difference in the number of patients with DD detected in the sitting and supine positions.

The study was approved by the Ethics Committee of the Medical University of Warsaw, Poland (KB/178/2019). The results of this study will be submitted to a peer-reviewed journal no later than 1 year after data collection. The abstract will be presented at relevant national and international conferences.

NCT06924957.