Evaluation of anal and rectal function

Anorectal manometry (ARM) is an objective and widely applied clinical procedure in the evaluation of both anal and rectal function. In this study, a high-resolution ARM test was measured by using a water-perfused manometric system (a pressure catheter with outer diameter of 4.2 mm and a rectal balloon connected to the distal end; GAP-36A, Ningbo Maida Medical Device, Inc.) (Wu et al., 2020). The manometric catheter was lubricated and then inserted into the anorectum. After resting for a few minutes, the subject was asked to contract the anus three times and then strain it three times. The anorectal inhibitory reflex was then evaluated by inflating the balloon attached to the tip of the catheter with a hand-held syringe to a volume from 0-50 ml. Finally, a syringe was used to inflate the balloon gradually until reaching the subject’s maximum tolerance (Meunier and Gallavardin, 1993; Diamant et al., 1999); during the ramp distention, the patient was asked to report first sensation, desire to defecate, urge to defecate and maximum tolerance.