Anorectal manometry: Should it be performed in a seated position?

Background Anorectal manometry (ARM) is typically preformed in a lateral position. This non‐physiological testing position has produced an unexpected negative rectoanal pressure gradient (RAPG, i.e. difference between rectal and anal pressure) with normal defecation. This study was designed (i) to study differences in ARM parameters between water‐perfused and solid‐state sensors and between lateral and seated positions and (ii) to investigate the roles of ARM parameters in predicting balloon expulsion. Methods ARM was performed in 18 healthy volunteers (HV) and 60 patients with functional constipation (FC) under three randomized conditions: water‐perfused in lateral position, solid‐state in lateral position, and solid‐state in seated position, followed by a balloon expulsion test in seated position. Key Results i) Under the same lateral position, solid‐state sensors produced higher rectal resting pressure and RAPG than water‐perfused sensors. ii) Using the solid‐state sensors, ARM in the seated position revealed higher resting rectal pressure (34.9 vs 10.9 mmHg in HV, 30.9 vs 10.6 mmHg in FC, both P