O27 The diameter of an anorectal physiology catheter in the anal canal influences the results

Abstract

Abstract Introduction Conventional “catheter-based” anorectal physiology systems may influence anal canal pressures by stretching the sphincters thereby increasing tension. Anal acoustic reflectometry (AAR) is a “catheter-less” technique as the flexible thin catheter does not distort the anal canal. The aim of this study was to explore whether the size of rigid tube in the anal canal had any effect on tension. Method Participants with no anorectal dysfunction were included. Baseline resting/squeeze AAR measurements were recorded, then repeated with a 6 mm and 10 mm rigid tube placed along-side the AAR catheter. This process was repeated for anorectal manometry (ARM) and Opening pressure (AAR) and mean resting pressure (MRP) were used to calculate tension (pressure (mmHg) x radius (mm)). Result 9 participants were included (7 female/2male) with median age 22 years (21–31 years). Tension at rest (no additional tube) for AAR and ARM was 14 and 135 N/m respectively and 33 and 238 N/m during squeeze. Tension increased in a linear fashion, for both resting and squeeze, as the size of additional rigid tube increased. The largest increase in tension from baseline AAR and ARM measurements was recorded with the 10 mm additional tube (1,807% and 102% respectively). Conclusion The thin AAR catheter exerted the lowest tension at baseline. A large increase in tension was observed as the size of tube increased and therefore the diameter of catheter used in the assessment of anal physiology will affect the results. ARM measurements carried out by devices of different diameter will not be comparable. Take-home Message The diameter of the anorectal physiology catheter in the anal canal influences the results.