Introduction Anal acoustic reflectometry (AAR) is a new test that uses reflected sound waves to investigate patients with faecal incontinence (FI). AAR methodology and variables of opening pressure (OP), opening elastance (OE), closing pressure (CP), closing elastance (CE), hysteresis (HY), squeeze opening pressure (SOP) and squeeze opening elastance (SOE) have previously been described. The aim of this study was to establish the response to stretch of the anal canal.

Method Prospective randomised cohort study in a tertiary pelvic floor unit. Patients were recruited and randomised into 2 groups of 25; the first group received normal rate AAR (5 cmH₂0/3secs) then manometry (maximum resting pressure MRP and maximum squeeze pressure MSP) followed by a 2 min rest and then fast rate AAR (5 cmH₂O/1secs) then manometry. The order was reversed for the second group. Clinical details and Vaizey score were recorded for all patients.

Results 50 patients, 40 (80%) women, median age 62 (30–78), 27 (54%) mixed FI, 15 (30%) urge FI and 8 (16%) passive FI. The groups were matched for age (p = 0.6), sex (p = 0.27), type of FI (p = 0.06) and Vaziey score (p = 0.13).

No difference was found between the normal and fast rate of AAR (values shown are means) for all AAR; OP 37.2 v 39.7 cmH₂O p = 0.08, OE 0.97 v 0.98 cmH₂O/mm²p = 0.87, CP 31.5 v 30.5 cmH₂O p = 0.44, CE 0.94 v 0.95 cmH₂O/mm²p = 0.67, HY 24.2 v 23.7% p = 0.73, SOP 66.1 v 62.2 cmH₂O p = 0.06, SOE 1.06 v 1.07 cmH₂O/mm²p = 0.82. Following AAR measurement no difference in manometry values were found; MRP 37.6 v 39.8 cmH₂O p = 0.34, MSP 65.9 v 66.6 cmH₂O p = 0.73.

Conclusion Prior investigation with either fast or normal rate AAR does not influence manometry findings. Within the parameters of this study, the anal canal does not appear to respond differently to a faster rate of stretch, validating a faster method of performing AAR and suggesting that the response of the anal canal to stretch is already maximal at the lower rate of stretch.

Disclosure of interest None Declared.