The use of a balloon catheter to improve evaluation in anorectal manometry

The squeeze pressure in the anal canal reflects the contribution of the external anal sphincter and is normally assessed manometrically by asking patients to contract their anal muscles. However, this is an artificial situation as normally the external sphincter contracts to retain rectal content. Some patients with normal anal sphincter anatomy and innervation record low squeeze pressures suggesting that the concept of voluntary squeeze is foreign. The aim of this study was to examine whether squeezing to retain a balloon mimics the physiology of defaecation more accurately. Patients undergoing routine anorectal manometry testing had in addition the inflation of a balloon catheter to the volume of the first and sustained sensation to simulate a faecal bolus within the rectum. The patient was asked to retain it when the balloon was subjected to gentle traction, thus contracting their anal sphincter to prevent passage of the balloon. Squeeze pressure was measured in response to voluntary contraction, the pressure generated to retain the balloon, then voluntary contraction again. Eighteen women and 2 men were tested. The median maximal squeeze pressures with the routine assessment was 131.0 cmH2O. This increased to 210.0 cmH2O when the patients attempted to retain the balloon and fell to 165.4 cmH2O when patients were reassessed with voluntary squeeze postintervention. 15 of the patients improved their squeeze pressures with traction on the balloon. External anal sphincter contraction is difficult for some patients to perform on request. With traction on a balloon catheter anal squeeze pressures improved in most patients. This indicates that many patients perform maximal anal squeeze pressures better once that muscle group has been tested in a more normal physiological function. This simple technique could improve the accuracy of anorectal manometry results and evaluation in a larger population of symptomatic patients is warranted.