Evaluation of anal sphincter resistance and distensibility in healthy controls using EndoFLIP ©

Ano-rectal disorders are common in the general population. Although they are not life threatening conditions, they do represent a social stigma and a reduced quality of life for the sufferer. The underlying physiology of muscle function contributing to ano-rectal competence is complex and there is room for a much better understanding so that treatments can improve.

A cylindrically shaped, liquid filled bag (12 cm long), mounted on a catheter was inserted into the anus and positioned straddling the ano-rectal region in 20 healthy volunteers (10 females). Series of volume-controlled distensions (40 mL min(-1) to 40 mL) were carried out and data on 16 CSA at 5 mm apart and bag pressure were recorded. Provocative tests using squeeze and cough at bag volumes of 20, 30, and 40 mL were carried out.

Ramp distension of the anal canal showed that the opening pressure for females (mean, 11 mmHg) was higher than for males (mean, 5 mmHg) (P < 0.001). Geometric profile of the anal canal at low distension volumes showed narrow bands at proximal and distal ends of the anal profile and shortening of a middle narrow zone at higher volumes. Inter-individual differences were observed in the behavior of the proximal end and the distal end of the anal profile during squeeze.

This distensibility technique provides an important new way of studying the anal canal and hence may have a role in testing sphincter competence in patients with disorders.