Measuring recto-anal Inhibitory reflex using functional lumen imaging probe: A pilot study

Maha M. Alqudah, Asbjørn Drewes, Barry P. McMahon

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review


Faecal incontinence is a multi-factorial challenging problem. The maintenance of faecal continence relies on a complex voluntary and involuntary coordination between anal and colorectal activity. The aim of this study is to introduce a new method for measuring anal sphincter distensibility and function during voluntary manoeuvres like squeezing and straining as well as involuntary manoeuvres like recto-anal inhibitory reflex (RAIR) testing and slow rectal distension. A modified functional lumen imaging probe (FLIP) consisted of the rectal balloon to distend and measure the pressure in the rectum and the anal bag which contained 16 sensing electrode capable of measuring serial cross-sectional areas (CSA) of the anal bag. The CSAs were converted to functional images of the anal canal geometry. The bag pressure was also measured during anal distension. The probe was bench tested and the CSA measured by EndoFLIP system was calibrated. Four healthy volunteers (2 males/2 females) and one faecal incontinence patient were recruited for the studies. The probe was inserted in the anal canal with 2cm of the anal bag located outside the anal verge. The anal bag was distended from 0ml to 50ml, and then the volunteers were asked to rest, squeeze and strain voluntarily at specific step volumes in the anal bag. RAIR and slow rectal distension tests were also measured at three step distensions in the anal bag. The results showed that the distal end relaxed more than the proximal end during ramp distension. The anal canal length decreased as a linear function of the distending bag volume. The functional images measured during manoeuvres showed the contraction of the proximal part of the anal canal by 12mm 2 during squeezing and the relaxation by 10mm 2 during straining test. During the RAIR test, the distal part of the anal canal relaxed by 14mm 2. The distal part of the anal canal relaxed by 20mm 2 and the proximal part contracted by 10mm 2 during the slow rectal distension which mimics the defecation. In conclusion the modified EndoFLIP was capable of describing the anal distensibility and sphincteric function for different manoeuvres.

Original languageEnglish
Title of host publication4th IEEE Middle East Conference on Biomedical Engineering, MECBME 2018 : Conference Booklet
Number of pages6
Publication date2018
ISBN (Electronic)978-1-5386-1462-4
Publication statusPublished - 2018
Event2018 IEEE 4th Middle East Conference on Biomedical Engineering (MECBME) - Ramada Plaza Hotel, Gammarth, Tunisia
Duration: 28 Mar 201830 Mar 2018
Conference number: 4


Conference2018 IEEE 4th Middle East Conference on Biomedical Engineering (MECBME)
LocationRamada Plaza Hotel
Internet address


  • Destinsibility
  • Endolumenal functional lumen imaging probe
  • Maximum tolerable volume
  • Rectoanal inhibatory reflex


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