Correlation of Anal Acoustic Reflectometry Parameters With Degree of Rectal Intussusception and Prolapse

Anal Acoustic Reflectometry (AAR) is a reliable and reproducible technique that has been studied in our department over the last 6 years. Sound waves pass into a balloon placed in the anal canal and are used to measure the cross-sectional area. By gradually increasing and decreasing the pressure in the balloon the investigators can measure the pressure at which the cross-sectional area starts to increase and decrease, and the anal canal starts to open and close. This assessment mimics the natural opening and closing of the anal canal and the effect of squeezing the muscles.

Rectal intussusception occurs when the rectal wall telescopes into itself distally and is termed prolapse when it protrudes through the anal canal. Not all patients will require surgery and, for some, it can lead to debilitating symptoms of constipation, pain and faecal incontinence. Currently, the Oxford grading system through radiological testing is used for classifying severity of rectal intussusception and prolapse; however this does not give us sufficient information about the anal sphincter muscles.

The gold standard investigation of the anal sphincter muscles has been manometry which measures anal canal pressure at rest and during squeeze. However, it has limitations. In previous studies AAR has shown promise in the assessment of faecal incontinence and, that unlike manometry, it has been able to distinguish between different types of incontinence. Thus far, it has not been studied in patients with rectal intussusception and it is hoped that AAR parameters may provide an indication of when rectal intussusception becomes overt rectal prolapse. This can inform the clinician to guide further management of a group of patients with a condition that can have significant impact on quality of life.