At the same time, a pressure- and volume-building balloon or, as in our department, ideally a large-volume barostat bag is placed in the rectum (barostat measurement), which can measure rectal sensitivity on the one hand and rectal volume on the other.
There are several possible causes of incontinence:
- Weakness of the sphincter resting pressure (M. sphincter ani internus)
- Insufficient clamping pressure (M. sphincter ani externus)
- Decreased rectal sensitivity with consecutive overfilled rectum and unnoticed loss of stool (passive or overflow incontinence)
- Increased rectal sensitivity (imperative urge to defecate with urge incontinence)
- The assessment of rectal sensitivity, which is typically increased in this case, can contribute to the investigation of urge symptoms.
In the case of constipation, the examination can provide information about existing dyssynergistic defecation (imbalance between sphincter relaxation and abdominorectal pressure build-up for defecation) or pelvic floor dysfunction (see general information). Examination of rectal sensitivity is also an important addition in the case of constipation: This could be reduced and thus promote the development of a megarectum due to a lack of urge to defecate and maintain the constipation.
A rare aganglionosis (e.g. Hirschsprung’s disease) can be excluded with the physiologically present rectoanal inhibition reflex (relaxation of the anal sphincter during sudden rectal filling with 10 to 50 ml).