Puborectalis forms a U-shaped sling around the anorectal junction, creating the anorectal angle (normally 90 degrees) that is the primary structural mechanism of faecal continence. During defaecation, it must relax to straighten the anorectal angle.
| Origin | Pubic bone — posterior surface, on both sides |
|---|---|
| Insertion | Loops behind the anorectal junction — no bony insertion, forms a muscular sling |
| Nerve Supply | Pudendal nerve and direct sacral nerve branches (S3, S4) |
| Blood Supply | Internal pudendal artery |
| Actions | Maintains the anorectal angle — the primary continence mechanism; Creates the 90-degree angle between rectum and anal canal that prevents faecal leakage; Paradoxically contracts during straining to resist defaecation |
|---|
Puborectalis dyssynergia (non-relaxing puborectalis) produces obstructed defaecation — the muscle fails to relax during straining, preventing the anorectal angle from opening. Biofeedback therapy retrains puborectalis relaxation. In cases of faecal incontinence, the puborectalis sling can be augmented by sacral nerve stimulation. MRI defaecography assesses puborectalis function dynamically.
Assessed by digital rectal examination (the puborectalis sling is palpated as a posterior ledge) and by MRI defaecography.
Non-relaxing puborectalis producing obstructed defaecation syndrome with straining and incomplete evacuation, managed by biofeedback therapy for paradoxical puborectalis contraction.
