The short-term effects of posterior tibial nerve stimulation on anorectal physiology in patients with faecal incontinence: a single centre experience

Background: Posterior tibial nerve stimulation (PTNS) is a novel treatment for patients with faecal incontinence (FI) and may be effective in selected patients; however, its mechanism of action is unknown. We sought to determine the effects of PTNS on anorectal physiological parameters. Methods: Fifty patients with FI underwent 30 min of PTNS treatment, weekly for 12 weeks. High-resolution anorectal manometry, bowel diaries and Vaizey questionnaires were performed before and after treatment. Successful treatment was determined as a greater than 50% reduction in FI episodes. Results: Fifty patients with FI were studied; 39 women, median age 62 years (range 30–82). Compared with pretreatment, there were reductions in episodes of urgency (16.0 versus 11.4, p = 0.006), overall FI (14.5 versus 9.1, p = 0.001), urge FI (5.4 versus 3.2, p = 0.016) and passive FI (9.1 versus 5.9, p = 0.008). Vaizey score was reduced (16.1 versus 14.5, p = 0.002). Rectal sensory volumes (ml) decreased (onset 40.3 versus 32.6, p = 0.014, call 75.7 versus 57.5, p < 0.001, urge 104.1 versus 87.4, p = 0.004). There was no significant change in anal canal pressures (mmHg) (maximum resting pressure 41.4 versus 44.2, p = 0.39, maximum squeeze pressure, 78.7 versus 88.2, p = 0.15, incremental squeeze pressure 37.2 versus 44.1, p = 0.22). Reduction in FI episodes did not correlate with changes in physiological parameters (p > 0.05). Treatment success of 44% was independent of changes in manometric parameters (p > 0.05). Conclusions: PTNS has a measureable physiological effect on rectal sensory volumes without an effect on anal canal pressures. It also reduces FI episodes; however, this effect is independent of changing physiology, suggesting that PTNS has a complex mechanism of action.