Systematic review of the impact of sacral neuromodulation on clinical symptoms and gastrointestinal physiology

BACKGROUND Sacral neuromodulation (SNM) has emerged as a treatment option for faecal incontinence (FI). However, its objective effect on symptoms and anorectal function is inconsistently described. This study aimed to systematically review the impact of SNM on clinical symptoms and gastrointestinal physiology in patients with FI, including factors that may predict treatment outcome. METHODS An electronic search of MEDLINE (1946-2014)/EMBASE database was performed in accordance with PRISMA guidelines. Articles that reported the relevant outcome measures following SNM were included. Clinical outcomes evaluated included: frequency of FI episodes, FI severity score and success rates. Its impact on anorectal and gastrointestinal physiology was also evaluated. RESULTS Of 554 citations identified, data were extracted from 81 eligible studies. Meta-analysis of the data was precluded due to lack of a comparison group in most studies. After permanent SNM, 'perfect' continence was noted in 13-88% of patients. Most studies reported a reduction in weekly FI episodes (median difference of the mean -7.0 (range: -24.8 to -2.7)) and Wexner scores (median difference of the mean -9 (-14.9 to -6)). A trend towards improved resting and squeeze anal pressures and a reduction in rectal sensory volumes were noted. Studies failed to identify any consistent impact on other physiological parameters or clinicophysiological factors associated with success. CONCLUSION SNM improves clinical symptoms and reduces number of incontinence episodes and severity scores in patients with FI, in part by improving anorectal physiological function. However, intervention studies with standardized outcome measures and physiological techniques are required to robustly assess the physiological impact of SNM.