A systematic review of sacral nerve stimulation mechanisms in the treatment of fecal incontinence and constipation.

BACKGROUND: Sacral nerve stimulation (SNS) is now well established as a treatment for fecal incontinence (FI) resistant to conservative measures and may also have utility in the management of chronic constipation; however, mechanism of action is not fully understood. End organ effects of SNS have been studied in both clinical and experimental settings, but interpretation is difficult due to the multitude of techniques used and heterogeneity of reported findings. The aim of this study was to systematically review available evidence on the mechanisms of SNS in the treatment of FI and constipation. METHODS: Two systematic reviews of the literature (performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses framework) were performed to identify manuscripts pertaining to (a) clinical and (b) physiological effects of SNS during the management of hindgut dysfunction. KEY RESULTS: The clinical literature search revealed 161 articles, of which 53 were deemed suitable for analysis. The experimental literature search revealed 43 articles, of which nine were deemed suitable for analysis. These studies reported results of investigative techniques examining changes in cortical, gastrointestinal, colonic, rectal, and anal function. CONCLUSIONS & INFERENCES: The initial hypothesis that the mechanism of SNS was primarily peripheral motor neurostimulation is not supported by the majority of recent studies. Due to the large body of evidence demonstrating effects outside of the anorectum, it appears likely that the influence of SNS on anorectal function occurs at a pelvic afferent or central level.

The effect of sacral nerve stimulation on distal colonic motility in patients with faecal incontinence.

BACKGROUND: Sacral nerve stimulation (SNS) is an effective treatment for neurogenic faecal incontinence (FI). However, the clinical improvement that patients experience cannot be explained adequately by changes in anorectal function. The aim of this study was to examine the effect of SNS on colonic propagating sequences (PSs) in patients with FI in whom urgency and incontinence was the predominant symptom. METHODS: In patients with FI a high-resolution fibre-optic manometry catheter, containing 90 sensors spaced at 1-cm intervals, was positioned colonoscopically and clipped to the caecum. A unipolar or quadripolar tined electrode was implanted into the S3 sacral nerve foramen. Colonic manometry was evaluated in a double-blind randomized crossover trial, using true suprasensory stimulation or sham stimulation. Each stimulation period, lasting 2 h, was preceded by a 2-h basal manometric recording. RESULTS: All 11 patients studied showed a colonic response to SNS. In ten patients there was a significant increase in the frequency of retrograde PSs throughout the colon during true stimulation compared with sham stimulation (P = 0·014). In one outlier, with baseline retrograde PS frequency nine times that of the nearest patient, a reduction in retrograde PS frequency was recorded. Compared with sham stimulation, SNS had no effect on the frequency of antegrade PSs or high-amplitude PSs. CONCLUSION: SNS modulates colonic motility in patients with faecal urge incontinence. These data suggest that SNS may improve continence and urgency through alteration of colonic motility, particularly by increasing retrograde PSs in the left colon.

Pancolonic motor response to subsensory and suprasensory sacral nerve stimulation in patients with slow-transit constipation.

BACKGROUND: Sacral nerve stimulation (SNS) is emerging as a potential treatment for patients with constipation. Although SNS can elicit an increase in colonic propagating sequences (PSs), the optimal stimulus parameters for this response remain unknown. This study evaluated the colonic motor response to subsensory and suprasensory SNS in patients with slow-transit constipation. METHODS: Patients with confirmed slow-transit constipation were studied. Either a water-perfused manometry catheter or a high-resolution fibre-optic manometry catheter was positioned colonoscopically to the caecum. A temporary electrode was implanted transcutaneously in the S3 sacral nerve foramen. In the fasted state, three conditions were evaluated in a double-blind randomized fashion: sham, subsensory and suprasensory stimulation. Each 2-h treatment period was preceded by a 2-h basal period. The delta (Δ) value was calculated as the frequency of the event during stimulation minus that during the basal period. RESULTS: Nine patients had readings taken with a water-perfused catheter and six with a fibre-optic catheter. Compared with sham stimulation, suprasensory stimulation caused a significant increase in the frequency of PSs (mean(s.d.) Δ value - 1·1(7·2) versus 6·1(4·0) PSs per 2 h; P = 0·004). No motor response was recorded in response to subsensory stimulation compared with sham stimulation. Compared with subsensory stimulation, stimulation at suprasensory levels caused a significant increase in the frequency of PSs (P = 0·006). CONCLUSION: In patients with slow-transit constipation, suprasensory SNS increased the frequency of colonic PSs, whereas subsensory SNS stimulation did not. This has implications for the design of therapeutic trials and the clinical application of the device.

Novel diagnostics and therapy of colonic motor disorders.

Colonic motor abnormalities are implicated in several gastrointestinal disorders including constipation, irritable bowel syndrome and functional diarrhoea. Defining the colonic abnormalities is difficult and several novel techniques including, high-resolution fibre optic manometry, wireless motility capsules, ultrasound and magnetic resonance imaging have emerged to help in the diagnosis of these conditions. Coupled with the developing techniques are the novel treatments that look to restore normal colonic motility. These treatments include pharmacological agents (pharmabiotics, serotonin agonist, secretagogues) and medical devices (sacral nerve stimulation, transcutaneous electrical stimulation and biofeedback). This review summarizes the novel techniques used to record and define colonic motor abnormalities and the current status of the emerging treatments used to treat them.

Surgical management of constipation.

This review addresses the range of operations suggested to be of contemporary value in the treatment of constipation with critical evaluation of efficacy data, complications, patient selection, controversies and areas for future research.