At this year’s ESCP meeting in Dublin, Ireland, Professor Charles Knowles  (Professor of Surgical Research at Queen Mary University of London and Consultant Colorectal Surgeon at Barts Health NHS Trust, London, UK), will assess the role of sacral nerve stimulation (SNS) for bowel disorders in one of several keynote presentations.

In this interview, Professor Knowles discusses the benefits, limitations and evidence supporting its use…

Charles KnowlesHe explained that the main advantage of SNS is its relative safety compared with direct surgical intervention to the anal sphincter, and that it is the only surgical intervention in which the dose can be modified and the procedure completely reversed if it does not work. In the UK, access to the procedure is currently governed by NICE guidance so it can only be offered to patients who have failed a battery of conservative measures.

“We currently have little handle on predicting who best responds to SNS in the long-term,” said Professor Knowles. “It is clear that patients with and without sphincter defects can benefit. My own feeling is that patients with concurrent problems of rectal evacuation leading to a pattern of post-defaecatory leakage do less well as do those with significant chronic polysymptomatology e.g. functional bowel problems, chronic pain syndromes and psychological disorders. The future need for MRI spine is also a current contra-indication although this may change with technological advances.”

He added that there are some disadvantages associated with the procedure, primarily costs, which coupled with some uncertainty regarding clinical effectiveness and experimental efficacy have led to some ongoing scepticism regarding the therapy and probably limited its wider adoption internationally. There are some published data that show high ongoing costs e.g. for reprogramming or re-intervention that add to the direct equipment costs at first implantation.

“There is a wealth of observational data (over 100 case series and thousands of patients) that attest to the general effectiveness of SNS. There are very few data from randomised trials and all current trials have methodological limitations. Long-term prospective registry/cohort data have conflicting results” he said. “An ongoing problem is our collective failure to understand mechanism of action. While studies are ongoing, this knowledge gap has limited our ability to stratify patients to this treatment based on robust physiological biomarkers.”

There are a standard list of absolute contraindications e.g. pregnancy and anatomical limitations preventing electrode placement, although most are rare in practice. Relative contra-indications are poorly evidence-based; common ones include: future need for MRI; diabetic enteropathy; functional diarrhoea, neuropathic pain syndromes; inability to comply with needs of ongoing therapy (e.g. cognitive impairment, lifestyle and psycho-behavioural issues).

“I would consider that severe disruption to the anal sphincter would also render the therapy invalid (at least in isolation),” Professor Knowles added. “The rectal evacuation issue is one that is receiving recent attention. It is probable that patients with dynamic structural defects to the pelvic floor e.g. functioning rectocele and high grade rectal intussusception should have these treated first.”

He said that surgeons performing this procedure should adhere to the procedural optimisation proposed by Siegel et al. [Williams ER, Siegel SW. Procedural techniques in sacral nerve modulation. Int. Urogynecology J. 2010; 21 Suppl 2:S453-60] which in his view undoubtedly leads to better electrode positioning.

In addition, Knowles stressed the importance of the role of the multidisciplinary team (MDT) in terms of pre- and post-operative care. For example, at his practice at Barts Health NHS Trust London all patients are discussed in an MDT to determine whether the patient meets the criteria for SNS and whether alternative treatments might have greater benefit. Such an MDT must have urogynaecological input to recognise that faecal incontinence in women is rarely an isolated problem. He said that it is likely that documentation of such MDT discussions will become mandatory in the NHS based on draft NHS England specialist commissioning guidance.

With regards to technological advances, he explained that the existing core technology manufacturer has an ongoing programme of device modifications to improve patient and clinician experience, adding that MRI compatible and rechargeable devices will become available for selected patients in the next few years, with the market also open to new device manufacturers.

As well as discussing SNS, he added that percutaneous tibial nerve stimulation (PTNS) has a role in treating bowel disorders, stating that there are data from several case series that show benefit and acceptability of PTNS for the treatment of faecal incontinence. However, the recent publication of the NIHR-funded CONFIDeNT study in the Lancet (Knowles et al. Percutaneous tibial nerve stimulation versus sham electrical stimulation for the treatment of faecal incontinence in adults (CONFIDeNT): a double-blind, multicentre, pragmatic, parallel-group, randomised controlled trial. The Lancet. August 2015) failed to demonstrate significant short-term clinical efficacy of PTNS when compared with sham electrical stimulation in a blinded RCT.

“My feeling is that there is still a place for PTNS in patients whose predominant symptom is urgency having excluded any problem with rectal evacuation” he concluded. “Its application should be considered as an adjunct to other conservative measures in patients who are happy to engage with the time commitments of this therapy. There are insufficient data to support its use for other bowel disorders at the current time.”

Professor Knowles’ Keynote Lecture, ‘Sacral nerve stimulation for bowel disorders’, will be presented at the 10th Scientific and Annual Meeting of the ESCP at 15:15 on Wednesday 23rd September.

ESCP Affiliates