Should sacral nerve stimulation be a first line therapy for fecal incontinence?
Fecal incontinence (FI) — the unintentional loss of solid or liquid stool — affects a reported 7 to 15 percent of community-dwelling U.S. adults. The true incidence may be much higher, however, because the condition is rarely discussed or diagnosed — as many as half of people with fecal incontinence don't report it to their doctors. The average nursing home prevalence is higher still — around 45 percent. For those affected, the emotional, physical, social and economic consequences can be devastating.
The pathophysiological mechanisms underlying FI include diarrhea, anal and pelvic floor weakness, and abnormal rectal sensation. Sometimes a single cause exists, but more often, multiple factors are involved. Addressing these pathologies can restore or improve continence and quality of life. Although total continence isn't always possible, most patients can experience an improvement in symptoms.
Traditional treatments for FI include dietary and lifestyle changes, pelvic floor retraining, biofeedback or behavior modification, and surgery. More recently, various experimental modalities have been introduced, including sacral nerve stimulation (SNS), which was approved in 2013 for patients resistant to conservative therapies.
Paul D. Pettit, M.D., a urogynecologist and reconstructive surgeon at Mayo Clinic's campus in Jacksonville, Florida, says despite sacral nerve stimulation's acceptable safety profile and demonstrated long-term efficacy, less-invasive therapies should be tried first, except in patients with recent obstetric issues.
Trial and error
In SNS, a surgically implanted neurostimulator transmits mild electrical impulses to a lead wire close to the sacral nerve plexus. The appropriate nerves are identified using a test needle and temporary lead wire. A patient's response to the stimulation is determined by a two-week trial during which only the lead is implanted and an external battery pack delivers the electrical impulse. Patients who have at least 50 percent improvement in symptoms during the trial are eligible for long-term therapy, which requires a second procedure to implant the neurostimulator.
"The biggest message about sacral nerve stimulation is that almost every patient is a candidate, but no test other than the device itself can tell whether it will work or not," says Heidi K. Chua, M.D., a colon and rectal surgeon at Mayo Clinic 's campus in Rochester, Minnesota. "Once the device is implanted, the patient will know if it works because symptoms usually improve in three to five days. Putting the device in is fairly straightforward from a technical standpoint, so you don't lose much by trying it out."
In the first Food and Drug Administration-regulated multicenter prospective study of SNS, 80 percent of 120 patients achieved therapeutic success — defined as a 50 percent or greater reduction in incontinent episodes — and significant improvement in quality of life 12 months post-implant. Subsequent research, including a study published in Diseases of the Colon & Rectum in 2011, found sustained improvement among nearly 90 percent of patients at three years. In that study, the number of incontinent episodes a week decreased from a mean at baseline of 9.4 to 1.7, with 40 percent of patients achieving perfect continence.
A 2014 study in Annals of Surgery described a favorable outcome for 60 of 101 patients five years post-implant. Forty-one patients reported an unfavorable outcome, 24 of whom had the device permanently explanted or switched off.
Dr. Chua observes that a 50 percent reduction in symptom frequency or severity may not always translate to improved quality of life. "We strive to achieve perfect continence, but don't always get there. We may get patients to the point where they can get out of the house, but they still may have anxiety about accidents, be constantly looking for a bathroom and wearing a pad. Some patients have discomfort or complications, such as infections.
"Symptoms also may get worse, especially when both urinary and fecal incontinence are present. Still, we will tweak the program — try stimulating various combinations of four implanted leads — before we decide SNS isn't working," she says.
At Mayo Clinic, results are encouraging. Ninety percent of patients have a 50 percent reduction in symptoms while the device is in place, although symptoms return with removal. Still, no other treatment option for FI has demonstrated similar success rates. The exact mechanism of action isn't well-understood, but Dr. Chua and others believe SNS improves sensation.
"The first line surgical treatment for fecal incontinence is fixing the sphincter mechanism, but maybe we should start with the sacral nerve, and if that doesn't work, then try other options," Dr. Chua says. "The algorithm for FI treatment may be shifting; we should do what is easiest first and then move on from there."
For more information
Mellgren A, et al. Long-term efficacy and safety of sacral nerve stimulation for fecal incontinence. Diseases of the Colon & Rectum. 2011;54:1065.
Maeda Y, et al. Outcome of sacral nerve stimulation for fecal incontinence at 5 years. Annals of Surgery. 2014;259:1126.