What is the InterStim (Intestinal Stimulation) procedure?

InterStim Procedure for Fecal Incontinence

Sacral nerve stimulation (InterStim) is a safe and effective treatment option for patients with moderate to severe fecal incontinence who have failed conservative measures and biofeedback therapy. 1

What is the InterStim Procedure?

The InterStim procedure involves sacral nerve stimulation (SNS) to treat fecal incontinence through electrical modulation of the sacral nerves that control bowel function. It is a minimally invasive surgical approach that consists of two phases:

1. Test Phase (Phase I):

   • Temporary percutaneous placement of a lead near the S3 sacral nerve
   • Test period of at least 14 days to evaluate effectiveness
   • Success defined as ≥50% reduction in fecal incontinence episodes

2. Permanent Implantation (Phase II):

   • Implantation of a permanent neurostimulator device
   • Typically performed under local anesthesia as an outpatient procedure
   • Involves placement of a small pulse generator in the upper buttock region

Effectiveness and Outcomes

InterStim therapy has demonstrated significant clinical benefits:

• Success rate: 88-90% of patients who undergo test stimulation qualify for permanent implantation 2, 3
• Symptom reduction: 83-86% of patients achieve ≥50% reduction in incontinent episodes at 12-36 months 4, 3
• Complete continence: Achieved in 40-41% of patients 4, 3
• Long-term efficacy: Benefits maintained for at least 3 years in follow-up studies 4

Patient Selection

InterStim is indicated for patients who meet the following criteria:

• Moderate to severe fecal incontinence (typically >2 episodes per week)
• Failed conservative management including:
  • Dietary modifications
  • Fiber supplementation
  • Bowel training programs
  • Anti-diarrheal medications
• Failed pelvic floor retraining with biofeedback therapy (3-month minimum trial)
• No contraindications to the procedure 1, 5

Stepwise Approach to Fecal Incontinence Management

InterStim therapy should be considered within a stepwise approach:

1. First-line: Conservative measures (dietary modifications, medications, bowel training)
2. Second-line: Pelvic floor biofeedback therapy
3. Third-line: Minimally invasive interventions:
   • Perianal bulking agents (e.g., dextranomer injection)
   • Sacral nerve stimulation (InterStim)
4. Fourth-line: More invasive surgical options:
   • Sphincteroplasty (primarily for postpartum women or recent sphincter injuries)
   • Artificial anal sphincter/dynamic graciloplasty
   • Colostomy (as last resort) 1, 5

Safety Profile

The InterStim procedure has a favorable safety profile:

• Common side effects: Implant site pain (28%), paresthesia (15%), changes in stimulation sensation (12%) 4
• Infection rate: Approximately 10% 4
• Device removal: Rarely needed, typically for chronic pain or infection
• No reported unanticipated adverse device effects 4, 3

Advantages Over Traditional Surgical Approaches

InterStim offers several advantages over traditional surgical approaches:

• Less invasive than sphincteroplasty or artificial sphincter placement
• Reversible procedure
• Test phase allows prediction of success before permanent implantation
• Outpatient procedure with minimal recovery time
• Lower morbidity compared to traditional surgical approaches 2

Common Pitfalls to Avoid

1. Premature progression to surgical intervention before adequate trials of conservative therapy and biofeedback
2. Failure to identify and treat underlying causes of fecal incontinence (e.g., diarrhea, evacuation disorders)
3. Inadequate patient selection - best results occur in patients who have truly failed conservative measures
4. Not addressing anatomic defects - major defects like rectovaginal fistula or rectal prolapse should be surgically corrected before considering InterStim 1, 5

InterStim therapy represents an important advancement in the treatment of fecal incontinence, offering a minimally invasive option with demonstrated long-term efficacy for patients who have failed conservative management approaches.