Video-Assisted Anal Fistula Treatment (VAAFT): Equipment, Technique, and Patient Selection

はじめに

The management of anal fistulas remains a significant challenge in colorectal surgery, requiring a delicate balance between eradicating the fistula tract and preserving anal sphincter function. Traditional surgical methods, such as fistulotomy, often achieve high cure rates but carry a risk of incontinence, particularly for complex fistulas involving a significant portion of the sphincter muscles. This has spurred the development of numerous sphincter-preserving techniques, each with its own advantages and limitations.

Video-Assisted Anal Fistula Treatment (VAAFT), introduced by Meinero in 2006, represents a novel and minimally invasive approach that utilizes endoscopic visualization to treat anal fistulas. This technique employs a specialized fistuloscope, allowing direct visualization of the entire fistula tract from the internal opening to the external opening, including any secondary tracts or abscess cavities. The VAAFT procedure consists of two distinct phases: a diagnostic phase (fistuloscopy) for mapping the fistula anatomy and a therapeutic phase for obliterating the tract and closing the internal opening.

The key innovation of VAAFT lies in its ability to provide direct, magnified visualization of the fistula tract’s internal structure, which is not possible with conventional techniques relying on probing or imaging alone. This allows for precise identification of the internal opening, accurate mapping of complex anatomy, targeted debridement of the tract lining under vision, and controlled closure of the internal opening. By working entirely within the fistula tract and avoiding extensive external dissection, VAAFT aims to minimize tissue trauma, preserve sphincter integrity, and facilitate faster recovery.

Since its introduction, VAAFT has gained increasing interest and adoption globally as a sphincter-preserving option for various types of anal fistulas, including complex and recurrent cases. The technique offers potential advantages in terms of diagnostic accuracy, targeted treatment, and minimal invasiveness. However, it requires specialized equipment, specific training, and careful patient selection to achieve optimal outcomes. Success rates reported in the literature vary, highlighting the importance of understanding the technical nuances and factors influencing efficacy.

This comprehensive review provides a detailed examination of the VAAFT procedure, covering the specialized equipment, surgical technique, patient selection criteria, clinical outcomes, advantages, limitations, and future directions. By synthesizing the current evidence and practical insights, this article aims to equip clinicians with a thorough understanding of this innovative endoscopic approach to anal fistula management.

免責事項: This article is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. The information provided should not be used for diagnosing or treating a health problem or disease. Invamed, as a medical device manufacturer, provides this content to enhance understanding of medical technologies. Always seek the advice of a qualified healthcare provider with any questions regarding medical conditions or treatments.

Principles and Rationale of VAAFT

Core Concepts

1. Endoscopic Visualization: Direct, magnified view of the entire fistula tract.
2. Diagnostic Accuracy: Precise mapping of primary and secondary tracts, identification of internal opening.
3. Targeted Therapy: Treatment applied directly to the pathological tissue under vision.
4. Minimally Invasive: Access through existing fistula openings, minimal external dissection.
5. Sphincter Preservation: Avoidance of sphincter muscle division.
6. Two-Phase Approach: Distinct diagnostic (fistuloscopy) and therapeutic phases.

Rationale for Endoscopic Approach

1. Limitations of Conventional Methods: Blind probing, reliance on indirect imaging (MRI, EUS), potential for missed tracts or inaccurate internal opening identification.
2. Improved Anatomical Understanding: Direct visualization overcomes limitations of external examination and probing.
3. Precision Treatment: Allows targeted destruction of epithelial lining and granulation tissue.
4. Reduced Tissue Trauma: Avoids large external incisions and extensive dissection in the intersphincteric or ischioanal spaces.
5. Potential for Reduced Pain and Faster Recovery: Minimal tissue disruption compared to traditional flap procedures or fistulotomy.
6. Applicability to Complex Cases: Ability to navigate and treat branching tracts or cavities under vision.

Mechanism of Action

1. Diagnostic Phase (Fistuloscopy):
   • Accurate identification of the internal opening.
   • Mapping of the primary tract course.
   • Detection and exploration of secondary tracts or abscess cavities.
   • Assessment of tract lining characteristics.
2. Therapeutic Phase (Tract Ablation & Closure):
   • Mechanical debridement of the tract using specialized brushes.
   • Thermal ablation of the tract lining using an electrode passed through the fistuloscope.
   • Destruction of epithelial cells and granulation tissue.
   • Stimulation of fibrosis and healing within the tract.
   • Secure closure of the internal opening using sutures or a stapler.
   • Prevention of reinfection from the bowel lumen.

Comparison with Other Techniques

1. vs. Fistulotomy: VAAFT preserves sphincter; Fistulotomy divides sphincter.
2. vs. Seton Placement: VAAFT aims for definitive closure; Seton provides drainage/gradual division.
3. vs. Advancement Flap: VAAFT avoids external flap creation; Flap involves more extensive dissection.
4. vs. LIFT Procedure: VAAFT works intraluminally; LIFT involves intersphincteric dissection.
5. vs. Fistula Plug/Glue: VAAFT actively destroys tract lining; Plugs/glue rely on passive occlusion/scaffolding.
6. vs. FiLaC (Laser Closure): Both use intraluminal energy; VAAFT uses electrocautery/brushing, FiLaC uses laser energy. VAAFT provides continuous visualization during ablation.

Equipment and Instrumentation

The Meinero Fistuloscope Set

1. Fistuloscope: Rigid endoscope (typically 3.3mm or 4.8mm outer diameter) with an oblique eyepiece (e.g., 30 degrees) and integrated working channel (1.2-1.8mm).
2. Optical System: High-resolution optics for clear visualization.
3. Light Source: Connection for standard endoscopic light source (Xenon or LED).
4. Irrigation Channel: Continuous irrigation with saline or glycine solution for clear view and distension of the tract.
5. Working Channel: Allows passage of instruments (electrode, brush, forceps).
6. Camera System: Connection to standard endoscopic camera head and video monitor.

Specialized Instruments

1. Unipolar Electrode: Flexible electrode passed through the working channel for thermal ablation of the tract lining.
2. Fistula Brush: Cylindrical brush passed through the working channel for mechanical debridement of the tract.
3. Grasping Forceps: Small forceps for removing debris or tissue fragments (optional).
4. Guide Wire/Probe: Used initially to navigate the tract and facilitate fistuloscope insertion.
5. External Retractor/Speculum: Used for visualizing and accessing the internal opening (e.g., Parks retractor).

Ancillary Equipment

1. Electrosurgical Unit (ESU): Standard ESU providing coagulation current for the unipolar electrode.
2. Irrigation System: Fluid pump or pressure bag for continuous irrigation (typically saline or 1.5% glycine).
3. Video Tower: Monitor, light source, camera control unit, recording device.
4. Suturing Materials: Absorbable or non-absorbable sutures for internal opening closure (e.g., 2-0 or 3-0 Vicryl, PDS, Prolene).
5. Stapling Device (Optional): Linear or circular stapler for internal opening closure in selected cases.
6. Standard Anorectal Tray: Probes, retractors, gauze, etc.

Setup and Preparation

1. Equipment Check: Ensure all components are functional (fistuloscope, light source, camera, ESU, irrigation).
2. Sterilization: Proper sterilization of reusable components.
3. Irrigation Fluid: Prepare saline or glycine solution.
4. Electrode Connection: Connect electrode to ESU, set appropriate coagulation settings (typically 20-40W).
5. Video System Setup: Connect camera and light source, adjust monitor settings.
6. Patient Positioning: Lithotomy or prone jackknife position.
7. Anesthesia: General, regional, or deep sedation usually required.

Surgical Technique: Step-by-Step

Phase 1: Diagnostic Fistuloscopy

1. Examination Under Anesthesia (EUA): Confirm external and internal opening locations, assess surrounding tissues.
2. Tract Cannulation: Gently insert the fistuloscope into the external opening, potentially over a guide wire or probe.
3. Irrigation Initiation: Start continuous irrigation to distend the tract and clear debris.
4. Advancement and Visualization: Slowly advance the fistuloscope along the primary tract under direct vision.
5. Anatomical Mapping: Identify the course of the primary tract, its relationship to sphincters (indirectly assessed), and any branching points.
6. Secondary Tract Exploration: Systematically explore any identified secondary tracts or cavities.
7. Internal Opening Identification: Advance the scope until the internal opening is visualized from within the tract. Confirm its location relative to the dentate line.
8. Assessment of Tract Lining: Observe the nature of the tract lining (granulation tissue, epithelialization, debris).
9. Documentation: Record findings, potentially with video or images.

Phase 2: Therapeutic Intervention

1. Mechanical Debridement: Introduce the fistula brush through the working channel. Perform thorough brushing of the entire tract lining (primary and secondary tracts) to remove granulation tissue, debris, and epithelial cells. Repeat as necessary.
2. Thermal Ablation: Introduce the unipolar electrode through the working channel.
   • Starting near the internal opening, systematically apply coagulation current to the tract wall while slowly withdrawing the fistuloscope.
   • Aim for homogenous whitening of the tissue, indicating thermal destruction.
   • Ensure 360-degree treatment of the tract circumference.
   • Treat all identified secondary tracts and cavities similarly.
   • Maintain continuous irrigation to cool tissues and clear smoke/debris.
   • Avoid excessive energy application to prevent deep thermal injury.
3. Debris Removal: Use irrigation and potentially grasping forceps to remove charred tissue and debris.
4. Internal Opening Closure: This is a critical step.
   • Suture Closure: Using an anal retractor for exposure, close the identified internal opening with sutures (absorbable or non-absorbable). Techniques include figure-of-eight or simple interrupted sutures incorporating submucosa.
   • Stapler Closure: In selected cases (e.g., wide internal opening, favorable anatomy), a linear or circular stapler can be used to excise and close the internal opening.
   • Advancement Flap (Optional): In complex or recurrent cases, closure may be reinforced with a mucosal or full-thickness advancement flap (though this deviates from pure VAAFT).
5. External Opening Management: The external opening is typically left open or only loosely approximated to allow drainage of any residual fluid or exudate.
6. Final Inspection: Ensure hemostasis and confirm closure of the internal opening.

Technical Pearls and Pitfalls

1. Irrigation Management: Maintain adequate flow for visualization but avoid excessive pressure which could force debris into tissues.
2. Gentle Handling: Avoid forceful advancement of the scope to prevent false passage creation.
3. Systematic Exploration: Ensure all tracts and cavities are identified and treated.
4. Controlled Ablation: Avoid overly aggressive thermal energy application; aim for superficial destruction.
5. Internal Opening Closure: Secure closure is paramount to prevent reinfection and recurrence.
6. Secondary Tracts: Thorough treatment of secondary tracts is crucial for success.
7. Learning Curve: Recognize the need for specific training and experience (estimated 15-20 cases).
8. Pitfall – Missed Internal Opening: Failure to correctly identify the true internal opening leads to failure.
9. Pitfall – Incomplete Ablation: Leaving viable epithelial remnants can lead to recurrence.
10. Pitfall – Overly Aggressive Ablation: Can cause excessive scarring or damage to adjacent structures.

Patient Selection Criteria

Ideal Candidates

1. Fistula Type: Primarily indicated for complex anal fistulas, especially high transsphincteric, suprasphincteric, or extrasphincteric types where fistulotomy is contraindicated.
2. Tract Characteristics: Well-defined tracts, including those with secondary branches or small cavities that can be navigated endoscopically.
3. Recurrent Fistulas: Suitable for patients who have failed previous sphincter-preserving attempts (e.g., plug, LIFT, flap).
4. Patient Factors: Patients prioritizing sphincter preservation, those with pre-existing continence issues, or those seeking minimally invasive options.
5. Underlying Disease: Can be considered in selected patients with Crohn’s disease, provided inflammation is well-controlled.

Relative Contraindications

1. Very Short or Superficial Tracts: Fistulotomy may be simpler and more effective.
2. Extremely Narrow or Tortuous Tracts: Difficulty navigating with the rigid fistuloscope.
3. Large Abscess Cavities: May require initial drainage and delayed VAAFT.
4. Active Sepsis: Procedure should be deferred until infection is controlled (e.g., after seton drainage).
5. Severe Anal Stenosis: Difficulty accessing the internal opening.
6. Poor Tissue Quality: E.g., post-radiation changes, severe scarring.

Absolute Contraindications

1. Anal Malignancy: Requires oncological management.
2. Inability to Identify Internal Opening: VAAFT relies on visualizing and closing the internal source.
3. Patient Unfit for Anesthesia.

Preoperative Evaluation Summary

• Thorough clinical assessment (history, examination, anoscopy).
• Imaging (MRI or EUS) often recommended, especially for complex or recurrent cases, to guide intraoperative exploration.
• Assessment of baseline continence.
• Evaluation and optimization of underlying conditions (e.g., Crohn’s disease control).
• Informed consent discussing success rates, risks, alternatives, and potential need for further procedures.

Clinical Outcomes and Evidence

Success Rates and Healing

1. Reported Success Rates: Vary significantly in the literature, ranging from 60% to over 90% in different series.
2. Meta-Analysis Findings: Pooled success rates typically range from 70% to 80%.
3. Factors Influencing Success: Surgeon experience, patient selection (complex vs. simple fistulas), underlying disease (Crohn’s vs. cryptoglandular), technique variations (e.g., method of internal opening closure).
4. Healing Time: Complete healing usually occurs within 4-12 weeks.
5. Recurrence: Most recurrences happen within the first 6-12 months. Recurrence rates are reported between 10% and 30%.

Functional Outcomes

1. Continence Preservation: Excellent results reported, with minimal impact on sphincter function. Postoperative incontinence rates are typically very low (<2-3%), often related to pre-existing issues or other factors rather than the VAAFT procedure itself.
2. Pain: Generally associated with low postoperative pain compared to more invasive procedures.
3. Recovery: Patients typically return to normal activities within a few days to a week.
4. Patient Satisfaction: Generally high due to minimal invasiveness, low pain, and sphincter preservation.

Complications

1. Intraoperative: Bleeding (usually minor), false passage creation (rare), difficulty navigating tract.
2. Early Postoperative: Pain (usually mild), bleeding, temporary drainage/discharge (common), urinary retention (rare), infection/abscess formation (uncommon, <5%).
3. Late Postoperative: Recurrence/persistence of fistula (most common complication), delayed healing.
4. Serious Complications: Extremely rare, but theoretical risks include deep thermal injury or perforation if technique is improper.

Comparison with Other Techniques

• VAAFT vs. LIFT: Some studies suggest similar success rates (around 70-80%), but VAAFT may offer better visualization for complex tracts. LIFT may be technically simpler in some cases.
• VAAFT vs. Advancement Flap: Flaps may have slightly higher success rates for complex fistulas but involve more extensive surgery and potentially higher morbidity/impact on continence.
• VAAFT vs. Fistula Plug/Glue: VAAFT generally demonstrates higher success rates.
• VAAFT vs. FiLaC: Limited direct comparisons. Both are minimally invasive energy-based techniques. Success rates appear comparable, but VAAFT offers direct visualization during ablation.
• Need for High-Quality RCTs: More comparative studies are needed to definitively position VAAFT relative to other sphincter-preserving techniques.

Advantages and Limitations

Advantages of VAAFT

1. Minimally Invasive: Avoids large external wounds and extensive dissection.
2. Sphincter Preservation: Designed to protect sphincter muscles, minimizing incontinence risk.
3. Direct Visualization: Allows accurate mapping of complex anatomy and targeted treatment.
4. Diagnostic Capability: Can identify previously missed tracts or internal openings.
5. Low Postoperative Pain: Generally well-tolerated with minimal discomfort.
6. Fast Recovery: Quick return to normal activities.
7. Repeatability: Can potentially be repeated in case of failure without compromising future options significantly.
8. Applicability: Useful for complex and recurrent fistulas where other options may be limited or have failed.

Limitations and Disadvantages

1. Specialized Equipment: Requires investment in the fistuloscope and associated instruments.
2. Learning Curve: Requires specific training and experience to master the technique.
3. Variable Success Rates: Outcomes can be inconsistent, influenced by various factors.
4. Not Suitable for All Fistulas: Limitations in very narrow, tortuous, or short tracts; less ideal for simple fistulas where fistulotomy is safe.
5. Internal Opening Closure: Success heavily relies on achieving secure closure of the internal opening, which can be challenging.
6. Cost: Higher procedural cost compared to simpler techniques like fistulotomy or seton placement due to equipment and potentially longer operative time initially.
7. Limited Long-Term Data: While increasingly used, very long-term (>5-10 years) outcome data is still accumulating.

Future Directions

Technological Enhancements

1. Improved Optics: Higher resolution, wider field of view, flexible fistuloscopes.
2. Advanced Energy Sources: Integration of different energy modalities (e.g., laser, radiofrequency) with visualization.
3. Robotic Assistance: Potential for enhanced dexterity and precision in complex cases.
4. Integrated Imaging: Combining fistuloscopy with real-time ultrasound or other imaging.
5. Disposable Components: Development of cost-effective single-use fistuloscopes or instruments.

Procedural Refinements

1. Optimized Ablation Techniques: Standardizing energy settings and application methods.
2. Enhanced Internal Opening Closure: Development of novel suture techniques or devices.
3. Combination Therapies: Integrating VAAFT with biological agents (e.g., stem cells, growth factors) applied under vision.
4. Standardized Protocols: Consensus guidelines for technique and patient selection.

Research Needs

1. Comparative Trials: High-quality RCTs comparing VAAFT with other sphincter-preserving techniques (LIFT, Flap, FiLaC).
2. Long-Term Follow-up: Studies with follow-up beyond 5 years.
3. Predictive Factors: Identifying patient and fistula characteristics that predict success.
4. Cost-Effectiveness Analyses: Evaluating the economic value relative to other treatments.
5. Learning Curve Studies: Defining optimal training pathways.

結論

Video-Assisted Anal Fistula Treatment (VAAFT) represents a significant advancement in the minimally invasive, sphincter-preserving management of anal fistulas. By providing direct endoscopic visualization of the fistula tract, VAAFT allows for accurate diagnosis, precise mapping of complex anatomy, and targeted therapeutic intervention. The technique involves meticulous fistuloscopy followed by mechanical and thermal ablation of the tract lining and secure closure of the internal opening.

The primary advantages of VAAFT include its minimal invasiveness, excellent sphincter preservation potential, low postoperative pain, and rapid recovery. It is particularly valuable for complex fistulas (e.g., high transsphincteric) and recurrent cases where traditional fistulotomy is contraindicated or previous repairs have failed. Reported success rates are generally favorable, ranging from 70% to 80% in meta-analyses, although variability exists.

However, VAAFT requires specialized equipment and a distinct learning curve. Success is contingent upon careful patient selection, meticulous technique (especially secure internal opening closure), and surgeon experience. It may not be the optimal choice for all fistula types, particularly very simple or superficial ones.

As with many innovative surgical techniques, further research, including high-quality comparative trials and long-term follow-up studies, is needed to fully define the role of VAAFT in the treatment algorithm for anal fistulas. Technological enhancements and procedural refinements may further improve outcomes. Nonetheless, VAAFT currently stands as a valuable tool in the colorectal surgeon’s armamentarium, offering a unique diagnostic and therapeutic approach for challenging anal fistula cases while prioritizing the preservation of patient continence and quality of life.

免責事項: This information is for educational purposes only and not a substitute for professional medical advice. Consult a qualified healthcare provider for diagnosis and treatment. Invamed provides this content for informational purposes regarding medical technologies.