Overview
Definition:
Perianal Crohn's disease refers to the manifestation of Crohn's disease in the perianal region, often presenting as fistulas, abscesses, skin tags, and fissures
Seton placement is a surgical technique used for drainage and/or partial closure of complex perianal fistulas, aiming to manage sepsis, preserve continence, and facilitate healing while addressing the underlying inflammatory process.
Epidemiology:
Perianal involvement occurs in approximately 25-35% of patients with Crohn's disease
Complex perianal fistulas, those that are high, multiple, or associated with abscesses, often require surgical intervention, including seton placement
It is more common in younger adults and can significantly impact quality of life.
Clinical Significance:
Uncontrolled perianal Crohn's disease can lead to significant morbidity, including chronic pain, recurrent sepsis, incontinence, and a high risk of anal strictures or loss of sphincter function
Effective seton strategies are crucial for managing these complex cases, preventing complications, and optimizing patient outcomes in surgical practice.
Clinical Presentation
Symptoms:
Painful perianal mass or swelling
Anal discharge, which may be purulent, bloody, or feculent
Perianal itching or irritation
Fecal incontinence or urgency
Fever and malaise, indicative of abscess
Palpable perianal fistula tracts.
Signs:
Visible external fistula openings
Erythema and tenderness around the anus
Induration suggestive of abscess or thickened fistula tract
Perianal skin tags or fissures
Proctitis or mucosal inflammation on digital rectal examination or anoscopy
Palpable internal and external sphincter involvement in some cases.
Diagnostic Criteria:
Diagnosis is primarily clinical, supported by imaging
Symptoms suggestive of perianal disease in a patient with known or suspected Crohn's disease
Physical examination revealing perianal abnormalities
Confirmation of fistula tract and abscess by imaging modalities like MRI pelvis or endoanal ultrasound is essential for surgical planning.
Diagnostic Approach
History Taking:
Detailed history of bowel habits, stool consistency, and any leakage or pain
Previous perianal procedures or infections
History of Crohn's disease diagnosis, location of disease, and current medical management
Assessment of nutritional status and any systemic symptoms of active Crohn's disease
Inquiry about continence and quality of life.
Physical Examination:
Gentle perianal inspection and palpation
Digital rectal examination to assess sphincter tone, internal openings, and intersphincteric plane involvement
Careful assessment for abscesses, induration, and external fistula openings
Anoscopy to visualize internal openings and mucosal disease
Avoid aggressive examination that may precipitate sepsis.
Investigations:
Magnetic Resonance Imaging (MRI) of the pelvis with fistula protocol is the gold standard for characterizing fistula anatomy, including internal and external openings, tract course, presence of sepsis, and extent of sphincter involvement
Endoluminal Ultrasound (EUS) can be useful for detailing the relation to the sphincter complex
Laboratory tests include CBC (leukocytosis may indicate sepsis), ESR, CRP (markers of inflammation), and stool studies to rule out infection
Colonoscopy may be used to assess the extent of intestinal Crohn's disease.
Differential Diagnosis:
Simple anal fissure
Perianal abscess of non-Crohn's etiology
Hidradenitis suppurativa
Pilonidal sinus disease
Sexually transmitted infections causing perianal lesions
Tuberculosis of the perianal region
Lymphogranuloma venereum.
Management
Initial Management:
Management of active sepsis is paramount
This includes prompt drainage of perianal abscesses
Medical management with antibiotics (e.g., ciprofloxacin and metronidazole) for suspected or confirmed infection
Pain control with appropriate analgesics
Nutritional support.
Medical Management:
While not curative for fistulas, medical therapy aims to control underlying inflammation and may promote healing
Immunomodulators (azathioprine, 6-mercaptopurine) and biologics (infliximab, adalimumab) are cornerstone treatments for Crohn's disease, including perianal manifestations
Antibiotics are used for infection control.
Surgical Management:
Surgical goal is to control sepsis, preserve sphincter function, and promote healing
Seton placement is a key strategy for complex perianal fistulas
Types of setons include: Loose setons (draining, allowing gradual closure), cutting setons (slowly cutting through the sphincter), and videolaparoscopic-assisted anal fistula treatment (VAAFT) combined with seton drainage
Indications for seton placement include complex, high, multiple, or recurrent anal fistulas, especially those involving a significant portion of the sphincter complex or associated with abscesses
The choice of seton depends on fistula complexity, risk of incontinence, and surgeon preference.
Supportive Care:
Wound care and hygiene are critical
Regular sitz baths can help with comfort and cleanliness
Nutritional optimization with adequate protein and micronutrients
Psychological support to address the impact of chronic illness and body image concerns
Multidisciplinary team approach involving gastroenterologists, surgeons, radiologists, and stoma nurses.
Seton Strategies
Indications For Seton:
Transsphincteric or extrasphincteric fistulas involving >30-50% of the sphincter complex
Recurrent fistulas after previous treatment
Abscesses requiring drainage in the setting of significant sphincter involvement
To avoid immediate fistulotomy in patients with high risk of incontinence
To promote granulation and partial closure of draining fistulas.
Types Of Setons:
Draining setons (e.g., silk, latex bands) used to keep fistula tracts open and drain pus, allowing healing from the base upwards
Cutting setons (e.g., heavy silk, braided nylon) used to slowly divide the sphincter muscle over time, reducing incontinence risk
Plug or biologics used in conjunction with seton or as an alternative for specific fistula types.
Placement Techniques:
Performed under anesthesia
Identify internal and external openings
Gently probe the fistula tract
Pass a suitable seton material through the tract
Tie the ends securely but not too tightly to allow drainage
Draining setons are often loosely tied, while cutting setons are tightened periodically
Adjunctive procedures like curettage of the tract may be performed
MRI guidance can be helpful for complex anatomy.
Post Seton Management:
Regular follow-up to monitor for drainage, pain, and signs of infection
Gentle cleaning of the perianal area
Periodic tightening of cutting setons if indicated
Oral antibiotics if infection develops
Pain management
Patient education on wound care and signs of complications
Gradual removal of draining setons as tracts close or when surgical intervention for definitive treatment is planned.
Complications
Early Complications:
Pain at the seton site
Bleeding
Infection or abscess formation around the seton
Migration or extrusion of the seton
Urosepsis if the tract is near the urinary system.
Late Complications:
Incontinence (temporary or permanent), especially with cutting setons
Rectovaginal or urethrocutaneous fistula formation
Anal stricture
Recurrence of fistula
Failure of seton to adequately drain or promote healing.
Prevention Strategies:
Careful patient selection and accurate fistula mapping with MRI
Judicious use of cutting setons in patients with risk factors for incontinence
Proper placement and secure fixation of the seton
Aggressive management of any early signs of infection or abscess
Adequate pain control
Patient education on wound care.
Prognosis
Factors Affecting Prognosis:
Extent and complexity of the fistula
Degree of sphincter involvement
Presence and control of active Crohn's disease elsewhere
Response to medical therapy
Adherence to wound care and follow-up
Surgeon's experience.
Outcomes:
Seton therapy is primarily a temporizing or palliative measure to control sepsis and preserve function
Complete healing may occur in some patients, particularly with draining setons
For many, it allows for better control while awaiting definitive surgery or as part of a long-term management strategy
Rates of healing vary widely, with some studies reporting up to 50-70% healing with appropriate medical and surgical management, including setons.
Follow Up:
Long-term and regular follow-up is essential
This includes clinical assessment, imaging as needed (e.g., repeat MRI if symptoms recur), and monitoring for complications
Patients require ongoing management of their underlying Crohn's disease
Transition to definitive surgical management (e.g., advancement flap, LIFT procedure, or proctectomy in refractory cases) may be considered after seton treatment.
Key Points
Exam Focus:
Understand the indications for seton placement in perianal Crohn's disease
Differentiate between draining and cutting setons and their respective roles
Recognize the importance of MRI in fistula characterization
Know the complications associated with seton therapy, especially incontinence
Recall the multimodal approach to perianal Crohn's disease management.
Clinical Pearls:
Always consider sepsis first and drain abscesses
MRI is indispensable for surgical planning
When in doubt about sphincter involvement, err on the side of caution with seton placement over immediate fistulotomy
Involve a multidisciplinary team
Educate patients thoroughly about the process and expectations.
Common Mistakes:
Performing aggressive digital rectal exams that can worsen sepsis
Undertaking blind fistulotomy in high transsphincteric fistulas without adequate imaging
Neglecting underlying Crohn's disease activity
Inadequate patient follow-up and wound care
Premature removal of setons before tracts are sufficiently healed.