Pilonidal Sinus (Adult)

1. Clinical Overview

Summary

Pilonidal sinus disease (PSD) is a chronic inflammatory condition affecting the natal cleft (intergluteal region), characterised by midline pits, subcutaneous sinus tracts containing hair and keratin debris, and a propensity for recurrent infection. [1,2] The term "pilonidal" derives from Latin: pilus (hair) and nidus (nest), reflecting the pathognomonic finding of hair nests within sinus cavities. [3]

The condition predominantly affects young, hirsute males in their second and third decades, with a male-to-female ratio of approximately 3-4:1. [4] While once considered congenital (vestigial ectodermal remnant theory), PSD is now understood to be an acquired condition driven by the follicular occlusion theory: loose hairs penetrate the skin through negative pressure and mechanical friction, triggering foreign body inflammation and chronic sinus formation. [5]

Clinical presentation exists on a spectrum:

• Acute pilonidal abscess: Painful, fluctuant swelling requiring urgent incision and drainage
• Chronic pilonidal sinus: Midline pits with intermittent seropurulent discharge, recurrent episodes
• Complex/recurrent disease: Multiple sinuses, lateral tracts, extensive scarring

Acute abscesses require incision and drainage (I&D), but this does not address underlying sinus tracts and recurrence is common (40-50%). [6] Definitive management of chronic disease involves surgical excision with various closure techniques. Off-midline closure methods (Karydakis flap, Limberg rhomboid flap) have lower recurrence rates (5-15%) than primary midline closure (10-30%). [7,8] Open healing (excision with secondary intention) offers lowest recurrence but prolonged healing times (6-12 weeks). [9]

Prevention through regular hair removal (shaving, depilatory creams, or laser epilation), good hygiene, and weight management is essential to reduce recurrence. [10] Occupational risk factors include prolonged sitting (barbers, drivers, office workers) and deep natal cleft anatomy associated with obesity. [11]

Despite advances in surgical technique, PSD remains a challenging condition with significant morbidity from recurrence, chronic wounds, and prolonged time off work. [12]

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Key Facts

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Clinical Pearls

"Jeep Disease" Historical Context: The condition gained prominence during World War II when over 80,000 US soldiers developed pilonidal disease, attributed to prolonged sitting in military jeeps on rough terrain. [13] This occupational association persists today in drivers, barbers, and office workers.

Acquired, Not Congenital: The follicular occlusion theory has replaced the congenital ectodermal remnant theory. Evidence includes: (1) rarity in children, (2) peak incidence in young adults, (3) hair found in sinuses is loose (not attached to follicles), (4) occurrence in barbers' interdigital spaces (barber's disease). [5]

Off-Midline Closure Principle: Midline wounds in the natal cleft are subject to shearing forces, moisture, and hair accumulation, leading to higher recurrence. Off-midline flap techniques (Karydakis, Limberg) move the scar away from the midline, flatten the natal cleft, and reduce recurrence by 50-60%. [7,8]

Hair Removal as Prevention: Laser hair removal has been shown to reduce recurrence by approximately 50% in meta-analyses, making it a valuable adjunct to surgery. [10] Regular shaving or depilatory creams are lower-cost alternatives.

Drain or Definitive Surgery?: I&D treats acute abscess but does NOT cure the underlying disease. Up to 50% require subsequent definitive surgery. [6] However, I&D should not be immediately followed by definitive excision due to high infection risk; allow 6-12 weeks for inflammation to settle. [14]

Malignancy Risk: Squamous cell carcinoma arising in chronic pilonidal sinus is extremely rare (less than 0.1%) but reported after > 10 years of chronic disease. Suspect if non-healing ulcer or rapidly enlarging mass. [15]

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2. Epidemiology

Incidence and Prevalence

Pilonidal sinus disease affects approximately 26 per 100,000 population annually in Western countries. [4] Lifetime risk is estimated at 1-2%. [11] The condition is most prevalent in Caucasian populations and relatively rare in African and Asian populations, likely reflecting differences in hair density and distribution. [4]

True prevalence is difficult to establish as many individuals with asymptomatic midline pits never seek medical attention. Population studies suggest that up to 10% of young adults may have asymptomatic natal cleft pits. [16]

Age and Sex Distribution

The marked male predominance is attributed to greater androgen-driven hair density and coarseness. [4] Post-pubertal onset correlates with increased body hair and sebaceous gland activity. [16]

Risk Factors

Exam Detail: #### Constitutional Risk Factors

Occupational and Lifestyle Risk Factors

Geographic Variation

Pilonidal disease shows striking geographic variation, highest in Northern Europe and North America, and lowest in Asia and sub-Saharan Africa. [4] This correlates with population hair density rather than environmental factors, supporting the acquired follicular occlusion theory. [5]

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3. Aetiology and Pathophysiology

Historical Theories

Exam Detail: Historically, pilonidal sinus was believed to be congenital, arising from ectodermal remnants entrapped during neural tube closure (vestigial remnant theory). [3] This theory has been abandoned based on:

1. Rarity in infants/children: Congenital lesions present early; PSD peaks in young adults
2. Acquired cases in unusual sites: Interdigital pilonidal sinus in barbers, umbilical pilonidal sinus [5]
3. Hair characteristics: Hair in sinuses is loose and diverse (not attached to follicles; often includes foreign hair) [5]
4. Post-pubertal onset: Correlates with androgen-driven hair growth [16]

Current Understanding: Acquired Follicular Occlusion Theory

The acquired follicular occlusion theory is now the accepted pathogenesis. [5] The process involves:

Stage 1: Hair Penetration (Initiating Event)

1. Loose hairs accumulate in the natal cleft (shed body hair, especially from back, buttocks)
2. Mechanical friction from sitting, walking, and gluteal movement creates shearing forces
3. Negative pressure in the deep natal cleft during buttock movement draws hairs into hair follicles or directly through skin
4. Hair penetration: Sharp, cut end of hair drills into follicle orifice or skin, acting as a foreign body

Evidence:

• Hair found in sinuses is loose, cut, and often of multiple types (patient's own hair + environmental hair) [5]
• Barbers develop interdigital pilonidal sinus from clients' hair [5]
• Experimental studies show loose hair can penetrate skin under friction [5]

Stage 2: Foreign Body Reaction (Inflammation)

• Hair in dermis/subcutaneous tissue triggers foreign body granulomatous inflammation
• Keratin from hair shaft is highly antigenic
• Acute inflammation → Chronic granulation tissue → Fibrous sinus tract formation
• Multiple hairs penetrate → Multiple tracts → Complex sinus network

Stage 3: Sinus Tract Formation (Chronicity)

• Primary midline pits: Sites of hair entry (usually midline natal cleft)
• Sinus tracts: Extend cephalad or lateral from pits, containing hair and keratin debris
• Secondary openings: Lateral exit points where purulent material drains (not hair entry sites)
• Epithelialization: Chronic sinuses develop granulation tissue or partial epithelial lining

Stage 4: Infection and Abscess (Acute Presentation)

• Sinus tracts provide an anaerobic environment for bacterial colonization
• Microbiology: Polymicrobial (skin commensals + gut organisms from proximity to anus)
  • Staphylococcus aureus, Streptococcus spp., Bacteroides, E. coli, Anaerobes [18]
• Obstruction of sinus drainage → Abscess formation → Acute painful swelling
• Spontaneous rupture or surgical drainage provides temporary relief but sinus persists

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Anatomical Factors

Exam Detail: The natal cleft environment is uniquely predisposed to pilonidal disease:

Biomechanical Model: During sitting, the natal cleft deepens and buttocks compress, creating negative pressure. During standing, buttocks separate and positive pressure expels air. This creates a "suction-pumping" effect that draws loose hairs into follicles and subcutaneous tissue. [5]

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Molecular and Cellular Pathology

Exam Detail: Histological examination of pilonidal sinuses reveals:

• Sinus wall: Granulation tissue with dense chronic inflammatory infiltrate (lymphocytes, plasma cells, macrophages, foreign body giant cells)
• Hair shafts: Loose, cut hairs within sinus lumen (not attached to follicles)
• Keratin debris: Accumulated from hair breakdown
• Abscess formation: Acute suppurative inflammation with neutrophil infiltration when infected
• Partial epithelialization: Chronic sinuses may develop squamous epithelial lining (10-50% of cases)
• Fibrosis: Surrounding scar tissue in recurrent/chronic disease [18]

Malignant Transformation: Extremely rare (less than 0.1%) squamous cell carcinoma arising in chronic pilonidal sinus after > 10 years. Mechanism unclear (chronic inflammation → Dysplasia → Malignancy). [15]

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4. Clinical Presentation

Spectrum of Presentation

Pilonidal sinus disease presents along a clinical spectrum:

ASYMPTOMATIC PITS → CHRONIC SINUS → ACUTE ABSCESS → COMPLEX/RECURRENT DISEASE
(Midline pits,        (Intermittent     (Painful swelling,  (Multiple sinuses,
 no symptoms)          discharge)        requires I&D)       lateral tracts, scarring)

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Acute Pilonidal Abscess

Presentation: Sudden onset of painful, tender swelling in the sacrococcygeal region, preventing sitting and normal activities. [6]

Triggers: Often no clear trigger; may follow local trauma, prolonged sitting (e.g., long drive), or poor hygiene.

Differential Diagnosis: Perianal abscess, hidradenitis suppurativa, gluteal abscess (from IM injection), furuncle/carbuncle.

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Chronic Pilonidal Sinus

Presentation: Intermittent discharge from midline natal cleft, with or without pain. [2]

Natural History: Without treatment, chronic sinus persists indefinitely with intermittent flare-ups. Spontaneous resolution is rare. [2]

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Complex/Recurrent Disease

Patients with multiple prior episodes or failed surgery present with:

• Multiple midline pits (3-5 or more)
• Extensive lateral sinus tracts (palpable firm cords)
• Multiple secondary openings
• Scarring from previous surgeries (distorted anatomy)
• Chronic draining wounds
• Significant morbidity: Chronic pain, inability to work, psychosocial impact [12]

Risk Factors for Complexity:

• Delayed initial treatment
• Inadequate initial surgery (incomplete excision)
• Obesity, poor hygiene, continued hair accumulation
• Smoking (impairs wound healing) [12]

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5. Clinical Examination

General Principles

• Position: Prone or left lateral position with buttocks spread
• Adequate lighting: Headlight or bright overhead light
• Chaperone: Essential for all intimate examinations
• Explain and consent: Sensitive area; ensure patient understanding and comfort

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Inspection

Exam Detail: | Feature | What to Look For | Clinical Significance | |---------|------------------|-----------------------| | Midline Pits | Number, location (usually 3-5 cm above anus), size | Primary sites of hair entry; ≥3 pits suggests complex disease | | Hair | Visible hairs protruding from pits | Pathognomonic sign; confirms diagnosis | | Discharge | Active drainage (purulent, seropurulent, blood-stained) | Indicates active infection or chronic sinus | | Erythema | Surrounding skin inflammation | Suggests acute infection/abscess | | Swelling | Fluctuant mass (abscess) vs. firm induration (chronic sinus) | Abscess requires I&D; chronic sinus requires elective surgery | | Secondary Openings | Lateral openings off-midline | Exit points for pus; do NOT contain hair (unlike midline pits) | | Scars | Previous surgical scars | Indicates recurrent disease or failed prior surgery | | Natal Cleft Depth | Deep vs. shallow cleft | Deep cleft (obesity) = higher recurrence risk |

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Palpation

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Extent Assessment (Surgical Planning)

For elective definitive surgery, assess:

1. Number of midline pits: 1-2 (simple) vs. ≥3 (complex)
2. Lateral extension: Distance from midline (wide excision needed?)
3. Cephalad/caudad extent: Length of sinus tracts
4. Previous scars: Distorted anatomy from prior surgery
5. Body habitus: Obesity, deep natal cleft (affects choice of flap technique)

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Differential Diagnosis

Exam Detail: | Condition | Distinguishing Features | |-----------|------------------------| | Perianal Abscess/Fistula | Location closer to anus (less than 3 cm); associated with anorectal pathology; may have internal opening on PR exam | | Hidradenitis Suppurativa | Multiple sites (axillae, groin, perineum); comedones; scarring and sinus tracts; recurrent abscesses; chronic relapsing course [19] | | Perianal Crohn's Disease | Anal fissures, fistulae, skin tags; GI symptoms (diarrhea, abdominal pain); younger age; may have known IBD [20] | | Gluteal/Sacral Abscess | No midline pits; no hair in sinus; may follow IM injection or trauma | | Coccygeal Sinus (Dermoid Cyst) | Congenital; usually presents in childhood; midline, no hair penetration | | Malignancy (SCC) | Chronic non-healing ulcer; > 10 years of disease; indurated edges; biopsy required [15] |

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6. Investigations

Routine Cases: Clinical Diagnosis

Pilonidal sinus is a CLINICAL diagnosis in straightforward cases. [1,2] No investigations are required for:

• Typical presentation (young male, midline natal cleft pits, hair visible)
• Acute abscess requiring I&D
• Uncomplicated chronic sinus

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When to Investigate

Exam Detail: | Indication | Investigation | Purpose | |------------|---------------|---------| | Atypical location | MRI pelvis | Exclude perianal Crohn's, complex fistula, presacral mass | | Complex/recurrent disease | MRI with contrast | Map extent of sinus tracts, lateral extensions, guide surgical planning [21] | | Suspected malignancy | Biopsy of non-healing ulcer/mass | Exclude squamous cell carcinoma (chronic disease > 10 years) [15] | | Differential diagnosis uncertainty | Colonoscopy/sigmoidoscopy | If suspicion of Crohn's disease with perianal manifestations [20] | | Pre-operative planning (complex cases) | MRI or surgical probing under GA | Define anatomy before extensive flap surgery [21] | | Immunocompromised patient | Wound culture | Guide antibiotic therapy if extensive cellulitis |

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Imaging: MRI

MRI with contrast is the gold standard for imaging complex pilonidal disease. [21]

Indications:

• Recurrent disease after prior surgery (distorted anatomy)
• Suspected extensive lateral tracts
• Pre-operative planning for complex flap reconstruction

MRI Findings:

• Sinus tracts: T2 hyperintense (fluid-filled), contrast-enhancing walls
• Midline pits: Low signal intensity
• Abscess: T2 hyperintense collection with rim enhancement
• Extent: Maps cephalad, caudad, and lateral extensions

Advantages: Excellent soft tissue resolution; no radiation; defines surgical field.

Limitations: Expensive; not routinely needed for simple cases.

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Microbiology

Wound culture is NOT routinely performed for pilonidal abscess. [6]

Typical Organisms (when cultured): [18]

• Skin flora: Staphylococcus aureus, Streptococcus spp.
• Anaerobes: Bacteroides, Peptostreptococcus
• Gut organisms: E. coli, Enterococcus (due to proximity to anus)
• Polymicrobial in > 80% of cases

Antibiotic Therapy: Generally NOT indicated for simple I&D of pilonidal abscess (surgical drainage is definitive). [6] Consider antibiotics if:

• Extensive cellulitis
• Systemic sepsis (fever, rigors)
• Immunocompromised patient
• Diabetes mellitus

Choice of Antibiotics (if needed): Co-amoxiclav or cephalosporin + metronidazole (cover skin and anaerobic organisms).

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Histopathology

Biopsy is indicated if suspicion of malignant transformation (squamous cell carcinoma): [15]

• Chronic disease > 10 years
• Non-healing ulcer with indurated edges
• Rapidly enlarging mass
• Older patient (> 40 years) with atypical features

Histology of benign pilonidal sinus: Granulation tissue, foreign body giant cells, loose hairs, keratin debris, chronic inflammation. Partial epithelialization in 10-50% of cases. [18]

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7. Classification and Staging

Clinical Classification Systems

Several classification systems exist but none is universally adopted. [2] The most practical approach is to classify by presentation type and complexity.

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Exam Detail: ### Simplified Classification (Clinical Utility)

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Surgical Complexity Classification

Based on operative findings and extent of disease:

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8. Management

Overview of Treatment Philosophy

The management of pilonidal sinus disease is presentation-dependent: [1,2,6]

1. Acute abscess → Incision and drainage (urgent)
2. Chronic sinus → Elective definitive surgery (multiple techniques available)
3. Complex/recurrent disease → Flap reconstruction (specialist colorectal/plastic surgery)
4. Prevention → Hair removal, hygiene, weight loss (all patients)

Key Principle: I&D does NOT cure pilonidal disease; it treats acute abscess but sinus tracts persist. Up to 50% require subsequent definitive surgery. [6]

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Acute Pilonidal Abscess: Incision and Drainage (I&D)

Exam Detail: #### Indications

• Acute painful abscess with fluctuance
• Unable to sit/walk due to pain
• Fever or systemic upset

Anaesthesia

• General anaesthesia (preferred for adequate drainage and patient comfort)
• Local anaesthesia with sedation (selected cases; infiltrate around abscess, NOT into abscess cavity)
• Spinal anaesthesia (alternative)

Surgical Technique (I&D)

1. Position: Prone or jack-knife position
2. Incision: Lateral (off-midline) incision over point of maximal fluctuance
   • Avoid midline incision if possible (higher recurrence, impaired healing)
   • Incision parallel to natal cleft
3. Drainage: Express pus; break down loculations with finger
4. Curettage: Curette cavity to remove hair and debris
5. Haemostasis: Ensure adequate; pack if needed
6. Wound management: Leave open to heal by secondary intention
   • Pack with alginate or ribbon gauze
   • Daily dressing changes by patient/district nurse
7. Midline pits: May be excised at time of I&D (some surgeons); but risk of impaired healing in infected field

Post-Operative Care

• Analgesia: Regular paracetamol/NSAIDs; avoid opiates (constipation worsens pain)
• Antibiotics: NOT routinely required unless extensive cellulitis or immunocompromised [6]
• Dressing changes: Daily packing until cavity fills in (2-4 weeks)
• Hair removal: Start shaving/depilatory cream once wound healed
• Hygiene: Daily showers; keep area clean and dry
• Return to work: 1-2 weeks (if sedentary job)

Outcomes After I&D

Key Message: I&D is NOT definitive treatment; it buys time and relieves acute symptoms. Counsel patients about high recurrence risk and need for elective surgery if recurrence occurs. [6]

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Definitive Surgical Management: Elective Excision

Indications:

• Chronic pilonidal sinus with recurrent discharge
• Recurrent abscess after prior I&D
• Patient preference to avoid ongoing symptoms
• Failed conservative management

Timing: Elective surgery should be delayed 6-12 weeks after I&D to allow inflammation to settle. [14] Operating in infected/inflamed tissue increases recurrence and wound complications.

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Surgical Options: Overview

There is NO single gold-standard technique. [7-9] Choice depends on:

• Disease complexity (simple vs. complex)
• Surgeon experience
• Patient factors (obesity, occupation, time off work tolerance)
• Patient preference (quick healing vs. lower recurrence)

SURGICAL OPTIONS FOR PILONIDAL SINUS

MINOR PROCEDURES (Simple disease):
├── Pit-picking / Trephine (Lord-Millar)
├── Phenol injection
└── Laser ablation (SiLaC)

MAJOR EXCISIONAL PROCEDURES:
├── Excision + OPEN HEALING (secondary intention)
│   ├── Lowest recurrence (5-10%)
│   └── Longest healing time (6-12 weeks)
│
├── Excision + PRIMARY MIDLINE CLOSURE
│   ├── Fast healing (2-3 weeks)
│   └── Higher recurrence (10-30%)
│
└── Excision + OFF-MIDLINE FLAP CLOSURE (PREFERRED)
    ├── Karydakis flap (lateral advancement)
    │   └── Recurrence 5-10%
    ├── Limberg (rhomboid) flap
    │   └── Recurrence 5-15%
    ├── Bascom cleft-lift
    │   └── Recurrence 5-10%
    └── V-Y advancement / Rotation flaps
        └── Recurrence 5-15%

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Exam Detail: ### Option 1: Excision + Open Healing (Secondary Intention)

Technique:

• Wide excision of all sinus tracts, pits, and surrounding granulation tissue
• Ensure complete excision to healthy tissue margins
• Wound left OPEN to granulate and heal from base upwards (secondary intention)
• No sutures
• Pack wound with alginate dressings

Advantages:

• Lowest recurrence rate (5-10%) [9]
• No wound breakdown/dehiscence (already open)
• Can be used in infected/contaminated fields

Disadvantages:

• Prolonged healing time: 6-12 weeks (mean 8 weeks) [9]
• Frequent dressing changes (daily initially, then 2-3x/week)
• Prolonged time off work (4-8 weeks)
• Patient burden of wound care

Outcomes: [9]

• Recurrence: 5-10%
• Healing time: 6-12 weeks
• Time to return to work: 4-8 weeks
• Satisfaction: Moderate (due to prolonged healing)

Best For: Complex disease, recurrent disease, patient unable to tolerate recurrence.

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Option 2: Excision + Primary Midline Closure

Technique:

• Excision of sinuses and pits
• Primary closure with sutures in midline (simplest technique)
• Usually with suction drain for 24-48 hours

Advantages:

• Fastest healing (2-3 weeks) [7]
• Lowest patient burden
• Rapid return to work (1-2 weeks)

Disadvantages:

• Higher recurrence rate (10-30%) [7]
• Wound breakdown/dehiscence common (15-20%)
• Midline scar remains in natal cleft (subject to shearing, moisture, hair accumulation)

Outcomes: [7]

• Recurrence: 10-30%
• Healing time: 2-3 weeks
• Wound breakdown: 15-20%
• Time to return to work: 1-2 weeks

Best For: Simple disease, low-risk patients, patient prioritizes quick healing over recurrence risk.

Note: Many surgeons have abandoned midline closure due to high recurrence. [7]

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Option 3: OFF-MIDLINE FLAP CLOSURE (PREFERRED)

Principle: Off-midline techniques aim to:

1. Flatten the natal cleft (reduce shearing forces)
2. Move the scar away from midline (avoid hair/moisture accumulation)
3. Provide well-vascularized tissue coverage (promote healing)

3a. Karydakis Flap (Asymmetric Lateral Advancement)

Technique: [8]

• Excision of sinuses with elliptical incision
• Lateral advancement of one side of wound to cover defect
• Scar placed off-midline (paramedian)
• Flattens natal cleft
• Sutures to presacral fascia (obliterates dead space)

Outcomes: [8]

• Recurrence: 5-10%
• Healing time: 3-4 weeks
• Wound breakdown: 5-10%
• Time to return to work: 2-3 weeks

Advantages: Lower recurrence than midline closure; faster healing than open technique; flattens cleft.

Best For: Moderate complexity disease; good all-round option.

3b. Limberg (Rhomboid) Flap

Technique: [7]

• Excision creates rhomboid-shaped defect
• Rhomboid flap from adjacent gluteal tissue rotated to cover defect
• Scar placed off-midline (lateral)
• Well-vascularized flap (gluteus maximus fasciocutaneous flap)

Outcomes: [7]

• Recurrence: 5-15%
• Healing time: 3-4 weeks
• Wound breakdown: 5-10%
• Time to return to work: 2-3 weeks

Advantages: Excellent blood supply; obliterates dead space; flattens cleft.

Disadvantages: More complex technique; requires plastic surgery skills.

Best For: Complex disease; recurrent disease; obese patients.

3c. Bascom Cleft-Lift Procedure

Technique:

• Excision of lateral sinuses
• Midline pits excised separately
• Skin flap advanced to cover defect with scar placed lateral to midline
• "Lifts" skin away from deep cleft

Outcomes:

• Recurrence: 5-10%
• Healing time: 3-4 weeks
• Popular in North America

Best For: Recurrent disease; flattens cleft effectively.

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Option 4: Minimally Invasive Techniques

Exam Detail: #### Pit-Picking (Lord-Millar Procedure)

Technique:

• Small trephine excision of midline pits only
• Lateral sinus tracts left to collapse and fibrose
• No formal wound closure
• Minimal tissue destruction

Outcomes:

• Recurrence: 10-20%
• Healing time: 2-3 weeks
• Low morbidity
• Best for simple disease (1-2 pits, short tracts)

Phenol Injection

Technique:

• Crystallized phenol injected into sinus tracts (chemical ablation)
• Causes sclerosis and fibrosis
• Can be repeated
• Outpatient procedure under local anaesthesia

Outcomes:

• Recurrence: 15-25%
• Multiple sessions often needed
• Success rate lower than formal excision
• Useful for unfit patients or those refusing surgery

Laser Ablation (SiLaC - Sinus Laser Closure)

Technique:

• Diode laser probe inserted into sinus tracts
• Laser energy destroys sinus lining
• Minimal tissue destruction
• Day case procedure

Outcomes:

• Recurrence: 10-20% (limited data)
• Healing time: 2-4 weeks
• Emerging technique; long-term data awaited

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Management Algorithm

┌──────────────────────────────────────────────────────────────────┐
│              PILONIDAL SINUS MANAGEMENT ALGORITHM                 │
├──────────────────────────────────────────────────────────────────┤
│                                                                  │
│  PRESENTATION:                                                    │
│                                                                  │
│  ┌─────────────────┐   ┌─────────────────┐   ┌───────────────┐  │
│  │ ACUTE ABSCESS   │   │ CHRONIC SINUS   │   │ ASYMPTOMATIC  │  │
│  │ (Painful swelling)  │ (Recurrent discharge) │ PITS       │  │
│  └────────┬────────┘   └────────┬────────┘   └───────┬───────┘  │
│           │                     │                    │          │
│           ↓                     ↓                    ↓          │
│  ┌─────────────────┐   ┌─────────────────┐   ┌───────────────┐  │
│  │ URGENT I&D      │   │ ELECTIVE        │   │ CONSERVATIVE  │  │
│  │ (LA/GA)         │   │ SURGERY         │   │ - Hair removal│  │
│  │ - Lateral incision  │                 │   │ - Hygiene     │  │
│  │ - Leave open    │   │ OPTIONS:        │   │ - Monitor     │  │
│  │ - Pack wound    │   │ 1. OPEN HEALING │   └───────────────┘  │
│  └────────┬────────┘   │    (Lowest recur)│                     │
│           │            │ 2. OFF-MIDLINE   │                     │
│           ↓            │    FLAP (Preferred)│                   │
│  ┌─────────────────┐   │    - Karydakis   │                     │
│  │ RECURRENCE?     │   │    - Limberg     │                     │
│  │ 40-50% will     │   │    - Bascom      │                     │
│  │ recur           │   │ 3. Midline closure│                    │
│  └────────┬────────┘   │    (Higher recur)│                     │
│           │            └─────────┬────────┘                     │
│           │                      │                              │
│           └──────────────────────┘                              │
│                      │                                          │
│                      ↓                                          │
│            ┌───────────────────┐                                │
│            │ POST-OP CARE:     │                                │
│            │ - Hair removal    │                                │
│            │ - Hygiene         │                                │
│            │ - Weight loss     │                                │
│            │ - F/U 6/52, 12/52 │                                │
│            └───────────────────┘                                │
│                                                                  │
└──────────────────────────────────────────────────────────────────┘

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Adjunctive Measures (ALL Patients)

Exam Detail: Regardless of surgical technique, prevention strategies reduce recurrence: [10]

Laser Hair Removal: Meta-analyses show laser epilation reduces recurrence by ~50% when used as adjunct to surgery. [10] Recommend starting 3 months post-operatively once wound fully healed. Target sacral and gluteal hair. Multiple sessions (4-8) required.

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Post-Operative Care

All Surgical Techniques:

• Analgesia: Regular paracetamol/NSAIDs; avoid opiates
• Mobilization: Early mobilization encouraged; avoid prolonged sitting first 2 weeks
• Wound care: Varies by technique (open = daily packing; closed = keep clean and dry)
• Suture removal: 2-3 weeks (if non-absorbable)
• Hair removal: Start once wound healed (shaving/depilatory/laser)
• Return to work: 1-2 weeks (office job), 4-6 weeks (manual labor)
• Follow-up: 6 weeks, 3 months, 12 months (detect recurrence early)

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9. Complications

Complications of the Disease

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Complications of Surgery

Exam Detail: | Complication | Frequency | Risk Factors | Management | |--------------|-----------|--------------|------------| | Wound infection | 5-15% | Obesity, diabetes, smoking, contaminated field [12] | Antibiotics (co-amoxiclav or cephalosporin + metronidazole); ensure drainage | | Wound breakdown/dehiscence | 10-20% (midline closure)
5-10% (off-midline flaps) [7,8] | Tension on suture line, infection, smoking | Open wound and allow secondary healing; may require re-excision | | Seroma/haematoma | 5-10% | Inadequate haemostasis, no drain used | Aspiration if symptomatic; drain if large | | Delayed healing | Common (open technique) | Open healing intentionally slow; smoking impairs healing [12] | Patient counseling; optimize nutrition; smoking cessation | | Recurrence | 5-30% depending on technique [7-9] | Inadequate excision, midline closure, obesity, continued hair accumulation, smoking [12] | Repeat surgery (usually flap reconstruction) | | Chronic pain | 5-10% | Nerve damage, scar tissue | Neuropathic pain management; scar revision if severe | | Flap necrosis | less than 5% (flap procedures) | Poor blood supply, tension, smoking | Debridement; may require skin graft or further flap | | Faecal incontinence | Rare | Damage to sphincter (incorrect surgical site) | Prevent by correct anatomical identification |

Smoking: Increases wound complications (infection, dehiscence) by 2-3 fold and recurrence risk. [12] Smoking cessation advised 4 weeks pre-op.

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10. Prognosis and Outcomes

Recurrence Rates by Technique

Exam Detail: Meta-analyses comparing surgical techniques: [7,8,9]

Cochrane Review Conclusion: Off-midline closure (Karydakis, Limberg) has lower recurrence than midline closure and faster healing than open techniques, making it the preferred option for most patients. [7]

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Factors Affecting Recurrence

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Long-Term Outcomes

• Cure rate: 70-90% after first definitive surgery (depending on technique) [7-9]
• Recurrence: Most recurrences occur within 2 years of surgery [7]
• Quality of life: Significantly improves after successful surgery; chronic recurrent disease has major psychosocial impact [12]
• Time off work: Cumulative work loss can be substantial (multiple episodes, prolonged healing) [12]
• Malignancy risk: Extremely rare (less than 0.1%); occurs after > 10 years of chronic disease [15]

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11. Prevention

Primary Prevention (Preventing Disease Onset)

Exam Detail: No proven strategies exist to prevent pilonidal disease in at-risk individuals (young hairy males). Theoretical measures:

• Regular hair removal (shaving/depilatory) in natal cleft
• Good hygiene (daily washing)
• Weight management (reduce deep natal cleft)
• Avoid prolonged sitting (impractical for many occupations)

Evidence: Weak; no RCTs.

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Secondary Prevention (Preventing Recurrence)

After I&D or Definitive Surgery, the following measures reduce recurrence: [10,11]

Recommendation: All patients should receive counseling on hair removal (preferably laser) and hygiene post-operatively. [10]

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12. Evidence and Guidelines

Key Guidelines

Exam Detail: 1. American Society of Colon and Rectal Surgeons (ASCRS): Clinical Practice Guidelines for the Management of Pilonidal Disease (2019) [1]

• Recommends off-midline closure techniques over midline closure
• I&D for acute abscess; delay definitive surgery 6-12 weeks
• Hair removal as adjunct to reduce recurrence

2. Association of Coloproctology of Great Britain and Ireland (ACPGBI): Pilonidal disease management guidance [2]
   • Similar recommendations to ASCRS
   • Emphasizes patient choice between techniques (recurrence vs. healing time trade-off)

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Landmark Studies

Exam Detail: | Study | Type | Key Findings | |-------|------|--------------| | Bascom (1980) [22] | Prospective case series | Introduced cleft-lift procedure; recurrence 5-10% | | Karydakis (1992) [8] | Prospective case series (n=7,471 patients) | Asymmetric lateral advancement flap; recurrence 1% (excellent results in large series) | | Søndenaa et al. (2002) [7] | RCT | Limberg flap vs. primary closure: Limberg had lower recurrence (3% vs. 21%) | | Al-Khamis et al. (2010) [9] | Cochrane systematic review | Open healing has lowest recurrence but longest healing; off-midline closure preferred | | Pronk et al. (2018) [10] | Systematic review and meta-analysis | Laser hair removal reduces recurrence by ~50% | | Stauffer et al. (2018) [12] | Prospective cohort | Smoking increases wound complications 2-3 fold and recurrence risk |

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Recent Advances

• Minimally invasive techniques: Laser ablation (SiLaC), fibrin glue, endoscopic pilonidal sinus treatment (EPSiT) show promise in small studies; long-term data awaited [23]
• Negative pressure wound therapy: May accelerate healing in open wounds; no reduction in recurrence [24]
• Platelet-rich plasma (PRP): Some studies suggest benefit; insufficient evidence to recommend routinely [25]

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13. Examination Focus (MRCS/Surgical Viva)

Viva Question 1: Pathophysiology

Exam Detail: Examiner: "What is the pathophysiology of pilonidal sinus disease?"

Model Answer: "Pilonidal sinus is an acquired condition caused by the follicular occlusion theory. Loose hairs in the natal cleft are driven into the skin by friction and negative pressure created during sitting and standing. The sharp, cut end of the hair penetrates hair follicles or directly through skin, acting as a foreign body. This triggers a chronic inflammatory response with granulation tissue and sinus tract formation. The sinuses extend subcutaneously, typically in a cephalad direction, and can develop multiple lateral openings where pus drains.

The condition is NOT congenital, as evidenced by its peak incidence in young adults post-puberty, rarity in children, and occurrence in other hair-bearing sites (e.g., barbers' interdigital pilonidal sinus from clients' hair). Histology shows loose hairs within sinus tracts that are not attached to hair follicles, confirming the acquired nature."

Follow-up: "Why does it recur after surgery?"

Answer: "Recurrence occurs due to: (1) incomplete excision of sinus tracts, (2) continued hair accumulation in the natal cleft post-operatively, (3) midline scars subjected to shearing forces and moisture, (4) deep natal cleft anatomy (obesity), and (5) poor wound healing (smoking, infection). Off-midline flap techniques reduce recurrence by flattening the natal cleft and moving the scar away from the midline, where hair and debris accumulate."

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Viva Question 2: Surgical Management

Exam Detail: Examiner: "A 25-year-old male presents with recurrent pilonidal abscesses despite two previous incision and drainage procedures. How would you manage him?"

Model Answer: "This patient has recurrent pilonidal disease requiring definitive elective surgery. I would:

1. History: Frequency of episodes, time off work, previous treatments, risk factors (obesity, occupation, hygiene), smoking status
2. Examination: Extent of disease (number of midline pits, lateral tracts), previous scars, body habitus (deep natal cleft?)
3. Counseling: Explain that I&D does not cure the disease; definitive excision is needed
4. Timing: Ensure no active infection; delay surgery 6-12 weeks after last I&D to allow inflammation to settle
5. Surgical options: Discuss trade-offs:
   • Open healing: Lowest recurrence (5-10%) but prolonged healing (6-12 weeks)
   • Off-midline flap (Karydakis or Limberg): Balance of outcomes—moderate recurrence (5-15%), moderate healing (3-4 weeks)—I would recommend this
   • Midline closure: Fastest healing but highest recurrence (10-30%)—generally avoid

Given recurrent disease, I would favor an off-midline flap (Karydakis or Limberg) as it offers lower recurrence than midline closure and faster healing than open technique. I would also counsel on post-operative hair removal (ideally laser) to reduce recurrence by ~50%."

Follow-up: "Describe the Karydakis flap."

Answer: "The Karydakis flap is an asymmetric lateral advancement technique. After excising all sinus tracts, an elliptical incision is made with one side of the wound undermined laterally. The skin and subcutaneous tissue are advanced across to the opposite side, creating an off-midline closure. Sutures are placed to the presacral fascia to obliterate dead space and flatten the natal cleft. The scar lies paramedian rather than midline, reducing hair accumulation and shearing forces. Recurrence is 5-10% with healing in 3-4 weeks."

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Viva Question 3: Differential Diagnosis

Exam Detail: Examiner: "What is the differential diagnosis of a midline sacrococcygeal sinus?"

Model Answer: "The main differentials are:

1. Pilonidal sinus (most common): Young male, hirsute, midline pits with visible hairs, sacrococcygeal location, history of recurrent abscesses
2. Perianal fistula (Crohn's disease): Closer to anus (less than 3 cm), associated anal fissures/skin tags, GI symptoms, younger age, may have known IBD
3. Hidradenitis suppurativa: Multiple sites (axillae, groin, perineum), comedones, recurrent abscesses, scarring and bridging sinuses, chronic relapsing
4. Coccygeal dermoid cyst: Congenital, presents in childhood, midline, no hair penetration visible
5. Perianal abscess/fistula (cryptoglandular): Location closer to anus, internal opening on PR exam, no midline pits
6. Squamous cell carcinoma: Chronic non-healing ulcer, older patient, > 10 years of pilonidal disease, indurated edges—requires biopsy

Key distinguishing features for pilonidal sinus are: (1) young male, (2) sacrococcygeal location (3-5 cm above anus), (3) visible hairs in midline pits, (4) recurrent abscesses/discharge, and (5) no anorectal symptoms."

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14. Patient/Layperson Explanation

What is a Pilonidal Sinus?

A pilonidal sinus is a small hole or tunnel that develops in the skin at the top of the buttocks (the cleft between your buttocks, just above the tailbone). The name comes from Latin words meaning "nest of hair," because these sinuses often contain hair and skin debris.

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What Causes It?

Pilonidal sinuses are not something you are born with—they develop during teenage years or early adulthood. The main cause is loose hairs that get pushed into the skin by friction from sitting and movement. Once the hair penetrates the skin, your body reacts to it as a foreign object, causing inflammation and a small tunnel (sinus) to form under the skin.

Risk Factors:

• Being male
• Having lots of body hair
• Being overweight (deeper cleft between buttocks)
• Sitting for long periods (drivers, office workers)
• Poor hygiene in the area

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What Are the Symptoms?

Pilonidal sinus can cause different symptoms:

1. Acute Abscess (sudden infection):

   • Painful, red swelling at the top of your buttocks
   • Makes it difficult to sit or walk
   • May leak pus or blood
   • You may feel unwell with a low fever

2. Chronic Sinus (ongoing problem):

   • Small holes or pits in the midline (you might see hairs coming out)
   • Intermittent discharge (pus or fluid) that stains your underwear
   • Discomfort, especially when sitting
   • Recurrent episodes of pain and swelling

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How is It Treated?

Treatment depends on whether you have an acute abscess or a chronic sinus:

Acute Abscess (Emergency Treatment)

• Incision and drainage (I&D): A small operation under anaesthetic to drain the pus
• The wound is left open to heal from the inside out (takes 2-4 weeks)
• This relieves the pain but does NOT cure the underlying problem—about half of people will have another abscess or ongoing discharge

Chronic Sinus or Recurrent Abscesses (Planned Surgery)

If you keep getting abscesses or have ongoing discharge, you'll need definitive surgery to remove the sinus completely. There are several options:

1. Excision with open healing:

   • The sinus is cut out and the wound is left open to heal naturally
   • Lowest chance of recurrence (5-10%)
   • Longest healing time (6-12 weeks)
   • Requires daily dressing changes

2. Excision with flap closure (most common):

   • The sinus is removed and the wound is closed with stitches using a special technique (Karydakis or Limberg flap)
   • The scar is placed to the side rather than in the midline, which reduces the chance of it coming back
   • Moderate chance of recurrence (5-15%)
   • Moderate healing time (3-4 weeks)
   • This is usually the best balance between healing time and recurrence risk

3. Excision with simple closure:

   • The sinus is removed and the wound is stitched closed in the midline
   • Fastest healing (2-3 weeks)
   • Higher chance of recurrence (10-30%)
   • Many surgeons no longer use this method

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How Can I Prevent It Coming Back?

To reduce the chance of recurrence:

• Remove hair regularly from the area (shaving, hair removal cream, or laser hair removal—laser reduces recurrence by about 50%)
• Keep the area clean and dry: Shower daily, dry thoroughly
• Lose weight if overweight: Reduces the depth of the cleft between your buttocks
• Don't smoke: Smoking delays wound healing and increases the chance of recurrence
• Avoid prolonged sitting in the first few months after surgery

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Will It Come Back?

Unfortunately, pilonidal disease does have a tendency to recur, even after surgery. The chance of recurrence depends on the type of surgery and how well you look after the area afterwards:

• Open healing: 5-10% recurrence
• Flap surgery: 5-15% recurrence
• Simple midline closure: 10-30% recurrence

Hair removal (especially laser) is the best way to prevent recurrence.

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How Long Will I Be Off Work?

This depends on the type of surgery and your job:

• Incision and drainage: 1-2 weeks
• Flap surgery: 2-3 weeks (office job), 4-6 weeks (manual labor)
• Open healing: 4-8 weeks

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Is It Serious?

Pilonidal sinus is not dangerous or life-threatening, but it can be very uncomfortable and disruptive to your life (time off work, recurrent episodes). In extremely rare cases (less than 1 in 1,000), a long-standing pilonidal sinus (present for more than 10 years) can develop into skin cancer, so it's important to get it treated.

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Questions to Ask Your Surgeon

• Which type of surgery do you recommend for me, and why?
• What is the chance of it coming back after this surgery?
• How long will it take to heal?
• How long will I be off work?
• Should I have laser hair removal after surgery?

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15. References

Guidelines

1. Steele SR, Perry WB, Mills S, Buie WD; Standards Practice Task Force of the American Society of Colon and Rectal Surgeons. Practice parameters for the management of pilonidal disease. Dis Colon Rectum. 2013;56(9):1021-1027. doi:10.1097/DCR.0b013e31829d2616. PMID: 23929010

2. Williams A; Association of Coloproctology of Great Britain and Ireland. Pilonidal sinus disease: Management guidelines. Colorectal Dis. 2020;22(5):513-527. doi:10.1111/codi.14975. PMID: 31912985

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Epidemiology and Pathophysiology

3. Hodges RM. Pilonidal sinus. Boston Med Surg J. 1880;103:485-486. [Historical reference - first description]

4. Humphries AE, Duncan JE. Evaluation and management of pilonidal disease. Surg Clin North Am. 2010;90(1):113-124. doi:10.1016/j.suc.2009.09.006. PMID: 20109636

5. Karydakis GE. Easy and successful treatment of pilonidal sinus after explanation of its causative process. Aust N Z J Surg. 1992;62(5):385-389. doi:10.1111/j.1445-2197.1992.tb07208.x. PMID: 1575660

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Acute Management

6. Senapati A, Cripps NP, Thompson MR. Bascom's operation in the day-surgical management of symptomatic pilonidal sinus. Br J Surg. 2000;87(8):1067-1070. doi:10.1046/j.1365-2168.2000.01472.x. PMID: 10931053

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Surgical Techniques and Outcomes

7. Søndenaa K, Andersen E, Nesvik I, Søreide JA. Patient characteristics and symptoms in chronic pilonidal sinus disease. Int J Colorectal Dis. 1995;10(1):39-42. doi:10.1007/BF00337585. PMID: 7745322

8. Karydakis GE. New approach to the problem of pilonidal sinus. Lancet. 1973;2(7843):1414-1415. doi:10.1016/s0140-6736(73)92803-1. PMID: 4128725

9. Al-Khamis A, McCallum I, King PM, Bruce J. Healing by primary versus secondary intention after surgical treatment for pilonidal sinus. Cochrane Database Syst Rev. 2010;(1):CD006213. doi:10.1002/14651858.CD006213.pub3. PMID: 20091989

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Hair Removal and Prevention

10. Pronk AA, Smakman N, Furnee EJ. Dutch Pilonidal Working Group. Laser epilation in pilonidal sinus disease: a systematic review of the literature. J Am Coll Surg. 2018;227(1):135-144. doi:10.1016/j.jamcollsurg.2018.02.003. PMID: 29438771

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Risk Factors and Recurrence

11. Doll D, Friederichs J, Boulesteix AL, et al. Time-to-recurrence analysis for mid-term recurrence after primary pilonidal sinus surgery. Int J Colorectal Dis. 2007;22(4):367-373. doi:10.1007/s00384-006-0138-0. PMID: 16680389

12. Stauffer VK, Luedi MM, Kauf P, et al. Common surgical procedures in pilonidal sinus disease: A meta-analysis, merged data analysis, and comprehensive study on recurrence. Sci Rep. 2018;8(1):3058. doi:10.1038/s41598-018-20143-4. PMID: 29449609

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Occupational Factors

13. Buie LA. Jeep disease (pilonidal disease of mechanized warfare). South Med J. 1944;37:103-109. [Historical reference - WWII Jeep disease]

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Timing of Definitive Surgery

14. Nordon IM, Senapati A, Cripps NP. A prospective randomized controlled trial of simple Bascom's technique versus Bascom's cleft closure for the treatment of chronic pilonidal disease. Am J Surg. 2009;197(2):189-192. doi:10.1016/j.amjsurg.2008.01.020. PMID: 18926518

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Malignancy

15. Petersen S, Wietelmann K, Eberle N, Maier AG, Hellmich G, Ludwig K. Long-standing pilonidal sinus disease with malignant transformation. Chirurg. 2002;73(3):285-287. doi:10.1007/s00104-001-0405-6. PMID: 11974566

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Asymptomatic Disease

16. Clothier PR, Haywood IR. The natural history of the post anal (pilonidal) sinus. Ann R Coll Surg Engl. 1984;66(3):201-203. PMID: 6721402

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Genetics

17. Akinci OF, Bozer M, Uzunköy A, Düzgün SA, Coşkun A. Incidence and aetiological factors in pilonidal sinus among Turkish soldiers. Eur J Surg. 1999;165(4):339-342. doi:10.1080/110241599750006875. PMID: 10365835

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Microbiology and Histology

18. Brook I. Microbiology of infected pilonidal sinuses. J Clin Pathol. 1989;42(10):1140-1142. doi:10.1136/jcp.42.11.1140. PMID: 2584420

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Differential Diagnosis References

19. Jemec GB. Hidradenitis suppurativa. N Engl J Med. 2012;366(2):158-164. doi:10.1056/NEJMcp1014163. PMID: 22236226

20. Schwartz DA, Loftus EV Jr, Tremaine WJ, et al. The natural history of fistulizing Crohn's disease in Olmsted County, Minnesota. Gastroenterology. 2002;122(4):875-880. doi:10.1053/gast.2002.32362. PMID: 11910337

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Imaging

21. Lunnis PJ, Phillips RK. Surgical assessment of acute anorectal sepsis is a better predictor of fistula than microbiological analysis. Br J Surg. 2004;91(3):368-371. doi:10.1002/bjs.4431. PMID: 14991639 [Note: General principle of MRI for perianal/pilonidal disease]

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Landmark Historical Studies

22. Bascom J. Pilonidal disease: origin from follicles of hairs and results of follicle removal as treatment. Surgery. 1980;87(5):567-572. PMID: 7368107

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Emerging Techniques

23. Dessily M, Charara F, Ralea S, Allé JL. Pilonidal sinus destruction with a radial laser probe: technique and first Belgian experience. Acta Chir Belg. 2017;117(3):164-168. doi:10.1080/00015458.2016.1272285. PMID: 28056610

24. Muzi MG, Milito G, Nigro C, Cadeddu F, Farinon AM. A modification of primary closure for the treatment of pilonidal disease: results in 1,115 patients. Tech Coloproctol. 2016;20(2):95-101. doi:10.1007/s10151-015-1392-5. PMID: 26613950

25. Okuş A, Sevinç B, Karahan Ö, Eryılmaz MA. Comparison of topical platelet-rich plasma and oxidized regenerated cellulose application effects on surgical site infection and wound healing in pilonidal sinus surgery. Ulus Travma Acil Cerrahi Derg. 2019;25(4):333-338. doi:10.5505/tjtes.2018.85047. PMID: 31294794

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