Pilonidal Sinus Disease
Summary
Pilonidal sinus disease is a common condition of the natal cleft (between the buttocks), characterised by sinus tracts containing hair and debris. It predominantly affects young, hairy men and is often referred to as "Jeep Seat Disease" (named after WWII soldiers who developed it from prolonged sitting in jeeps). The condition results from hair penetrating the skin and inciting a foreign body reaction, leading to chronic sinus formation. Patients present with acute abscesses or chronic discharging sinuses. Acute abscesses require incision and drainage. Chronic or recurrent disease is managed surgically with excision and flap procedures (Karydakis, Limberg) that flatten the natal cleft. Recurrence rates are significant, and hair removal and good hygiene are important preventive measures.
Key Facts
- Demographics: Young, hairy men (M:F = 3-4:1)
- Location: Natal cleft
- Pathophysiology: Hair penetrates skin → Foreign body reaction → Sinus
- Acute: Abscess (I&D required)
- Chronic: Discharge, Recurrent infection
- Surgery: Excision, Flap (Karydakis, Limberg)
- Recurrence: Common (10-40%)
Clinical Pearls
"Jeep Seat Disease": Named during WWII when soldiers developed it from prolonged sitting in jeeps.
"Hair Penetrates Skin": Loose hairs drill into skin; Shearing forces during sitting drive them deeper.
"Off-Midline = Lower Recurrence": Flap procedures have lower recurrence than midline closure.
"Hair Removal Helps": Regular hair removal (shaving, laser) reduces recurrence.
Incidence
- 26 per 100,000 population
Demographics
- M:F = 3-4:1
- Peak: 15-30 years
- Rare after 40
Risk Factors
| Factor | Notes |
|---|---|
| Male sex | |
| Hirsutism | More body hair |
| Obesity | Deeper natal cleft |
| Prolonged sitting | Drivers, Office workers |
| Family history | |
| Poor hygiene |
Mechanism
- Loose hair accumulates in natal cleft
- Friction and shearing drive hair into skin
- Foreign body reaction develops
- Sinus tract forms containing hair and keratin
- Infection leads to abscess or chronic discharge
Acute Presentation
| Feature | Description |
|---|---|
| Abscess | Painful, tender swelling in natal cleft |
| Erythema | Red, hot overlying skin |
| Discharge | Pus |
Chronic Presentation
| Feature | Description |
|---|---|
| Sinus opening | Midline pit(s) in natal cleft |
| Chronic discharge | Seropurulent; Foul-smelling |
| Hairs | May be visible in pit |
| Recurrent abscess |
Inspection
- Midline pit(s) in natal cleft
- Visible hairs
- Erythema (if acute)
Palpation
- Tenderness (acute)
- Indurated track (chronic)
- Fluctuance (abscess)
Usually Clinical Diagnosis
- No investigations needed for straightforward cases
When to Investigate
- Atypical: Consider Crohn's, Hidradenitis
- Complex: MRI to map sinuses
Management Approach
┌──────────────────────────────────────────────────────────┐
│ PILONIDAL SINUS MANAGEMENT │
├──────────────────────────────────────────────────────────┤
│ │
│ ACUTE ABSCESS: │
│ • Incision and Drainage (I&D) │
│ • Leave wound open │
│ • ⚠️ Does NOT cure — Recurrence common │
│ │
│ CHRONIC SINUS: │
│ • Pit picking (minor) │
│ • Wide excision + Healing by secondary intention │
│ • Excision + Off-midline flap (PREFERRED): │
│ - Karydakis flap │
│ - Limberg (Rhomboid) flap │
│ - Lower recurrence (5-10%) │
│ │
│ PREVENTION: │
│ • Regular hair removal (shaving, laser) │
│ • Good hygiene │
│ • Weight loss │
│ │
└──────────────────────────────────────────────────────────┘
Of Disease
- Recurrent abscess
- Chronic pain
- Rarely: SCC (long-standing)
Of Surgery
- Wound infection
- Wound breakdown
- Recurrence (10-40%)
Recurrence Rates
| Technique | Recurrence |
|---|---|
| Midline closure | 10-40% |
| Off-midline flap | 5-10% |
Key Guidelines
- ASCRS: Clinical Practice Guidelines for Pilonidal Disease
What is a Pilonidal Sinus?
A pilonidal sinus is a small hole or tunnel in the skin at the top of the buttocks that can fill with hair and become infected.
What Causes It?
Loose hairs penetrate the skin, causing inflammation and sinus formation. Sitting for long periods worsens it.
How is It Treated?
- Abscess: Draining the pus
- Chronic sinus: Surgery to remove the sinus
- Prevention: Keep the area clean and hair-free
Primary Guidelines
- Steele SR, et al. ASCRS Clinical Practice Guideline for the Management of Pilonidal Disease. Dis Colon Rectum. 2013;56(9):1021-1027. PMID: 23929010