Pilonidal Sinus
Summary
Pilonidal sinus is a common condition affecting the natal cleft (between the buttocks), characterised by a sinus tract containing hair and debris. It predominantly affects young, hairy men (hence "pilonidal" = nest of hair). The condition can present acutely as a painful abscess or chronically with recurrent discharge and discomfort. It is thought to result from hair penetrating the skin and causing a foreign body reaction. Acute abscesses require incision and drainage. Chronic or recurrent disease is managed surgically with wide local excision or flap procedures (Karydakis, Limberg). Recurrence rates are significant, and good wound care and hair removal are important preventive measures.
Key Facts
- Demographics: Young, hairy men (20s-30s)
- 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 Closure = Lower Recurrence": Flap procedures (Karydakis, Limberg) 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 (hair follicle activity decreases)
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 (sitting) drive hair into skin
- Foreign body reaction develops
- Sinus tract forms containing hair and keratin
- Infection leads to abscess or chronic discharge
The Natal Cleft
- Warm, moist, hairy environment
- Deep cleft = Higher risk
Acute Presentation
| Feature | Description |
|---|---|
| Abscess | Painful, tender swelling in natal cleft |
| Erythema | Red, hot overlying skin |
| Discharge | Pus (if draining) |
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)
- Abscess swelling
Palpation
- Tenderness (acute)
- Indurated track (chronic)
- Fluctuance (abscess)
Extent Assessment
- Multiple pits?
- Secondary openings?
- Size of affected area
Usually Clinical Diagnosis
- No investigations needed for straightforward cases
When to Investigate
| Indication | Investigation |
|---|---|
| Atypical location | Consider other diagnoses (Crohn's, hidradenitis) |
| Complex disease | MRI to map sinuses |
| Recurrent disease | Exclude underlying pathology |
Management Approach
┌──────────────────────────────────────────────────────────┐
│ PILONIDAL SINUS MANAGEMENT │
├──────────────────────────────────────────────────────────┤
│ │
│ ACUTE ABSCESS: │
│ • Incision and Drainage (I&D) │
│ • Under local or general anaesthesia │
│ • Leave wound open to heal by secondary intention │
│ • Regular packing / dressings │
│ • ⚠️ DOES NOT CURE — Recurrence common │
│ │
│ CHRONIC SINUS (Elective): │
│ │
│ MINOR PROCEDURES: │
│ • Pit picking (trephine) — for simple pits │
│ • Phenol injection (chemical ablation) │
│ • Laser ablation │
│ │
│ MAJOR PROCEDURES: │
│ • Wide local excision + Healing by secondary intention │
│ (Open technique — Low recurrence, Slow healing) │
│ • Excision + Primary midline closure │
│ (Quick healing, Higher recurrence) │
│ • Excision + Off-midline flap (PREFERRED): │
│ - Karydakis flap (asymmetric closure) │
│ - Limberg (Rhomboid) flap │
│ - Lower recurrence (5-10%) │
│ │
│ PREVENTION (ALL PATIENTS): │
│ • Regular hair removal (shaving, waxing, laser) │
│ • Good hygiene │
│ • Weight loss (if obese) │
│ • Avoid prolonged sitting │
│ │
└──────────────────────────────────────────────────────────┘
Of Disease
- Recurrent abscess
- Chronic pain
- Rarely: Squamous cell carcinoma (very rare, after years)
Of Surgery
- Wound infection
- Wound breakdown
- Recurrence (10-40% depending on technique)
- Delayed healing (especially open techniques)
Recurrence Rates
| Technique | Recurrence |
|---|---|
| Midline closure | 10-40% |
| Off-midline flap | 5-10% |
| Healing by secondary intention | 5-15% |
Long-Term
- Many patients have recurrence
- Optimise prevention measures
Key Guidelines
- ASCRS: Clinical Practice Guidelines for Pilonidal Disease
Key Evidence
Off-Midline vs Midline
- Cochrane review supports off-midline closure for lower recurrence
What is a Pilonidal Sinus?
A pilonidal sinus is a small hole or tunnel in the skin at the top of the buttocks (the cleft between them). It can fill with hair and skin debris and become infected.
Who Gets It?
It mainly affects young, hairy men. Sitting for long periods can make it more likely.
What Are the Symptoms?
- A painful lump or abscess if infected
- Discharge of pus or blood
- A smell from the area
How is It Treated?
- Abscess: Needs draining (a small cut under anaesthetic)
- Chronic sinus: Surgery to remove the sinus — several techniques depending on severity
- Prevention: Keep the area clean and free of hair
Will It Come Back?
Unfortunately, pilonidal disease often comes back. Regular hair removal and good hygiene help prevent recurrence.
Primary Guidelines
- Steele SR, et al. Clinical Practice Guideline for the Management of Pilonidal Disease. ASCRS. Dis Colon Rectum. 2013;56(9):1021-1027. PMID: 23929010
Key Studies
- Søndenaa K, et al. Rhomboid excision and Limberg flap for recurrent pilonidal sinus disease. Dis Colon Rectum. 2002;45(1):91-95. PMID: 11786770