Pilonidal Disease (Cyst, Abscess, Sinus)

Risk factors

• Male sex, hirsutism (especially coarse dark hair)
• Obesity
• Prolonged sitting (truck drivers, students, military)
• Sedentary lifestyle, poor hygiene
• Family history
• Local trauma, friction, sweating
• Deep natal cleft anatomy

Pathophysiology

Loose hairs are drawn into a midline pit at the natal cleft (where keratin and skin debris accumulate). The hair acts as a foreign body, provoking a chronic inflammatory and granulomatous reaction in the subcutaneous tissue. The cavity enlarges, may become acutely infected (abscess), and decompresses through lateral sinus tracts onto the skin, producing chronic recurrent drainage. The disease is acquired, not congenital.

Clinical presentation

Differential diagnosis

• Perianal/perirectal abscess or fistula — Located near anal verge, not in natal cleft above coccyx; cryptoglandular origin
• Hidradenitis suppurativa — Recurrent abscesses with sinus tracts in apocrine-bearing areas (axilla, groin, buttocks); double comedones; chronic relapsing course
• Sacral dermoid cyst (congenital) — Congenital, often midline, may have dermoid contents; usually present in childhood
• Furuncle/carbuncle — Folliculitis with central necrosis; can occur anywhere; not anchored to natal cleft
• Anal fistula extending posteriorly — Internal opening at anal crypt visible on exam; tract follows Goodsall rule
• Cutaneous Crohn disease — Other GI/perianal manifestations; biopsy shows granulomas
• Sacrococcygeal teratoma (rare adult) — Mass with cystic and solid components on imaging

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Natal cleft midline pits<br/>± drainage / abscess] --> B{Acute abscess?}
  B -->|Yes| C[I&D off midline<br/>+ curettage and hair removal]
  B -->|No, chronic sinus| D{Disease extent}
  D -->|Limited| E[Pit picking Bascom I<br/>+ lateral drainage]
  D -->|Extensive / recurrent| F[Flap procedure<br/>Karydakis or Bascom cleft lift]
  C --> G[Postop: local hygiene<br/>laser/shave hair removal<br/>weight loss, avoid prolonged sitting]
  E --> G
  F --> G

Complications

• Recurrence (10-30%; higher with midline closure techniques)
• Chronic nonhealing wound
• Cellulitis, necrotizing soft-tissue infection (rare)
• Squamous cell carcinoma arising in chronic pilonidal sinus (very rare, after decades of disease)
• Postoperative wound dehiscence, hematoma, seroma
• Loss of work/school time during prolonged healing

PANCE pearls

• Pilonidal disease is acquired, not congenital — counsel patients on the role of hair, hygiene, and friction.
• Drain abscesses off midline whenever possible — midline wounds in the natal cleft heal poorly because of constant moisture, friction, and tension.
• Antibiotics alone never cure a pilonidal abscess — I&D is required.
• Laser hair removal reduces recurrence and should be part of standard postoperative care.
• Recurrent or extensive disease benefits from cleft-flattening flap procedures (Karydakis or Bascom cleft lift) rather than repeated midline excisions.

References

• ASCRS 2019 — American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Pilonidal Disease (Johnson et al., Dis Colon Rectum 2019)
• EAES 2020 — European Association for Endoscopic Surgery and other Interventional Techniques (EAES) consensus on the management of pilonidal sinus disease