Internal Medicine

Pilonidal disease

Common anorectal infection under the skin in the gluteal cleft.

Common anorectal infection under the skin in the gluteal cleft.

  • 3:1 male predilection


Pilonidal means nest of hair and is derived from the Latin words for hair (pilus) and nest (nidus). Herbert Mayo is credited with the first description of this disease in 1833, and R.M. Hodges coined the term pilonidal in 1880. Buie noted its prevalence in male, military recruits who drove jeeps and thus characterized it as “jeep disease.” Pilonidal disease was most notable during World War II when an estimated 80,000 soldiers became afflicted and lost significant time from active duty.


Risk factors:

  • Family history
  • Local trauma
  • Sedentary occupation
  • Obesity

Pathogenic formula (Karydakis GE):

Pilonidal disease = Hair (H) x Force (F) x Vulnerability (V)2


Hair follicles in the gluteal cleft become infected with keratin resulting in local infection and abscess formation while local suction forces cause hairs to enter the infected pit and lodge in the abscess cavity. Secondary pits then result from subcutaneous burrowing of hair and additional hairs enter through the pits.

  • Pilonidal sinus (PNS): Sinus tract (small channel), that may originate from the source of infection and open to the surface of the skin.
  • Material from the cyst drains through the pilonidal sinus
  • A pilonidal cyst is usually painful, but with draining the patient might not feel pain


  1. Midline pit develops that may be a hair follicle, which has shed its own hair and then allows debris to occupy the pit
  2. Loose semi-curved roots of hair fall and migrate to the cleft where they become vertically oriented and insert into the pit via their roots
  3. Foreign body granuloma develops in the subcutaneous fat
  4. Depth of the natal cleft is associated with anaerobic environment with moisture and pressure that can lead to increased hair insertion
  5. Direction of the follicle determines the direction of the tract.
Pathogenesis. Hair invading skin at the natal cleft causes a pilonidal abscess and sinus tracts. | Mayo Foundation for Medical Education and Research

Clinical features

May arise in one of three forms:

Acute pilonidal abscess:

Pain, tenderness, swelling, and erythema in the gluteal cleft with/without drainage from the involved area
  • Fever, chills, and pain
An acute presentation of pilonidal sinus disease, with an abscess in the natal cleft. Treatment should be with incision and drainage, the incision made away from the midline | Jonathanlund – CC BY-SA 4.0,

Chronic pilonidal abscess (draining sinus tracts):

Chronic pilonidal sinus cavity with recurrent drainage due to retained hair and infected residue
  • Sinus tracts: intermittent discharge or bleeding
  • Opaque yellow (purulent) or bloody discharge from the tailbone area
  • Unexpected moisture in the tailbone region
  • Discomfort sitting on the tailbone, doing sit-ups or riding a bicycle—any activities that roll over the tailbone area
Two pilonidal cysts that have formed in the gluteal cleft | JerryTahl – Public Domain,


Trephine punch biopsy:

Differential diagnosis:

  • Dermoid cyst (germ cell tumor)
  • Aacrococcygeal teratoma


Conservative management:

  • Shaving/depilation (preventive and therapeutic):
    • Shave until complete healing has occurred

Surgical management

  • Minimal-to-moderate disease:
    • Incision & drainage
    • Unroofing & secondary healing
    • Incision with marsupialisation
    • Bascom chronic abscess curettage with midline pit excision (Bascom I)
    • Primary closure with flap procedures
  • Severe and recurrent disease:
    • Karydakis flap
    • Bascom cleft lift closure (Bascom II)
    • Rhomboid excision with Limberg/modified Limberg flap
    • V-Y advancement flap
    • Z-plasty
    • Gluteus maximus myocutaneous flap

Incision & drainage:

Limited off-midline incision is combined with excising a small ellipse of overlying skin to promote drainage
Off-midline incision and drainage of pilonidal abscess. Lateral incision for drainage is made even when the abscess is primarily in the midline. | Nelson and Billingham

Unroofing and open secondary healing:

Excision of midline tracts followed by an open wound leads to prolonged healing. Unroofing of the tracts minimizes the midline wound and shortens healing accordingly. This approach is effective in the presence of a concomitant abscess.

Incision with marsupialization:

Opening the sinus tracts in the midline to include any secondary tracts. The posterior and lateral fibrous tissue is then left in situ and sutured to the skin edge or dermis. The goal is to reduce the effective wound healing area thus reducing the time of healing.
Marsupialization: Skin edge sutured to base of wound. | Mayo Foundation for Medical Education and Research

Bascom I surgery:

Bascom chronic abscess curettage with midline pit excision
  • Midline pits conservatively excised with removal of contiguous hair and debris in pits
  • Concomitant lateral incision, parallel to midline wound made to curette debris from cavity connecting sinus pits
  • All incisions left open to heal by secondary intention
  • Wounds followed closely to remove hair that may gravitate into the wound
  • Careful and frequent wound care essential
(A) Bascom lateral drainage. (B) Subcutaneous undermining and excision of sinus pits. | Modified from Nelson and Billingham.

Karydakis flap:

Karydakis procedure. (A) An asymmetric elliptical incision is carried down to the postsacral fascia. (B) The wound is undermined and (C) closed off midline. | Mayo Foundation for Medical Education and Research

Bascom cleft lift closure (Bascom II):


Negative pressure wound therapy:

Negative pressure wound therapy: (A) Complex pilonidal disease. (B) Excision of all involved tissue. (C) Primary V.A.C. device placement. | Mayo Foundation for Medical Education and Research

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