Pilonidal Disease

Pilonidal is derived from the Latin words for 'hair' (pilorum) and 'nest' (nidum).

What is pilonidal disease?

Pilonidal disease is a skin infection occurring in the crease of the buttocks (natal cleft) near the tailbone (coccyx).

It is unclear what causes pilonidal disease. One explanation is that you are born with a minor abnormality in the skin of the natal cleft, where the hairs grow into your skin rather than outwards. Another explanation is that you develop skin dimples (skin pits) in the skin of the natal cleft due to local pressure or friction damaging the structures below your skin responsible for making hairs (hair follicles). Because of local pressure, growing hair in your natal cleft may become pushed into your skin pits.

Once hair fragments become stuck in your skin they irritate it and cause inflammation. Inflamed skin quickly becomes infected so a repeated or persistent infection tends to develop in the affected area. The infection causes an abnormal channel (sinus) to develop which often contains broken pieces of hair.

Who gets pilonidal disease?

Pilonidal disease affects about 26 in 100,000 people each year. It usually occurs in the 15 to 40-year-old age group.

Certain factors increase the risk of developing pilonidal disease:

  • Male gender
  • Hormonal changes at puberty
  • Thick coarse body hair
  • Deep natal cleft
  • Family history of the disease
  • Obesity
  • Long periods of sitting
  • Inactive lifestyle
  • Previous persistent irritation or injury to the affected area

What are the symptoms of pilonidal disease?

Symptoms can be acute or chronic.

Rapid-onset (acute) symptoms – pilonidal abscess

You may develop increasing pain and swelling over a number of days due to skin infection and build up of infected fluid (pus) in the sinus. This can become very painful and tender.

Persistent (chronic) symptoms

About 4 in 10 people have repeated symptoms. You may develop pain which is less intense than the acute symptoms. Usually the sinus discharges some pus, which releases the pressure and the pain eases off. However, the infection never clears completely. This means the cycle of pain and discharge can last long-term or flare up from time to time, until the sinus is treated by surgery.

How is pilonidal disease diagnosed?

Pilonidal disease is diagnosed through a clinical examination by your doctor.

What is the treatment of pilonidal disease?

Rapid-onset (acute) symptoms - pilonidal abscess

The recommended treatment is an emergency operation to incise and drain the pus. This is usually done in hospital.

Persistent (chronic) symptoms

In most cases, an operation will be recommended. Surgery involves excision of the midline pits and any fistulous tracts and sinuses. The wound can be treated in several ways:

  • Leave open: The wound is left open to heal from the base – a process called 'healing by secondary intention'. New scar tissue grows at the base of the wound and gradually fills in the cavity.
  • Primary closure: The wound is closed with sutures (without flattening the natal cleft).
  • Flap repair: The surrounding skin is moved across the natal cleft and sutured so that the scar is off midline. Flap surgery flattens the natal cleft so hairs are less likely to gather there. This eliminates potential entry points for hairs sticking into the skin at the base of the cleft and reduces the risks of recurrence.