DermNet NZ

Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Pilonidal disease

What is pilonidal disease?

Pilonidal disease is a chronic skin problem found most often in the sacrococcygeal region. This is the cleft between the buttocks just below the base of the spine. It is characterised by one or more sinus tracts; these are cavities with a narrow opening on the skin surface (pilonidal sinus). In most cases, the cavity is filled with nests of hair, hence the name pilonidal (pilus meaning hair and nidal meaning nest). A non-inflamed lump is known as a pilonidal cyst. If the sinus becomes infected a pilonidal abscess may form.

Pilonidal sinus Pilonidal sinus
Pilonidal sinuses

What causes pilonidal disease?

The exact reason why pilonidal disease occurs is still unclear. Possible causes include:

Who gets pilonidal disease?

Pilonidal disease affects both men and women usually between the ages of 20-40 years. It is 2-3 times more common in men than women. Other factors that increase the risk of pilonidal disease include:

What are the signs and symptoms?

Signs and symptoms can vary from a small painless pit or dimple at the base of the spine to a large painful abscess. Most patients go to the doctor complaining of progressive tenderness, particularly after prolonged periods of sitting, such as during a long drive. Signs and symptoms include:

What treatment is available?

A pilonidal cyst that isn't causing any problems doesn't require any treatment. The patient should be advised to keep the area clean and free of hair by shaving or using a hair removal agent every 2-3 weeks. The cyst may resolve itself. If the cyst persists or becomes very inflamed (acute pilonidal abscess) you should see your doctor as it will need to be incised (cut into) and its contents drained out to reduce inflammation and pain. Occasionally the abscess cavity may be cut out completely to remove hair nests and skin debris; this reduces the rate of recurrence to about 15%.

Persistent, complex or recurrent pilonidal sinus disease must be treated surgically. Procedures vary from taking the roof off the sinuses to wide and deep excision (i.e. all affected areas are completely cut out). In all cases, the cavity is scrubbed and scraped out to remove hair and abnormally healing granulation tissue. Biopsy may show characteristic histopathological features of pilonidal sinus associated with foreign body reaction. Several techniques are available for wound healing and closure; these include dressing or packing open wounds, marsupialization (forming a pouch) which provides the patient with a smaller wound compared to wounds that are left open to granulate, and closure using skin flaps for wide excisions.

Related information


On DermNet NZ:

Other websites:

emedicine, the online textbook:

Books about skin diseases:

See the DermNet NZ bookstore

Author: Vanessa Ngan, staff writer.

DermNet NZ does not provide an on-line consultation service.
If you have any concerns with your skin or its treatment, see a dermatologist for advice.