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Pilonidal Sinus Disease

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Last updated: August 30, 2020
Revisions: 19

Last updated: August 30, 2020
Revisions: 19

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Pilonidal sinus disease is a disease of the inter-gluteal region*, characterised by the formation of a sinus in the cleft of the buttocks. It most commonly affects males aged 16-30 years .

*The term pilonidal is derived from the Latin pilus (hair) and nidus (nest). 


The most widely accepted theory for pilonidal sinus disease development is starting from a hair follicle in the intergluteal cleft becoming infected or inflamed.

This inflammation obstructs the opening of the follicle, which extends inwards, forming a ‘pit’ (a characteristic feature of pilonidal sinus disease). A foreign body-type reaction may then lead to formation of a cavity, connected to the surface of the skin by an epithelialised sinus tract (Fig. 1).

Figure 1 – A pilonidal cyst with its sinus tract

Risk Factors

Pilonidal sinus disease most commonly affects Caucasian males with coarse dark body hair. Classically, it is associated with those who sit for prolonged periods, such as lorry drivers or office workers.

Other associated factors are increased sweating, buttock friction, obesity, poor hygiene, or local trauma. Typically, pilonidal disease does not occur after 45 years of age.

Clinical Features

Pilonidal sinus disease most commonly presents as an intermittent red, painful, and swollen mass in the sacrococcygeal region. There is commonly discharge from the sinus, and there may be systemic features of infection.

The main distinguishing feature compared to a perianal fistula is that a pilonidal sinus opens up onto the skin, but does not communicate with the anal canal; if there is any uncertainty on initial inspection, a rigid sigmoidoscopy or MRI imaging can be performed to assess for any internal opening of a tract.

Further imaging is rarely required.

Fig 2 - A) Openings to two pilonidal sinuses within the gluteal cleft. B) A pilonidal abscess.

Figure 2 – A) Openings to two pilonidal sinuses B) A pilonidal abscess


Non-Surgical Management

Pilonidal disease eases with age and does not always require surgical management. Conservative treatment of a pilonidal sinus involves shaving the affected region and plucking the sinus free of any hair that is embedded. Any accessible sinuses can be washed out with water to prevent infection.

Whilst antibiotics can be used in septic episodes, any abscess present will require surgical drainage.

Surgical Management

The exact surgical management of a pilonidal sinus is dependant on whether the disease is acute or chronic.

For any abscess that has developed, an incision and drainage with washout is required. It can be difficult to remove the sinus tract in the same operation and patients may require further surgery.

Treatment of chronic disease is the removal of the pilonidal sinus tract. There are two main methods:

  • The first involves excising the tract and laying open the wound, allowing closure by secondary intention
    • This has low rates of recurrence yet can take a long time to heal and has an increased risk of infection
  • The second involves excising the tract, followed by primary closure of the wound
    • This has higher rates of recurrence and patients may require reconstructive surgery due to tissue loss from this operation

Key Points

  • Pilonidal sinus disease occurs from the infection or inflammation of hair follicles in the cleft of the buttocks
  • Most cases are associated with those who sit for prolonged periods
  • Pllonidal abscesses require incision and drainage, whereas chronic disease needs to be treated with removal of the actual pilonidal sinus tract