Pilonidal Sinus Disease

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Last updated: February 23, 2022
Revisions: 22

Last updated: February 23, 2022
Revisions: 22

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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 a discharging and intermittently painful sinus in the sacrococcygeal region (Fig. 2A).

A pilonidal abscess can form when a pilonidal sinus becomes infected. This will present as a swollen and erythematous region. On examination, there will be a fluctuant and tender mass, as well as systemic features of infection.

The main distinguishing feature compared to a perianal fistula is that a pilonidal sinus 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.

Figure 2 (A) Openings of two pilonidal sinuses B) A pilonidal abscess


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

For any pilonidal 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. Multiple techniques for this have been described  including excision and laying open, excision and primary closure, excision and advancement flaps (e.g. Karydakis procedure or a V–Y flap), or excision and rotational flaps (e.g. Limberg flap)

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 pilonidal sinus tract