Pilonidal Sinus Disease

Original Author: Will Hunt
Last Updated: March 25, 2019
Revisions: 14

Pilonidal sinus disease is a disease of the anorectal region*, characterised by the formation of a sinus in the cleft of the buttocks. It most commonly affects males aged 15-30 years.

In this article, we shall look at the risk factors, clinical features and management of pilonidal sinus disease.

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


The most widely accepted theory for pilonidal sinus disease development is:

  • A hair follicle in the intergluteal cleft becomes 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.

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 and taxi drivers.

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

Fig 1 - A pilonidal cyst and sinus tract.

Fig 1 – A pilonidal cyst and sinus tract.

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.

It is often difficult to distinguish pilonidal sinus from other anorectal conditions, such as anal fistulae. Yet the main distinguishing feature is that a pilonidal sinus opens up onto the skin but does not continue into the anal canal like a fistula; this distinction can be identified with rigid sigmoidoscopy in clinic.

Extensive sinus formation and fistulisation may be assessed by MRI scanning of the natal cleft and buttocks, but further imaging is rarely necessary.

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

Fig 2 – A) Openings to two pilonidal sinuses within the gluteal cleft. 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.

Antibiotics can be used in septic episodes, although 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.

In acute disease, surgical management involves the drainage and washout of any abscess that is present. It can be difficult to remove the sinus tract in the same operation and most patients will 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 drainage and washout, whereas chronic disease needs to be treated with removal of the actual pilonidal sinus tract


Question 1 / 4
Which structure is implicated in the development of a pilonidal sinus?


Question 2 / 4
Which of the following is NOT a risk factor for pilonidal sinus disease?


Question 3 / 4
How can a pilonidal sinus be differentiated from an anal fistula?


Question 4 / 4
What is the usual surgical management of an acute pilonidal abscess?


Medico Digital

Further Reading

Healing by primary versus secondary intention after surgical treatment for pilonidal sinus
McCallum I et al., Cochrane Database

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