Causes and symptoms
There is nearly a consensus that pilonidal sinus disease is acquired, not congenital, probably resulting from hair penetration beneath the skin, for reasons that are not totally clear. It has been postulated that hair penetrates into the subcutaneous tissues through dilated hair follicles, thought to occur particularly in late adolescence.
- Caucasian males
- Hirsute flexure, coarse hair
- Excess sweating and/or poor hygiene
- Sedentary lifestyle or occupations involving long hours in a sitting position
- Deep natal cleft, and presence of hair within the natal cleft
- Obesity is a risk factor for recurrent disease
The spectrum of Pilonidal Sinus Disease ranges from chronically inflamed sinus tract with persistent drainage to the more acute presentation of abscesses or extensive subcutaneous tract. Chronic PSD can encompass recurrent abscess with intervening of periods of resolution or a persistent non-healing, indolent wound.
Diagnosis and symptoms
The diagnosis of pilonidal sinus disease is typically based on patient history and physical examination. Usually, the patient is afebrile and nontoxic. The most common manifestation of PSD is a painful, swelling or mass in the sacrococcygeal region (upper buttocks area). Local examination may show a relatively unremarkable sinus tract but, usually at ED presentation, the patient has typical findings of an abscess, including redness, warmth, local tenderness, and fluctuance with or without induration. A tender mass with sinus drainage may be present.  Loose hair may be seen projecting from the site. 
In the early stages preceding the development of an abscess, cellulitis or folliculitis is present. The abscess is formed when folliculitis extends into the subcutaneous tissue or when a pre-existing foreign body granuloma becomes infected. Once bacteria proliferate and debris collects under the skin the tissue can become necrotic
Treatment of pilonidal abscess consists of prompt incision and drainage of the abscess followed by placing ribbon wound packing to occupy the space and allow further passive drainage. Management of chronic pilonidal disease varies and can be contentious. Surgical procedure is often down to the expertise of the surgeon and their preference.
There are various surgical options from drainage of any abscess and simple excision of the sinus, to excision of the pits (pit picking) & laying open of the extensions, to extensive, complex flap procedures for the more complex multi-recurrent disease. Depilation of the natal cleft using laser or other means has been suggested as an adjunct.
The wound is either closed immediately, or after a delay (healing by primary intention), or is left open, packed and allowed to heal (healing by secondary intention).
A significant minority (10%) of patients fail to heal after surgery and this results in a chronic sacrococcygeal wound with consequent pain, discharge and lost productivity. There is no concrete data on the incidence of non-healing PSD following surgery, but recurrences and complex pilonidal sinus following surgical treatment range between 0 and 46%. Currently there are limited medical or surgical options available for the management of these indolent sacrococcygeal wounds, which represents a real un-met medical need.
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