Pilonidal Sinus

pilonidal sinus

A sinus tract is a small abnormal channel (a narrow tunnel) in the body. A sinus tract typically goes between a focus of infection in deeper tissues to the skin surface. This means that the tract may discharge pus from time to time on to the skin.

A pilonidal sinus is a sinus tract which commonly contains hairs. It occurs under the skin between the buttocks (the natal cleft) a short distance above the anus. The sinus track goes in a vertical direction between the buttocks.

What causes a pilonidal sinus?

The exact cause is not clear. There are various theories. For example, one theory is that the problem may develop from a minor congenital or hereditary abnormality in the skin of the natal cleft. Another theory is that you develop skin dimples (skin pits) in the skin between the buttocks. These may develop from damaged hair follicles due to local pressure or friction. Because of local pressure, growing hair in the natal cleft may get pushed into the skin pits.

Whatever the cause, once hair fragments become 'stuck' in the skin they irritate the skin and cause inflammation. Inflamed skin quickly becomes infected and so a recurring or persistent infection tends to develop in the affected area.

Certain factors increase the risk of developing the condition and include:

  • Sedentary occupation (sitting a lot).
  • Obesity.
  • A previous persistent irritation or injury to the affected area.
  • Having a hairy, deep natal cleft.
  • A family history of the condition.
What are the symptoms of pilonidal sinus?

A pilonidal sinus may not cause any symptoms at first. However, in most cases, symptoms develop at some stage and can be 'acute' or 'chronic'.

Acute (rapid onset) symptoms

You may develop increasing pain and swelling over a number of days as an infected abscess (ball of pus and surrounding skin infection) develops in and around the sinus. This can become very painful and tender.

Chronic (persistent) symptoms

You may develop some pain which is less intense than the 'acute' symptoms. Usually the sinus discharges some pus. This releases the pressure and so the pain tends to ease off and not become severe. However, the infection never clears completely. This then can mean that the symptoms of pain and discharge can persist long-term, or flare up from time to time, until the sinus is treated by an operation.

What is the treatment for pilonidal sinus?

If you have no symptoms

If you have no symptoms then you will normally be advised to clear the affected area of hairs (by shaving etc) and to keep the area clean with good personal hygiene.

If you have acute symptoms

If you have an infection then you may be given some antibiotics. Painkillers (such as paracetamol and/or ibuprofen) may be very helpful to improve the pain. It may be that you need to have an emergency operation to incise (puncture) and drain the abscess. This is usually done in hospital.

If you have chronic (persistent) symptoms

In most cases, an operation will be advised.
  • Wide excision and healing by secondary intention. This operation involves cutting out the sinus but also cutting out a wide margin of skin which surrounds the sinus. The wound is not stitched but just left to heal by normal healing processes (healing by 'secondary intention'). This usually means that the wound can take several weeks to heal and requires regular dressing until it heals. The advantage of this method is that all inflamed tissue is removed and the chance of recurrence is low.
  • Excision and primary closure. This means taking out the section of skin which contains the sinus and stitching together the two sides of the ellipse. The advantage for this is, if successful, the wound heals quite quickly. However, the risk of a recurrence, or of developing an infection of the wound after the operation, is higher than the above procedure.
  • In some cases, where the sinus recurs or is extensive, a plastic surgery technique may be advised.

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