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Pilonidal Sinus

The word "pilonidal" means "nest of hairs" while a sinus is a tract or an abnormal channel that leads to the outside of the body.

Pilonidal sinuses (PNS) start as small abscesses that develop under the skin at the top of the buttocks (the natal cleft). They usually contain hair, dirt, and debris such as skin cells and can cause severe pain. As infection develops they track beneath the skin near the end of the tail bone, an area known as the natal cleft. The sinus tract travels in a vertical direction between the buttocks and may discharge onto the skin in the area.

This is a condition that mostly affects men and is also common in young adults. It’s also more common in people who have jobs requiring them to sit for long periods such as truck drivers or cab drivers.

The exact cause of this condition is not known.

Some predisposing factors are –

  • Obesity
  • Excessive hair growth in the area
  • A deep natal cleft
  • A family history of the condition may indicate an inherited minor skin or hair growth pattern abnormality in the area.
  • Friction from clothes or from pressure at the site causing trauma to the site


You may not have any noticeable symptoms at first, other than a slight dimpling on the surface of the skin. However, once the area becomes infected, an abscess and then a sinus tract will quickly form.

Rapid onset symptoms

  • You may experience increasing pain and tenderness as an abscess (ball of pus) forms when sitting or standing
  • Redness of the skin as infection develops in and around the sinus.
  • Swelling of the area
  • Hair protruding from the lesion
  • Formation of more than one sinus tract, or holes in the skin with pus or blood draining from the abscess.
  • A foul odour.

Persistent (chronic) symptoms

  • About 4 in 10 people have a recurrence
  • Pain may be less intense that with a rapid onset
  • Usually the sinus discharges some pus, which relieves the pressure, easing the pain
  • Chronic infection means that the condition can partially resolve but flare up from time to time until the sinus is treated surgically.

Conservative Treatment

If you have no symptoms then clearing the affected area of hairs (by shaving etc.) and good personal hygiene will be advised.

If you have rapid onset (acute) symptoms and infection you may be given broad-spectrum antibiotics. These will treat a wide range of bacteria. Analgesics for pain relief, such as paracetamol and/or ibuprofen will be prescribed for pain relief. It’s important to realise that this won’t heal the sinus tract, but it will control the infection.

You will be advised to have a follow-up examination, regularly remove hair or shave the site, and pay particular attention to hygiene.

An emergency procedure in hospital to incise (puncture) and drain the abscess may be necessary.

Drainage of the abscess

Before this procedure, you will be given a general anaesthetic. Your surgeon will then use a scalpel to open the abscess and clean away any hair, blood, and pus from inside.

Once this process is complete, the surgeon will stitch the wounds closed.

The wound will be packed with a sterile dressing and allowed to heal from the inside out. The dressings will need to be changed daily. When home a family member will be instructed in how to do this or if no one is available to do this, a visit from the district nurse will be arranged.

The wound usually heals within four weeks, and many patients do not require any further treatment.


If you have a recurring PNS or if you have more than one sinus tract, your doctor will recommend a surgical procedure.

Wide excision and healing by secondary intention.

This operation involves cutting out (excision of) the sinus but also cutting out a margin of skin, which surrounds the sinus (sinuses). The wound is not closed but just left open to heal by natural healing processes (healing by ‘secondary intention’). This usually takes several months of regular daily dressing changes until it heals fully. You will need to be seen fortnightly by your surgeon to ensure optimal healing. The advantage of this method is that all inflamed tissue is removed and the chance of the condition coming back (recurrence) is low.

Excision and primary closure.

This is done by cutting out an oval-shaped (ellipse) flap of skin either side of the sinus, which takes out the sinus, and stitching together the two sides of the ellipse. The advantage of this is if successful, the wound may heal more quickly. The risk of a recurrence or of developing a wound infection after the operation is higher than the above procedure.

To reduce this risk a wound technique is used in which the line of stitches is moved away from between the buttocks. The excision is made off and to the side of the midline, thus reducing the chance of recurrence of the sinus tract through the surgically disturbed tissues and incision.

Risks and Complications

Although this type of surgery is almost always safe, complications are a risk factor, just as they are with any kind of surgery.

Some potential complications relating to this surgery are:

  • Anaesthesia complications – nausea and reaction to the anaesthetic
  • Pain – analgesics will be prescribed to relieve pain
  • Bleeding of the wound
  • Scarring
  • Blood clots—rarely these can form in the legs due to immobility after surgery. Occasionally a blood clot can break off and travel through the blood stream to the lungs, making it difficult for you to breathe
  • Partial breakdown of the wound—this is more common if the wound is closed with stitches. The risk increases if there is an infection at the time of surgery. The wound may need to be opened and packed until it heals
  • Slow healing—healing can take up to eight weeks or longer, especially if the wound is packed
  • Feeling numb—it is common to have numbness around the wound

Conditions and Management

Investigative Procedures

Useful Links

  • Jessie McPherson Private Hospital
  • MonashHealth
  • St John of God Health Care
  • Monash University
  • Royal Australasian College of Surgeons
  • Valley Private Hospital
  • West Gippsland Healthcare Group