Pilonidal means a 'nest of hairs'.
A sinus tract is a narrow tunnel (a small abnormal channel) in your body. A sinus tract typically goes between a focus of infection in deeper tissues to your skin surface. This means that the tract may discharge pus from time to time on to your skin.
A pilonidal sinus is a sinus tract which commonly contains hairs. It occurs under your skin between your buttocks (the natal cleft) a short distance above your back passage (anus). The sinus tract goes in a vertical direction between your buttocks. Rarely, a pilonidal sinus occurs in other sites of your body.
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 an infection then you may be given some medicines called 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. This procedure punctures (incises) and drains the ball of pus with the surrounding skin infection (abscess). This is usually done in hospital.
In most cases, an operation will be advised. There are various operations which are done to cure this problem. Your surgeon will be able to give the details and the pros and cons of each operation. The options include the following:
Wide excision and healing by secondary intention. This operation involves cutting out (excision of) the sinus but also cutting out a wide margin of skin which surrounds the sinus. The wound is not closed but just left open to heal by natural healing processes (healing by 'secondary intention'). This usually requires several weeks of regular dressing changes until it heals fully. The advantage of this method is that all inflamed tissue is removed and the chance of the condition coming back (a recurrence) is low.
Excision and primary closure. This means taking out the section of skin which contains the sinus. This is done by cutting out an oval-shaped (ellipse) flap of skin either side of the sinus, which takes out the sinus. The two sides of the ellipse are then stitched together. The advantage for this is that, if successful, the wound heals quite quickly. The risk of a recurrence or of developing a wound infection after the operation is higher than with the above procedure. This risk may be reduced by using a wound technique in which the line of stitches is moved away from between the buttocks.
A plastic surgery technique. In some cases, where the sinus recurs or is extensive, plastic surgery may be advised to remove the sinus and refashion the nearby skin.
There are variations on the above procedures, depending on your circumstances, the size and extent of the sinus, and whether it is a first or recurrent problem. Your surgeon will be able to discuss with you in detail the most suitable type of operation.
New techniques are being researched to try to improve the recovery after having an operation.