Pilonidal Sinus Disease

Pilonidal sinus disease is a tract with an opening on the skin leading to a collection of hair. It most commonly occurs in the natal cleft(in the midline between the buttocks) but it can also occur elsewhere - eg in hands(especially in barbers) and around the belly button.

How Pilonidal Sinus Develops

The natal cleft is often moist. The hair shafts (which under the microscope look like barbs) drill into the soft moist skin when one sits(the buttocks can also create a suction type effect - suckiing in the hair deeper). This may be then lead to localized inflammation(folliculitis) which further weakens the skin. Over time a nest full of hair forms under the skin. This may be connected to the outside skin by a small sinus tract.

Interestingly, the sinus may also be congenital(present from birth) in some people. This may explain why people who are not hairy develop pilonidal sinus disease too.


An abscess can develop when an infection forms within this nest of hair and the tract is not able let the pus drain out. This can be very painful. In addition, it may be complicated by sepsis (with high fever) and surrounding skin infection(cellulitis).

The emergency treatment for this is to drain the abscess - it is important that the incision is placed to one side of the midline(this is so that in future when curative surgery is performed, the scar from the incision can be excised as well)


The principles of surgery for pilonidal sinus disease is :

(i) To excise the sinus tract and the nest of hair

(ii) To leave a scar away from the midline to reduce the risk of recurrence

(iii) To make the natal cleft shallower to have less chance for hair to reaccumulate or be sucked inwards

The operation involves:

1. Marking out the area prior to making the incisions and putting in local anaesthetic around the area

2. Excising the sinus tract and the nest of hair- this is identified by prior iinjection with blue dye. This is done in a way which will leave the resulting scar away from the midline

3. Raising a local flap of skin to cover to allow closure of the wound - ensuring that the wound stays away from midline and the natal cleft becomes shallower

(This operation is known also as the Modified Karydakis operation)

Other options:

1. Direct excision and closure - but this will leave a scar in the midline and has a high recurrence rate (20-30% - info from the Australian Colorectal Society website)

2. Excision and closure with other types of flaps including rhomboid flaps- again the principle is the same

3. Excision and wound left open - this will take months to heal.

4. Excision of pit/sinus tract, removal of hairs and cleaning of the tract(Bascom type operation) - this is a smaller operation hence recovery is quicker. This can be done in the rooms under local anaesthesia. Advantages: smaller wounds, less pain postop, no deformity to buttocks. Disadvantages : The drawback is a higher recurrence rate hence close long term follow up is essential. 

Risks of Surgery

1. Recurrence - the Modified Karydakis has a very low recurrence rate(1-3%).

2. Bleeding - there is a risk of a small amount of bleeding and bruising. During the operation, any bleeding blood vessels would be cauterized to reduce the risk of a haematoma developing after the operation.

3. Wound infection / breakdown - this would need treatment with antibiotics and occassionally surgical drainage. This may lead to an area that would take longer to heal. To reduce the risk, intravenous antibiotics is given at the time of surgery.

4. Pain in the wound as with any other cuts.

Useful link: www.pilonidal.org


Dr George Karydakis was a surgeon from Greece who has performed thousands of pilonidal sinus surgery using the technique he first described in the Lancet in 1973.

Mr Paul Kitchen is the surgeon who coined the term "Karydakis operation" in his publication in the ANZ Journal of Surgery in 1981. He has had the opportunity to learn from Dr George Karydakis himself(in London in 1973) and also from Dr John Bascom(and his son Dr Tom Bascom) in Oregon, US. He has performed over 300 pilonidal sinus surgery(probably the highest number in Australia) since 1973. He is a fantastic teacher of surgery. He also has an amazing knowledge of theology and can speak in fluent Arabic(from years of charity work in the Middle East)

The author, Mr LP Cheah, has had the privilege of training under Mr Paul Kitchen - a Senior Lecturer at the University of Melbourne and senior surgeon at St Vincent's Hospital.  To date, he has performed over 150 pilonidal sinus surgery.

If you are from interstate and is seeing Mr LP Cheah in the rooms with a view of having a Bascom operation, please ring ahead to arrange the operation on the same day.