A pilonidal sinus is a small hole that develops in the natal cleft, the area at the top of the buttocks.
It is a reasonably common condition that occurs mainly in young people. It occurs in males more frequently and in people from regions around the Mediterranean region.
The exact cause is uncertain. It usually arises after puberty when skin secretions thicken. A hair follicle ruptures after blockage and a sinus forms. Other hairs (usually from outside of the area) can then burrow into the deep natal cleft, setting up a foreign body reaction leading to infection.
Some people just have a small sinus (hole) in the natal cleft without any symptoms. A common presentation is with an acute abscess (collection of pus) that usually occurs adjacent to the midline pit. Other people have a less acute presentation with some intermittent swelling and pain in the natal cleft with occasional discharge. An infection in the area may be a ‘one-off’ but frequently recurrent problems occur.
A diagnosis is usually straight forward and can be made by simple inspection of the area.
An asymptomatic pilonidal sinus does not require any intervention.
A pilonidal abscess needs to be incised and drained. This can sometimes be done under local anaesthetic but larger ones are done in the operating theatre under general anaesthetic.
Chronic pilonidal sinus disease with ongoing symptoms or recurrent abscesses needs definitive surgery. There are many operations described and each has advantages and disadvantages. The most common procedures are