What is Pilonidal Sinus?

The pilonidal area is at the base of the spine, over the lower sacrum. Loose hairs can work their way through tiny openings in the skin called pits; the hairs can accumulate and often get infected leading to pain and swelling. If an abscess develops it can track away from the pit and lead to a larger opening nearby - this is called a sinus.


The hairs that get into the sinus tend to get intermittently infected. This can lead to an abscess or simply some discharge. Commonly an abscess presents at first as a painful lump which your GP might treat with antibiotics. This will often improve symptoms but the natural history of a pilonidal sinus is that it recurs intermittently with a cycle of pain, swelling discharge and resolution, either complete or partial. When it does not resolve completely there is a persistent discharge from the sinus which needs daily dressing.


A pilonidal sinus will always have one or more ‘pits’ – tiny openings and these are always in the midline. There is often a track leading to one side under the skin to a discharging spot. For the majority a clinical diagnosis is straightforward. Occasionally a pilonidal sinus can be difficult to tell from an anal fistula. There are a few rare conditions that give similar symptoms and for these an MRI scan is useful.


Antibiotics can help to settle an acute flare up and shaving the area to keep it free from hairs can also help but if symptoms continue then surgery is often necessary. There are a number of different surgical approaches to the problem - a testament to the fact that there is no single technique that is clearly the best. The aim of surgery is to excise the abscess cavity and clear the deeper tissues of hairs while minimizing the chance of recurrence in a variety of ways. The midline pits should also be removed. It helps too if the surgical incision is not in the midline as this may result in delayed healing.

It some circumstances it is best not to operate and in others, more complex procedures performed by plastic surgeons may be needed. Your surgeon will assess the individual situation and recommend a sensible way forward with a full explanation of the pros and cons.