It is a small hole or tunnel in the skin at the top of the buttocks, where they divide (the cleft). It does not always cause symptoms and only needs to be treated if it becomes infected. Symptoms can be acute if it gets infected and if pus starts to collect under the skin forming an abscess. This usually requires urgent operation called incision and drainage, where the abscess cavity is incised and left open to heal gradually with time. Alternatively, you might develop less intense symptoms such as mild pain, a lump, or discharge.
There are numbers of treatment options for symptomatic pilonidal sinus. Examples of these options include excision and laying open, excision and primary closure, advancement flaps like Karydakis flap, or rotational flab such as Limberg flap. Other minimally invasive techniques include injection of fibrin glue and endoscopic sinus treatment. If surgery is required, these options will be discussed with you carefully and choose the most suitable for your case.