A pilonidal sinus is an abnormality where a small pit occurs at the bottom of the tailbone, in the cleft above the buttocks. Infection of the pilonidal sinus is known as a pilonidal abscess. A pilonidal abscess will not respond to conventional antibiotics and requires surgical intervention.
There are several types of surgery, Dr Mastakov will discuss with you which type of surgery is suitable for you.
Further reading: Better Health Channel
Further reading: Source 1