A pilonidal cyst is a small sac inside the skin that is usually located near the tailbone at the top of the buttocks crease. Pilonidal (say: “pie-low-NYE-dull”) means “nest of hairs.” A pilonidal cyst can contain hair, skin fragments and other abnormal tissue.
Anyone can have a pilonidal cyst, but it is more common in young men.
A pilonidal cyst may not have any symptoms besides a small pit or dimple on the skin. However, sometimes pilonidal cysts become infected. When this happens, the cyst can become a painful abscess—a swollen, inflamed sac filled with pus (a thick, whitish-yellow fluid). Rarely, an infected pilonidal cyst can cause a fever.
Doctors disagree on the causes for pilonidal cysts. Some doctors think that ingrown hairs may be the cause. Ingrown hairs are loose hairs that re-enter the skin though pressure from skin rubbing skin, tight clothing or long periods of sitting. Other doctors think that pilonidal cysts form around a ruptured hair follicle (the structure from which a hair grows).
Some babies are born with a small dimple just above the crease of the buttocks, called a sacral dimple. Sacral dimples can become infected and form a pilonidal abscess.
Your doctor will be able to diagnose your pilonidal cyst by examining it. Your doctor will probably also ask you about your symptoms.
If you have an infected pilonidal cyst, your doctor will numb the area where the cyst is located. He or she will drain any pus and remove hairs or any other fragments in the cyst. Your doctor will then loosely pack the abscess with gauze to help it heal from the inside. You may need to have the gauze changed several times until the cyst heals. Most people who have pilonidal cysts do not need any other treatment.
If you have a pilonidal cyst that gets infected often, you may need surgery. Your doctor will make an incision to remove any pus, hair and skin fragments from the abscess. The doctor may choose to leave your wound open and pack it with gauze, or he or she may choose to stitch the wound closed. If your doctor tells you need surgery for your pilonidal cyst, talk to him or her about the advantages and disadvantages of leaving the wound open or closed.
Written by familydoctor.org editorial staff