A pilonidal cyst is a small sac that forms along the tailbone (coccyx), at the top of the cleft between the buttocks. These cysts usually contain hair and skin debris. They form when a hair on the buttocks grows inward, becomes trapped under the skin, and forms a cyst. One cyst or a row of them can occur. A pilonidal cyst may be harmless. If it becomes infected, it causes symptoms. These cysts affect more men than women, most often young adults, usually before the age of 40.
The reason cysts form is unknown. Friction and pressure may force hairs down into skin. The body treats the hair as a foreign substance and makes a cyst around it. Friction can occur from tight clothing, bicycling, or long periods of sitting. These cysts occur more often in people with a family history of them. People who have a lot of hair in the buttock area, are overweight, or are inactive have higher risks of getting these cysts. People who have poor hygiene, sweat a lot, or sit a lot are also more likely to have them.
Pilonidal cysts are often harmless but can become infected and painful. Symptoms of infection are pain, tenderness, warmth, redness, and swelling. Pus or an oily discharge can occur.
The health care provider makes a diagnosis from the medical history and physical examination.
The two main treatments are drainage and surgical removal of the cyst. Draining the pus is simple and is done if the cyst flares up. Because cysts tend to come back, after the flare-up has quieted down, surgery is often suggested.
Surgery involves removing the cyst while people are awake and the area is numbed. The surgeon cuts out the cyst and some tissue around it. The cut is usually left open to heal and close itself. Most people go home from the hospital that day. Recovery takes several days. Surgical treatment usually means a complete cure. A small scar will remain.
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