A pilonidal dimple is a small pit or hollow area (sinus) in the area at the very top of the crease between the buttocks (sacral area).

Most pilonidal dimples are harmless pits of small depressions that are present from birth. There may be increased hairiness around the area.

The pilonidal dimple may also be a deep tract, rather than a shallow depression, leading to a hollow space (sinus) that may contain hair. These can become infected and drain. On rare occasions, the sinus may extend into the spinal cord.

During adolescence, the dimple or tract may become infected, forming what is called a pilonidal abscess. It is also called a pilonidal cyst, although a true cyst may not be present. These may require surgical drainage or total removal to prevent reinfection.

• Congenital pilonidal dimple
• Congenital dermal sinus (of which the dimple is the mildest form)

Keep pilonidal dimples clean and free of debris during regular bathing. Report any drainage of fluid from the dimple, either clear or containing pus, to your health care provider.

Call your health care provider if you notice swelling, redness, drainage or tenderness around the pilonidal dimple.

You will be asked for your medical history and given a physical examination. In the vast majority of cases, the examining physician will merely comment that you or your infant or child has a pilonidal dimple and that you should not worry. Sometimes you may be asked for the following information:

• Has there been any change in the appearance of the pilonidal dimple?
• Has there been any drainage from the dimple?
• Are any other symptoms developing?
• What other symptoms are also present?
• Is there any numbness or loss of movement in the legs?
• Has there been any change in bladder control?

If there is infection present, you or your child may need surgery to address the abscess or cyst. Studies may be done to determine if the pilonidal dimple or sinus extends to the spinal cord.