Pilonidal sinus

# Overview
A pilonidal sinus is an infected tract under the skin, usually between the buttocks, in the natal cleft. It is usually a small cavity containing a tuft of hair and possibly can be oozing pus.
A sinus tract is a small abnormal channel (like a small tunnel) in the body. A tract typically goes from the source of infection, often deep within the body, to the skin's surface. A sinus can be developed after an abscess is cleared (by itself or by medical treatment), then one of more of the small openings (tracts) join the cavity to the skin surface. This is not always the case as some people can develop a pilonidal sinus without ever having a pilonidal abscess.
Anyone can develop a pilonidal sinus. However, it mainly affects people between the age of 16 and 30.

# Causes
Pilonidal means "nest of hairs". Ingrown hairs can be one of many causes of pilonidal sinus. Discussion with a number of hair stylists indicate the pilonidal sinus have occurred on arms and other areas of the body due to the burrowing of hair.
Pilonidal sinus between the buttocks could be caused by ingrown hairs. Due to increase moisture and pressure around the buttocks area, ingrown hairs find it easier to bury into the skin. Pressure around the buttocks inhibits the body to reject the hair and thus allow it to continue to bury deeper until infection occurs.

# Treatment
In some cases, it can be treated with antibiotics and ointment. In more severe cases, surgery is required. Surgery involves either drainage of the sinus, or complete excision.
Drainage is the preferred method of treatment; however, sinus can return even if it has been drained. The doctor lances the abscess and drains all the pus. Then the abscess is washed with saline. The wound is left open and packed by a piece of gauze, which can fall out a few days later or be changed daily. This is a small operation and can cure the problem. Forty per cent of patients have a recurrence of pilonidal disease. To fully erase all chances of it returning, excision is required.
Full-excision surgery is one way of removing the abscess and sinus tracts. The surgeon uses a scalpel to remove the cavity and sinus tracts. The wound can then be left open to heal, which causes new scar tissue to grow at the base of the wound which gradually fills in the cavity (this process is called granulation). Another way is to partially close the wound, which is called marsupialisation. The edges of the wound down to deeper tissues are stitched with absorbable stitches. This procedure ensures that the centre of the wound is healing as quickly as the sides.
Surgeons can also excise the sinus and repair with a reconstructive flap technique which is done under general anesthetic. This is mainly for complicated pilonidal disease, or those who have reoccuring pilonidal disease. The surgeon cuts out the infected tissue, then moves the surrounding skin to the natal cleft and stitches it. This method leaves little to no scar as it is hidden. This method also flattens the region between the buttocks, reducing the risk of recurrence.

# Diagnosis

## Physical Examination

### Skin
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.
- Pilonidal sinus. With permission from Dermatology Atlas.