What is a pilonidal sinus?
A pilonidal sinus is a small opening or tunnel beneath the skin near the tailbone, usually in the cleft between the buttocks. Hair and debris can become trapped and lead to infection.
A pilonidal sinus often causes repeated swelling, pain or discharge. Pilonidal disease is separate from an anal fistula, which usually opens closer to the anus.
What are the symptoms of a pilonidal sinus?
Common symptoms are:
- Pain, swelling or redness in the cleft between the buttocks, near the tailbone
- Pus or fluid leaking from small openings in the skin
- A wound that does not heal after an earlier drainage
- Discomfort when sitting for long periods
- Fever or spreading redness, which may mean an abscess and needs prompt care
How is a pilonidal sinus diagnosed?
The surgeon examines the openings, swelling, scars and the extent of affected tissue. Previous drainage or surgery, repeated infections, work, sitting and wound-care support all influence the plan. Imaging is not routinely needed unless the diagnosis or extent is uncertain.
When does a pilonidal sinus need surgery?
An acute abscess is treated by incision and drainage. Antibiotics may be added for surrounding skin infection or another clinical reason, but they do not replace drainage.
Surgery is advised for discharge, repeated abscesses or recurrent disease. A planned procedure treats the sinus tract and lowers the chance of it coming back.
How is a pilonidal sinus treated, and what are the risks?
Laser pilonidal ablation is used in selected patients. It treats the sinus tract through small openings, so the wounds are smaller. More extensive or recurrent disease is treated by surgical excision. When a wound is closed, using an off-midline flap repair (such as a Karydakis or Limberg flap) keeps the scar away from the deep midline cleft. In a Limberg flap, the diseased area is removed in a diamond shape and nearby skin is moved across to close it.
Risks include pain, bleeding, infection, wound separation, slow healing and recurrence. The most suitable operation depends on disease extent, previous treatment and the practical demands of wound care.
Recovery after pilonidal sinus surgery
An open wound may need dressings for several weeks. A closed wound may heal sooner, although infection or separation can delay recovery. Confirm who will provide dressings and when sitting, driving, exercise and work can resume.
Follow instructions about washing, dressings and hair management. Seek advice if pain increases, discharge changes or fever develops. Do not shave the area unless your clinician has advised a safe method.
When to seek urgent care
Seek prompt medical care for a painful swelling, pus or bleeding at the top of the buttock cleft. Fever, spreading redness or feeling unwell may mean an abscess. Do not squeeze or try to drain it yourself.