Pilonidal Sinus (Pilonidal Cyst)

A pilonidal sinus, commonly known as a “pilonidal cyst”, is a condition that usually occurs in the upper part of the cleft between the buttocks, around the tailbone. Small holes form in the skin, and beneath them channels develop that may contain hairs or tissue debris.

The condition is thought to develop when shed hairs are pushed into the skin by friction and pressure and cause an inflammatory reaction there. For this reason, the common belief that “the hair grows backwards from the inside” is not always correct.

A pilonidal cyst is most often seen after puberty and in young adulthood. Although it is more common in men, it can also develop in women. It is not a life-threatening condition; however, because of abscesses, pain and recurrent discharge it can have a considerable effect on daily life [1,2].

Not every pilonidal sinus needs to be operated on straight away. Small sinuses that cause no complaints and show no signs of inflammation can be monitored after assessment by a doctor [1].

What symptoms does a pilonidal cyst cause?

In some people, only one or a few small holes are seen over the tailbone and there may be no complaints at all.

When the condition becomes inflamed, the following symptoms may develop:

• Pain and tenderness over the tailbone
• Discomfort that gets worse especially when sitting or standing up
• Swelling and redness in the area
• Bloody or pus-like discharge from the holes in the skin
• Staining of underwear
• An unpleasant smell caused by the discharge
• Severe, throbbing pain when an abscess develops
• Fever, shivering or feeling generally unwell

Not every patient has a fever. A painful swelling suggests that an abscess may have developed, even if there is no fever.

Why does a pilonidal cyst develop?

There is no single cause behind the development of the condition. Factors that can increase the risk include:

• A deep cleft between the buttocks
• Dense or coarse body hair
• Shed hairs collecting in the area
• Sitting for long periods
• Friction and repeated local irritation
• Excess weight
• Sweating and moisture
• Tight or poorly ventilated clothing
• A family history of pilonidal sinus
• Having had the condition in the same area before

A pilonidal cyst is not caused only by poor personal hygiene. Regular care of the area can help to keep the condition under control; however, pilonidal sinus can also develop in people who are very clean.

The diagnosis is usually made by examination. By assessing the tailbone area and the cleft between the buttocks, the doctor can see small sinus openings, discharge, swelling or an abscess.

Most patients do not need imaging methods such as ultrasound or MRI. However, imaging may be requested if the condition is closer to the anus than to the tailbone, if there have already been several operations, or if another condition such as an anal fistula (perianal fistula) is suspected [1].

During the examination, the following conditions are also taken into account:

• Skin abscess
• Anal fistula
• Hidradenitis suppurativa
• Inflamed skin cyst
• Problems around the anus related to Crohn’s disease

Especially if the discharging opening is very close to the anus, it is important to distinguish whether this is a pilonidal sinus or an anal fistula.

There is no single treatment method for pilonidal sinus that is best for everyone. The choice of treatment depends on:

• Whether there is an abscess
• Whether the disease is limited or extensive
• Whether treatment has been given before
• The number and location of the sinus openings
• The patient’s work and daily life
• The surgeon’s experience with the method concerned

and is tailored to the individual [1,2].

Should a pilonidal cyst that causes no complaints be treated?

In people who have no pain, swelling or discharge and have not had an abscess before, an immediate preventive operation is not always necessary. Keeping the area clean, preventing hairs from collecting, and having an examination if a new complaint develops may be recommended [1].

The decision to monitor should be made together with the doctor, based on how the sinus looks on examination and the patient’s characteristics.

What is done when an abscess develops?

A painful, red, tense swelling over the tailbone suggests an abscess. The main treatment for a pilonidal abscess is to drain the pus through a small incision. This procedure can usually be carried out under local anaesthesia [1,2].

Antibiotics on their own generally do not clear the pus inside an abscess. If there is fever, redness spreading to the surrounding tissues, a problem with the immune system or another situation the doctor considers necessary, antibiotics may be used in addition to drainage.

Draining the abscess brings the pain and infection under control; however, the sinus beneath the skin may not disappear completely. If complaints persist or attacks recur after the abscess has healed, the definitive treatment is planned separately.

What non-surgical and minimally invasive methods are there?

Care of the area and hair control

Keeping the area clean and dry, preventing shed hairs from collecting in the buttock cleft and avoiding prolonged moisture can support treatment.

Frequent shaving with a razor can cause skin irritation and small cuts in some people. For this reason, the method of hair removal should be decided together with the doctor.

Laser hair removal can provide long-lasting reduction of hair in suitable patients. A recent controlled study involving young patients showed that laser hair removal added to standard care reduced the risk of the condition recurring within one year [4]. However, laser hair removal on its own does not treat every active or extensive sinus, and it usually requires several sessions.

Phenol application

Phenol is a chemical substance applied inside the sinus channel. It can be used together with cleaning of the sinus in limited disease without an abscess.

The procedure may need to be repeated more than once. Whether phenol treatment is suitable depends on the extent of the disease and the experience of the centre where the method is used [1,2].

Removal of small sinus openings

In limited disease, “pit-picking”-type methods can be used, in which only the small sinus openings in the skin are removed and the channels beneath them are cleaned.

Because the incisions are small, pain and the time needed to return to daily life are generally less. However, they may not be suitable for extensive, deep or previously recurrent disease.

Endoscopic treatment

In the endoscopic method, the sinus channels are viewed with the help of a thin camera, and the hairs and inflamed tissue inside are cleaned out. Because it is carried out through small incisions, it may offer advantages in terms of pain after the operation and the time needed to return to work.

Nevertheless, it is not suitable for every patient. Long-term recurrence results may vary according to the surgeon’s experience and the technique used [1].

What surgical methods are there?

Removal of the sinus with the wound left open

The diseased tissue is removed, and the wound is not closed with stitches but left to heal from the bottom upwards with dressings.

With this method there is no problem of the stitch line coming apart; however, regular dressings are needed and complete healing may take longer than several weeks.

Removal of the sinus with the wound closed

After the diseased area has been removed, the wound is closed with stitches. Healing and return to daily life may be faster than with methods in which the wound is left open.

Current guidelines and systematic reviews recommend that, if the wound is to be closed with stitches, the stitch line should not be left exactly in the middle of the deep cleft between the buttocks. This approach, called “off-midline closure”, may reduce the risk of the wound opening, infection and recurrence compared with conventional midline closure [1,3].

Flap methods

In extensive, deep or recurrent disease, operations in which healthy skin and the tissue beneath it are moved across may be performed. The Karydakis, Bascom cleft-lift and Limberg flap are examples of these methods.

The main aim of these operations is not only to remove the diseased tissue but also to make the deep cleft between the buttocks shallower, reducing the build-up of hair, friction and moisture.

Flap methods can be effective particularly in recurrent or complex disease. The most suitable technique is decided according to the location of the disease and the surgeon’s experience [1,2].

The recovery time varies according to the method used:

• After abscess drainage: The pain usually eases within a short time. Return to daily life can begin within a few days.
• After minimally invasive procedures: Many patients can go back to school or to desk work within a few days.
• After operations in which the wound is closed with stitches: Return to daily life usually takes place within about 1–3 weeks.
• After operations in which the wound is left open: Regular dressings are needed, and complete closure may take several weeks, sometimes longer.
• After flap operations: Recovery varies according to the method, the size of the wound and the work you do.

These times are approximate. Returning to physically demanding work, heavy exercise or sport may take longer.

What should you pay attention to during recovery?

• Follow the advice on dressings and wound care.
• Keep the area clean and dry.
• Prevent shed hairs from collecting around the wound.
• Avoid heavy exercise and activities that cause friction until your doctor allows them.
• Do not sit in the same position for long periods; stand up at short intervals.
• Eat a sufficient and balanced diet.
• If you smoke, get support to stop; smoking can have a negative effect on wound healing.
• Do not miss your follow-up appointments.

It is not necessary after every operation to lie face down for long periods or not to sit at all. Restrictions on sitting and movement should be set by the surgeon according to the method used.

When should you see a doctor?

You should contact your healthcare team if any of the following develops:

• Pain that keeps getting worse
• A new or growing swelling
• Fever or shivering
• Spreading redness
• Foul-smelling or increasing pus-like discharge
• Bleeding that does not stop
• Obvious opening of the stitches
• Deterioration in your general condition

1. Ojo D, Gallo G, Kleijnen J, et al. European Society of Coloproctology Guidelines for the Management of Pilonidal Disease. British Journal of Surgery. 2024;111(10). https://pubmed.ncbi.nlm.nih.gov/39397672/
2. Johnson EK, Vogel JD, Cowan ML, et al. The American Society of Colon and Rectal Surgeons’ Clinical Practice Guidelines for the Management of Pilonidal Disease. Diseases of the Colon & Rectum. 2019;62(2):146–157. https://pubmed.ncbi.nlm.nih.gov/30640830/
3. Cai Z, Li Z, Zhang C, et al. Midline and Off-midline Wound Closure Methods After Surgical Treatment for Pilonidal Sinus. Cochrane Database of Systematic Reviews. 2024;1. https://pubmed.ncbi.nlm.nih.gov/38226663/
4. Minneci PC, Halleran DR, Lawrence AE, et al. Laser Epilation as an Adjunct to Standard Care in Reducing Pilonidal Disease Recurrence in Adolescents and Young Adults: A Randomized Clinical Trial. JAMA Surgery.2024;159(1):19–26. https://pubmed.ncbi.nlm.nih.gov/37938854/