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Pilonidal sinus

A pilonidal sinus is a small pit that occurs at the bottom of the tailbone or coccyx that can become infected and filled with pus.

Once infected, it is known as a pilonidal abscess. Pilonidal abscesses look like a boil at the bottom of the tailbone, just above the crack of the buttocks. It is more common in men than in women and usually happens in the late teens or early 20s.

Illustration of pilonidal abscess

Pilonidal sinus causes

Most doctors think that ingrowing hairs cause pilonidal sinuses. Pilonidal means "nest of hair". It is common to find hair follicles inside the sinus.

Another theory is that pilonidal sinuses appear after an injury to the sacrococcygeal region (the region relating to both the sacrum [the lower vertebrae] and coccyx). During World War II, more than 80,000 soldiers developed pilonidal sinuses that required a hospital stay. People thought the sinuses were due to irritation from riding in bumpy vehicles. For a while, in the US the condition was actually called "Jeep disease".

Pilonidal sinus symptoms

The symptoms experienced by someone with a pilonidal sinus include the following:

  • Pain at the bottom of the spine.
  • Swelling at the bottom of the spine.
  • Redness at the bottom of the spine.
  • Draining pus.
  • Fever.

When to seek medical care

A pilonidal sinus is an abscess or boil. It needs to be drained, or lanced, to help it resolve. Like other boils, it does not usually improve with antibiotics alone. If any of the following symptoms occur, seek medical advice:

  • Pain at the bottom of the spine.
  • Swelling at the bottom of the spine.
  • Redness at the bottom of the spine.
  • Pus draining from the sinus.
  • Raised temperature with any of the above symptoms.

Examinations and tests

The doctor can diagnose a pilonidal sinus by taking a history (asking about the patient's history and symptoms regarding the sinus) and performing a physical examination. The doctor may find the following conditions:

  • Tenderness, redness and swelling between the cheeks of the buttocks.
  • Raised temperature.
  • Increased white blood cells on a blood sample (not always taken).
  • Inflammation of the surrounding skin.

Pilonidal sinus treatment self-care at home

Early in an infection of a pilonidal sinus, the redness, swelling and pain may be minimal. Sitting in a warm bath may decrease the pain and may also decrease the chance that the sinus will develop to the point of requiring incision and drainage.

Medical treatment

Antibiotics alone do not heal a pilonidal sinus. Doctors have a number of procedures available, including the following treatments:

The preferred technique for a first pilonidal sinus is incision and drainage of the sinus, removing the hair follicles, and packing the cavity with gauze.

  • Advantage - This is a simple procedure done under local anaesthesia
  • Disadvantage - This requires frequent changing of the gauze packing until the sinus heals, which sometimes takes up to three weeks
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