A pilonidal abscess and sinus is a common condition and usually
affects relatively young patients in the age range of 15 to 30 years.
The term comes from the Latin pilo~, meaning hair, and nidus~, meaning
nest. It is caused by body hair penetrating the skin of the natal
cleft and causing infection.
Although a harmless condition, a pilonidal abscess and sinus
frequently runs a chronic and recurrent course and can be a most
debilitating condition for a young person to experience. Symptoms
usually involve recurrent abscess formation with discharge and
discomfort or even pain on sitting for prolonged periods. The
discharge is often malodorous and stains clothing, causing severe
embarrassment. Once established it virtually never heals completely of
its own accord and surgical intervention is required.
There is still much debate as to how the hairs get under the skin. The
acquired theory is that the hairs dig their way into the skin by
rubbing and pressure and, because of the shape and arrangement of the
keratin scales (like a fir tree under the microscope), continue to
move in one direction only — inwards. The congenital theory is that
epidermal hair cells form too deeply under the skin during embryonic
formation, and eventually grow up from the deep layer of the skin,
piercing the skin and letting in bacteria. Either way, bacteria are
able to enter the subcutaneous tissues and cause infection which
eventually develops into a pilonidal abscess.
In the early stages of the infection there may just be some
superficial cellulitis that will settle with antibiotics. However,
this may develop into an abscess, identifiable by the severe degree of
pain and the obvious presence of a fluctuant subcutaneous mass.
Antibiotics are contraindicated for such abscesses and urgent surgical
incision and drainage is required. Most pilonidal sinuses will start
as a pilonidal abscess. When the first abscess has formed and been
drained, there will be one of two outcomes. Either there is complete
healing of the abscess or a sinus forms which does not heal and
discharges either pus or serious fluid continuously.
Even if the abscess apparently heals, it can lie dormant and
subsequently form another abscess which is a sign that there are still
numerous hairs trapped under the skin. The development of a sinus or
of recurrent abscesses usually indicates that definitive surgery is
Careful research within the surgical literature identifies the causes
of recurrent pilonidal problems. In essence, the factors that
predispose to either wound breakdown or early recurrence are a midline
wound, a deepened natal cleft (bumcrack) and wound tension. Surgery
for pilonidal sinus should not only aim to cure the problem but avoid
the factors that cause the sinus or recurrence in the first place.
Simple excision with healing by dressings:
Due to the cumulative recurrence rate and the tendency for multiple
recurrence, surgery by excision leaving an open wound with healing by
secondary intention is still the most commonly performed operation for
all pilonidal disease. This requires wound packing and daily dressings
either at the general practice surgery or by the local district nurse,
and it can take about six to twelve weeks to heal. This is a
time-consuming and frustrating period for both practitioner and
patient. It can be three months until the patient’s normal duties can
resume, often resulting in significant loss of income. The recurrence
rate is very high as by the time healing has occurred more hairs have
grown into the wound starting the whole process again. This type of
surgery is outdated and no longer necessary.
The most commonly performed operations for pilonidal sinus that are
aimed at achieving primary closure are simple excision with primary
closure and the Karydakis procedure.
Simple excision with primary closure:
The simple excision with primary closure is aimed at removing the
disease by excising a centrally placed ellipse of tissue and then
primary closure by approximating the two resulting edges. This
operation results in a midline scar which is under tension and often
produces a deepened natal cleft. It is therefore not surprising that
this operation is associated with high rates of wound breakdown and
recurrence. Wound breakdown will require packing and dressing to
achieve full healing due to the size of the wound that is left after
The Karydakis procedure:
The Karydakis procedure is similar to simple excision with primary
closure, but aims to remove an eccentrically placed ellipse so that
the resulting wound is not in the midline and in so doing flattening
(rather than deepening) the natal cleft. However, in order to achieve
this, a larger than necessary excision is sometimes required which
results in significant wound tension. It is therefore prone to wound
breakdown (albeit less than the simple excision with primary closure),
leaving the patient with a large open wound that will require repeated
packing and dressings.
In order to achieve a tension-free, primarily closed wound, which
avoids a scar in the midline and at the same time flattens the natal
cleft, some type of flap procedure is required. The Karyadakis
procedure is frequently referred to as a flap procedure but this is
not strictly the case.
Rhomboid rotation flap
My preferred operation for pilonidal sinus is the rhomboid rotation
flap, which excises the diseased tissue and closes the wound in a
tension-free manner by rotating a similar-sized flap of tissue from
the neighbouring buttock. It also avoids a midline wound and in the
process flattens the natal cleft.
The rhomboid rotation flap operation produces excellent primary
healing and a very low recurrence rate. Most patients return to work
with a fully healed wound after two weeks, to normal non-sporting
activities within four weeks and to contact sport after six weeks.
Many surgeons are critical of flap procedures due to their complexity
and the need to involve tissue from the neighbouring buttock, but very
few complaints are received from patients with a nicely healed wound
at two weeks. Nevertheless, flap surgery is complicated and highly
specialised so requires experience and specific training in this type
of surgery to achieve ideal results.
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