An abscess is a cavity full with pus. It can happen anywhere in the body but it
happens particularly frequently around the anus. The obvious reason is that the
area of the anus is inhabited by billions of bacteria which, although they are not
usually harmful, they can multiply out of control and cause infection under
Pain is the commonest symptom. The pain is located around the anus but
sometimes it may be felt deep inside the rectum or towards the coccyx. It is
usually constant and throbbing and does not subside with painkillers.
There is associated swelling and the patient can usually feel a lump appearing
around the anus. This lump feels tender and hot. It appears red and sometimes
it can have a puncture on top which leaks pus. There may also be fever,
shivering and malaise.
What causes a perianal abscess?
Any injury, such as after an anal fissure or after an operation in the area.
Cancer (very rarely, when a rectal tumour perforates in the area).
Other rare infections such as hidradenitis suppurative, tuberculosis etc.
Abscess develop more frequently on people who are “immuno-compromised”, i.
e. their body defenses are low. This may be anyone who is seriously ill, has
cancer, is on immunosuppressive drugs such as steroids, has HIV infection,
Men develop abscesses more often than women.
Abscesses vary in location around the anus and, depending on their relation to
the sphincter muscles and the pelvic floor they are classified into
Generally, the closer an abscess lies to the skin the easier is to treat. The higher
an abscess lies the more difficult is to eradicate the infection and there is higher
chance of chronic or recurrent problems with it.
Once it is formed, an abscess has a tendency to burst towards the nearest “exit”
which may be the skin, the anal canal or rectum or even other structures within
the pelvis. The drainage is achieved through formation a "fistula" which is sinus
track. Spontaneous drainage is sometimes also spontaneous cure. Nevertheless
spontaneous drainage is not ideal because in many cases it leaves behind a
fistula as a long term problem. Also spontaneous drainage may be too late and
serious infection may occur in the area. This is why we should never rely on
spontaneous drainage and delay surgical treatment of the abscess.
In most cases spontaneous drainage does not occur that easily. In that case
treatment is surgical and consists of “Incision and Drainage” of the pus. Often
curettage of the abscess cavity and debridement is necessary. If an associated
fistula is found then this is usually laid open at the same time. The wound is
always left open and packed with gauze and antiseptic solutions. Dressings are
required for several days. Depending on the size, the wound cavity may take a
few weeks to heal. However it is not painful and usually after the first week it can
be treated with salt baths and simple covering with Vaseline gauze. The patient
does not need to stay in bed and can fully mobilize and resume normal activities,
work etc. while the wound is healing slowly.
Antibiotics are often given in order to fight surrounding infection (cellulitis) but it
is important to remember that antibiotics alone cannot cure an abscess because
they cannot enter the cavity. Surgery is almost always necessary.
If left untreated the perianal abscess can result into serious complications such
as gangrene of the perineum and general sepsis.
A significant number of perianal abscesses will recur within a year or two,
particularly if there are pre-disposing factors. A number of them will give rise to
“fistula in ano” which is discussed separately.
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