been made in the treatment of HIV
infection (see antiretroviral drugs).
antral irrigationIrrigation of the max-
illary antrum, one of the nasal sinuses.
More commonly known as sinus wash-
out, this procedure is used to diagnose
and treat persistent sinusitis. Antral irri-
gation is performed less often since the
introduction of nasal endoscopy.
anuriaComplete cessation of urine out-
put. Anuria may be caused by a severe
malfunction of the kidneys, but a more
common cause is a complete blockage
of urine flow, due to enlargement of the
prostate gland (see prostate,enlarged),
a bladder tumour, or a stone (see calcu-
lus,urinary tract). Failure of the kidneys
to produce urine may be due to oxygen
depletion as a result of reduced blood
flow through the kidneys, as occurs in
shock, or to severe kidney damage
caused by a disease such as glomer-
ulonephritis. Anuria requires urgent
investigation. Treatment of the cause
may restore urine production, but any
delay can result in permanent kidney
damage, leading to uraemia.
anusThe end of the alimentary tract
through which faeces are expelled from
the body. The orifice at the end of the
anal canal is open only during defaeca-
tion; at other times it is kept closed by
the muscles of the anal sphincter. (See
also digestive system.)
anus, cancer ofA rare cancer of the
skin of the anus. Possible early signs
are development of swelling or an ulcer
at the anus accompanied by bleeding
and discomfort. Treatment is by surgical
removal and/or radiotherapy.
anus, disorders ofMost anal disor-
ders affect adults and are minor, but
they may cause discomfort. Rarely, the
anus may fail to develop normally and
surgical treatment is needed (see anus,
imperforate). In anal stenosis, the anus
is too narrow to allow the passage of
faeces. Anal fissures originate from
tears in the lining of the anus, usually
as a result of straining to pass faeces.
Cancer of the skin around the anus is
rare (see anus,cancer of). Haemorrhoids
are enlarged blood vessels under the
anal lining. An anal fistulais an abnor-
mal channel connecting the anal canalwith the skin surrounding the anus.
Itchingof the anus is common and may
be due to haemorrhoids or other disor-
ders such as threadworm infestation.
anus, imperforateA rare congenital
abnormality in which the anal opening
is missing or covered over. The severity
of the condition varies from complete
absence of the anal canal to only a layer
of skin covering the anal opening.
Treatment involves surgery. A colos-
tomymay be needed initially before
definitive surgery to construct an anus.
anxietyAn unpleasant emotional state
ranging from mild unease to intense
fear. Various physical symptoms are
associated with anxiety; the most com-
mon include palpitations, chest pains, a
feeling of tightness in the chest, and
a tendency to overbreathe (see hyper-
ventilation). Muscle tension leads to
headaches and back pains. Gastroin-
testinal symptoms include dry mouth,
bloating, diarrhoea, nausea, and diffi-
culty in swallowing. Other symptoms
include sweating, blushing, pallor, light-
headedness, and a frequent need to
urinate or defaecate. Anxiety is a nor-
mal response to stressful situations and
prepares the mind and body to respond
effectively. However, anxiety that occurs
without reason may be a symptom of an
anxiety disorderor another psychologi-
cal disorder such as depression.
People suffering from anxiety may be
helped by counsellingor psychotherapy.
If there is an underlying disorder such
as depression, treatment with antianx-
iety drugscan help. Antianxiety drugs
are used for short-term control of symp-
toms but are avoided for long-term
treatment because they are addictive.
anxiety disordersA group of mental
illnesses, including several specific syn-
dromes, in which symptoms of anxiety
are the main feature. These disorders are
common and mainly affect young adults.
In generalized anxiety disorder, there
is persistent tension and apprehension
that has no specific focus or cause,
together with physical or psychological
symptoms that disrupt normal activity.
Panic disorders are characterized by
sudden attacks of extreme, unreason-
able anxiety. Phobias are irrational fears,ANTRAL IRRIGATION ANXIETY DISORDERSA