Bma Illustrated Medical Dictionary

stone in the bladder (see calculus, urin-
ary tract), and enlargement or tumour
of the prostate (see prostate, enlarged;
prostate, cancer of). In females, causes
include pressure on the urethra from
uterine fibroidsor from a fetus. In either
sex, the cause may be a bladder tumour.
Retention may also be due to defective
functioning of the nerve pathways sup-
plying the bladder as a result of general
or spinal anaesthesia, drugs affecting
the bladder, surgery, injury to the nerve
pathways, or disease of the spinal cord.
Complete retention causes discomfort
and lower abdominal pain, except when
nerve pathways are defective. The full
bladder can be felt above the pubic bone.
However,chronic or partial retention
may not cause any serious symptoms.
Retention can lead to kidney damage
and, often, a urinary tract infection.
Treatment of retention is by catheteri-
zation (see catheterization, urinary). The
cause is then investigated. Obstruction
can usually be treated; if nerve damage
is the cause, permanent or intermittent
catheterization is sometimes necessary.
urinary systemSee urinary tract.

urinary tractThe part of the body con-

cerned with the formation and excretion

of urine. The urinary tract consists of

the kidneys(with their blood and nerve

supplies), the renal pelvises (funnel-

shaped ducts that channel urine from

the kidneys), the ureters, the bladder,

and the urethra.

The kidneys make urine by filtering

blood. The urine collects in the renal

pelvises and is then passed down the

ureters into the bladder by the actions

of gravity and peristalsis. Urine is stored

in the bladder until there is a sufficient

amount present to stimulate micturi-

tion. When the bladder contracts, the

urine is expelled through the urethra.

urinary tract infectionAn infection

anywhere in the urinary tract.It has

differing symptoms, depending on the

area affected. Urethritiscauses a burn-

ing sensation when urine is being

passed. Cystitiscauses a frequent urge

to pass urine, lower abdominal pain,

haematuria, and, often, general malaise

with a mild fever. Pyelonephritiscauses

fever and pain in the back under the

ribs. Cystitis and pyelonephritis are

URINARY TRACT

URINARY SYSTEM URINARY TRACT INFECTION

U

Adrenal gland

(cross section)

Kidney
(whole)

Renal
artery

Prostate
gland

Urethra

Aorta

Kidney (cross section)

Renal vein

Peritoneum folded back

Ureter

Bladder

Ureter Bladder

MALE FEMALE

Urethra