Other effects of serious damage include
nephrotic syndromeand kidney failure.
kidney failure A reduction in the func-
tion of thekidneys.Kidney failure can be
acuteor chronic. In acute kidney failure,
kidney function often returns to normal
once the underlying cause has been dis-
covered and treated; in chronic kidney
failure, function is usually irreversibly
lost. Causes of acute kidney failure in-
clude a severe reduction in blood flow
to the kidneys, as occurs in shock; an
obstruction to urine flow, for example
due to a bladder tumour; or certain
rapidly developing types of kidney dis-
ease, such as glomerulonephritis.Chronic
kidney failure can result from a disease
that causes progressive damage to the
kidneys, such as hypertension, long-
standing obstruction to urine flow, and
excessive use of analgesic drugs.
The most obvious symptom of acute
kidney failure is usually oliguria (reduced
volume of urine). This leads to a build-up
of urea and other waste products in the
blood and tissues, which may cause
drowsiness, nausea, and breathlessness.
Symptoms of chronic kidney failure de-
velop more gradually and may include
nausea, loss of appetite, and weakness.
If acute kidney failure is due to sudden
reduction in blood flow, blood volume
and pressure can be brought back to
normal by saline intravenous infusionor
blood transfusion.Surgery may be needed
to remove an obstruction in the urinary
tract. Acute kidney disease may be treat-
ed with corticosteroid drugs. Treatment
may also involve diuretic drugs and tem-
porary dialysis(artificial purification of
the blood). A high-carbohydrate, low-
proteindiet with controlled fluid and
salt intake is important for both types
of kidney failure. Chronic kidney failure
may progress over months or years
towards end-stage kidney failure, which
is life-threatening. At this stage, long-
term dialysisor a kidney transplantis
the only effective treatment.
kidney function testsTests performed
to investigate kidney disorders. Urinalysis
is a simple test in which a urine sample is
examined under a microscope for blood
cells, pus cells, and casts (cells and
mucousmaterial that accumulate in the
tubules of the kidneys and pass into the
urine). Urine may be tested for sub-
stances, such as proteins, that leak into
the urine when the kidneys are damaged.
Kidney function can be assessed by
measuring the concentration in the
blood of substances, such as ureaand
creatinine, that the kidneys normally
excrete. Kidney function may also be
assessed by kidney imagingtechniques.
kidney imaging Techniques for visual-
izing the kidneys, usually performed for
diagnosis. Ultrasound scanningcan be
used to identify kidney enlargement, a
cystor tumour, and the site of any
blockage. Conventional X-raysshow the
outline of the kidneys and most kidney
stones. Intravenousurography shows the
internal anatomy of the kidney and ure-
ters.Angiographyis used to image
blood circulation through the kidneys.
CT scanningand MRIprovide detailed
cross-sectional images and can show
abscesses or tumours. Two types of
radionuclide scanning are used for the
kidney: DMSA and DTPA scanning. DMSA
is a substance given by intravenous in-
jection that binds to cells in the kidney
tubule, giving a single, static picture of
the kidneys. DTPA, also given intraven-
ously, is filtered in the kidneys and
passes out in the urine. Pictures taken at
intervals record its passage through the
urinary tract and show kidney function.
kidney, polycysticAn inherited disorder
in which both kidneysare affected by
numerous cyststhat gradually enlarge
until most of the normal kidney tissue
is destroyed. Polycystic kidney disease is
distinguished from multiple simple kid-
ney cysts, which occur commonly with
age. There are 2 types of polycystic dis-
ease. The most common usually becomes
apparent in middle age, producing ab-
dominal swelling, pain, and blood in the
urine. As the disease progresses, hyper-
tensionand kidney failuremay result.
The rare type causes enlargement of the
kidneys and kidney failure in infants and
young children. There is no effective
treatment for preserving kidney func-
tion in either type, but symptoms of
kidney failure can be treated by dialysis
and kidney transplant.
kidney stone See calculus, urinary tract.KIDNEY FAILURE KIDNEY STONE
K