KIDNEY CYST
K
DISORDERSOFTHE KIDNEY
The
k i d n e y s
are susceptible to a wide
range of disorders. Only one normal
kidney is needed for good health,
however, so disease is rarely life-
threatening unless it affects both kidneys
and is at an advanced stage.
H y p e r t e n s i o n
(high blood pressure) can be both a
cause and an effect of kidney damage.
Other effects of serious damage include
n e p h r o t i c s y n d r o m e
and
k i d n e y f a i l u r e .
Congenital and genetic disorders
Congenital abnormalities, such as
d u p l e x
k i d n e y
(in which a kidney is partially
duplicated) and
h o r s e s h o e k i d n e y
(in
which the two kidneys are joined at their
base), are fairly common and usually
harmless. Serious inherited disorders
include polycystic kidney disease (see
k i d n e y , p o l y c y s t i c ) ,
in which multiple cysts
develop on both kidneys; and
F a n c o n i s
s y n d r o m e
and
r e n a l t u b u l a r a c i d o s i s ,
in
which the kidney tubules function
abnormally so that certain substances
are inappropriately lost in the urine.
Impaired blood supply
Various conditions may cause damage
to, or lead to blockage of, the blood
vessels within the kidneys, impairing
blood flow. Such conditions include
s h o c k , h a e m o l y t i c - u r a e m i c s y n d r o m e , p o l y -
a r t e r i t i s n o d o s a , d i a b e t e s m e l l i t u s ,
and
s y s t e m i c l u p u s e r y t h e m a t o s u s .
Impaired
blood flow through the kidneys can lead
to tissue damage, hypertension, and
kidney failure.
Autoimmune disorders
G l o m e r u l o n e p h r i t i s
includes a group of
autoimmune disorders (in which the
immune system attacks the body’s own
tissues) that cause the filtering units of
the kidneys to become inflamed and
unable to function normally.
Drugs
Allergic reactions to drugs, prolonged
treatment with
a n a l g e s i c d r u g s
(pain-
killers), and some
a n t i b i o t i c s
can damage
kidney tubules.
Tumours
Noncancerous
k i d n e y t u m o u r s
are rare;
k i d n e y c a n c e r
is uncommon.
Metabolic disorders
Diabetes mellitus is the commonest cause
of kidney failure in developed countries.
Other metabolic disorders, such as
h y p e r u r i c a e m i a
, may cause kidney stones
to form (see
c a l c u l u s , u r i n a r y t r a c t ) .
Infection
Infection of the kidney is called
p y e l o -
n e p h r i t i s
and can be a complication of
c y s t i t i s . A
predisposing factor to infection
is obstruction of urine flow through the
urinary tract due to a kidney or ureteral
stone, tumour, or congenital defect.
Other disorders
H y d r o n e p h r o s i s
(a kidney swollen with
urine) is caused by obstruction of the
urinary tract.
C r u s h s y n d r o m e
is a
condition in which kidney function is
disrupted by proteins released into the
blood from damaged muscle.
INVESTIGATION
Kidney disorders are investigated by
kidney imaging
techniques such as
ultrasound scanning, urography,
angiography,
and
CTscanning
or MRI;
by
kidney biopsy
(removal of a small
amount of tissue for analysis; by
blood
tests;
and by
kidneyfunction tests
such
as
urinalysis
.
w h o
h a v e t a k e n
c e r t a i n
a n a l g e s i c d r u g s
f o r a l o n g t i m e . B l o o d i n t h e u r i n e i s a
c o m m o n s y m p t o m ;
h y d r o n e p h r o s i s
( d i s -
t e n s i o n o f t h e k i d n e y w i t h u r i n e ) m a y
o c c u r d u e t o b l o c k a g e o f t h e u r e t e r .
DIAGNOSIS, TREATMENT, AND OUTLOOK
T h e
d o c t o r
w i l l
c o n d u c t
a
p h y s i c a l
e x a m i n a t i o n a n d t e s t a u r i n e s a m p l e f o r
t h e p r e s e n c e o f b l o o d . D i a g n o s i s c a n b e
c o n f i r m e d
b y
u l t r a s o u n d s c a n n i n g
,
C T
s c a n n i n g
,
M R I
,
o r i n t r a v e n o u s
u r o g r a p h y
.
A l l
t y p e s
o f k i d n e y
c a n c e r
r e q u i r e
s u r g i c a l r e m o v a l o f t h e a f f e c t e d k i d n e y
a n d s o m e t i m e s a l s o
o f t h e
u r e t e r
.
A n y
r e m a i n i n g c a n c e r o u s c e l l s a r e d e s t r o y e d
u s i n g
r a d i o t h e r a p y
a n d / o r t r e a t m e n t w i t h
a n t i c a n c e r d r u g s
( f o r e x a m p l e ,
i n t e r l e u k i n
o r
m e d r o x y p r o g e s t e r o n e
a r e g i v e n t o t r e a t
s o m e c a s e s o f r e n a l c e l l c a r c i n o m a ) .
S u r v i v a l r a t e s v a r y , d e p e n d i n g o n t h e
t y p e o f c a n c e r a n d h o w e a r l y t r e a t m e n t
i s c o m m e n c e d . I n t h e c a s e o f n e p h r o -
b l a s t o m a ,
a b o u t
f o u r
i n
e v e r y
f i v e
a f f e c t e d c h i l d r e n s u r v i v e ; c u r e r a t e s f o r
t h i s f o r m o f k i d n e y c a n c e r a r e r e l a t i v e l y
h i g h e v e n i f i t h a s s p r e a d b y t h e t i m e
d i a g n o s i s i s m a d e .
k id n e y c y st
A
f l u i d - f i l l e d
s a c
i n
t h e
k i d n e y
.
C y s t s
c o m m o n l y d e v e l o p i n p e o p l e o v e r
5 0 ,
a n d c a n o c c u r e i t h e r s i n g l y o r m u l t i p l y
i n o n e o r b o t h k i d n e y s . M o s t c y s t s o c c u r
f o r n o k n o w n r e a s o n , a r e n o n c a n c e r o u s ,
a n d d o n o t u s u a l l y p r o d u c e s y m p t o m s
u n l e s s
t h e y
b e c o m e
l a r g e
e n o u g h
t o
c a u s e l o w e r b a c k p a i n d u e t o p r e s s u r e
o n s u r r o u n d i n g t i s s u e s . L a r g e n u m b e r s
o f k i d n e y c y s t s , h o w e v e r , m a y b e a s s o c i -
a t e d w i t h p o l y c y s t i c k i d n e y d i s e a s e ( s e e
k i d n e y , p o l y c y s t i c
) , w h i c h o f t e n l e a d s t o
k i d n e y f a i l u r e
.
S i m p l e
c y s t s
d o n o t u s u a l l y
r e q u i r e
t r e a t m e n t . F o r c a s e s i n w h i c h t h e c y s t s
a r e p a i n f u l o r r e c u r r e n t , h o w e v e r , a s p i -
r a t i o n ( w i t h d r a w a l o f f l u i d )
o r s u r g i c a l
r e m o v a l m a y b e c a r r i e d o u t .
k id n e y , d u p le x
S e e
d u p l e x k i d n e y
.
k id n e y fa ilu r e
A
r e d u c t i o n
i n
t h e
f u n c t i o n
o f
t h e
k i d n e y s .
K i d n e y
f a i l u r e
c a u s e s
w a s t e
p r o d u c t s s u c h a s u r e a a n d e x c e s s f l u i d
t o a c c u m u l a t e i n t h e b o d y , a n d a l s o p r o -
d u c e s o t h e r c h e m i c a l i m b a l a n c e s i n t h e
b l o o d a n d b o d y t i s s u e s .
TYPES
K i d n e y f a i l u r e c a n b e a c u t e o r c h r o n i c .
I n t h e a c u t e f o r m , k i d n e y f u n c t i o n o f t e n
r e t u r n s t o n o r m a l o n c e t h e u n d e r l y i n g
c a u s e h a s b e e n d i s c o v e r e d a n d t r e a t e d .
I n c h r o n i c k i d n e y f a i l u r e , h o w e v e r , k i d -
n e y t i s s u e i s p r o g r e s s i v e l y d a m a g e d o v e r
s e v e r a l m o n t h s o r y e a r s . T h i s c o n d i t i o n
m a y
d e v e l o p
i n t o
e n d - s t a g e
k i d n e y
f a i l u r e ,
a
l i f e - t h r e a t e n i n g
c o n d i t i o n
i n
w h i c h
k i d n e y
f u n c t i o n
i s
u s u a l l y
i r r e v e r s i b l y l o s t .
CAUSES
C a u s e s o f a c u t e k i d n e y f a i l u r e i n c l u d e a
s e v e r e
r e d u c t i o n i n b l o o d f l o w t o t h e
k i d n e y s , a s o c c u r s i n
s h o c k
;
a n o b s t r u c -
t i o n t o u r i n e f l o w , f o r e x a m p l e d u e t o a
b l a d d e r
t u m o u r ;
o r
c e r t a i n
r a p i d l y
d e v e l o p i n g
t y p e s
o f
k i d n e y
d i s e a s e ,
s u c h a s
g l o m e r u l o n e p h r i t i s
.
C h r o n i c
k i d n e y
f a i l u r e
c a n
b e
t h e
r e s u l t o f a d i s e a s e t h a t c a u s e s p r o g r e s -
s i v e
d a m a g e
t o
t h e
k i d n e y s ,
s u c h
a s
p o l y c y s t i c
k i d n e y
d i s e a s e
( s e e
k i d n e y ,
448
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