THROMBOSIS, DEEP VEIN
i s
n e i t h e r
a
t e n d e n c y
t o
b l e e d
n o r
t o
f o r m
c l o t s
( s e e
b lo o d c lo t tin g ).
T h r o m b o s i s
c a n
o c c u r
i f t h i s
m e c h a -
n i s m i s d i s t u r b e d i n f a v o u r o f c l o t t i n g .
( S e e
t h ro m b o p h ilia .)
I n
a r t e r i e s ,
t h r o m b u s
f o r m a t i o n
i s
e n c o u r a g e d b y
a t h e ro s c le ro s is
( a b u i l d -
u p
o f f a t t y
d e p o s i t s
o n
t h e
w a l l s
o f
a r t e r i e s ) ,
s m o k i n g ,
h y p e rt e n s io n
( h i g h
b l o o d p r e s s u r e ) , a n d d a m a g e t o b l o o d
v e s s e l w a l l s f r o m i n f l a m m a t i o n i n
a rte ri-
tis
a n d
p h le b it is .
A n i n c r e a s e d c l o t t i n g
t e n d e n c y m a y o c c u r i n
p re g n a n c y ,
w i t h
t h e u s e o f
o ra l c o n tra c e p t iv e s ,
o r t h r o u g h
p r o l o n g e d i m m o b i l i t y .
SYMPTOMS
A n
a r t e r i a l
t h r o m b o s i s
m a y
c a u s e
n o
s y m p t o m s
u n t i l
t h e
b l o o d
f l o w
i s
i m p a i r e d . W
h e n t h i s o c c u r s , i t l e a d s t o
r e d u c e d f u n c t i o n i n t h e t i s s u e s u p p l i e d
b y t h e
a f f e c t e d a r t e r y ,
a n d s o m e t i m e s
s e v e r e
p a i n .
V e n o u s
t h r o m b o s i s
m a y
c a u s e p a i n a n d s w e l l i n g .
DIAGNOSIS AND TREATMENT
D i a g n o s i s o f t h r o m b o s i s i s b y d o p p l e r
u lt ra s o u n d .
I n s o m e c a s e s ,
a n g io g ra p h y
o r
v e n o g ra p h y
m a y a l s o b e u s e d . T r e a t m e n t
m a y i n c l u d e
a n tic o a g u la n t d ru g s
o r
th ro m -
b o ly tic
d ru g s ,
n o n s t e ro id a l
a n ti-in fla m -
m a to ry d ru g s,
a n d , i n s o m e c a s e s ,
a n tib io tic
d ru g s .
I n l i f e - t h r e a t e n i n g c a s e s ,
t h ro m b e c -
to m y
( s u r g i c a l
r e m o v a l
o f
t h e
b l o o d
c l o t ) m a y b e n e e d e d .
th ro m b o s is , d e e p v e in
T h e
f o r m a t i o n
o f
a
t h ro m b u s
( b l o o d
c l o t ) w i t h i n d e e p - l y i n g v e i n s i n t h e l e g .
CAUSES
T h e c a u s e i s u s u a l l y a c o m
b i n a t i o n o f
s l o w
b l o o d f l o w t h r o u g h
o n e p a r t o f
t h e b o d y ( s u c h a s w h e n s i t t i n g f o r l o n g
p e r i o d s o r w h e n t h e t i s s u e s a r e c o m
-
p r e s s e d , a s o c c u r s i n l o n g - h a u l a i r c r a f t
f l i g h t s )
a n d a n i n c r e a s e i n t h e c l o t t i n g
t e n d e n c y o f t h e b l o o d , w h i c h o c c u r s i n
d e h y d r a t i o n ,
a f t e r
s u r g e r y
o r
i n j u r y ,
d u r i n g
p r e g n a n c y ,
i n
s o m e
i n h e r i t e d
c o n d i t i o n s
( s e e
t h r o m b o p h ilia
) ,
a n d i n
w o m
e n t a k i n g
o ra l c o n t ra c e p t iv e s
.
D e e p
v e i n
t h r o m b o s i s
m a y
a l s o
b e d u e t o
p o ly c y t h a e m ia
( i n c r e a s e d n u m -
b e r s
o f r e d
c e l l s i n t h e b l o o d ) .
D e e p
v e i n t h r o m b o s i s i s c o m
m
o n i n p e o p l e
w i t h
h e a rt f a ilu re
a n d t h o s e w h o
h a v e
h a d a
s tro k e ;
i t a l s o c o m m o n l y o c c u r s i n
p e o p l e w h o h a v e b e e n b e d r i d d e n .
SYMPTOMS
C l o t s i n t h e l e g v e i n s m a y c a u s e p a i n ,
t e n d e r n e s s , s w e l l i n g , d i s c o l o r a t i o n , a n d
u l c e r a t i o n o f t h e s k i n , b u t t h e y c a n b e
s y m p t o m l e s s . A d e e p v e i n t h r o m b o s i s i s
n o t n e c e s s a r i l y s e r i o u s i n i t s e l f , b u t p a r t
o f t h e c l o t m a y b r e a k o f f a n d t r a v e l i n
DEEP VEIN THROMBOSIS
Thrombi, or clots, tend to form when
blood flow is sluggish or if there is a
rise in the level of coagulation factors
in the blood. Once a clot has formed,
it may provide a site for further clotting,
so that a long, snaky clot may grow
along the length of a vein. There is
a riskthat the end of such a clot may
break off into the circulation. Thrombi
form most commonly in the leg veins
and may interfere with the drainage
of blood from a leg (below right),
causing signs and symptoms of
varying severity.
Partly blocked vein
Healthyvein
Normal and obstructed vein
Thrombi tend to form at points where a vein
lining is damaged and maythen grow to obstruct
blood flow. The main danger is that a piece of
clot will detach and be carried to the heart and
lungs to cause a potentially fatal obstruction.
Femoral
vein
Iliac
vein
Example of deep vein thrombosis
This MRI of the leg of a patient with deep
vein thrombosis shows the vein blocked
by a thrombus (blood clot).
Calfvein thrombosis
When clots are localized in the
lower-leg veins, there is usually
some pain in the calf but there
may be little swelling.
Femoral vein thrombosis
If clots are present in the femoral
and the lower-legveins, there is
usually pain and swelling up to
the region above the knee.
Iliac vein thrombosis
Clots in the iliac vein may
affect drainage of blood from
the whole leg, causing severe
pain and swelling in the leg.
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