INTESTINAL IMAGING
s m a l l n o t c h e s i n e a c h s i d e o f t h e
v e r t e -
b r a e .
S u c h g a p s a r e t h e e x i t p o i n t s f o r
t h e p e r i p h e r a l n e r v e s b r a n c h i n g f r o m
t h e
s p i n a l c o r d .
in t e s t in a l im a g in g
S e e
b a r i u m X - r a y e x a m i n a t i o n s .
in t e s t in a l lip o d y s tro p h y
S e e
W h i p p l e ’s d i s e a s e .
in te s tin e
T h e m a j o r p a r t o f t h e d i g e s t i v e t r a c t ( s e e
d i g e s t i v e s y s t e m ) ,
e x t e n d i n g
f r o m
t h e
e x i t o f t h e s t o m a c h t o t h e a n u s . I t f o r m s
a l o n g t u b e d i v i d e d i n t o t w o m a i n s e c -
t i o n s : t h e s m a l l a n d l a r g e i n t e s t i n e s .
SMALL INTESTINE
T h e
s m a l l i n t e s t i n e
i s
a b o u t
6 . 5
m
i n
l e n g t h a n d h a s t h r e e s e c t i o n s : t h e
d u o d e -
n u m ,
t h e
j e j u n u m
a n d t h e
i l e u m .
P a r t i a l l y
d i g e s t e d f o o d f r o m t h e s t o m a c h i s f o r c e d
a l o n g t h e i n t e s t i n e b y
p e r i s t a l s i s .
T h e
s m a l l
i n t e s t i n e
i s
c o n c e r n e d
w i t h t h e
d i g e s t i o n a n d a b s o r p t i o n o f
f o o d .
D i g e s t i v e
e n z y m e s
a n d
b i l e ,
w h i c h
b r e a k
d o w n
f o o d
t o
r e l e a s e
n u t r i e n t s ,
a r e
a d d e d
t o
t h e
p a r t l y
d i g e s t e d f o o d i n t h e d u o d e n u m v i a t h e
b i l e
a n d
p a n c r e a t i c
d u c t s
( s e e
b i l i a r y
s y s t e m ) .
G l a n d s w i t h i n t h e w a l l s o f e a c h
s e c t i o n o f t h e s m a l l i n t e s t i n e p r o d u c e
m u c u s a n d o t h e r e n z y m e s , w h i c h a l s o
h e l p
t o
b r e a k
d o w n
t h e
f o o d .
B l o o d
v e s s e l s
i n
t h e
i n t e s t i n a l
w a l l s
a b s o r b
n u t r i e n t s a n d c a r r y t h e m t o t h e
l i v e r
f o r
d i s t r i b u t i o n t o t h e r e s t o f t h e b o d y .
LARGE INTESTINE
T h e l a r g e i n t e s t i n e i s a p p r o x i m a t e l y 1 . 5 m
l o n g .
T h e
m a i n
s e c t i o n ,
t h e
c o l o n ,
i s
d i v i d e d i n t o a n a s c e n d i n g , a t r a n s v e r s e ,
a d e s c e n d i n g , a n d a p e l v i c p o r t i o n ( t h e
s i g m o i d c o l o n ) . T h e
a p p e n d i x
h a n g s f r o m
a p o u c h ( t h e
c a e c u m )
b e t w e e n t h e s m a l l
i n t e s t i n e a n d t h e c o l o n . T h e f i n a l s e c t i o n
b e f o r e t h e
a n u
s i s t h e
r e c t u m
.
U n a b s o r b e d
m a t e r i a l
l e a v e s
t h e
s m a l l i n t e s t i n e a s l i q u i d a n d f i b r e . A s
t h i s m a t e r i a l p a s s e s t h r o u g h t h e l a r g e
i n t e s t i n e ,
w a t e r
a n d
m i n e r a l
s a l t s
a r e
a b s o r b e d i n t o t h e b l o o d s t r e a m , l e a v i n g
f a e c e s t h a t a r e m a d e u p o f u n d i g e s t e d
f o o d r e s i d u e , f a t , v a r i o u s s e c r e t i o n s , a n d
b a c t e r i a . T h e f a e c e s a r e c o m p r e s s e d a n d
p a s s i n t o t h e r e c t u m f o r e v a c u a t i o n .
in te s tin e , c a n c e r o f
A m
a l i g n a n t t u m
o u r o c c u r r i n g i n t h e
s m a l l o r t h e l a r g e i n t e s t i n e . C a n c e r o f
t h e s m a l l i n t e s t i n e i s r a r e ; c a n c e r o f t h e
l a r g e i n t e s t i n e i s o n e o f t h e m
o s t c o m
-
m
o n
c a n c e r s
( s e e
c o l o n ,
c a n c e r
o f ;
r e c t u m , c a n c e r o f
).
B o t h t h e
s m a l l a n d
l a r g e i n t e s t i n e m a y d e v e l o p
c a r c i n o i d
t u m o u r s
( c a u s i n g
c a r c i n o i d s y n d r o m e
)
a n d
l y m p h o m a s
.
in te s tin e , o b s tru c tio n o f
A p a r t i a l o r
c o m p l e t e b l o c k a g e o f t h e
s m a l l o r l a r g e i n t e s t i n e .
CAUSES
P o s s i b l e c a u s e s i n c l u d e a s t r a n g u l a t e d
h e r n i a
( p r o t r u s i o n
o f
t h e
i n t e s t i n e s
t h r o u g h t h e a b d o m i n a l w
a l l ) ; s t e n o s i s
( n a r r o w i n g ) o f t h e i n t e s t i n e , o f t e n d u e
t o
c a n c e r
i n
t h e
i n t e s t i n e ;
i n t e s t i n a l
a t r e s i a
( c o n g e n i t a l
c l o s u r e ) ;
a d h e s i o n s
( s c a r
t i s s u e ) ;
v o l v u l u s
( t w i s t i n g
o f
l o o p s o f b o w e l ) ; a n d
i n t u s s u s c e p t i o n
( i n
w
h i c h
t h e
i n t e s t i n e
t e l e s c o p e s
i n s i d e
i t s e l f ) .
I n t e s t i n a l
o b s t r u c t i o n
c a n a l s o
o c c u r i n d i s e a s e s t h a t a f f e c t t h e i n t e s t i -
n a l
w a l l ,
s u c h
a s
C r o h n ’s
d i s e a s e
o r
p a r a l y s i s o f t h e m u s c l e s i n t h e i n t e s t i -
n a l w a l l ( s e e
i l e u s , p a r a l y t i c
) .
L e s s c o m m o n l y , a n i n t e r n a l b l o c k a g e
o f t h e i n t e s t i n e i s c a u s e d b y i m p a c t e d
f o o d ,
f a e c a l i m p a c t i o n
,
g a l l s t o n e s
,
o r b y
a n o b j e c t o f s o m e k i n d t h a t h a s b e e n
a c c i d e n t a l l y s w a l l o w e d .
SYMPTOMS
A b l o c k a g e i n t h e s m a l l i n t e s t i n e u s u a l l y
c a u s e s
i n t e r m i t t e n t
c r a m p l i k e
p a i n
i n
t h e c e n t r e o f t h e a b d o m e n w i t h i n c r e a s -
i n g l y f r e q u e n t
b o u t s
o f v o m i t i n g
a n d
f a i l u r e
t o
p a s s
w i n d
o r
f a e c e s .
A n
o b s t r u c t i o n i n t h e l a r g e i n t e s t i n e c a u s e s
p a i n ,
d i s t e n s i o n o f t h e a b d o m e n ,
a n d
f a i l u r e t o p a s s w i n d o r f a e c e s .
TREATMENT
T r e a t m e n t s i n v o l v e e m p t y i n g t h e s t o m -
a c h v i a a
n a s o g a s t r i c t u b e
a n d r e p l a c i n g
l o s t f l u i d s t h r o u g h a n i n t r a v e n o u s d r i p i n
s o m e i n s t a n c e s , t h i s m e a s u r e w i l l b e s u f -
f i c i e n t t o c o r r e c t t h e p r o b l e m . I n m a n y
c a s e s , h o w e v e r , s u r g e r y t o d e a l w i t h t h e
c a u s e o f t h e b l o c k a g e i s n e c e s s a r y .
in te s tin e , tu m o u rs o f
C a n c e r o u s o r n o n c a n c e r o u s g r o w t h s i n
t h e i n t e s t i n e . C a n c e r o u s t u m o u r s c o m
-
m o n l y
a f f e c t
t h e
l a r g e
i n t e s t i n e
( s e e
c o l o n ,
c a n c e r o f
;
r e c t u m ,
c a n c e r o f
) ;
t h e
s m a l l
i n t e s t i n e
i s
o n l y r a r e l y a f f e c t e d .
L y m p h o m a s
a n d c a r c i n o i d t u m o u r s ( l e a d -
i n g t o
c a r c i n o i d s y n d r o m e
) m a y s o m e t i m e s
d e v e l o p i n t h e i n t e s t i n e . N o n c a n c e r o u s
t u m o u r s
i n c l u d e
p o l y p s
i n
t h e
c o l o n ,
DISORDERS OF THE INTESTINE
The intestine is subject to the effects of
many infective organisms and parasites.
It may also be affected by tumours,
structural defects, and other disorders.
Infection and inflammation
Generalized inflammation of the intestine
may be caused by viral or bacterial
infections such as
f o o d p o i s o n i n g , t r a v e l l e r ' s
d i a r r h o e a
,
c h o l e r a , t y p h o i d f e v e r , a m o e b i a s i s ,
or
g i a r d i a s i s ,
or to infestation with
r o u n d w o r m s
or
t a p e w o r m s .
It may also have
noninfectious causes, as in
u l c e r a t i v e c o l i t i s
and
C r o h n ’s d i s e a s e . G a s t r o e n t e r i t i s
is the
term commonly applied to inflammation
of the stomach and intestines. Sometimes,
inflammation is localized, as in
a p p e n d i c i t i s
and
d i v e r t i c u l a r d i s e a s e
.
Tumours
Tumours of the small intestine are rare,
but noncancerous growths,
l y m p h o m a s
,
and carcinoid tumours (causing
c a r c i n o i d
s y n d r o m e )
may occur.Tumours of the
large intestine are common (see
c o l o n ,
c a n c e r o f ; r e c t u m , c a n c e r o f ) .
Some forms
of familial
p o l y p o s i s ,
a condition causing
the development of noncancerous
growths, may progress to cancer.
Structural abnormalities
Structural defects may be congenital
(present from birth) or may develop
later. They include
a t r e s i a
(congenital
closure),
s t e n o s i s
(narrowing), and
v o l v u l u s
(twisting of loops of bowel).
These abnormalities can cause blockage
of the intestine (see
i n t e s t i n e , b l o c k a g e
o f
). In newborn babies with cystic
fibrosis, meconium (fetal intestinal
contents) is much thicker than normal
and may block the intestine.
Obstruction
Impaired blood supply (
i s c h a e m i a
) to
the intestine may result from partial or
complete obstruction of the arteries in
the abdominal wall (from diseases such
as
a t h e r o s c l e r o s i s
) or from the blood
vessels being compressed or trapped, as
in
i n t u s s u s c e p t i o n
or
h e r n i a s .
Loss of
blood supply may cause
g a n g r e n e
.
Other disorders
Other disorders that affect the intestine
include
p e p t i c u l c e r s , d i v e r t i c u l o s i s ,
m a l a b s o r p t i o n , c o e l i a c d i s e a s e ,
and
i r r i t a b l e b o w e l s y n d r o m e .
432
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