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so before we delve into the many
abnormalities that can be found within
the abdomen on an x-ray
let's review first some of the normal
findings on an abdominal film and a
normal approach so most abdominal
imaging and diagnosis involves the use
of ultrasound CT or MRI
however radiographs are often used as a
quick first step to help you decide what
further imaging is needed next if any so
what can be evaluated on abdominal plain
films the bowel gas pattern is a very
important thing you could always
evaluate for free air which is something
that you really don't want to miss
abnormal calcifications can be seen on
abdominal radiographs or abnormal masses
so these are the four major points that
you want to keep in mind when you're
taking a look at an abdominal radiograph
so let's come up with a general approach
as with Olive radiology it's important
to have a standard approach so that you
make sure that you look at every aspect
of the film so what I do is I start off
with the lung bases even though we're
performing an abdominal film oftentimes
a patient may have an abnormality at the
lung base that you don't want to miss I
then look for free air because this is a
finding that you really don't want to
miss on an abdominal plane film next I
look at the bell gas pattern and then I
evaluate the solid organs I then look
for any abnormal soft tissue masses any
abnormal calcifications and lastly I
take a look at all of the bony
structures so before we look at the
abdominal normal Anatomy on a radiograph
let's just review what normal abdominal
Anatomy looks like on a diagram so a
large part of the upper abdomen is
encompassed by the liver it's
essentially seen in the right upper
abdomen but also extends over to the
left upper abdomen adjacent to it is the
spleen and oftentimes on a radiograph
you can see the outline of both the
spleen and the liver the gallbladder is
usually not well seen on an abdominal
plane film however it if it has
calcifications in it such as gall stones
that may be visualized and then the
majority of the rest of the abdomen is
encompassed by large bowel which is seen
peripherally and then small bowel which
is usually seen centrally so let's
review some radiographic anatomy so
again
start off by taking a look at the lung
bases and you can see them on every
abdominal radiograph so you can see the
diaphragm here on the right and then you
can see the left hemidiaphragm here and
just above it are the lung bases and a
small portion of the heart in the left
upper abdomen you can see the stomach
bubble it usually has a little bit of
air and then it has an air fluid level
which is again normal you can see the
outline of the liver primarily
encompassing the right upper abdomen and
then you can see air within the large
and small bowel in terms of bony
structures you can take a look at the
iliac crests which really should be
included on every abdominal radiograph
and you can see the thoracic and lumbar
spines so how can you differentiate
between small and large bowel on a
radiograph when there's a bowel
abnormality it's important to try and
see which bowel it's involving so the
small bowel is located centrally and it
has valvular markings called valve you
leak on event days they cross the entire
width of the small bowel and they're
spaced very close together they have the
classic stacked coin appearance so if
you take a look at these stacks of coins
the small barrel actually looks very
similar to that and that's a very
classic appearance of small bowel large
bowel on the other hand is usually
located peripherally and it contains
house draw so the house tray either do
not connect from one wall to the other
or they're spaced a lot wider apart than
the valve you leak on event azar so if
you take a look at this image here the
house tour do actually go all the way
from one end of the wall to the other
however they're not the typical stacked
coin appearance that you would expect
from a small bowel they're much wider
apart this is another example of the
large bowel again seen predominantly in
the periphery periphery of the abdomen
and you can see air within small pieces
of small bowel seen more centrally so
how do you assess bowel gas pattern but
normal bowel gas pattern in the small
bowel usually has about two or three air
fluid levels it's normal to see air
within the small bowel and usually the
bowel is not more than about three
centimeters in diameter
large bow on the other hand usually
doesn't have air fluid levels because a
lot of the fluid is absorbed within the
large bowel it does contain air and
that's normal and it can have a very
variable diameter so it's hard to rely
on large bowel diameter to tell whether
or not it's abnormal so let's take a
look at this this is a cone down view of
the right upper abdomen you can see a
somewhat mottled appearance here so what
do you think that represents it doesn't
follow the typical features of small or
large bowel so this is an example of
normal stool within the colon it appears
as very small bubbles of gas that are
partially solid and they appear within
the expected location of the colon
so abdominal films can be performed in
three different projections and each one
has different uses so typically it's
performed as an upright film air is
gravity dependent so it's very useful to
evaluate for free air so the air will
rise up to the top and can often be seen
just underneath the diaphragm it's also
used to evaluate for air fluid levels
which could indicate stasis and ileus or
bowel obstruction so when the patient is
standing upright again the air will rise
to the top of the bowel and you can see
the air fluid level because the fluid
will be at the bottom of the bowel
usually these are obtained with the
patient sitting or ideally in the
standing position a left lateral
decubitus is usually used in patients
that aren't able to stand upright so
this is performed really as just a
substitute for an upright film it also
allows for evaluation of air fluid
levels and it allows for evaluation of
free air so the patient lies on their
left side down the right side is up and
again air will rise to the top part of
the of the body and so you can see it
adjacent to the liver on the right here
ideally again is performed on the left
side down because the liver forms a
solid organ on the right which allows
you to see the difference between the
air and the density of the liver
if you perform it the other way you have
a lot of bow on the left side and you
may not see the difference between air
within the bowel and air outside of the
bowel so supine film is also very
commonly perform and it's usually
performed in addition
to an upright or a decubitus this
provides a general overview of the
abdomen and it's the one that's used to
look for calcifications or abnormal soft
tissue masses this is obtained with the
patient lying on their back and it's
really best when it's used again in
conjunction with another examination
either the upright or the decubitus so
incidentally this patient has a finding
in their pelvis so what do you think
this is
this is actually an intrauterine device
or an IUD it's used as a contraceptive
device and this is very commonly seen
and in women this is a t-shaped metallic
structure which is why it appears so
dense it's actually a little bit more
dense than the surrounding bony
structures so the takeaway points from
this lecture I think are that you really
need to look for air fluid levels and
free air within the abdomen those are
the two most important findings and
these are really best seen on an upright
or a decubitus view free air is most
easily seen on these views as well and
it's a finding that you really don't
want to miss so hopefully now that you
have the background knowledge of the
abdominal anatomy we can move on to
discussing some pathology and the
appearance of pathology on an abdominal
plane film
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