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so one of the most common reasons for
performing an abdominal imaging study is
to evaluate for bowel obstruction or
Ilias so let's take a look at these
findings that we would see this is 25
year old patient that came in with right
lower abdominal pain it's a female
patient let's take a look at this case
and see what you can see here and keep
this in mind until we get through the
lecture and then we'll go back to this
at the very end so what do you look for
when you're looking for a bowel
obstruction you want to look for dilated
loops of large or small bowel you want
to see if it's focal or diffuse you want
to take a look at air fluid levels you
want to see if there's air within the
rectum and you want to see if there's a
transition point when you're performing
a CT so what's the difference between a
functional ileus and a mechanical
obstruction a functional ileus is loss
of normal peristaltic function due to
irritation a mechanical obstruction is a
physical obstruction in the small or
large bowel and this may be partial or
it may be complete a functional ileus
may be localized or generalized and a
mechanical obstruction as we said could
be either complete or partial a
functional ileus usually affects the
small bowel and it doesn't tend to have
a transition point while with a
mechanical obstruction you do have a
transition point and this is the point
at which the bowel changes Calibur from
being dilated to being collapsed the
small bowel caliber is typically less
than three centimeters in a functional
ileus so it's not significantly dilated
in a mechanical obstruction the small
bowel can become significantly dilated
and the caliber is usually more than
about three centimeters in a functional
Ilyas you would see air within the
rectum because the air continues to pass
past the site of a peristalsis while in
a mechanical obstruction if you have a
complete obstruction you would have no
air within the rectum because nothing is
getting past that point of obstruction
so a partial or early small bowel
obstruction within the first day or two
can appear identical to an ileus
so it's actually very hard to
differentiate and usually what we do is
follow-up imaging to see how it evolves
so in a localized functional Ilyas you
would have dilatation of a loop or a few
loops of small bowel and these are
called the sentinel loops this is caused
by adjacent irritation it can result
from really any kind of abdominal
pathology that causes focal inflammation
types of pathologies include acute
cholecystitis pancreatitis appendicitis
diverticulitis or even ureteral stones
so anything that causes pain in the
patient can cause a localized functional
ileus a generalized functional ileus is
most often post operative and it can
involve the entire bowel both small and
large so if you take a look at this
patient here you have multiple dilated
loops of both large and small bowel
they're actually so dilated that we
really aren't able to tell the
difference between large and small bowel
and you can see that this patient is
post operative they have surgical
staples along the midline of the abdomen
a small bowel obstruction is usually
caused by a lesion that obstructs the
lumen of the bowel it results in
dilatation of the bowel proximal to the
obstructing lesion and then compression
of the bowel after the obstructing
lesion this is an example of a normal
large bowel and a normal small bowel on
the right we have an image of a small
bowel obstruction so the large bowel is
slightly decreased in caliber because
there's less air getting through the
point of obstruction which is right here
at the terminal ileum the small bowel
that's proximal to this part point of
obstruction is dilated there are many
different causes of small bowel
obstruction
the most common include adhesions from
prior surgery tumors a hernia and we'll
take a look at an example of this
inflammatory bowel disease can cause
multiple small bowel obstructions
intussusception which is bowel tunneling
within other bowel it's kind of like a
telescoping effect where a piece of
bowel tunnels within another piece of
bowel and can cause an obstruction at
that level intraluminal lesions other
than tumors can also cause small bowel
obstruction and they can be from a
variety of different reasons including
an ingested foreign body you can have a
gallstone ileus which is when a
gallstone penetrates through the gob
a wall and enters the small bowel and
causes an obstruction within the small
bowel or you can have bees wires which
are abnormal collections that the
patient may be ingests certain
psychiatric patients may ingest
different types of foreign bodies that
can collect together and cause an
obstruction so this is an example of a
patient that's presenting with abdominal
pain let's take a look at this film so
how does this Bal gas pattern look
this patient has a prominent loop of
small bowel in the left upper abdomen
the differential of this includes a
focal Ilyas or an early or partial small
bowel obstruction as we said it's really
hard to differentiate in a patient
that's presenting with symptoms that
lasted less than one to two days because
early on both can have similar imaging
findings the following day however the
patient had a repeat film because they
had increased increasing abdominal pain
so what do you see on these films here
here we have a supine film and then this
one is an upright film so as you can see
there's increasing dilatation of
multiple loops of small bowel now a
majority of the small bowel loops appear
dilated you can see that on this supine
film you also have increasing air fluid
levels which we can see best on this
upright film this is very concerning for
a small bowel obstruction so what else
can you perform to help you figure out
why this is occurring so in this patient
a CT scan was performed here we have two
axial images from an adduct aminal CT
scan and we have a coronal image so
let's take a look at each of these
images here on this axial CT image we
have what looks like a little
outpouching of the anterior abdominal
wall that contains a loop of bowel on
this next image we again have a loop of
bowel that looks a little bit dilated in
the same region as the outpouching and
it has a mottled appearance and here we
have a decompressed loop of bowel on
this coronal image you can see a large
loop of small bowel that appears dilated
so this is a thickened loop of bowel
within a ventral hernia that's causing a
bowel obstruction and here we have a
transition point at the level of
obstruction this modeled loop of small
bowel here is what we call the small
bowel feces sign so you normally should
not have any stool within the small
bowel when you do have stool within the
small bowel you should suspect a small
bowel obstruction and that's called a
small bowel feces sign
so what are some CT findings of small
bowel obstruction you should see dilated
loops of small bowel greater than about
three centimeters you may or may not see
a transition point you should see
collapsed bowel distal to the transition
point and you may see the small bowel
feces sign so what is a closed loop
obstruction this is an obstruction of a
loop of bowel in two separate places you
normally don't see any significant
dilatation proximal to the closed loop
and often this is caused by adhesions
from prior surgery this could actually
result in strangulation so this is a
surgical emergency it can cause blocked
blood flow to the bowel which can result
in necrosis on imaging we see a
thickened wall and you may see decreased
enhancement of the bowel wall so close
loop obstruction needs immediate
surgical treatment because there's a
very high risk of perforation from this
strangulation
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you