So let's move on to large bowel obstruction.
This is usually cause by a mechanical obstruction of the large bowel
and the cecum is usually the part of the bowel that dilates the most.
The small bowel is often not dilated unless the obstruction is so severe
that it makes the ileocecal valve incompetent.
In a large bowel obstruction, you don't want to administer oral barium
because it couldn't become impacted within the bowel
as water is absorbed from it.
So you wanna start of by doing a plain film
and if you suspect the large bowel obstruction,
then don't administer the oral contrast.
So let's move one to volvulus
a volvulus is essentially a closed loop obstruction
involving the large bowel. It's most commonly seen in the caecal area
and then it's followed by the sigmoid area.
Sigmoid volvulus tends to produce
a characteristic coffee bean shape appearance on radiographs.
With the caecal volvulus you actually see a very dilated cecum
that often rotates to the left upper abdomen.
On this film you can see what it appears to be a very dilated cecum.
It remains within the pelvis in this patient.
The small bowel will become dilated with the volvulus
and as with the small bowel volvulus,
there's a very high risk of strangulation.
So let's take a look at this film, you can see the green line
showing you are very dilated loop of large bowel.
So what is this represent?
This is actually an example of a sigmoid volvulus
and you can see this is the characteristic coffee bean shape
that you would expect. This is a surgical specimen
demonstrating the same thing, a sigmoid volvulus.
So a colonoscopy is used to reduce the volvulus most often.
Occasionally, you can use a contrast enema.
However, you have to be careful
because when you reduce the volvulus there is a high risk of perforation.
So what are other secondary signs of volvulus?
You can see the whirl sign which is swirling of the mesentery
and that can be seen with both large volvulus
and small bowel closed loop obstruction.
You can also see what?s called the beak sign
which is tapering of the colon to the point of obstruction.
So let's take a look at these images.
This is an axial CT image in a patient that has a closed loop obstruction
and here you can see what's called the beak sign.
So you can see tapering of the colon
producing the appearance of the beak.
And then on the coronal image, keep your eye on this area right here
as I scroll through. You can see what looks like a swirling
of this mesentery and this is another secondary sign of volvulus.
So Ogilvie Syndrome is actually massive dilatation of the colon
without mechanical obstruction.
So as you recall normal large bowel obstruction
is often due to a mechanical obstruction.
This is one of the causes of a non mechanical obstruction
that can cause dilatation of the colon.
Usually this is due to anticholinergics
which result in loss of peristalsis of the colon.
So let's go back to this case that we saw at the very beginning.
This is our 25-year-old female, that presents
with the right lower abdominal pain.
What do you see on this film?
So we see multiple loops of large bowel that contain air
and that's normal, but how about right here?
What is that represent?
So this is a prominent loop of airfield small bowel
that seen in the left upper abdomen
and this is consistent with the focal ileus.
As you can see here, it has that stacked coin appearance
that we talked about.
So what's the next step?
How do you figure out what's going on?
Why is this patient have a focal ileus?
So you wanna obtain a CT of the abdomen and pelvis
with contrast to take a look for any kind of causes.
Remember there are multiple different causes
of the small bowel focal ileus.
So let?s take a look at this axial contrast enhanced CT scan
and if you looked right here,
you actually have a very thick walled appendix
with periappendiceal fat stranding.
Let's take a closer look. So this portion right here is all appendix.
Normally, appendix should have a little bit of air
or a little bit of contrast within it.
But you actually don?t see the lumen at all
because the wall is so thick and if you looked around it,
let's take a look at normal mesentery.
So this area right here is normal mesentery,
surrounding the appendix, the mesentery has a more grayish appearance
and this is because of surrounding inflammation.
So this patient has an acute appendicitis that cause for focal ileus.
So we've gone over multiple different causes
of large and small bowel obstruction.
Again, this is a very common finding that you wanna look out for
when you see a patient coming in with abdominal pain.