00:01
Now let's talk about the
portosystemic anastomosis.
00:04
So what are these?
These are anastomosis
like we'd be familiar with before.
00:10
But instead of two arteries
uniting together and
forming those anastomosis
coming from two different origins,
this is going to be an anastomosis
between the portal system
and the systemic
circulation of the body.
00:25
So the systemic portal anastomosis,
these are going to be unions
between the portal system and the
general venous return of the body.
00:33
And they happen typically around
four different places.
00:37
Why do they happen though?
This is the normal blood flow,
the venous return.
00:42
Superior mesenteric vein is
going to be bringing blood
oxygen low nutrient
rich into the liver.
00:49
Alongside the inferior
mesenteric vein
which we see here draining
into the splenic vein.
00:54
So here we can see the formation
of the hepatic portal vein,
which is now carrying all
of that nutrient rich blood
after the food has
been ingested from
the stomach and small intestines.
01:05
The hepatic portal vein then
takes this nutrient rich blood
into the liver where deamination
for example can occur
before that blood is then returned
to the systemic circulation
via the hepatic vein.
01:17
But what we can see is if
we have liver cirrhosis, tumors,
or general liver disease.
01:23
The flow of blood through the liver
can be compromised.
01:27
Because the normal
architecture of the blood vessels
within the liver can become damaged.
01:33
We don't get the normal flow.
01:36
As we have limited flow
going through the liver
that can build up the blood
pressure within this system.
01:42
That means the blood has
to find alternative routes
via the portal system and
the general systemic circulation.
01:51
So let's have a look
at a few of these.
01:53
So as we've seen, we've got
esophageal and gastric veins.
01:57
We have paraumbilical and
epigastric veins,
We have colic and
retroperitoneal veins.
02:03
And we also have some rectal veins
at the bottom as well.
02:07
So let's start with the esophageal
and gastric reins.
02:10
So here we see the esophageal
and the gastric veins
supplied around
this junction between
the esophagus and the stomach.
02:18
So here we have the
gastroesophageal junction.
02:21
We can see the left gastric vein
is giving rise to esophageal veins.
02:25
And here, we can have anastomosis
with the azygos and
hemiazygos venous supply.
02:32
So these esophageal veins
will then actually join
and form an anastomosis
with both the azygos
and the hemizygos system of
veins which we can see here.
02:41
Now, the problem with this is that
these veins are typically very small
because they don't usually
have that much blood
of a high pressure and high volume
passing through them.
02:51
And because that they can expand
and lead to esophageal varices.
02:56
And here we can
see them in the image.
02:58
These are expansions of
these venous blood vessels
passing into the lumen
of the esophagus.
03:03
They can likely rupture and
bleed out into the esophagus,
and the patient can often
cough up blood.
03:09
Let's have a look at a
second one of these,
and this is between the
around the rectum.
03:14
Here we're gonna see
the terminal branches
of the superior rectal vein.
03:18
These are going to pass into
the inferior mesenteric vein.
03:22
What we also have here is the
middle and inferior rectal veins.
03:26
And again, these will be
draining some of the blood away
from the bottom
portion of the rectum.
03:31
But if there's no increased blood
pressure within the portal system,
this can lead to increased
blood now passing through
the middle and inferior
rectal veins,
which will pass into
the internal iliac vein.
03:44
The problem here is very similar
to that of the esophageal varices.
03:49
Except this time,
we call them hemorrhoids.
03:52
And these were the expansion of
those blood vessels in the rectum
can then bulge out of the rectum.
03:58
And these again can
cause lots of bleeding,
especially upon defecation.
04:03
Let's then have a look
at the final two.
04:05
Here we have the paraumbilical
and epigastric veins.
04:09
Now, this can lead to a whole
series of enlarged venous structures
along the anterior abdominal wall,
as blood additional blood
is now passing through
inferior epigastric veins.
04:21
So here we can see the umbilicus.
04:23
And remember that the umbilicus
and these power umbilical veins
are really important, as they
used to be embryologically
quite active, quite open, allowing
blood to pass through this region.
04:33
Within this region, we have these
paraumbilical veins
which are helping to drain blood
from this region.
04:39
Now, with increased blood
pressure around here,
blood can now be forced
into the superficial veins
alongside the abdominal wall.
04:47
And this will feed into the
inferior epigastric veins.
04:51
We've seen the inferior
epigastric blood vessels
which lie very superficial
on the abdominal wall.
04:56
The veins we're
running alongside them,
and the same process happens here.
05:00
Blood wouldn't typically be
running in these veins
because they're very small.
05:04
And now we end up with
these very large undulations
on the anterior surface
of the abdomen
where the blood is now
accumulated in these regions,
where it typically
wouldn't be found.
05:16
The final one is between here.
05:18
The colic veins which are
draining the desending sigmoid
aspects of the colon,
and retroperitoneal veins.
05:25
These are veins which are draining
the posterior abdominal wall.
05:28
And again, blood can
now find a route back
to the systemic circulation
by utilizing this pathway.
05:35
And here we have colic veins
anastomosing
with retroperitoneal veins
to form the four of these
portosystemic anastomosis.