hi let's talk about the hepatic portal system in this video we'll discuss the hepatic portal
system and differentiate it from the caval system in particular differentiating the
hepatic portal vein from the hepatic veins we'll also discuss examples of portocaval anastomoses
so a portal system is any system of vasculature which connects to capillary beds in the case of
the hepatic portal system we're dealing with a venous portal system and this is going to
connect all of the capillaries within the walls of the gastrointestinal tract
from the abdominal part of the esophagus through the rectum and anal canal and it's going to
deliver that blood to hepatic sinusoids so there are very many tributaries if you think about all
of the branches of the celiac trunk and superior mesenteric artery and inferior mesenteric artery
which supply the gastrointestinal tract with blood there are typically commensurate veins which drain
that gastrointestinal tract with blood now the major pathways are going to include the
inferior mesenteric vein the superior mesenteric vein and the splenic vein
here on the right we can see examples of this in the the cadaveric photograph
we have we can see the superior mesenteric vein coming up here meeting the splenic vein
into which the inferior mesenteric vein drains that inferior mesenteric vein typically drains
into the splenic vein but it may also drain into the superior mesenteric vein
where the splenic vein and superior mesenteric vein coalesce which we can see right there um
that vessel is the hepatic portal vein sometimes just called the portal vein
the origin of the portal vein is typically just posterior to the neck of the blood of sorry
the pancreas and that portal vein is going to be conveyed up to the porta hepatis of the liver
within the hepatoduodenal ligament so blood then is going to those hepatic sinusoids
another source of blood from those or to those hepatic sinusoids
will be from the hepatic artery proper or hap so blood from the hepatic artery proper
and blood from the hepatic portal system is going to mix in the hepatic sinusoids
and then blood from those hepatic sinusoids will drain from the liver via hepatic veins
typically there are three hepatic veins and they're draining into the inferior vena cava
so any vessel that drains into either the superior or inferior vena cava
are what we would refer to as part of the caval system whereas any vessel that drains into the
hepatic portal vein is part of the portal system so we can differentiate these two venous systems
one from another and there are cases where these two systems come in contact with one another
now portal hypertension is an increase of pressure within the hepatic portal system generally this
is a result of impeded blood flow to through or away from the liver but its most typical cause is
from cirrhosis of the liver with cirrhosis of the liver or any other impedance to the flow of blood
pressure builds within the portal system this increase of pressure may lead to varices between
both portal tributaries and nearby caval tributaries so as a for instance
in the distal esophagus which we can see here there are going to be branches from
the left gastric vein these branches of the left gastric vein which are portal in nature
are draining similar submucosa as esophageal veins these esophageal veins are part of the caval
system they feed into the azygous system which feeds into the superior vena cava so with increased
portal pressure blood can be shunted from the portal to the caval and we can see dilations
of these veins in the submucosa that we refer to as varices so esophageal varices
tend to be very frequently associated with portal hypertension but there are also other regions
where these portal caval anastomoses can occur and varices may occur so for instance another
is within the umbilical region very umbilical region is the area around the belly button
where there are superficial epigastric veins these are not to be confused with the superior
and inferior epigastric veins that are found within the rectus abdominis these
are found within the hypodermis and these are going to drain down into the
femoral veins what can happen with portal hypertension is that the para umbilical vein
can become dilated and this can shunt blood into these superficial epigastric veins
and cause them to dilate and the dilation of these veins about the umbilicus produces a very
distinctive pattern of swirls and torturosities of these veins this is referred to as capet
medusi or the head of Medusa because it
superficially resembles Medusa's head with the snakes this isn't exactly the uh
the nicest way to refer to this particular morphology but um you will hear this sometimes
in the clinic another region um or regions where we see varices occur are between various
retroperitoneal veins any place that we have a secondarily retroperitoneal organ veins which
drain these veins that are adjacent to the lumbar veins of the body wall we can we can see this
occur and then also we can see these vertices in the rectum and superior anal canal in particular
in the the submucosa of the anorectal region here we have superior rectal veins which are portal
that are pushing blood out to both middle and inferior rectal veins which are caval
so the middle rectal veins are feeding into the internal iliac vein whereas the inferior rectal
veins are feeding into the pudendal i'm sorry internal pudendal veins which then feed into
the internal iliac veins so um we'll talk about this more when we discuss the the rectum
and anal canal some people refer to these varices as internal hemorrhoids but more on that later
portal hypertension is a is a symptom which can be reduced surgically so as to prevent any bleeds
from these varices so the the modern treatment for this is something called a TIPS procedure
TIPS is short for trans jugular intrahepatic portosystemic shunt this is when an interventional
radiologist is going to guide a wire through the uh the internal jugular vein down through the
brachiocephalic and superior vena cava through the right atrium into the inferior vena cava
and then into the hepatic veins and in to the liver where a shunt is introduced between
the hepatic veins and the hepatic portal veins so this allows an increased pressure in the portal
system to flow directly into the caval system and it does bypass the liver sinusoids
another older method of shunting involves placing a shunt between the
left renal vein and the splenic vein the left renal vein and the splenic vein are in very
close association with one another they're both very large bore veins and so you might also hear
on the boards or see on the boards examples of left renal vein splenic vein shunting
so we've discussed the hepatic portal system its tributaries areas where
portal veins and caval veins come into close contact and we can see
shunting or portal cable anastomosing this is your summary slide thank you for your time