Portal Vein and portocaval Anastomosis. Anatomy of portal vein, tributaries, branches and course, formations and relations. Anatomy of portal vein and adjacent structures, their relation to liver and intestine, relation to IVC and Aorta, clinical and applied anatomy for both undergraduates and postgraduates. portal hypertension is an increase in blood pressure, however, rather than being systematic, it's localized to the portal system. Portal hypertension is most commonly caused by liver cirrhosis which in itself can be caused by alcoholism or other liver disease. It can also be caused by blood clots in the portal vein and schistosomiasis amongst other things. This increase in blood pressure can affect areas of anastomosis between the portal vasculature which we just discussed and the caval musculature which are classified as the vessels not relating to the portal system resulting in pressure pushing larger blood volumes into these anastomotic areas. This in turn can cause the vessels to dilate and form varicose veins which can result in potentially fatal hemorrhage. Some of these important porto-caval anastomotic areas are listed below – the first vein being the portal vein and the second vein being the caval vein – the superior rectal and inferior rectal veins, the left gastric and esophageal veins, the colonic veins and the retroperitoneal veins and the para-umbilical and epigastric veins. In severe cases, the last anastomosis mentioned between the para-umbilical veins which are the small veins that run within the round ligament of the liver and the epigastric veins which are found in the anterior abdominal wall can form large dilations. These dilations can form the clinical presentation caput medusa or the head of the medusa as the dilated veins look like the snakes of the head of the medusa or Gorgon from Greek mythology. In this image on the right, we can only see the beginnings of a presentation of the caput medusa as in a true caput medusa, the veins would be raised and enlarged. Hello everyone! This is Nicole from Kenhub, and today we're going to talk about the hepatic portal vein. We are going to discuss the hepatic portal vein and to do so we'll be using this image here which is a ventral view of the portal hepatic vein with the central portion of the liver cut out so we can see the portal vein and other portal vessels. You can also see the aorta just here as well as the inferior vena cava just posterior to the portal hepatic vein. The portal venous system is an important system that has its own unique flow and we'll talk about how this works in tandem with the venous system in the coming slides. The portal vein is one of the most important vessels in the body. Its main functions are to direct blood to the liver from the gastrointestinal tract and receive nutrient rich blood from the intestines. The portal hepatic vein also receives blood from the spleen, the pancreas and the gallbladder which are channels within the vessel.

1. Portal Vein and Portocaval
anastomosis
Dr Rajiv Verma
Associate Professor and Head
Department of Surgery
Dated: 03/05/2023

3. Learning objectives:
• On completing this study unit, you should be able to:
• Identify the hepatic portal vein.
• Name and identify the tributaries and branches of the hepatic portal
system.
• Describe the course of the hepatic portal vein.

7. The development of the intestine:
The primitive endodermal tube of the gut is divided into:
• The fore-gut (supplied by the coeliac axis) extending as far as the
entry of the bile duct into the duodenum;
• The mid-gut (supplied by the superior mesenteric artery) continuing
as far as the distal transverse colon;
• The hind-gut (supplied by the inferior mesenteric artery) extending
thence to the ectodermal part of the anal canal.

8. • The hepatic portal system is responsible for the venous drainage of
many structures within the abdomen.
• One of the most important structures of the portal system is the
hepatic portal vein.
• The hepatic portal vein is formed by the union of the superior
mesenteric and splenic veins and as a result receives nutrient-rich
venous blood from the spleen, pancreas, gallbladder and upper parts
of the gastrointestinal tract.

10. • It travels within the hepatoduodenal ligament, alongside the proper
hepatic artery and bile duct to reach the porta hepatis of the liver.
• The hepatic portal vein functions to transport venous blood from
regions within the abdomen to the sinusoids of the liver, where it can
then be processed and filtered.
• Within the liver, filtered venous blood is received by the right,
intermediate and left hepatic veins which empty into the inferior vena
cava of the systemic venous system.

12. • Portal venous system (PVS) drains blood from the gastrointestinal
tract (apart from the lower section of rectum), spleen, pancreas, and
gallbladder to the liver.
• The portal vein (PV) is the main vessel of the PVS, resulting from the
confluence of the splenic and superior mesenteric veins, and drains
directly into the liver, contributing to approximately 75% of its blood
flow.
• Hepatic artery provides the remaining hepatic blood flow. Once in the
liver, PV forms branches and reaches the sinusoids, with downstream
blood being directed to the central vein at the hepatic lobule level,
then to the hepatic veins and inferior vena cava (IVC) to reach the
systemic venous system.

13. Why it is called a Portal Vein:
• Because its main tributary, SMV begins in one set of capillaries (in the
gut) and portal one end of another set of capillaries in Liver.
• In the Liver, Portal vein breaks up into sinusoids which is drain by
hepatocytes and then to Inferior vena cava.

14. Anatomy of Liver
There are 2 distinct sources that supply blood
to the liver, including the following:
Oxygenated blood flows in from the hepatic
artery (25%)
Nutrient-rich blood flows in from the hepatic
portal vein (75%)
The liver holds about 13% of the body's blood
supply at any given moment.
The liver consists of 2 main lobes.
Both are made up of 8 segments that consist of
1,000 lobules (small lobes).

15. • hepatic portal vein
• ventral view of the portal hepatic vein with the central
portion of the liver cut out so we can see the portal vein and
other portal vessels.
• Aorta just here as well as the inferior vena cava just
posterior to the portal hepatic vein.

16. The portal vein is one of the most important vessels in the
body.
Its main functions are to direct blood to the liver from the
gastrointestinal tract and receive nutrient rich blood from the
intestines.
The portal hepatic vein also receives blood from the spleen, the
pancreas and the gallbladder which are channels within the
vessel to the liver.
Once inside the liver, these blood can be filtered and processed
while also being cleansed of bacteria and toxins in a process
called detoxification.

17. The process which involves the liver as
a processing station looks a little bit like
the cycle below. Veins carrying nutrient-
rich blood from the gastrointestinal
tract such as the superior mesenteric
vein and the splenic vein which then
carry blood to the portal vein itself and
then through the portal triad which is a
triad of structures found in the porta
hepatis. Once in the liver, the blood is
filtered of bacteria and toxins which are
eliminated through bile or urine where
the filtered blood is sent back to the
inferior vena cava.

19. • The hepatic portal vein –
highlighted in green – can be
found in the upper right
quadrant of the abdomen.
• The portal vein is valveless and
generally reaches a length of 8
centimeters or 3 inches in
adults.
• The portal vein extends
obliquely to the liver behind
the duodenum.
As it descends, it runs within the
right free border of the lesser
omentum along with two other
structures – the hepatic artery
proper and the common bile duct
– to form a structure known as
the portal triad

21. • The lesser omentum which in this
image is highlighted in green.
• The lesser omentum is a double-
layered band of peritoneum which
extends from the liver to the lesser
curvature of the stomach and the
first part of the duodenum.
• The nutrient-rich blood of the
hepatic portal vein runs with the
lesser omentum as it travels towards
the liver.

22. • In this image, the lesser
omentum has two ligamentous
parts – the hepatogastric
ligament highlighted in green
and the hepatoduodenal
ligament again highlighted in
green.
• In this image, you can see that
the lesser omentum has a free
border. This border is a
component of the
hepatoduodenal ligament and
houses the portal triad.

23. The lesser omentum has a free border. This border is a component of the hepatoduodenal ligament and
houses the portal triad.

24. • Like, inferior vena cava is formed
by the convergence of the right
and left common iliac veins, the
portal vein is also formed by
several vessels.
• The hepatic portal vein is usually
formed by the convergence of the
superior mesenteric vein and the
splenic vein.
• This confluence is often referred
to as the splenic-mesenteric
confluence

25. The superior mesenteric vein which is
highlighted in green on the right receives
the pancreaticoduodenal veins and the
gastroepiploic veins

26. The splenic vein
which you can now
see highlighted in
green on the right
receives the inferior
mesenteric vein

27. The superior
mesenteric vein
ascends close to the
superior mesenteric
artery which I'm
pointing out with an
arrow running
anterior to the
ureter and uncinate
process of the
pancreas

28. The superior mesenteric vein present deep to the neck of the pancreas joining the
splenic vein at the level of the L1 vertebra

30. • The superior mesenteric vein drains blood from several structures –
the small intestine, the stomach, the pancreas, the cecum and also
the ascending and transverse colons.
• Blood draining into this vessel is from the intestine and is nutrient-
rich as food that has been broken into large molecules is passed
through the small intestine and further broken down into smaller
molecules.
• This allows for the small nutrients to be absorbed into the blood
through the luminal wall of the jejunum and ileum.
• This blood then travels to the liver via the superior mesenteric vein
towards the portal vein then to the liver.

31. PDV
GEV
SMV
SV
IMV
SMA
The drainage of the splenic vein is important to
note as obstruction to the splenic vein or hepatic
portal vein leads to a reversal of venous flow and
can result in splenomegaly which is enlargement
of the spleen.
The inferior mesenteric vein drains into the
splenic vein and terminates along its course. The
inferior mesenteric vein drains venous blood from
the abdominal hindgut structures such as the
rectum, the sigmoid colon, the descending colon
and the distal transverse colon.

32. The portal hepatis – is a deep fissure found within the inferior
aspect of the liver.
The porta hepatis is significant for being the site where the
portal triad is located.
The portal triad is a collection of three closely related
structures – the hepatic portal vein, the hepatic artery proper
and the common bile duct.
The portal triad can also contain lymphatics and branches of
the vagus nerve.

33. The position of the portal triad is also significant because its
location in the hepatoduodenal ligament also makes it the anterior
border of the epiploic foramen otherwise known as the foramen of
Winslow.
The fissure of the porta hepatis over here as the portal triad within
the hepatoduodenal ligament creates the foramen of Winslow.
This foramen is significant because it is the entrance to the lesser
sac of the foramen.

34. once this nutrient-rich blood enters the liver which is
highlighted in green in this image, the liver can then perform its
job of nutrient storage and cleansing of toxins

35. Once done, this blood then drains directly into the inferior vena
cava which lies along the posterior border of the liver.

36. The blood is then transported back to the heart.
A ventral view of the abdomen with parts of the large intestine
and small intestine dissected away.
The inferior vena cava highlighted in green and its position
posterior to the liver.
IVC

38. Portal Hypertension
• Like regular hypertension, portal hypertension is an increase in blood
pressure localized to the portal system.
• Portal hypertension is most commonly caused by liver cirrhosis which in
itself can be caused by alcoholism or other liver disease.
• It can also be caused by blood clots in the portal vein and schistosomiasis
amongst other things.
• This increase in blood pressure can affect areas of anastomosis between
the portal vasculature and the caval musculature which are classified as the
vessels not relating to the portal system.
• This in turn can cause the vessels to dilate and form varicose veins which
can result in potentially fatal hemorrhage.

39. • Some of these important porto-caval anastomotic areas are listed
below
• the first vein being the portal vein the second vein being the caval vein
• the superior rectal and inferior rectal veins,
• the left gastric and esophageal veins,
• the colonic veins and the retroperitoneal veins and
• the para-umbilical and epigastric veins.

40. Porto-caval Anastomosis
• portocaval anastomosis also known as Porto-systemic anastomosis is the
collateral communication between the portal and the systemic venous
system.
• The portal venous system transmits deoxygenated blood from most of the
gastrointestinal tract and gastrointestinal organs to the liver.
• When there is a blockage of the portal system, portocaval anastomosis
enable the blood to reach the systemic venous circulation.
• Even though this is useful, bypassing the liver may be dangerous, since it is
the main organ in charge for detoxication and breaking down of substances
found in the gastrointestinal tract, such as medications but the poisons as
well.

41. Lower esophagus Left gastric veins (portal system) -> lower branches of
oesophageal veins (systemic veins)
Upper part of anal canal Superior rectal veins (portal) -> inferior and middle
rectal veins (systemic)
Umbilicus Paraumbilical veins (portal) -> epigastric veins
(systemic)
Area of the liver Intraparenchymal branches of right division of portal
vein (portal) -> retroperitoneal veins (systemic)
Hepatic and splenic flexures Omental and colonic veins (portal) -> retroperitoneal
veins (systemic)
Hepatic and splenic Ductus venosus (portal) -> inferior vena cava
(systemic)
Function of the porto-systemic anastomosis Provide alternative routes of venous blood circulation
when there is a blockage in the liver or portal vein.
Ensure that venous blood from the gastrointestinal
tract still reaches the heart through the inferior vena
cava without going through the liver.

42. Various veins drain into the portal vein. These
veins are:
• superior mesenteric vein: drains blood mainly from small intestine
• splenic vein: receives blood from short gastric, left gastroepiploic,
inferior mesenteric, and pancreatic veins
• right and left gastric veins: drain blood from the stomach and
oesophagus
• superior pancreaticoduodenal veins: drain blood from the pancreas
and duodenum
• cystic veins: drain blood from the gallbladder and the paraumbilical
vein

43. • From the portal vein, the blood is
drained into the left and right
branches of the portal vein into the
left and right side of the liver.
• Inside the liver it passes through
tiny capillary beds called venous
sinusoids of the liver and finally
into the hepatic vein which
transmits the blood into the
inferior vena cava (carries
deoxygenated blood to the heart).

46. • Normally, portal venous blood traverses the liver as described above
and
• empties into the systemic venous circulation via the hepatic vein and
inferior vena cava. This pathway may be blocked by a variety of
causes which are classified into:
• prehepatic — e.g. thrombosis or congenital obliteration of the portal vein;
• hepatic—e.g. cirrhosis of the liver;
• posthepatic—e.g. congenital stenosis of the hepatic veins. If obstruction from
any of these causes occurs, the portal venous pressure rises (portal
hypertension) and collateral pathways open up between the portal and
systemic venous systems.

51. Examination Question
• Q: Describe portal vein under the following headings:
• Formation
• Course and parts
• Relations
• Tributaries and branches