There are 2 venous equipment that drain abdominal structures – the portal venous system and the systemic venous system. The portal device transports venous blood come the liver because that processing, whilst the systemic venous mechanism returns blood come the right atrium of the heart.

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In this article, us shall think about the anatomy that these 2 venous equipment – the significant vessels involved, their anatomical course, and also their tributaries.

Systemic Venous System

The systemic venous device transports deoxygenated blood to the ideal atrium the the heart. The significant vessel in this system is the inferior vena cava.

Inferior Vena Cava

The inferior vena cava is the common convergence of venous drainage from every structures below the diaphragm. The is situated on the posterior abdominal wall; anteriorly come the vertebral column and also to the right of the abdominal aorta.

The ship is created by the union of the common iliac veins at the L5 vertebral level. The ascends superiorly, and also leaves the abdomen through piercing the central tendon that the diaphragm at the T8 level (the caval hiatus). Within the thorax, the worse vena cava drains into the right atrium of the heart.

During its long course, the worse vena cava share an anatomical connection with numerous ab structures – including the right typical iliac artery, the root of the mesentery, the head of the pancreas, the bile duct, the portal vein and also the liver.


The inferior vena cava is responsible for the venous drainage of every structures below the diaphragm. The receives tributaries from:

Common iliac veins – created by the external and internal iliac veins. They drain the lower limbs and also gluteal region.Lumbar veins – drainpipe the posterior abdominal muscle wall.Right testicular/ovarian vein – drainpipe the ideal testes or ovary dong in men and women (the left testicular/ovarian vein drains into the left renal vein).Right suprarenal vein – drains the right adrenal gland (the left adrenal vein drains right into the left renal vein).

There room no tributaries from the spleen, pancreas, gallbladder or the abdominal part of the GI street – as these frameworks are very first drained into the portal venous system. However, venous return from these frameworks ultimately enters the inferior vena cava via the hepatic veins (after gift processed by the liver).

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Fig 1.0 – The inferior vena cava and significant tributaries. Note exactly how the left adrenal vein and left testicular vein empty right into the left renal vein.

Portal Venous System

The portal system carries venous blood (rich in nutrients that have been extract from food) come the liver for processing.

The significant vessel that the portal mechanism is the portal vein. It is the suggest of convergence because that the venous drainage of the spleen, pancreas, gallbladder and the abdominal component of the cradle tract. The portal vein is created by the union of the splenic vein and also the superior mesenteric vein, posterior to the neck that the pancreas, in ~ the level the L2.

As that ascends towards the liver, the portal vein passes posteriorly come the superior part of the duodenum and the bile duct. Immediately before entering the liver, the portal vein divides right into right and also left branches i beg your pardon then enter the parenchyma that the liver separately.


The portal vein is developed by the union that the splenic vein and also superior mesenteric vein. The receives extr tributaries from:

Para-umbilical veins – drain the skin of the umbilical region.

Splenic Vein

The splenic vein is developed from a variety of smaller vessels as they leave the hilum the the spleen.

Unlike the splenic artery, the splenic vein is straight and also it maintains contact with the body of the pancreas together it the cross the posterior ab wall. As it will the neck of the pancreas, the splenic vein joins the remarkable mesenteric vein to kind the portal vein.


Tributaries to the splenic vein include:

Short gastric veins – drain the fundus of the stomach.Left gastro-omental vein – drains the better curvature the the stomach.

The inferior mesenteric vein drains blood from the rectum, sigmoid colon, to decrease colon and also splenic flexure. It begins as the premium rectal vein and also ascends, receiving tributaries indigenous the sigmoid veins and also the left colic veins. Together it ascends more it overcome posteriorly to the body of the pancreas and also typically joins the splenic vein.

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Fig 2 – The hepatic portal venous system.

Superior Mesenteric Vein

The premium mesenteric vein drains blood from the small intestine, cecum, ascending colon and also transverse colon. It starts in the right iliac fossa, as a convergence of the veins draining the terminal ileum, cecum and also appendix. The ascends in ~ the mesentery of the small intestine, and then travel posteriorly come the neck the the kidnize to join the splenic vein.


Tributaries come the exceptional mesenteric vein include:

Right gastro-omental vein – drains the higher curvature the the stomach.Ileocolic vein – drains the ileum, colon and also cecum.Right colic vein – drains the ascending colon.Middle colic vein – drains the transverse colon.

Many of these tributaries are developed as one accompanying vein because that each branch that the exceptional mesenteric artery.

Clinical relationship – Porto-Systemic Anastomoses

A porto-systemic anastomosis is a connection between the veins that the portal venous system, and the veins that the systemic venous system. The major sites of this anastomoses include:

Oesophageal – in between the oesophageal branch that the left gastric vein and also the oesophageal tributaries to the azygous system.Rectal – in between the superior rectal vein and the worse rectal veins.Retroperitoneal – between the portal tributaries of the mesenteric veins and also the retroperitoneal veins.Paraumbilical – in between the portal veins of the liver and also the veins the the anterior abdominal wall.
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Fig 3 – Endoscopic illustration of oesophageal varices. They can undergo rupture, top to huge volumes the blood loss.

When blood flow through the portal mechanism is obstructed (e.g due to cirrhosis, portal vein thrombosis, or external pressure from a tumour), the pressure within portal device increases. A portal venous push in overabundance of 20mmHg is defined as portal hypertension.

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In portal hypertension, blood might be re-directed through the porto-systemic anastomoses (as these are now under a reduced pressure). If a huge volume the blood passes through these anastomoses over a long period of time, the veins around the anastomosis can come to be abnormally dilated – well-known as varices. Rupture the oesophageal or rectal varices can an outcome in fatal blood loss.