Anatomy, Abdomen and Pelvis, Portal Venous System (Hepatic Portal System) (2024)

Introduction

The veins that drain the gastrointestinal organs parallel the major arteries that supply the foregut, midgut, and hindgut, including the celiac, superior mesenteric, and the inferior mesenteric arteries respectively. These veins eventually convene at the portal vein, forming a single venous inflow tract into the liver. The celiac vein drains the foregut structures, including the stomach, through the second part of the duodenum. The superior mesenteric vein drains the third part of the duodenum through the initial two-thirds of the transverse colon. Finally, the inferior mesenteric vein drains the remaining one-third of the transverse colon through the rectum. These veins comprehensively drain nutrients and toxins from the digestive intake and ultimately provide approximately 75% of the liver's blood supply, the remainder coming from the hepatic artery, eventually draining into the hepatic veins and systemic circulation.[1][2]

Structure and Function

The liver receives 25% of the total cardiac output during each cardiac cycle. The portal vein receives drainage from the gallbladder, spleen, pancreas, stomach, and small and large intestines. The portal vein forms from the confluence of the superior and inferior mesenteric veins, the splenic vein, gastric vein, and cystic vein. The portal veinenters the liver within the hepatoduodenal ligament, traveling posterior to the proper hepatic artery and the common bile duct. When the portal vein reaches the hilum of the liver, it divides into right and left branches and feeds into the liver sinusoids. This vasculature comprises the majority of the blood flow to the liver, as well as draining back toxins and nutrients from the drained gastrointestinal tract.Blood then empties into the inferior vena cava (IVC). Figure 1 demonstrates normal portal venous anatomy and branching patterns, as shown by contrast-enhanced CT.

The remaining minority 25% of blood flow to the liver is supplied by the proper hepatic artery. Hepatic parenchymal cells are some of the most richly-perfused cells in the entire human body due to this blood flow. They receive well-oxygenated blood from the hepatic artery and nutrient-rich blood from the splanchnic vessels via the portal venous system. This blood mixes within the hepatic sinusoids. The intrahepatic and portal venous pressures are regulated by portal venous sphincters. The portal vein branches as it enters the liver into the right and left portal veins and then further divides. The progressively smaller branches that come from the venous divisions form the portal venules. After the blood mixes within the sinusoids, it is collected within the terminal hepatic venule or central vein. These central veins then coalesce to form the hepatic vein, which drains the liver back to the IVC, allowing blood to return to the heart and systemic circulation.

There is a large volume of blood contained within the portal venous system and a similarly-large amount of blood contained within the liver. The volume of blood contained within this system affects the body’s response to fluid loss or excess. The blood contained within the portal vein is crucial to the liver’s functional role, including lipoprotein metabolism, drug metabolism, and toxin clearance, as well as endocrine homeostasis.[3][2]

Embryology

The embryology of the portal venous system begins during the fourth week of gestation and continues to the twelfth week. During development, the hepatic portal system is composed of the vitelline venous system in conjunction with the umbilical veins. The primitive venous system of the liver begins as the right and left vitelline veins. Over time, these two veins undergo selective involution involving the cranial portion of the left vitelline vein and their anastomoses. The dorsal and cranio-ventral anastomoses give rise to the main portal vein and the left portal vein, respectively.[2]

Physiologic Variants

Anatomical variants of the following venous morphologies occur in up to 35% of individuals.

Duplication of the portal vein and non-branching portal vein variants exist as well but are rare.

Congenital anomalies of the portal venous system can occur. The most common congenital anomaly is agenesis of the left or right portal vein. This variant can lead to the development of collateral vessels of the portal venous system as a result of portal hypertension. The most common of these collaterals are gastroesophageal, paraumbilical, inferior mesenteric, and splenorenal collateral vessels.[4]

Surgical Considerations

Knowledge of both normal and variant anatomy is of utmost importance, especially for surgery. The branching patterns of the portal venous system are often assessed prior to surgery via imaging techniques. Color Doppler Ultrasound (US) is the most useful imaging technique for identifying aneurysms and/or thrombosis of the portal vein. Helical CT is a valuable tool for visualizing the branching pattern of the portal venous system. [4]Anatomical variants of portal vein’s branching pattern are essential to recognize on imaging for liver surgery to maintain perfusion to the remaining liver segments. Additionally, the anatomy of the portal venous circulation is significant for liver transplantation in which both the donor’s venous anatomy and the recipient’s anatomy requires analysis to ensure appropriate donor and recipient selection.[2]

Portal vein thrombosis is a frequent occurrence in patients with hypercoagulable diseases, such as malignancy and cirrhosis, and can be a challenge at the time of liver transplantation. Due to the increased morbidity and mortality associated with this condition at the time of transplantation, this thrombotic state is considered a relative contraindication to a liver transplant.[5]Portal vein recanalization (PVR) and transjugular intrahepatic portosystemic shunts (TIPS) are safe options for patients with portal vein thrombosis in dire need of a liver transplant.[6]

Due to the large quantity of blood contained within the liver and flowing through the portal system, patients that suffer liver injuries are at increased risk for hemorrhagic shock and death from blood loss. Cross clamping the hepatic pedicle, known as the Pringle Maneuver, stops the blood flow to the liver and allows for better visualization of the surgical field and aids in preventing hemodynamic collapse.[7]

Clinical Significance

Portal hypertension is a disease that arises when blood flow through the liver is compromised, and blood pressures in the portal vein rise. This disease has many complications that result from increased pressure, including esophageal varices, ascites, and hepatorenal syndrome, which contribute to the high morbidity and mortality often seen in this condition.[8]The blood flow through the liver has a direct effect on renal function via a reflex mechanism. The liver detects the sensory afferent response via blood flow-dependent changes in the intrahepatic adenosine concentrations. The efferent response to changes in hepatic blood flow is affected by the renal sympathetic nerves, causing constriction of renal vasculature and release of renal vasoconstricting molecules resulting in renal dysfunction.[9] To date, the only definitive treatment of hepatorenal syndrome is a liver transplant.[10]

Additionally, ifa patient is under consideration for partial liver resection, portions of the portal veincan be embolized to enable hypertrophy of the remaining liver segments that still receive flow from other segments of the portal venous system. In a majority of patients, portal vein embolization results in adequate liver hypertrophy to allow surgery to proceed. However, should the portal vein embolization result in insufficient hypertrophy of the remaining liver segments, hepatic vein embolization may be an option to augment the effects of portal vein embolization.[11]

Another clinical consideration aforementioned is portal vein thrombosis, which can be pathologically acquired, as seen in cirrhosis, malignancy, liver tumors, and patients with a certainJAK2mutation. Portal vein thrombosis can present with varied symptoms, including abdominal pain, ischemic hepatitis, liver failure, and/or small intestine infarction. Patients generally receive treatment with anticoagulant medication. This treatment can incur further complications by the accompanying coagulopathy often seen in these patients. The surgeon may consider a transjugular intrahepatic portosystemic shunt (TIPS) procedure in patients who do not improve or continue to worsen despite anticoagulation.[12][13]

Figure

Figure 1.Normal portal vein branching patterns as visualized by contrast-enhanced CT imaging. Carneiro, C., Brito, J., Bilreiro, C., Barros, M., Bahia, C., Santiago, I., & Caseiro-Alves, F. (2019). All about portal vein: a pictorial display to (more...)

References

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Granger DN, Holm L, Kvietys P. The Gastrointestinal Circulation: Physiology and Pathophysiology. Compr Physiol. 2015 Jul 01;5(3):1541-83. [PubMed: 26140727]

2.

Carneiro C, Brito J, Bilreiro C, Barros M, Bahia C, Santiago I, Caseiro-Alves F. All about portal vein: a pictorial display to anatomy, variants and physiopathology. Insights Imaging. 2019 Mar 21;10(1):38. [PMC free article: PMC6428891] [PubMed: 30900187]

3.

Lautt WW. Hepatic Circulation: Physiology and Pathophysiology. Morgan & Claypool Life Sciences; San Rafael (CA): 2009. [PubMed: 21452433]

4.

Gallego C, Velasco M, Marcuello P, Tejedor D, De Campo L, Friera A. Congenital and acquired anomalies of the portal venous system. Radiographics. 2002 Jan-Feb;22(1):141-59. [PubMed: 11796904]

5.

Thornburg B, Desai K, Hickey R, Kulik L, Ganger D, Baker T, Abecassis M, Lewandowski RJ, Salem R. Portal Vein Recanalization and Transjugular Intrahepatic Portosystemic Shunt Creation for Chronic Portal Vein Thrombosis: Technical Considerations. Tech Vasc Interv Radiol. 2016 Mar;19(1):52-60. [PubMed: 26997089]

6.

Thornburg B, Desai K, Hickey R, Hohlastos E, Kulik L, Ganger D, Baker T, Abecassis M, Caicedo JC, Ladner D, Fryer J, Riaz A, Lewandowski RJ, Salem R. Pretransplantation Portal Vein Recanalization and Transjugular Intrahepatic Portosystemic Shunt Creation for Chronic Portal Vein Thrombosis: Final Analysis of a 61-Patient Cohort. J Vasc Interv Radiol. 2017 Dec;28(12):1714-1721.e2. [PubMed: 29050854]

7.

Imamura H, Kokudo N, Sugawara Y, Sano K, Kaneko J, Takayama T, Makuuchi M. Pringle's maneuver and selective inflow occlusion in living donor liver hepatectomy. Liver Transpl. 2004 Jun;10(6):771-8. [PubMed: 15162472]

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Simonetto DA, Liu M, Kamath PS. Portal Hypertension and Related Complications: Diagnosis and Management. Mayo Clin Proc. 2019 Apr;94(4):714-726. [PubMed: 30947834]

9.

Pillebout E. [Hepatorenal syndrome]. Nephrol Ther. 2014 Feb;10(1):61-8. [PubMed: 24388293]

10.

Facciorusso A, Chandar AK, Murad MH, Prokop LJ, Muscatiello N, Kamath PS, Singh S. Comparative efficacy of pharmacological strategies for management of type 1 hepatorenal syndrome: a systematic review and network meta-analysis. Lancet Gastroenterol Hepatol. 2017 Feb;2(2):94-102. [PubMed: 28403995]

11.

Piron L, Deshayes E, Escal L, Souche R, Herrero A, Pierredon-Foulongne MA, Assenat E, le Lam N, Quenet F, Guiu B. [Portal vein embolization: Present and future]. Bull Cancer. 2017 May;104(5):407-416. [PubMed: 28477870]

12.

Haris M, Thachil J. Portal vein thrombosis - a primer for the general physician. Clin Med (Lond). 2017 Jun;17(3):212-219. [PMC free article: PMC6297567] [PubMed: 28572222]

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Basit SA, Stone CD, Gish R. Portal vein thrombosis. Clin Liver Dis. 2015 Feb;19(1):199-221. [PubMed: 25454305]

Disclosure: Joshua Harkins declares no relevant financial relationships with ineligible companies.

Disclosure: Bareeqah Ahmad declares no relevant financial relationships with ineligible companies.

Anatomy, Abdomen and Pelvis, Portal Venous System (Hepatic Portal System) (2024)

FAQs

What is the anatomy of hepatic portal venous system? ›

The portal vein enters the liver within the hepatoduodenal ligament, traveling posterior to the proper hepatic artery and the common bile duct. When the portal vein reaches the hilum of the liver, it divides into right and left branches and feeds into the liver sinusoids.

What are the three portal systems in the body? ›

There are three portal venous systems – the hepatic portal system, the hypophyseal portal system, and the renal portal system. Unqualified, portal venous system usually refers to the hepatic portal system. For this reason, portal vein most commonly refers to the hepatic portal vein.

What is the difference between hepatic portal vein and hepatic portal system? ›

The hepatic portal system is a crucial part of the circulatory system. However, there are other systems of veins in the body that are referred to as the portal venous system. The hepatic portal vein is the largest vein in the abdominal cavity. It drains blood from the spleen and the gastrointestinal tract to the liver.

What is the hepatic portal system in the digestive system? ›

'Hepatic' means of or relating to the liver, therefore the hepatic portal vein is a blood vessel that sends nutrient-rich blood from the gastrointestinal tract and spleen to the liver, but also delivers toxins to the liver that will be chemically modified in the proces of detoxication.

What is the venous system of the abdomen? ›

Venous drainage of the abdomen is by the inferior vena cava and its tributaries. The blood from the portal vein passes through the liver and finally drains into the inferior vena cava. The inferior vena cava forms at the level of the fifth lumbar vertebra by the joining of left with the right common iliac veins.

What is the hepatic venous system? ›

The liver processes the nutrients in this blood and filters out toxic substances. The hepatic veins then carry the blood away from the liver and into the inferior vena cava, which leads to the right atrium, one of the four chambers of the heart.

Which organ is connected by the hepatic portal system? ›

The hepatic portal system is the venous system that returns blood from the digestive tract and spleen to the liver (where raw nutrients in blood are processed before the blood returns to the heart).

What organ does the portal vein connected to? ›

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 [1]. Hepatic artery provides the remaining hepatic blood flow.

Do humans have hepatic portal system? ›

In human anatomy, the hepatic portal system or portal venous system is the system of veins comprising the portal vein and its tributaries. The other portal venous systems in the body are the renal portal system, and the hypophyseal portal system.

What drains into the portal vein? ›

Tributaries of the portal vein

Your portal vein has several tributaries, or veins that drain into it. These include your: Superior mesenteric vein, which drains several organs in the middle of your belly, including your small intestine. Splenic vein, which drains your spleen.

What major vessels take blood to the hepatic portal vein? ›

Flexi Says: The major vessels that take blood to the hepatic portal vein are the superior mesenteric vein and the splenic vein. The superior mesenteric vein drains blood from the small intestine, while the splenic vein drains blood from the spleen, part of the stomach, and part of the pancreas.

Is hepatic portal a vein or artery? ›

A blood vessel that carries blood to the liver from the intestines, spleen, pancreas, and gallbladder. Also called portal vein.

Which two organs are connected by the hepatic portal vein? ›

The hepatic portal system is a unique circulatory system that connects two systems of capillary beds: one in sinusoidal area of the liver and the other in the wall of the small intestine and spleen. Its flow of blood to the liver is unique because it receives both deoxygenated and oxygenated blood.

What organs are in the hepatic system? ›

The hepatic system detoxifies blood, metabolizes glucose, and synthesizes proteins, and is a blood reservoir. The liver and heart are connected through the hepatic artery – which also receives 75% of the blood flow from the spleen, pancreas and stomach.

What is portal system anatomy? ›

The portal venous system and hepatic veins are a paired network of valveless veins responsible for blood from all of the abdominal viscera, excluding the kidneys and adrenal glands. Before reaching the heart the blood collected by the tributaries of the portal vein passes through the hepatic sinusoids.

What is the venous structure of the liver? ›

The hepatic veins are three large vessels that drain the venous blood from the liver into the inferior vena cava. The main hepatic veins are the right, intermediate and left hepatic veins. In addition, several smaller and somewhat inconsistent caudate lobe veins contribute to the venous drainage of the liver.

What are the three parts of the portal vein? ›

The portal vein (in light blue) and its tributaries. It is formed by the superior mesenteric vein, inferior mesenteric vein, and splenic vein. Lienal vein is an old term for splenic vein. The portal vein is not a true vein, because it conducts blood to capillary beds in the liver and not directly to the heart.

What is the anatomy of the hepatic artery? ›

Gross anatomy

The hepatic artery proper runs anteromedial to the portal vein and medial to the common bile duct to form the portal triad within the hepatoduodenal ligament 1. It terminates by bifurcating into the right and left hepatic arteries before entering the porta hepatis of the liver.

What are the three branches of the hepatic portal vein? ›

The most common variant is the so called “portal vein trifurcation” where the main portal vein divides into three branches: the left portal vein, the right anterior portal vein, and the right posterior portal vein (type 2, Fig. ​ 1B).

References

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