What are ligament of liver?
The upper surface of the liver is percussed at the level of the fifth intercostal space. Superior, anterior, posterior and right surfaces of the liver are continuous with each other and are related to the diaphragm and anterior abdominal wall.
The anterior surface is separated from the inferior (visceral) surface by a sharp anterior (inferior) border that is clinically palpable on deep inspiration. The inferior surface is related to the hepatic flexure (the area where the vertical ascending (right) colon takes a right-angle turn to become the horizontal transverse colon), right kidney, transverse colon, duodenum and stomach. The gallbladder straddles the undersurfaces of liver segments IVB and V.
There is an H-shaped fissure on the inferior surface of the liver. The right vertical arm of the H is formed by the gallbladder anteriorly and the inferior vena cava (IVC) posteriorly; it is incomplete, with the caudate process between the two. The left vertical arm of the H is formed by the ligamentum teres hepatis in front and the ligamentum venosum behind.
The transverse limb of the H is the porta hepatis (hilum), a 5-cm transverse fissure (slit) on the undersurface of the liver with the quadrate lobe in front and the caudate lobe behind. It contains the common hepatic duct (CHD) in front and to the right, the proper hepatic artery in front and to the left, and the portal vein behind, enclosed in the hepatoduodenal ligament (HDL), composed of 2 layers of lesser omentum.
Anatomically, the liver is divided into a larger right lobe and a smaller left lobe by the falciform ligament (see the image below). This division, however, is of no use surgically.
From a surgical point of view, the liver is divided into right and left lobes of almost equal (60:40) size by a major fissure (Cantlie’s line) running from the gallbladder fossa in front to the IVC fossa behind. This division is based on the right and left branches of the hepatic artery and the portal vein (see the image below), with tributaries of bile (hepatic) ducts following. The middle hepatic vein (MHV) lies in Cantlie's line. The left pedicle (left hepatic artery , left branch of the portal vein, and left hepatic duct) has a longer extrahepatic course than the right.
Each lobe is divided into 2 sectors. The right hepatic vein (RHV) divides the right lobe into anterior and posterior sectors; the left hepatic vein (LHV) divides the left lobe into medial (quadrate) and lateral sectors. While the falciform ligament and umbilical fissure mark the division between left lateral and left medial sectors on the surface of the liver, no surface marking is observed between right anterior and right posterior sectors. The posterior sector of the right lobe and the caudate lobe are not seen on a frontal view of the liver; the anterior sector of the right lobe forms the right lateral border in this view.
The sectors are further divided into segments (after Couinaud); each segment has its own blood supply and biliary drainage. The anterior sector of the right lobe contains superior (VIII) and inferior (V) segments. The posterior sector of the right lobe has superior (VII) and inferior (VI) segments. The medial sector of the left lobe (quadrate lobe, segment IV) is part of the left lobe from a surgical perspective but lies to the right of the midline; it is further divided into a superior subsegment (A) and an inferior subsegment (B) (note: Japanese surgeons call the superior subsegment B and inferior subsegment A). The lateral sector of the left lobe contains segments II and III.
The caudate lobe (segment I) lies in the lesser sac on the inferior surface of the liver between the IVC on the right, the ligamentum venosum on the left, and the porta hepatis in front (see the image below). The caudate lobe has three parts: a left spigelian lobe, a paracaval part, and a caudate process that connects the caudate lobe to the right lobe. The caudate lobe receives numerous small branches from the right hepatic artery (RHA), the LHA, the portal vein, and the confluence; bile ducts drain similarly.
NOTE Caudate 'lobe' is not a lobe but a segment (I); left lateral 'segment' is not a segment but a sector including two segments (II and III).
On computed tomography (CT), the portal vein branches (with the left being higher than right) divide the right and left lobes of the liver into superior and inferior halves. The superior half of liver is composed of (from right to left) segments VII, VIII, IVA and II; the inferior half is composed of (from right to left) segments VI, V, IVB and III.
Accordingly, the right portal vein divides the posterior sector of the right lobe into segments VII (superior) and VI (inferior) and the anterior sector of the right lobe into segments VIII (superior) and V (inferior). The left portal vein divides the medial sector of the left lobe (quadrate lobe) into subsegments A (superior) and B (inferior) and the lateral sector of the left lobe into segments II (superior) and III (inferior).
The falciform ligament (which divides the liver into a larger anatomical right lobe and a smaller anatomical left lobe) has 2 layers of peritoneum; it attaches the anterosuperior surface of liver to the anterior abdominal wall and diaphragm. The free edge of the falciform ligament contains the ligamentum teres hepatis (round ligament of the liver): the obliterated umbilical vein, which is attached to the inferior surface of the liver between segment IV on the right and segment III on the left. The ligamentum venosum (the obliterated ductus venosus) is attached to the inferior surface of the liver between the caudate lobe and the left lateral sector.
The superoposterior surface of the liver has coronary and left triangular ligaments; between the 2 leaves of the coronary ligament to the right of the IVC is the bare area of the liver, which is in contact with the inferior vena cava and inferior surface of the diaphragm. The falciform ligament is continuous with the anterior layer of the coronary ligament. On the left, the anterior and posterior layers of the coronary ligament unite to form the left triangular ligament. On the right, the anterior and posterior layers of the coronary ligament unite to form the right triangular ligament.
The posterior layer of the coronary ligament on the right side is called the hepatorenal ligament. The hepatorenal pouch is the area below the posterior layer of the right triangular and coronary ligament over the right kidney. The lesser omentum connects the liver with the lesser curvature of the stomach and the first part of the duodenum via hepatogastric and hepatoduodenal ligaments.
Inferior vena cava ligament is a bridge of tissue between posterior surface of right lobe and caudate lobe behind the inferior vena cava.
The liver has a unique dual blood supply (about 1500 mL/min) both from the proper hepatic artery (20-40%) and from the portal vein (60-80%; see the image below).
The celiac trunk (axis) comes off the anterior surface of the abdominal aorta at the level of T12 – L1 between the right and left crura of the diaphragm. It is a short structure (about 1 cm) that trifurcates into the common hepatic artery (CHA), the splenic artery, and the left gastric artery (LGA).
The CHA runs toward the right on the superior border of the proximal body of the pancreas. After giving off the gastroduodenal artery (GDA) behind the first part of the duodenum above the neck of the pancreas, it continues as the proper hepatic artery in the HDL (the free edge of the lesser omentum) to the left of the bile duct and in front of the portal vein. In the hepatic hilum, it divides in a Y-shaped manner into the RHA and the LHA, with the RHA ascending behind the CHD; the cystic artery is usually a branch of the RHA.
The portal vein, formed by union of the superior mesenteric vein (SMV) and the splenic vein behind the neck of the pancreas, collects blood from the gastrointestinal (GI) tract (SMV and inferior mesenteric vein ) and from the spleen and pancreas (splenic vein). It then ascends in the HDL behind the CBD and the proper hepatic artery and divides in a T-shaped manner into right and left portal vein branches in the hepatic hilum. The right portal vein divides within the liver parenchyma into a vertical right anterior sectoral branch (which then divides into segmental V and VIII branches) and a horizontal right posterior sectoral branch (which then divides into segmental VI and VII branches). The left portal vein runs below the base of segment IV to which it gives off several small branches; it then enters the liver parenchyma where it divides into branches to segments IV, III, and II.
The hilar plate is a condensation of fibroareolar tissue that lies on the undersurface of the hilum of liver, separating it from the biliovascular pedicle at the porta hepatis; it continues along the right and left portal pedicles as sleevelike sheaths.
The left portal vein connects to the umbilical vein through the ligamentum teres hepatis and to the left hepatic vein through the ligamentum venosum. The portal venous system (2 groups of capillaries, one in the organ being drained and the other in the liver) has no valves.
Portosystemic connections are present in the gastroesophageal area (between the esophageal tributary of the left gastric vein and the esophageal tributaries of the azygos vein), in the rectum (between the superior, middle, and inferior rectal veins), around the umbilicus (between the left portal, umbilical, and paraumbilical veins and the superficial and deep epigastric veins), and in the retroperitoneum (between the colic and splenic veins and renal and posterior parietal veins).
The three hepatic veins (RHV, MHV, and LHV) are largely intrahepatic and lie on the posterior surface of the liver. The MHV and the LHV may join to form a common trunk before draining into the IVC. The IVC lies on the posterior surface of the liver in a groove (or, sometimes, a tunnel) between the bare area on the right, the caudate lobe on the left, and the caudate process in front.
The vessels that communicate between the liver and adjacent structures require bridges between them. The bridges comprise the ligaments of the liver as follows: the falciform ligament, right and left coronary ligaments, lesser omentum including the hepatogastric ligament and hepatoduodenal ligament.
An accessory digestion gland, the liver performs a wide range of functions, such as synthesis of bile, glycogen storage and clotting factor production.
In this article, we shall look at the anatomy of the liver - its position, structure, and neurovascular supply.
The liver is predominantly located in the right hypochondrium and epigastric areas, and extends into the left hypochondrium.
When discussing the anatomical position of the liver, it is useful to consider its external surfaces, associated ligaments, and the anatomical spaces (recesses) that surround it.
The external surfaces of the liver are described by their location and adjacent structures. There are two liver surfaces – the diaphragmatic and visceral:
There are a number of ligaments that attach the liver to the surrounding structures. These are formed by a double layer of peritoneum.
In addition to these supporting ligaments, the posterior surface of the liver is secured to the inferior vena cava by hepatic veins and fibrous tissue.
The hepatic recesses are anatomical spaces between the liver and surrounding structures. They are of clinical importance as infection may collect in these areas, forming an abscess.
The liver is covered by a fibrous layer, known as Glisson's capsule. It is comprised of a large right lobe and smaller left lobe.
There are two further 'accessory' lobes that arise from the right lobe, which are located on the visceral surface of liver:
Separating the caudate and quadrate lobes is a deep, transverse fissure - known as the porta hepatis. It transmits all the vessels, nerves and ducts entering or leaving the liver with the exception of the hepatic veins.
Microscopically, the cells of the liver (known as hepatocytes) are arranged into lobules. These are the structural units of the liver.
Each anatomical lobule is hexagonal-shaped and is drained by a central vein. At the periphery of the hexagon are three structures collectively known as the portal triad:
The portal triad also contains lymphatic vessels and vagus nerve (parasympathetic) fibres.
The liver has a unique dual blood supply:
Venous drainage of the liver is achieved through hepatic veins. The central veins of the hepatic lobule form collecting veins which then combine to form multiple hepatic veins. These hepatic veins then open into the inferior vena cava.
The parenchyma of the liver is innervated by the hepatic plexus, which contains sympathetic (coeliac plexus) and parasympathetic (vagus nerve) nerve fibres. These fibres enter the liver at the porta hepatis and follow the course of branches of the hepatic artery and portal vein.
Glisson's capsule, the fibrous covering of the liver, is innervated by branches of the lower intercostal nerves. Distension of the capsule results in a sharp, well localised pain.
The lymphatic vessels of the anterior aspect of the liver drain into hepatic lymph nodes. These lie along the hepatic vessels and ducts in the lesser omentum, and empty in the coeliac lymph nodes which in turn, drain into the cisterna chyli.
Lymphatics from the posterior aspect of the liver drain into phrenic and posterior mediastinal nodes, which join the right lymphatic and thoracic ducts.
A percutaneous liver biopsy is procedure used to obtain a sample of liver tissue. A needle is inserted through the skin to access the liver.
The biopsy is required in several clinical scenarios:
During the procedure, the liver is located via ultrasound from a subcostal approach (under the ribs). Local and deep anaesthetic is injected where good liver tissue can be seen and the needle path is free of vessels. The patient is asked to hold their breath and the biopsy is obtained.
If a patient has abnormal clotting (a relative contraindication), a percutaneous biopsy while platelets are running, or a transvenous liver biopsy can be attempted. This involves cannulating the internal jugular vein, and passing the biopsy needle through to the hepatic veins, allowing for a biopsy sample to be taken.
