Anatomy of liver

Anatomy of liver

1. Anatomy of Liver Pratap Sagar Tiwari, DM Resident, Department of Hepatology , NAMS

2. Introduction: Liver The liver is largest internal organ & the largest gland in the human body . The normal liver extends from the 5th ICS in the Rt MCL down to the costal margin. It measures 12–15 cm coronally and 15–20 cm transversely.1 The median liver weight is 1,800 g in M and 1,400 g in F.1 Wanless I R. Physioanatomic Considerations. In: Schiff ER, Maddrey WC, Sorrell MF, editors. Diseases of the liver. 11 th edition. John Wiley & Sons Ltd;2012. Pic source : http://www.medicinenet.com/drug_induced_liver_disease/article.htm

3. Anatomical Position and Relations Anterior to the liver is the anterior abdominal wall ,xiphoid process and ribcage. Superior to the liver is the diaphragm (separating the abdominal cavity from the thoracic cavity) Posterior to the liver are the oesophagus , fundus of stomach , gallbladder, first part of the duodenum ,hepatic flexure of the colon,right kidney . Liver lies under the diaphragm in the right upper quadrant of abdomen and extends to the left upper quadrant. The liver has the general shape of a wedge, with its base to the right and its apex to the left .1 Wanless I R. Physioanatomic Considerations. In: Schiff ER, Maddrey WC, Sorrell MF, editors. Diseases of the liver. 11 th edition. John Wiley & Sons Ltd;2012.

4. Notes of the previous slides The abdomen is divided into nine regions by imaginary planes (two vertical and two horizontal) forming abdominal surface anatomy. The nine regions are of clinical importance when examining and describing pathologies related to the abdomen. The horizontal planes are of further importance as they provide useful landmarks on cross sectional imaging. Horizontal planes subcostal plane :corresponds to a line drawn joining the lowermost bony point of the rib cage - usually 10th costal cartilage body of the L3 vertebra; the origin of the inferior mesenteric artery and 3rd part of the duodenum lie on this plane transtubercular plane: corresponds to a line uniting the two tubercles of the iliac crests(The iliac tubercle is located approximately 5 cm (2 in) posterior to the anterior superior iliac spine on the iliac crest in humans.) upper border of the L5 vertebra and the confluence of the common iliac veins (i.e. IVC origin) lie on this plane Vertical planes The two vertical planes are similar on each side and follow a line joining the mid clavicular point to the mid inguinal point. It passes just lateral to the tip of the ninth costal cartilage - which is palpable as a distinct step along the costal margin. It roughly corresponds to the lateral border of the rectus abdominis muscle.

5. Liver Surfaces The external surfaces of the liver can be classified by the structures they lie in close proximity to. There are two liver surfaces – the diaphragmatic and the visceral. The diaphragmatic surface  refers to the anterosuperior surface of the liver. It is smooth and convex, fitting snugly beneath the curvature of the diaphragm. A section of this surface is not covered by visceral peritoneum, known as the ‘bare area’ of the liver. The visceral surface  is the posteroinferior surface related to the abdominal viscera. It is covered with peritoneum except for the fossa for the gall bladder and the porta hepatis . It bears multiple fissures and impressions from contact with other organs.

6. Visceral Surface of liver: relations

7. Peritoneal reflections & bare areas The liver is completely surrounded by a fibrous capsule and covered by peritoneum (except the bare areas). The bare area of the liver is an area of the liver on the diaphragmatic surface where there is no intervening peritoneum between the liver and the diaphragm. Boundaries of bare area : Anterior: superior layer of coronary ligament. Posterior: inferior layer of coronary ligament. Laterally: right and left triangular ligaments Other bare areas include porta hepatis ; fossa for gall bladder and grooves for IVC.

8. Fissures Two sagitally oriented fissures, linked centrally by the transverse porta hepatis,from the letter H on the visceral surface. The left fissure is the continuous groove formed: Anteriorly by the fissure for the round ligament. Posteriorly by the fissure for the ligamentum venosum . The right fissure is the continuous groove formed: Anteriorly by the fossa for the gall bladder. Posteriorly by the groove for the inferior vena cava.

9. Porta Hepatis The cross-bar of the "H" is the porta hepatis , or hilus of the liver. The limbs of the "H" are Fissure containing lig teres (obliterated left umbilical vein ) Fissure containing lig . venosum (obliterated ductus venosus ) the fossa containing the gallbladder the sulcus in which the inferior vena cava is lodged. Structures passing through the porta hepatis includes: Right and left hepatic ducts Right and left branches of hepatic artery. Right and left branches of the portal vein A few hepatic lymph nodes lie here: they drain the liver and gall bladder and send their efferent vessels to the celiac lymph nodes . It also transmits nerves . Sympathetic Nerves - these provide afferent pain impulses from the liver and gall bladder to the brain. Pain may be referred to the lower pole of the right scapula (T7). Hepatic branch of the Vagus Nerve (CN X).

10. Liver: ligaments Coronary ligaments ( left/ Rt ) / Triangular ligaments ( left/ Rt ) – attach superior surface of liver to diaphragm. The anterior and posterior layers converge on the rt & lt sides of the liver to form the rt triangular lig and left triangular lig , respectively. In between the two sides of the anterior layer, the reflection of peritoneum has an inferior continuation termed the falciform ligament. Falciform ligament – attaches the anterior surface of the liver to the ant abdominal wall. The free edge of this ligament contains the ligamentum teres (remnant of the UV).

11. Liver: ligaments Hepatogastric lig / gastrohepatic ligament connects the liver to the lesser curvature of the stomach. It contains the right and the left gastric arteries. The hepatoduodenal ligament is the portion of the lesser omentum extending between the porta hepatis & superior part of the duodenum. It sheathes the hepatic artery (HA), portal vein (PV), nerves, bile duct, and lymph vessels, all present within the porta hepatis . In the ligament the common bile duct lies to the right, the HA to the left, and the PV behind them. Manual compression of the hepatoduodenal ligament during surgery is known as the Pringle Maneuver.

12. Hepatic Recesses The hepatic recesses: spaces between the liver and surrounding structures. They are of clinical importance, as infected fluids can collect in these areas, forming an abscess. Subphrenic spaces (left and right) –  located between the diaphragm and liver, either side of the falciform ligament. Subhepatic space –  located between the inferior surface of the liver and the transverse colon. Morison’s pouch –  the posterosuperior aspect of the right subhepatic space, located between the visceral surface of the liver and the right kidney. This is the deepest part of the peritoneal cavity when supine (lying flat), and this is where fluid is likely to collect in a bedridden patient.

13. Left subphrenic space Left perihepatic space Posterior rt subhepatic space Ant rt Subhepatic space Rt Subphrenic space Rt Subhepatic space Right SMCS Left SMCS Inframesocolic space Supramesocolic space Post left perihepatic space Ant Left perihepatic space Ant Left subphrenic space Post Left subphrenic ( perisplenic ) space Transverse solon Not shown The PRSHS (AKA the hepatorenal fossa or Morison's pouch) separates the liver from the right kidney.This is the deepest part of the peritoneal cavity when supine (lying flat), and this is where fluid is likely to collect in a bedridden patient. Reference: Standring S (editor). Gray's Anatomy (39th edition). Churchill Livingstone. (2011 )

14. Lobes of liver The lobes of the liver can be described using two different aspects: morphological anatomy & functional anatomy. The traditional morphological anatomy is based on the external appearance of the liver and does not show the internal features of vessels and biliary ducts branching, which are of obvious importance in hepatic surgery. The entire liver is covered by a fibrous layer, known as  Glisson’s capsule ( orWalaeus ) . (Named for the British physician, anatomist, physiologist, and pathologist Francis Glisson (1597-1677). With reference to the attachment of the falciform ligament on the diaphragmatic surface of liver, Liver is divided into a right lobe and left lobe. On the visceral surface , there are two further ‘ accessory’ lobes The caudate and quadrate lobes which are classified with the right anatomical lobe of the liver.

15. Lobes of liver The caudate lobe is located on the upper aspect of the visceral surface. The caudate lobe of the liver is bounded below, by the porta hepatis ; on the right, by the fossa for the inferior vena cava; and, on the left, a fossa produced by the ligamentum venosum . The caudate lobe is named after the tail-shaped hepatic tissue (cauda; Latin, "tail") caudate process of the liver, which provides surface continuity between the caudate lobe and the visceral surface of the right lobe of the liver. The quadrate lobe is located on the lower aspect of the visceral surface. It lies between the gallbladder and a fossa produced by the ligamentum teres (a remnant of the fetal umbilical vein). Between the caudate and quadrate lobes is a deep fissure, known as the porta hepatis . It transmits all the vessels, nerves and ducts entering or leaving the liver.

16. Couinaud classification

17. Note to the previous slides The French surgeon and anatomist Claude Couinaud :1957(1922-2008) was the first to divide the liver into eight functionally independant segments allowing resection of segments without damaging other segments. And thus The Couinaud classification (pronounced kwee -NO) is used to describe functional liver anatomy. The segments are numbered in roman numerals I to VIII. The delineation of the segments is based on the fact that each segment has its own dual vascular inflow, outflow, biliary drainage and lymphatic drainage. In general each segment can be thought of as wedged shaped with the apex directed towards the hepatic hilum (porta hepatis ). At the apex a single segmental branch of the portal vein, hepatic artery and bile duct enter; whereas along the sides of each segment there is venous outflow through the hepatic veins so that a hepatic vein drains two adjacent segments. These veins run in 3 vertical planes that separate the segments: right hepatic vein located in the right intersegmental fissure, divides the right lobe into anterior and posterior parts middle hepatic vein lies in the main lobar fissure, divides the liver into right and left lobes (or right and left hemiliver ): this vertical plane runs from the inferior vena cava to the gallbladder fossa and is known as Cantlie's line . The Falciform ligament divides the left lobe into a medial- segment IV and a lateral part - segment II and III. left hepatic vein located in the left intersegmental fissure, divides the left lobe into medial and lateral parts A horizontal plane further divides the liver, known as the portal plane where the portal vein bifurcates and becomes horizontal, dividing the liver into superior and inferior units. These 4 planes (3 vertical and 1 horizontal) divide the liver into the 8 segments .

18. Note to the previous slides Segments segments II and III are to the left of the left hepatic vein and falciform ligament with II superior and III inferior to the portal plane segment IV lies between the left and middle hepatic veins; it is subdivided into IVa (superior) and IVb (inferior) subsegments segment IV includes the quadrate lobe Segment V to VIII make up the right hemiliver and are easier to describe: segment V is located below the portal plane between the middle and right hepatic veins segment VI is located below the portal plane to the right of the right hepatic vein segment VII is located above the portal plane to the right of the right hepatic vein segment VIII is located above the portal plane between the middle and right hepatic veins

19. Couinaud classification The right border of the liver is formed by segment V and VIII. Although segment IV is part of the left hemiliver , it is situated more to the right. Couinaud divided the liver into a functional left and right liver by a main portal scissurae containing the middle hepatic vein. This is known as Cantlie's line. Cantlie's line runs from the middle of the gallbladder fossa anteriorly to the inferior vena cava posteriorly.

20. Separating liver segments on CS imaging Left lobe: lateral(II/III) vs medial segment (IVA/B) Extrapolate a line along the falciform ligament superiorly to the confluence of the left and middle hepatic veins at the IVC (blue line). Left vs Right lobe: IVA/B vs V/VIII Extrapolate a line from the gallbladder fossa superiorly along the middle hepatic vein to the IVC (red line). Right lobe: anterior (V/VIII) vs posterior segment (VI/VII) Extrapolate a line along the right hepatic vein from the IVC inferiorly to the lateral liver margin (green line). Ref: http ://www.radiologyassistant.nl/en/p4375bb8dc241d/anatomy-of-the-liver-segments.html

21. Extra note Hypertrophy of the caudate lobe is seen in a number of conditions, including: cirrhosis : most common Budd-Chiari syndrome primary sclerosing cholangitis (PSC) (end stage) congenital hepatic fibrosis cavernous transformation of the portal vein

22. Transverse section This is a transverse image at the level of the left portal vein. At this level the left portal vein divides the left lobe into the superior segments (II and IVa ) and the inferior segments (III and IVb ). The left portal vein is at a higher level than the right portal vein. This figure is a transverse image through the superior liver segments, that are divided by the right and middle hepatic veins and the falciform ligament.

23. Transverse section This image is at the level of the right portal vein. At this level the right portal vein divides the right lobe of the liver into superior segments (VII and VIII) and the inferior segments (V and VI). The level of the right portal vein is inferior to the level of the left portal vein. At the level of the splenic vein, which is below the level of the right portal vein, only the inferior segments are visible.

24. Caudate lobe The caudate lobe or segment I is located posteriorly . The caudate lobe is anatomically different from other lobes in that it often has direct connections to the IVC through hepatic veins , that are separate from the main hepatic veins. The caudate lobe may be supplied by both right and left branches of the portal vein . This CT-image is of a patient with liver cirrhosis with extreme atrophy of the right lobe, normal volume of the left lobe and hypertrophy of the caudate lobe. Due to a different blood supply the caudate lobe is spared from the disease process and hypertrophied to compensate for the loss of normal liver parenchyma .

25. Surgical point of view Right hepatectomy segment V, VI, VII and VIII (± segment I). Extended Right or right trisectionectomy segment IV, V, VI, VII and VIII (± segment I). Left hepatectomy segment II, III and IV (± segment I). Extended Left or left trisectionectomy segment II, III, IV, V and VIII (± segment I). Ref: http ://www.radiologyassistant.nl/en/p4375bb8dc241d/anatomy-of-the-liver-segments.html

26. Surgical point of view Right posterior sectionectomy segment VI and VII Right anterior sectionectomy segment V and VIII Left medial sectionectomy segment IV Left lateral sectionectomy segment II and III Ref: http ://www.radiologyassistant.nl/en/p4375bb8dc241d/anatomy-of-the-liver-segments.html

27. Surface marking The upper border of the right lobe is on a level with the 5th rib at a point 2 cm medial to the right midclavicular line (1 cm below the right nipple). The upper border of the left lobe corresponds to the upper border of the 6th rib at a point in the left midclavicular line (2 cm below the left nipple). The lower border passes obliquely upwards from the 9th rib to the 8th left costal cartilage. It crosses the midline about midway between the base of the xiphoid and the umbilicus and the left lobe extends only 5 cm to the left of the sternum.

28. Next : circulation & collaterals References: Henryk clinical hepatology Schiff’s diseases of the liver Sherlock's Diseases of the Liver and Biliary System