Liver: Anatomy, Physiology & Normal Ultrasound :: Unit 3 :: Abdominal Ultrasound with Sononerds

Sononerds・2 minutes read

The liver, a vital organ for various functions, requires a deep understanding of its anatomy, physiology, and relationships, especially for sonographers and healthcare providers. Liver ultrasounds play a key role in diagnosing diseases, identifying structures, and assessing overall liver health, with specific protocols, patient preparation, and knowledge of key anatomical features essential for accurate assessments.

Insights

The liver, the largest peritoneal organ, is vital for various bodily functions and disease diagnosis through ultrasound.
Understanding liver anatomy and physiology is essential for sonographers, involving a detailed examination of its global position, coverings, microanatomy, and macroanatomy.
Liver division into lobes (right, left, caudate, quadrate) and segments (eight according to Couinaud's classification) is crucial for precise localization of masses or lesions within the liver.
Liver function tests, including AST, ALT, AFP, albumin, and PT, play a significant role in diagnosing liver health, monitoring disease progression, and evaluating reactions to medications.
Ultrasound imaging of the liver requires a thorough understanding of normal anatomy, landmarks, respiration effects, and the differentiation between hepatic and portal veins, aiding in comprehensive evaluation and diagnosis.

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Recent questions

What is the liver's main function?
The liver breaks down proteins, lipids, and toxins.
How does the liver detoxify the body?
The liver expels toxins through bile.
What are the key structures of the liver?
The liver is divided into four lobes.
How does the liver aid in blood clotting?
The liver produces blood clotting factors.
What are the functions of liver function tests?
Liver function tests diagnose liver issues.

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Summary

00:00

Liver Anatomy and Physiology for Sonographers

The liver is the largest peritoneal organ, crucial for various bodily functions and disease diagnosis via ultrasound.
Understanding liver anatomy, relationships, and functions is essential for sonographers.
Studying liver anatomy and physiology involves examining its global position, coverings, microanatomy, and macroanatomy.
Learning about liver physiology follows understanding its anatomy through diagrams.
Identifying key structures and landmarks by ultrasound is vital, along with liver protocols and patient preps.
Global anatomy of the liver involves understanding its surroundings and relational anatomy.
Embryology provides insights into organ origins, crucial for discussing congenital diseases.
The liver begins forming at four weeks gestation, engaging in hematopoiesis at week five.
The liver's relational anatomy includes the diaphragm, thoracic spine, right costal margin, and rectus abdominis muscles.
Ligaments like Glisson's capsule and peritoneum cover the liver, with specific roles and areas of coverage.

14:09

Liver Anatomy and Vascular System Overview

The liver is divided into four lobes using external anatomical landmarks, including the right lobe, left lobe, quadrate lobe, and caudate lobe.
The right lobe is the largest, typically six times bigger than the left lobe, located in the right hypochondrium, and divided from the left lobe by the falsiform ligament.
The left lobe varies in size among individuals, with some extending to the spleen, making it easy to see the pancreas, or being tiny.
The left lobe is divided from the right lobe by the falsiform ligament and further identified by the ligamentum venosum and ligamentum teres.
The caudate lobe is on the posterior side of the liver, superiorly positioned, bordered by the inferior vena cava, left lobe, and connected to the right lobe through the caudate process.
The caudate lobe may have a papillary process, sometimes mistaken for pathology, extending from it.
The quadrate lobe, typically considered part of the left lobe, has its own borders, including the porta hepatis, gallbladder fossa, ligamentum teres, and forms the liver's inferior edge.
The liver vasculature includes the portal vein, hepatic artery, and common bile duct entering and exiting through the porta hepatis, forming the portal triad.
The hepatic artery brings oxygenated blood to the liver, branching into the right and left hepatic arteries, with the right hepatic artery also supplying blood to the gallbladder through the cystic artery.
The portal vein brings nutrient-rich blood to the liver, formed by the confluence of the inferior mesenteric vein and splenic vein, joining the superior mesenteric vein to create the main portal vein, branching into left and right portal veins.

28:07

Liver Segmental Anatomy and Vascular Drainage Overview

The main portal vein branches into the left medial portal vein and the left lateral portal vein, as well as the right portal vein, which further divides into the right anterior portal vein and the right posterior portal vein.
The hepatic veins, distinct from the portal triad, include the right hepatic vein, middle hepatic vein, and left hepatic vein, draining the liver and confluencing at the inferior vena cava (IVC) before reaching the right atrium.
The caudate lobe has its own blood supply and venous drainage through emissary veins, directly draining into the IVC, making it independent from the rest of the liver and often spared during liver diseases.
The portal system, acting like a quasi-artery with branches, brings blood into the liver, while the hepatic veins drain blood out, returning it to the heart through the IVC.
Intra-segmental structures like the portal triad (portal vein, hepatic artery, bile duct) run within segments, while inter-segmental structures like hepatic veins run between segments, crucial for understanding liver division and segmental anatomy.
Segmental division of the liver, using internal landmarks like vessels and bile ducts, is vital for medical applications, enabling precise division into functional segments for procedures like liver donation or surgical resection of masses.
Anatomical lobe division yields four lobes (right, left, caudate, quadrate), while segmental division recognizes three lobes (right, left, caudate) and further divides them into five segments: left lateral, left medial, right anterior, right posterior, and caudate.
The hepatic veins, running inter-segmentally through fissures, help divide segments, with the right hepatic vein traversing the right hepatic fissure, the middle hepatic vein through the main lobar fissure, and the left hepatic vein through the left hepatic fissure and partially the ligamentum teres.
Segmental anatomy, further divided by Couinaud's classification into eight segments, involves the caudate lobe (segment 1), left lateral superior and inferior (segments 2 and 3), left medial superior and inferior (segments 4a and 4b), right anterior superior and inferior (segments 8 and 5), and right posterior superior and inferior (segments 7 and 6).
Understanding the division of liver segments is crucial for precise localization of masses or lesions within the liver, aiding radiologists and surgeons in treatment planning, with hepatic veins serving as key inter-segmental dividers.

43:57

Liver Anatomy and Variants Explained

The liver's division involves the portal triad and hepatic veins, with intrasegmental and intersegmental distinctions.
Understanding liver segments includes naming them, recognizing their anatomical features, and assigning Roman numerals to each.
The main lobar fissure and hepatic vein mark the true division between the right and left liver lobes.
Anatomical variants in the liver are often congenital and may not impact function unless related to organ genesis.
Situs inversus is a total body organ reversal, affecting the liver, spleen, and heart positioning.
Levocardia refers to a normal heart position amidst organ flip-flopping in situs inversus.
Sinus ambiguous or heterotaxy describes ambiguous organ positioning or midline appearance.
Left lobe variants include agenesis, where the left lobe may not form fully, and the beaver tail variant, an elongated left lobe extension.
Rydell's lobe on the right lobe is a tongue-like extension towards the right hip.
Hepatic vein variants, like separate right hepatic veins, can impact drainage patterns and may be identified through ultrasound imaging.

59:00

"Liver: Essential Functions and Detoxification Process"

Liver plays a crucial role in breaking down proteins from meat, eggs, and dairy into amino acids, using transamnases AST and ALT to process them.
Amino acids are essential for the body, but excess ammonia produced during their breakdown is converted to urea in the liver for excretion through urine by the kidneys.
Liver also aids in lipid metabolism, utilizing fats for energy, storage in adipose tissue, and transportation of cholesterol, with excess cholesterol excreted through bile.
Protein synthesis in the liver involves creating new proteins like albumin and blood clotting factors, crucial for maintaining blood pressure and clotting mechanisms.
Albumin also acts as a transporter for substances like drugs and hormones, with low levels leading to fluid accumulation and toxin buildup in the body.
Blood clotting factors, including fibrinogen and prothrombin, are produced in the liver to facilitate clot formation and stop bleeding when needed.
Liver stores glycogen, vitamins (A, D, E, K, B12), and minerals (zinc, iron, copper, magnesium) for various bodily functions, including blood clotting and metabolism.
Liver detoxifies the body by expelling foreign substances and excessive hormones through bile, particularly aiding in the breakdown and excretion of bilirubin.
Liver produces bile, incorporating electrolytes, bile acids, cholesterol, and other substances, which are stored in the gallbladder and released for fat emulsification in the duodenum.
Liver acts as a blood reservoir, holding about 10-15% of the body's total blood volume, and produces lymph in the space of Disse, contributing to the lymphatic system's protein and water transport functions.

01:13:11

Diagnosing and Treating Liver Function Issues

Hepatocytes not functioning properly can lead to liver suffering
Hepatocellular disease treated with supportive measures or medication
Obstructive disease involves blockage of bile excretion, leading to toxin buildup
Obstructive disease often treated with surgery to remove the obstruction
Ultrasound and lab tests help in diagnosing hepatocellular vs. obstructive disease
Liver function tests, like liver function test or paddock panel, help diagnose liver issues
Blood work can detect substances related to liver health, like AST and ALT
Liver function tests screen for liver infections, monitor disease progression, and side effects
Elevated AST and ALT levels indicate liver cell damage and leakage into the bloodstream
Liver function tests help monitor liver reactions to medications and disease progression

01:28:07

Liver Function Tests and Ultrasound in Diagnosis

AFP is normal in pregnant women due to fetal liver production, abnormal in men, non-pregnant women, and children, indicating concern for cancers, especially liver and germ cell cancers.
Elevated AFP levels suggest liver diseases, with moderate increases seen in non-cancerous liver conditions.
Six blood tests are discussed, all abnormal when increased, indicating potential liver issues.
Albumin, a liver-produced protein aiding in fluid transport and material transportation, is low in liver and renal diseases, particularly cirrhosis.
Prothrombin time (PT) measures blood clotting speed, with elevated levels indicating potential bleeding issues, often due to blood thinners or liver failure.
INR standardizes PT results, crucial for patients on blood thinners to prevent excessive bleeding during procedures.
Liver function tests include albumin (decreased in liver diseases) and PT (elevated in bleeding issues), with bilirubin also considered a liver function test.
Ultrasound of the liver focuses on normal anatomy, echogenicity, and measurements, with the liver parenchyma expected to appear homogenous, smooth, and fine-grained.
Liver measurements via ultrasound can be challenging due to liver variations, with hepatomegaly typically diagnosed via CT scans.
Landmarks like the diaphragm, ligamentum teres, and ligamentum venosum aid in identifying liver structures during ultrasound examinations.

01:42:08

"Respiration and Imaging: Liver Anatomy Evaluation"

Respiration affects the patient's anatomy, notably the opening and closing of structures during the cardiac cycle.
The inferior vena cava (IVC) can be traced into the right atrium with respiration, potentially revealing the left hepatic vein merging with the IVC.
Transversely imaging the body can capture the aorta and IVC alongside liver images, aiding in comprehensive evaluation.
Developing imaging skills allows for a holistic assessment of liver anatomy, including the left and right lobes, the celiac axis branching into the splenic and common hepatic arteries, and the main hepatic artery.
The porta hepatis marks the boundary of liver parenchyma, distinguishing intra-hepatic from extra-hepatic structures like the main portal vein.
Grayscale ultrasound displays liver vasculature and ducts as tubular anechoic structures, with location, appearance, and Doppler characteristics aiding in identification.
The portal triad, comprising the portal vein, hepatic artery, and common bile duct, is best visualized at the porta hepatis, forming the "Mickey Mouse sign."
Imaging the liver longitudinally reveals the aorta and IVC in a coronal approach, with the transducer likely positioned on the right flank.
Differentiating between hepatic and portal veins is crucial, with hepatic veins displaying thinner walls and more isochoic appearance, while portal veins have thicker walls and are more echogenic.
Understanding liver segment identification through ultrasound involves recognizing superior and inferior segments based on the presence of hepatic veins connecting to the IVC, aiding in comprehensive liver assessment.

01:56:21

Liver Ultrasound Protocols and Indications

The ligamentum teres serves as a landmark between the left lobe and the quadrate lobe, indicating segment four.
Liver ultrasound protocols vary among facilities, with providers needing to specify the exact type of exam in their orders.
Common ultrasound protocols involving the liver include liver protocol, right upper quadrant protocol, and abdomen complete protocol.
Indications for liver ultrasounds range from anorexia to post-liver transplant follow-ups, with jaundice and hepatomegaly being key signs.
Choosing the correct transducer, between 1-7 megahertz, is crucial for optimal detail in liver ultrasounds based on patient body habitus.
Patients undergoing liver ultrasounds, especially involving the biliary tree, should be NPO for 6-8 hours, with diabetic patients needing extra care regarding fasting.

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