abdominal anatomy week 3

Glisson’s capsule

Encased the liver and which is composed of a thick fibrous connective tissue that contains nerves, blood and lymphatic vessels.

The Couinaud’s classification system divides the liver

Into functional segments.

Each segments has its own

Portal vein, hepatic artery and bile duct.

Liver size is measured

In the superior –inferior dimension on the mid clavicular sagittal plane.

Hepatomegaly is indicated

With greater than 15 cm superior –inferior dimension or when the right lobe extends inferior to the lower pole of the right kidney.

Reidel’s lobe is

An inferior projection of the right lobe which is commonly seen in women.

Reidel’s lobe

May be mistaken with hepatomegaly when only measuring the superior –inferior dimension of the liver.

The normal liver is

Homogeneous and is slightly hyperechoic compared with the normal renal cortex.

Echogenicity is a

Term used to compare signal amplitude between structures.

Echogenicity of normal structures( decreasing echogenicity)from hyperechoic to hypoechoic

Renal sinus-Pancreas-Spleen/liver-Renal cortex.

Ligamentum teres

Triangular hyperechoic structure located in the left lobe of the liver.

Fibrous, round ligament formed by the obliterated left umbilical vein

Main lobar fissure:

The fissure may be identified between the GB neck and the junction of the right and left portal vein.

Main lobar fissure divide the anterior segment of the right lobe from the medial segment of the left lobe.

Right Intersegmental fissure:

Divides right lobe into anterior and posterior segments.

Left Intersegmental fissure:

Divides left lobe into medial and lateral segments.

Fissure of the ligamentum venosum

Divides left lobe of the liver from the caudate lobe

Remnant of the ductus venosus

Hepatic vein

The right, middle and left hepatic veins, drain the blood from the liver into the inferior vena cava

Hepatic artery

Supply the liver with oxygenated blood from the aorta

Portal vein

The main portal vein enters the liver at the porta hepatis posterior to the hepatic artery and common bile duct, it then divides into the right and left branches

Hepatic veins

Are intersegmental because course between the lobes and segments and have non-echogenic walls.

The ligamentum teres is

A remnant of the umbilical vein which runs from the umbilicus to the left portal vein. Shortly after birth, the umbilical vein contracts down forming the ligamentum teres. With portal hypertension ligamentum teres recanalizes to form portosystem venous collaterals.

The ligamentum venosum is

a remnant of the ductus venosum. It runs from the left portal vein to the IVC separating the left lobe from the caudate lobe of the liver.

Portal veins

Have brighter walls owing to collagen within the wall(because portal veins is encased by a fibrofattysheath which is named Glisson’s capsule giving it hyperechoic walls.

The branching angles have different orientation:

Portal veins branch horizontally and are oriented toward the porta hepatis

Hepatic veins branch longitudinally and are oriented toward the inferior vena cava

Difference in caliber

The caliber of the hepatic veins increases as it courses towards the diaphragm and inferior vena cava

The caliber of the portal vein decreases once it begins to branch out from the porta hepatis

Hepatic vein will show some variability in caliber with respiration

Hepatic vein course

between the lobes and segments(intersegmental and interlobar)

The portal triad course

to the center of each segment(intrasegmental)

Portal Triad:

Refers to the hepatic artery, bile duct and portal vein

It is commonly seen at the level of the porta hepatis

When there is a question as to dilated duct it is important for the sonographer to differentiate artery from duct and vein.

The liver utilizes vitamin K to form prothrombin

therefore people with liver disease will have poor clotting times

Liver Echotexture

The normal liver is homogenous

It contains fine level echoes, and is either minimally hyperechoic or isoechoic when compared to the normal renal cortex.

When the liver is compared to the spleen is said to be hypoechoic or isoechoic depending on the view.

Liver Scanning Technique

Sagittal (SAG) and Transverse (TRV) planes using different approaches

Liver Breathing Technique

Liver should be examined in deep held inspiration.

Transducer

Low frequency transd 3.0 to 3.5 MHz sector if liver is high within the rib cage

3.0 to 3.5 MHz convexed if liver is low below the costal margin

Higher frequencies are to be used with individuals with small body habitus (thin)

Patient Preparation for Liver Protocol

Liver alone no preparation required

Note: Please noted that since the liver is not evaluated as single organ is evaluated as part of an abdominal survey it is preferred to have these patients NPO for approximately 8 hours.

Portal Venous System

Supplies the greatest percentage of the total blood flow to the liver

Is formed by the confluence of three tributaries:

Splenic vein, Superior mesenteric vein and Inferior mesenteric vein

It carries blood from the spleen and bowel to the liver

Branches of the abdominal Aorta

Celiac Trunk, SMA, IMA and renal arteries.

Normal Portal Vein Waveform shows

Hepatopedal flow ( toward the liver) Above the baseline

Abnormal Portal vein Waveform

Hepatofugal or reversal flow ( Away from the liver) Below the baseline

Vessel that located superior to the pancreas

Celiac trunk

Largest major visceral branch of the inferior vena cava is the

Hepatic veins

The head of the pancreas is located anterior to the

IVC

The splenic artery is described as

Is tortuous, and courses along the superior aspect of the body and tail of the pancreas

The sonographic term “seagull appearance” refers to:

Celiac arteries

Celiac Trunks are formed by

Left gastric artery, hepatic artery and splenic artery

Echogenic linear line extending from the portal vein to the neck of the gallbladder

Main lobar fissure

The vessel that lies posterior to the pancreas

Splenic vein

Reidel’s Lobe

Tongue like extension of the right lobe

The vessel that courses along the posterior surface of the body and tail of the pancreas is the

Splenic vein

The splanchnic arteries comprises the

Celiac, SMA, IMA

Branches of the celiac axis include

Hepatic, splenic, and gastric arteries

Vessel supplies 75% of the blood to the liver

Portal vein

The portal triad is composed of

Portal vein, hepatic artery, and bile duct

Waveform you will see in the portal vein in a normal study

Mildly undulating and hepatopedal which is described as flow above the baseline toward the transducer.

An ultrasound evaluation of the liver cirrhosis should include a search for which associated complications

Portal hypertension

Hepatofugal flow in the portal vein is sign of:

Portal hypertension