Liver Ch 7 Textbook additional notes

Livers general location and shape

right hypochondrium and epigastric region, extending into the left hypochondrium.

Wedged shaped/triangular, with broad base to the right and the apex to the left

2 Layers that cover the liver

outer serous layer from visceral peritoneum and inner fibrous layer called Glisson capsule

area of liver not covered by visceral peritoneum

bare area and attachment regions such as porta hepatis and gallbladder fossa (glisson capsule still covers these areas)

Why is bare area clinically important

the missing peritoneal barrier can allow disease such as abscess or tumor to spread between the abdomen and thoracic cavity

What is the importance of Glisson capsule

It contains blood vessels, lymphatics, and nerves, is highly echogenic, and distention from disease/swelling can cause pain and lymphatic leakage into the peritoneal space

why are portal triad walls echogenic

Glisson capsule also surrounds the hepatic artery, portal vein, and bile duct of the portal triad

What is visceral surface of the liver and how is it oriented/shaped

The posteroinferior surface of the liver. it faces inferiorly and posteriorly and its uneven/concave surface is because of surrounding organs

4 lobes of the liver

right, left, caudate, and quadrate lobes

What landmark divides the right and left lobe on anterior surface

falciform ligament

What creates the H configuration on the visceral surface

the ligamentum venosum and ligamentum teres forms the vertical limbs, with the porta hepatis and main lobar fissure completing the configuration

What separates caudate and quadrate lobes and what separates those 2 from the right lobe

porta hepatis is between caudate and quadrate.

main lobar fissure separates them from the right lobe

Caudate lobe location

on posterosuperior liver, between IVC posteriorly and ligamentum venosum anteriorly. ligamentum venosum separates it from the left lobe but is considered part of medial segment of left lobe

Why is caudate lobe considered vascularly independent

It has its own arterial supply and venous drainage, with small caudate veins draining directly into IVC

Borders of quadrate lobe

porta hepatis posteriorly, inferior liver margin anteriorly, gallbladder fossa on the right, and fissure for ligamentum teres on the left

How do portal veins and hepatic veins differ (sonographic walls, branching direction, width of vessels, and doppler waveforms)

Portal veins have echogenic walls from Glisson capsule while hepatic vein walls are usually harder to see.

Portal vein branches point towards the porta hepatis while hepatic veins point towards IVC.

Hepatic veins enlarge as they approach IVC and portal veins become smaller as they branch away from porta hepatis.

Portal venous flow is relatively continuous and hepatic venous flow is pulsatile.

How/where do hepatic veins and portal veins course throughout the liver

Hepatic veins are interlodar/intersegmental

portal veins are intrasegmental

What is Riedel lobe and who is it more commonly found in

It is a common normal variant consisting of a finger/tongue like inferior projection of the right lobe, and can extend as far as iliac crest.

more common in women

What can riedel lobe mimic and how can it be distinguished

hepatomegaly or liver mass. it can be distinguished from hepatomegaly bc the rest of the liver will remain normal, while with hepatomegaly, the liver will have more rounded edges

How much of livers blood volume is supplied by portal vein

approx. 70-80%, carrying nutrient-rich venous blood

Normal size limits of Main portal vein

About 8 cm long with a maximum diameter of about 13 mm

How is main portal vein formed and where

by splenic vein and SMV near midline, anterior to IVC and posterior to pancreatic neck

What does main portal vein carry to the liver

nutrients and toxins from GI tract and venous blood from pancreas, gb, and spleen

Where does main portal vein lie in hepatoduodenal ligament

posterior to hepatic artery and common bile duct

What happens to main portal vein before/as it enters the liver

it divides into left and right portal veins

Which right-lobe segments are supplied by anterior and posterior branches of right portal vein

Anterior branch: segments 5 and 8

posterior branch: segments 6 and 7.

Where does caudate lobe receive portal venous blood from

branches from both right and left portal veins

How do hepatic artery, portal vein, and intrahepatic ducts course

run roughly parallel in portal triads. arterial and portal blood flow into the liver while bile flows out

What is a parallel-channel sign and how does doppler help

its a dilated intrahepatic bile duct seen beside a portal vein that suggests biliary obstruction.

doppler helps demonstrate flow in the vessel and no flow in bile duct

What plane are hepatic veins visualized

on transverse, angled towards patients head. right intercostal approach may also help

What accessory hepatic vein variant is mentioned

accessory inferior right hepatic vein (IRHV). it may preserve right-lobe drainage is main RHV is resected/compromised

What is Portal hepatis

A fissure where the portal vein and hepatic artery enter the liver and bile duct exits

How should bile duct be measured and normal measurements

from inner to inner wall, approx. 4-8mm

Mickey Mouse sign

transverse portal triad appearance formed by portal vein, hepatic artery, and bile duct

Microscopic structural unit of the liver and does it consist of

hepatic lobule. has a central vein surrounded by plates of hepatocytes and sinusoids

Liver-related tests mentioned in the tables of the textbook

ALT, AST, ALP, LDH, GGT/GGTP, PT, albumin, A/G ratio, and AFP

Patient prep for liver/biliary ultrasound

NPO after midnight or 6-8 hours prior, needed medications may be taken with sips of water, and smoking/chewing gum should be avoided

Why/what are breathing techniques used while evaluating liver

the liver moves with respiration so breathing helps get good acoustic windows/positions.

normal breathing for intercostal scans and deep suspended inspiration for subcostal scans because it lowers the liver below the ribs and moves bowel gas inferiorly.

could also have patient push their stomach out (belly-out technique)

Why have patient raise their arm above their head

it widens the intercostal spaces

How can LPO/LLD positioning help with liver imaging

It exposes more of the superior liver

How can RPO/LPO positioning help when enlarged liver compresses the IVC

changing positions may relieve the compression and improve IVC visualization.

RPO may also improve lower liver imaging bc it lets liver displace the duodenum and transverse colon inferiorly.

What planes do you scan the liver

sagittal and transverse, with oblique as needed

What should be assessed with complete liver exam

size, echotexture, intra and extrahepatic bile ducts, blood vessels, and pathology

What transducer is used for liver imaging

curved linear wide-sector for general liver imaging.

linear for anterior capsule/cirrhosis.

sector/vector for intercostal windows with rib artifacts.

What is main tradeoff of harmonic imaging in the liver

it can improve resolution but reduces penetration. turn it off or lower frequency of far field is obscured

How should Doppler wall filter, scale, and gain be optimized

Start wall filters low and raise as needed

Adjust velocity scale for each artery/vein to get fill without excessive aliasing

Raise gain to noise then back it down

What false finding can poor doppler settings create in portal vein

apparent absence of flow that can mimic portal vein thrombosis

How should Doppler angle correction be set

parallel to vessel flow/walls and generally less than 60 degrees

What normal structures/artifacts can mimic hepatic pathology

ligamentum teres, liver-kidney interface, pseudolesions, and fluid collections

What artifact is part of the simple hepatic cyst criteria

lateral wall refractive edge shadowing

What is an inheritance detail mentioned for isolated polycystic liver disease

it follows an autosomal dominant pattern

What is Hydatid sand

highly irritating particle material within echinococcal cyst

What sonographic forms can hydatid cysts take as they mature

Solitary cyst with or without wall calcification, mother/daughter cysts, septated honeycomb cysts, or a more solid-appearing lesion with or without calcification.

What is the concealed water-lily sign

The germinal layer separates from the pericyst and folds/floats within the cyst; as the cyst shrinks the folds may make it look more solid

What does aspired amebic abscess fluid look like

thick chocolate colored and becomes thinner with age

Why are opportunistic infections important in HIV/AIDS

They occur more often and more severe with impaired immunity

How does the frequency of benign and malignant hepatic tumors differ by age

Benign hepatic tumors are more common in neonates/infants.

In older children and adults, benign are less common than malignant tumors

Primary liver tumors arise from what tissue

parenchymal cells, bile duct epithelium, or a mix of both

How does sonography compare with CT for very small hemangiomas

Sonography may be more reliable, specifically for lesions <1cm

What is the characteristic CEUS pattern of a hemangioma

Peripheral nodular enhancement with centripetal progression and the lesion stays hyper-enhancing in the late phase

What is FNH sometimes referred to as and why

stealth lesion bc its can be subtle and isoechoic to normal liver

How can hereditary hemochromatosis lead to HCC

Excess iron accumulates in the liver, can cause cirrhosis, and may eventually lead to liver cancer

How can tumor thrombus differ from bland thrombus

Tumor thrombus can dilate the involved vein more and may show arterial signals on color/spectral Doppler

For what HCC size is ablation highlighted as most successful

< than about 3cm

How does embolization treat HCC, and why can normal liver survive it better

It blocks the hepatic arterial branch feeding the tumor; normal liver also receives portal venous blood

What does CEUS evaluate in focal liver lesions

Vascular enhancement and blood-flow characteristics, similar in concept to contrast CT/MRI

Why is CEUS useful when grayscale liver sonography is limited

Fatty/cirrhotic liver can obscure lesions and benign/malignant masses can overlap or be isoechoic

What are ultrasound contrast agents made of

Gas microbubbles stabilized by a lipid or protein shell. about 100-500million microbubbles (1.5-2.5 μm in diameter) in 1mL of contrast

Do CEUS microbubbles leave the vascular system, and how are they cleared

they remain intravascular. the gas is exhaled through lungs over approx. 6-10 minutes

practical advantages of CEUS

can be done during the same visit as the routine ultrasound and can help guide biopsy of an otherwise isoechoic lesion

Why is a low mechanical index used for CEUS

avoid prematurely destroying microbubbles

How should patient and transducer be managed during first few minutes of CEUS

Keep the transducer steady on the lesion, use quiet breathing, and avoid deep breaths that move the lesion out of view

When is CEUS timer started

time of contract injection

What is CEUS flash technique

brief high-MI pulse or color-Doppler burst used to destroy microbubble

How many contrast injections are recommended in one CEUS exam

No more than two. residual microbubbles should be cleared or destroyed before the second dose.

What are the timing ranges of the three CEUS liver phases

Arterial: ~10-20 to 30-45 sec

portal venous: ~30-45 to 120 sec

late: from ~120 sec until microbubble disappearance, about 4-6 min

What do hyper-, iso-, hypo-, and non-enhancing mean on CEUS

More enhancement than liver, equal enhancement, less enhancement, and no enhancement

What are wash-in and washout on CEUS

Wash-in is progressive enhancement to peak. washout is decreasing enhancement after the peak

What is the characteristic CEUS pattern of HCC

Arterial hyperenhancement with dysmorphic/basket-weave vessels followed by washout and hypo-enhancement in portal/late phases

How do metastases typically look on CEUS

Variable/chaotic or rim arterial enhancement followed by rapid washout; they become dark hypo-enhancing 'punched-out' lesions in portal/late phases

What CEUS feature is most useful for distinguishing malignant from benign liver lesions

Washout int he portal venous or late phase

What does liver elastography measure

liver stiffness as a non-invasive estimate of diffuse fibrosis

How does fibrosis affect shear-wave speed

Shear waves travel faster through stiffer fibrotic tissue

How is fibrosis staged

On a 0-4 scale, with the stage representing the amount of fibrosis

What cutoff approach does the SRU recommend for elastography interpretation

A low cutoff below which significant fibrosis is unlikely and a high cutoff above which advanced chronic liver disease is likely, rather than relying only on METAVIR cutoffs

What information should an elastography report include

Vendor/system, technique, probe, number of valid acquisitions, IQR/M, and stiffness value

Main clinical indication for liver elastography

Staging fibrosis in chronic liver disease, especially chronic viral hepatitis and NAFLD

Why is detecting cirrhosis by elastography important

It can trigger monitoring for complications such as HCC and portal hypertension

How else can elastography be used during treatment?

to monitor/assess response to therapy

What conditions can falsely elevate liver stiffness

Severe inflammation/elevated ALT-AST, biliary obstruction, acute hepatitis, and right-sided heart failure/congestion

What is transient elastography and does it provide image guidance

FibroScan; it uses a mechanical vibration and does not provide image guidance

What BMI limitation is highlighted for transient elastography

Accuracy may be reduced above roughly BMI 30-35 kg/m², even with an XL probe

Why can transient elastography fail with ascites

Ascitic fluid prevents the mechanical vibration from propagating effectively into the liver

Where is the transient-elastography probe commonly placed and how are results expressed

Usually in the 9th-11th intercostal space, with results in kPa

How is SWE different from transient elastography

SWE uses a standard ultrasound transducer with elastography software and gives image guidance of the liver

What does ARFI stand for and how long is its push pulse

Acoustic radiation force impulse; the highlighted push pulse is about 0.3 seconds

What are the two SWE methods

Point SWE (pSWE) and 2D-SWE

How do pSWE and 2D-SWE differ

pSWE uses a small ROI for a single measurement; 2D-SWE uses a larger color stiffness map and then a smaller ROI within it

In what units can SWE results be reported

Meters per second (m/s) or kilopascals (kPa)

How does tissue stiffness affect displacement

Stiffer tissue displaces less; softer tissue displaces more