GREATER VESSELS - VEINS AND PORTAL/HEPATIC SYSTEMS

% of blood in venous system

~70% of all blood resides in the venous sytem

there are more veins than arteries —> many veins are paired and run parallel to their counterpart artery

some are larger in caliber than the artery

valves

veins contain valves to prevent back flow of blood

(there are no valves in the arterial system)

venous system pressure

low pressure system w/ low to no pulsatility

slower blood flow, less pressure

more veins than arteries in the body —> because we have to maintain flow rate, so we need more or bigger veins to keep up

paired V’s and Arteries - deep vs superficial

common to have paired A’s and V’s (especially deep in the body)

more veins superficial w/out an arterial counterpart/pair

IVC flow (+diameter) is influenced by…

respiration!!

IVC diameter:

DECREASES with normal INSPIRATION (diaphragm pushes down on abdominal structures and puts pressure on the soft squishy veins)

^exception = holding a breath/suspended inspiration —> circulatory system still working —> so it will reexpand

INCREASES with normal EXPIRATION (and holding a breath/suspended inspiration)

*does opposite of lungs*

IVC blood flow and breathing

IVC BF is inferior to superior → TOWARDS the heart (opposite of aorta)

BF is reliant and affected by breathing

inflate = negative pressure in chest - positive pressure in abdomen

pumping of the heart pulls BF back into it from IVC to SVC

all V flow is influenced by respiration to a degree → we will manipulate it to help it show up on dopplers → valsalva maneuver

valsalva maneuver

a forceful attempted EXHALATION against a closed airway

IVC flow momentarily stops with this

helps put pressure on V system so we can get an augment on flow (momentarily stops flow) → especially in smaller vessels → helps color light up on doppler

IVC’s primary function

to return deoxygenated blood to the heart

returns deoxygenated blood from lower body to the R atrium of the heart

IVC end point

R atrium

IVC enters the right atrium

Major IVC tributaries (largest tributaries)

1. hepatic veins

2. renal veins

3. common iliac veins

hepatic veins

LARGEST VEINS IN THE LIVER

drains BF that’s been processed from the liver back to the IVC

L, middle and R (based on where they’re coming from on liver)

other DIRECT tributaries of the IVC

1. R adrenal (aka suprarenal) V

2. Right gonadal (aka testicular or ovarian) V

3. Inferior phrenic (diaphragm) V’s

(4. four lumbar veins)

(5. medial sacral vein)

Asymmetrical V’s

Adrenal + Gonadal → L suprarenal V and L gonadal V are tributaries of the L Renal V

IVC Bifurcation

Bifurcates at L5

bifurcates just INFERIOR to AORTA

Portal Triad

Portal Vein, Hepatic artery, common bile duct

these 3 run together everywhere in the liver → clumped together wherever they go

Right renal artery position to IVC

posterior to IVC

hepatic Veins - where they drains

H veins are divided into R, middle, and L → they all drain into the IVC at the level of the diaphragm

middle separates the R and L lobes → drains to both

BUNNY SIGN

L hepatic Vein identification

most likely L hepatic V if we can see caudate lobe

L renal vein position to aorta

anterior to aorta, posterior to SMA

can have abnormalities → can go under aorta → or one above one below (2 LRV’s)

Reval V diameter

RV is usually larger than RA’s

common Iliac veins

IVC is formed by R and L common iliac V’s

Common iliac are formed by internal and external

Veins are a bit more posterior in the body → vein is deeper

Portal system - what is it?

system is independent of the arterial and regular venous systems

job is to bring dirty blood to liver to get filtered (NOT to return deoxygenated blood to heart and lungs)

portal splenic confluence

Main portal V formed by Splenic V and SMV → R and L branch/split occurs at the liver hilum (AKA porta hepatic)

differentiating LPV vs MPV on US

PRV-LPV → tissue space between IVC and these

RPV-MPV → sits directly on top ov IVC (no/very little tissue space)

gastric V insertion

where they dump into the portal system is highly variable

L gastric = variable → either into splenic V (most common) or portal V

R gastric = empties into MPV

direct tributaries of the main portal vein

SMV and Splenic V

Portal splenic confluence

IMV joins splenic V before SMV (IMV is tributary of splenic V)

Splenic V

joins with SMV to create main portal V (portal splenic confluence)

travels from the splenic hilum along the posterior pancreatic border

runs across posterior margin of body and neck of pancreas

SMV

runs parallel to IVC

joins with splenic V to form PSC - main portal V

****What % of blood entering the liver is from the portal V?****

80%

****portal vein brings roughly 4x the amount of blood volume to the liver than the hepatic artery does → about 80/20****

the portal vein carries blood from the small intestine to the liver → blood comes from lots of other places too, not just the SI

Mickey Mouse sign

portal triad

peritoneum comes through hilum of liver and wraps around portal triad → adds to ethogenicity of triad

portal wall vs hepatic vein wall

PV is more echogenic due to greater thickness, collagen, perivascular fat, and its sheath of connective tissue (peritoneum)

hepatic veins drain the organ to the IVC (leaving liver)

angle of intonation = imp

angle of insonation

important to how bright the walls will be → projection or direction of sound waves → the straighter and flatter something is on the screen, the better reflections of the echoes we will get (less scattering, etc.)