Chapter 16: Abdominal Vasculature Flow Dynamics

An increase in returned echoes proportional to an increase in turbulence or flow disturbance

Spectral broadening

A range of frequency shifts displayed as velocities; allows visualization of the Doppler signal and provides quantitative data to evaluate the Doppler shift

Spectral doppler

The amount of blood ejected by the ventricles with each contraction

Stroke volume

The zero doppler shift on a spectral display

Baseline

What does flow above the baseline on a spectral display indicate?

Flow towards the transducer

What does flow below the baseline on a spectral display indicate?

Flow away from the transducer

The amount of blood pumped by each ventricle in 1 minute

Cardiac output

Relaxation of the heart muscles

Diastole

Provides information about blood flow velocity, flow direction, presence of flow disturbance or turbulence, and vascular impedance - the waveform is displayed on a graph;

Doppler spectral waveform

What does the y-axis represent on a Doppler spectral waveform?

Velocity or frequency

What does the x-axis represent on a Doppler spectral waveform?

Time

Real-time 2D imaging and pulsed Doppler capabilities used either simultaneously or sequentially

Duplex sonography

Flow direction away from the liver

Hepatofugal

Flow direction toward the liver

Hepatopetal

Arteries with low or reversed flow in diastole that supply organs that do not demand constant blood perfusion

High-resistance vessels

A form of potential energy - the pressure related to the weight of blood as compared to a reference point - the reference point in the human body is the right atrium - it is the effect that gravity has on the veins when the patient is erect

Hydrostatic pressure

Arteries supplying organs that demand constant forward blood flow or perfusion

Low-resistance vessels

Obtains the doppler frequency information that is displayed. It allows for selection of doppler-shifted echoes from specific depth according to arrival time

Sample volume or gate

Contraction of the heart muscles

Systole

Relatively signal-free area between the arterial doppler shift signal and the baseline during the systolic portion of a doppler spectral display

Systolic window

Determines the shape of the vein

Transmurual pressure

Intravascular pressure - interstitial pressure =

Transmurual pressure

A technique that significantly increases intrathoracic and intra-abdominal pressure, halting all venous blood return to the heart

Valsalva maneuver

What is the significance of color Doppler?

Allows for rapid identification of vessels, flow direction and high velocity jets that signify disturbance to flow

What is the significance of duplex sonography?

Supplies both structural and functional information of a vessel

Average diameter of aorta

2-2.5 cm

Average diameter of Celiac artery

0.7 cm

Average diameter of SMA

0.6 cm

Average diameter of IMA

0.3 cm

Average diameter of renal arteries

0.4 - 0.5 cm

Average diameter of IVC

2.5 - 3.5 cm

Average diameter of renal veins

0.4 - 0.6 cm

Average diameter of Hepatic veins

0.4 - 0.7 cm

Average diameter of SMV

0.6 - 0.7 cm

Average diameter of Splenic vein

0.4 - 0.6 cm

Average diameter of portal vein

1.3 cm

The AO lies slightly to the ---- and ---- to the vertebral column

Left - Anterior

The AO bifurcates into the common iliac arteries near the body of the ---- lumbar vertebra

4th

The Celiac artery is located ————- cm below the diaphragm at approximately the level of the ————- thoracic and ———- lumbar vertebrae.

- 1 - 3 cm

- 12th thoracic vertebrae

- 1st lumbar vertebrae

The Superior mesenteric artery is located ————— cm inferior to the origin of the Celiac axis.

1 - 2 cm

The left and right renal arteries originate from the ———— walls of the aorta approximately———— cm below the SMA

- Lateral

- 1 - 1.5 cm

Why is the right renal artery longer than the left?

It must pass posterior to the IVC and right renal vein to enter the hilum of the right kidney

Approximately what % of the population have anatomic variants to the mesenteric vessels?

20%

What is the most common anatomic variant of the mesenteric vessels?

- A replaced right hepatic artery

- Duplicated / accessory renal arteries

The abdominal AO is bordered anteriorly by:

- Stomach

- Pancreas

- Celiac axis

- Splenic vein

- SMA and SMV

The abdominal AO is bordered on the right by the ----

IVC

The abdominal AO is bordered on the left by the ---- and the ----

- Splenic vein

- Tail of pancreas

The normal measurement of the AO is ---- - it should never measure greater than ----

2-2.5 cm

3 cm

What does Poiseuille's Law determine?

Predicts the volume of flow in moving fluids

The parameters that determine impact on flow according to Poiseuille's law include

- Pressure gradient

- Radius and length of the tube

- Viscosity of the fluid

Poiseuille's equation

Q = ΔP(pressure gradient) πr4 / 8η(viscosity) L(length)

Bernoulli's Principle is based on what theory?

Theory of conservation of energy, which states that energy cannot be destroyed but it can be altered from one form to another

Bernoulli's principle demonstrates what?

The relationship between fluid velocity (kinetic energy) and pressure (potential energy)

Duplex sonography

Combines gray scale imaging and pulsed Doppler to create spectral waveform from specific area in a specific vessel

Normal peak systolic velocity of aorta

40 - 100 cm/s

Normal peak systolic velocity of Celiac

98, 50, 105 cm/s

Normal peak systolic velocity of hepatic

Less than 100 cm/s

Normal peak systolic velocity of SMA fasting

97 - 142 cm/s

Normal peak systolic velocity of SMA postprandial

2x increase of systole

3x increase of diastolic

Normal peak systolic velocity of renal

Less than 100 cm/s

Normal peak systolic velocity of IMA

93 - 198 cm/s

The hemodynamic pattern of the abdominal AO at the suprarenal portion is a ---- flow during diastole

—— resistance

—— diastolic

Forward; low; high

The hemodynamic pattern of the abdominal AO at the infrarenal portion is a ---- waveform

—— resistance

—— diastolic

Triphasic; high; low

The hemodynamic pattern of the celiac access is a —— resistance waveform with —— blood flow during cardiac cycle

Low; Constant

The hemodynamics waveform of the hepatic artery is characterized by ————— flow throughout systole and diastole.

Constant forward

The hemodynamic pattern of the SMA shows an increase in —— blood flow during diastole after ingestion of a meal

Forward

(after eating there should be less resistance bc the food needs to be digested and transported)

In the fasting state, there is relatively ——— resistance to arterial flow to the tissue of the gut.

High

In the fasting state, the Doppler spectral waveform from the SMA demonstrates a ———- diastolic flow; there may be brief period of ———— flow during early diastole.

Low; Reversed

Term meaning fasting

Preprandal

Term meaning after fasting

Postprandal

Hemodynamics flow patterns in normal renal arteries demonstrate —————- diastolic flow

High

The kidneys are ——— resistant organs that demand ————- blood flow to moderate their metabolic activity

Low; Constant

The normal waveform from the proximal renal artery may demonstrate a ———— systolic window, with minimal spectral broadening

Clear

When the waveform is turbulent you can't really see the ----

Spectral window

The IVC lies to the ---- of the abdominal AO and just ---- to the vertebral processes

Right - Anterolateral

The IVC lies ---- to the R kidney and ---- to the liver before coursing through the diaphragm to enter the right atrium of the heart

Medial - Posterior

The --- IVC has a complex "pulsatile" flow

Proximal

The ---- IVC has a phasic flow

Distal

The most common anatomic variants of the IVC

- Duplication of the entire length or short segments of the IVC

- Segmental absence of portions of the vessel

- Anatomic relocation of the suprarenal segment, infrarenal segment, or entire length of the IVC to the left of the aorta

Anatomic variant of the hepatic veins

Absence of one or more branches or a shared origin of the left and middle hepatic veins

The ---- have a pulsatile hemodynamic pattern - three phases (two toward the heart - one away from the heart) - flow is hepatofugal

Hepatic veins

The ---- have a minimally phasic flow - low peak and mean velocities - hepatopetal

Portal veins

The PV flow should be located ---- the baseline

Above (bc the PV heads towards the liver)

The renal veins have a ---- flow

Phasic

The IVC should appear as an anechoic tubular structure

- The ---- demonstrate echogenic wall margins

- The ---- lack echogenic wall margins

Portal veins

Hepatic veins

Common diagnostic tests for the IVC

- Vascular angiography (dye in vessels)

- Computed tomography angiography

- Magnetic resonance angiography

The hemodynamic pattern of the SMA is a —— resistance waveform with —— diastolic blood flow when fasting

High; Low

The blood flow in the proximal or suprarenal aorta supplies a —— vascular bed of its end organs - therefore the spectral waveform demonstrates continuous —— flow throughout diastole

Low-resistive;

Forward (ABOVE the baseline)

The distal or infrarenal aortic blood supply is principally to the —— peripheral arterial system of the lower extremities and lumbar arteries - therefore minimal or —— diastolic flow is seen

High resistance;

Reversed (below the baseline)

Which arteries demonstrate low resistance waveform - constant forward blood flow during the cardiac cycle

Renal arteries

The main portal vein courses ————- and —————— to the right for several centimeters before entering the liver through the portal hepatis

Superiorly; laterally

Sonographically, how do the walls of the main portal veins and it's branches appear?

Echogenic

A spectral waveform from a low resistive vessel will have

Constant forward flow is diastole

Replaced right hepatic artery

Poiseuille's

Radius

Metabolic need of a tissue or organ

Arterioles

Pressure and velocity

Volume and resistance