Abdominal Vascular System: Aorta/IVC

aortic root

section of AO that emerges from the heart (attached to heart)

ascending aorta and aortic arch

upward curve shortly after aorta leaves the heart + curve—”candy cane”

descending aorta

thoracic aorta (in chest)

aortic bifurcation

aorta branches into iliac arteries

function of circulatory system

• transport gases, nutrients, other essential substances to tissues

• transport waste products for excretion

anatomy of vascular structures

1. tunica intima

2. tunica media

3. tunica adventitia

tunica intima (inner layer)

• contains layer of endothelial cells (in lumen) and connective tissue

• elastic layer made up of network of elastic fibers

• SONO: echogenic

tunica media (middle layer)

• contains layer of smooth muscle, elastic fibers, and collagenous tissue

• thickest layer for greater elasticity to maintain steady blood flow

• SONO: anechoic

tunica adventitia (outer layer)

• contains layer of loose connective tissue with bundles of smooth muscle fibers and elastic tissue

• has "vaso vasorum” (tiny arteries and veins that supply the walls of blood vessels)

• SONO: echogenic

veins vs. arteries

• veins carry blood back to heart

  • veins have thinner walls than arteries because they handle lower blood pressure

  • only veins are collapsible due to lack of elastic tissue and contain valves

• arteries carry blood away from heart

where does the AO originate from?

left ventricle

location of AO

• retroperitoneal

• travels superior to inferior; to left of spine

• posterior to LLL, body of pancreas, SPL A, SPL V, LRV, and pylorus

• anterior to psoas muscle

aorta and crus (crura) of diaphragm

• crura=extensions from the lumbar vertebrae that anchor the diaphragm

• crura is anterior to AO

AO info

• largest artery in body

• tortuous

• pulsatile with no changes in respiration

function of AO

• provide oxygenated blood to organs and tissues

• ensure metabolism

• maintain blood pressure and homeostasis

• control bleeding

  • renin is released in the event of bleeding —> vasoconstriction to maintain BP

indications for imaging AO

• screening/evaluate for AAA; bruit or palpable mass

• lower back pain, flank pain, or abdominal pain

• hemodynamic compromise in legs

• assess diameter, arterial grafts, presence of calcification, thrombus, stenosis, or dissection

AO above how many cm is considered an aneurysm?

• 3 cm

  • exceeding 7 cm requires immediate medical intervention

aortic dissection

• blood splits the tunica walls, causing them to separate —> blood leakage between walls

• SONO: echogenic line running down the center of AO

type I dissecting aortic aneurysm

begins at root of AO and may extend entire length of arch, ascending, and descending AO

type II dissecting aortic aneurysm

involves ascending AO only

type III dissecting aortic aneurysm

begins at lower end of descending AO and extends into abdominal AO

patients must be NPO for how long with AO exams?

6 hours

scanning techniques for imaging AO

• pt. supine or slightly decubitus

• anterior or coronal approach

• curvilinear probe

• measure outer-to-outer wall; low to medium gain (to show walls but no lumen artifact)

• use breathing technique or “push belly out”

high resistance waveform

• sharp brisk systolic peak

• low diastole

• organs with intermittent flow (does not require constant blood flow)

low resistance waveform

• slow systolic upstroke

• high diastole

• organ needs constant blood flow

AO Doppler waveform

high and low resistant waveform; sharp brisk upstroke; significant reduced diastolic flow; no spectral broadening

PSV and EDV

• PSV=peak systolic velocity

• EDV=end diastole velocity

anterior branches of AO (in order)

1. celiac artery (CA)

2. superior mesenteric artery (SMA)

3. gonadal arteries (testicular or ovarian)

4. inferior mesenteric artery (IMA)

celiac trunk/artery/axis

• 1st branch off AO

• measures less than 1 cm

“seagull sign”

consists celiac trunk, common hepatic artery (right wing), and splenic artery (left wing)

CA Doppler waveform

• low resistant waveform (sharp brisk upstroke; significant diastolic flow)

• has spectral broadening

• no change in flow after meals

branches of CA

1. common hepatic artery

2. splenic artery

3. left gastric artery

left gastric artery (LGA)

• branch of CA

• courses superiorly (up esophagus) and to the left (descending along lesser curvature of stomach)

• supplies lower 3rd of esophagus and lesser curvature of upper right stomach

splenic artery (SPL A)

• branch of CA

• courses horizontally to the left along superior pancreas border

• supplies spleen, pancreas, and left side of greater curvature of stomach

common hepatic artery (CHA)

• branch of CA

• courses horizontally to the right

• branches into GDA and PHA

gastroduodenal artery (GDA)

• branch of CHA

• courses inferiorly

• supplies right side of greater curvature of stomach and pancreatic duodenal area

proper hepatic artery (PHA)

• branch of CHA (becomes PHA after GDA)

• courses right laterally and superiorly; supplies liver via HAs

  • LHA supplies LLL and caudate

  • RHA supplies RLL and GB via (cystic artery)

“Mickey Mouse” sign

• consists of portal vein (head), hepatic or bile duct (right ear), and hepatic artery (left ear)

• makes up the portal triad (in oblique TRANS)

superior mesenteric artery (SMA)

• 2nd branch off AO

• 1 cm inferior to celiac trunk

• follows anteroinferior course along AO and divides into several arteries

• branches supply the small intestine, ascending colon, part of transverse colon, pancreatic head, and duodenal area

• surrounded by echogenic fat (retroperitoneal fascia)

• SONO in TRANS: circular structure posterior to pancreas and anterior to AO and left renal vein

SMA Doppler waveform

• high resistant waveform (sharp brisk systolic upstroke; reduced diastolic flow)

• no spectral broadening

• ECA and post-prandial (changes to low resistant waveform after meals b/c body needs more blood for digestion)

gonadal arteries (testicular or ovarian)

• low resistance blood flow

• courses inferiorly along the psoas muscle

• inferior to SMA and renal artery

• left gonadal artery originates a bit superior to right artery

inferior mesenteric artery (IMA)

• courses anteroinferior to AO

• divides into arteries that feed the transverse colon, descending colon, sigmoid colon, and rectum

• SONO in TRANS: 1 o’clock dot on distal AO

mid/median sacral artery

• most inferior branch aside from iliacs

• supplies the sacrum and rectum

aortic bifurcations

• right and left common iliac artery that divide into external and internal iliac arteries

  • external CIA runs down the leg

• supplies the pelvis and lower extremities

lateral branches of AO

• phrenic arteries

• suprarenal/adrenal arteries

• renal arteries (RRA and LRA)

• lumbar arteries

phrenic arteries

• paired

• supplies the undersurface of diaphragm

suprarenal/adrenal arteries

• paired

• supplies the adrenal gland

renal arteries (RRA and LRA)

• inferior to SMA

• courses horizontally to supply the kidneys

RRA

RRA is longer than LRA and courses posterior to IVC (goes excuse me under the IVC)

??

RA Doppler waveform

• low resistant waveform (sharp brisk upstroke; significant diastolic flow)

• had spectral broadening

lumbar arteries

• 4 pairs

• posterolateral aspect of AO

• supplies muscle, skin, bone, and spinal cord

arteriosclerosis

occurs when arterial vascular system becomes thick and stiff —> HTN due to blood flow constriction

atherosclerosis

• a form of arteriosclerosis

• a buildup of plaque along arteries wall

• must note in preliminary report if seen

abdominal aortic aneurysm (AAA)

• permanent localized dilation of AO when diameter is greater than 1.5x the proximal AO or is more than 3 cm

• primary risk factors: dissection (3 types) and rupture

• tx: surgical repair via graft placement

types of AAA

1. fusiform

2. saccular

fusiform aneurysm

• circumferential enlargement of vessel with tapering at both ends

• resembles a football

saccular aneurysm

• localized dilation of vessel

• spherical structure connected by a vascular mouth

symptoms of AO rupture

• excruciating abdominal pain

• shock

• expanding abdominal mass

• mortality rate of 50%

s/s of AAA

• asymptomatic

• abdomen, back, or flank pain extending into groin, buttocks, or legs

• Grey Turner sign (bruising of flanks)

• become full easily

• n/v

AAA locations

• infrarenal (I)

• juxtarenal (II)

• pararenal (III)

• suprarenal (IV)

infrarenal AAA (I)

below RA

juxtarenal AAA (II)

just below, or at origin of RA

pararenal AAA (III)

involves area around RA

suprarenal AAA (IV)

involves area above and below RA

what should a sonographer note when they see a AAA?

• size (L x W x H in LONG and TRANS)

• shape (fusiform or saccular)

• location (infrarenal?)

• is there wall thickening, calcification, blood flow, or plaque?

true aneurysm

lined by all 3 AO layer

pseudoaneurysm

not lined by all 3 AO layers; blood is escaping from hole in intima layer —> outpouch and pseudo (“fake”) aneurysm

pseudoaneurysm with color Doppler

color appearance of “yin-yang” sign in sac (indicates pseudoaneurysm)

pseudoaneurysm with PW Doppler

• classic “to-and-fro” Doppler signal obtained in neck of pseudoaneurysm

• above baseline (positive)=blood going TO structure

• below baseline (negative)=blood going AWAY from structure

where does the IVC originate from?

common iliac veins

where does the IVC drain into?

right atrium

location of IVC

• retroperitoneal

• travels superiorly from the convergence of common iliac veins

• to right of spine and AO

• posterior to portal vein, intestine, liver

• medial to RK

IVC info

• tubular structure

• collapsible with changes in respiration

• many tributaries that empty deoxygenated blood into IVC

function of IVC

• return deoxygenated blood to heart using valves in its low-pressure system

• valves prevent retrograde or backflow of blood during diastole

indications for imaging IVC

• thrombus or tumor invasion

• IVC filter placement assistance

IVC Doppler waveform

• complex, spontaneous, above and below baseline

• variations with respiration cycle

IVC normal varients

• double IVC

• left positioned IVC

• absence of a portion (rare)

4 sections of IVC

1. hepatic (posterior to liver; HVs empty into IVC

2. prerenal (before renal veins)

3. renal (renal veins and other tributaries empty into IVC)

4. postrenal

IVC tributaries from convergence

• common iliac veins

• lumbar veins

• gonadal veins

• renal reins (RRV and LRV)

• suprarenal veins

• hepatic veins (HVs)

• inferior phrenic veins

common iliac veins

• paired (right and left)

• drains the pelvis and lower extremities

lumbar veins

• 4 pairs

• drains posterior abdominal wall

• empties into lateral aspect of IVC

gonadal veins (testicular or ovarian)

• courses parallel to IVC

• left empties into LRV

renal veins (RRV and LRV)

• posterior to SMA

• anterior to AO

• LRV is longer than RRV

renal vein Doppler waveform

spontaneous and variable (similar to IVC)

nutcracker syndrome

compression or LRV by AO and SMA

suprarenal veins

• arise from suprarenal gland

• right suprarenal vein drains directly into IVC

• left suprarenal vein drains into LRV

hepatic veins (HVs)

• largest visceral tributaries of IVC

• courses from inferior aspect of liver to superior aspect

• 3 HVs: left, middle, and right hepatic veins

• drains liver posteriorly into IVC

• thickens as it gets closer to IVC

function of HVs

returns deoxygenated blood from liver into IVC

LHV drains blood from where?

left lobe of liver

MHV drains blood from where?

central (caudate) lobe of liver

RHV drains blood from where?

right lobe of liver

inferior phrenic veins

drains the diaphragm

“reindeer” or “playboy bunny” sign

LHV, MHV, and RHV

HVs Doppler waveform

• complex, spontaneous, above and below baseline

• variations with respiration cycle

• hepatofugal

hepatofugal

flows AWAY from liver

hepatopedal

flows TOWARD liver

IVC pathology

• right ventricular failure (causes IVC to not collapse during inspiration or expiration)

• IVC and HV dilation

• compression from pregnancy —> edema of feet and ankles and varicose veins

• tumor or thrombus (heterogeneous mass looks the same in gray-scale, so use color Doppler)

IVC tumor

has blood flow

IVC thrombus

does not have blood flow