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ABDOMINAL VESSELS. I. Introduction/General Information A. Uses for ultrasound 1. Screening procedure for abdominal abnormalities 2. Localize/Characterize masses 3. Measurement, rate, direction of blood flow via Doppler .

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I. Introduction/General Information

  • A. Uses for ultrasound
  • 1. Screening procedure for abdominal abnormalities
  • 2. Localize/Characterize masses
  • 3. Measurement, rate, direction of blood flow via Doppler

General Information, continued …

B. Heart:

1. CVT used on adults

2. Ultrasound used in utero

    • C. Abdominal vessels
  • 1. Abdominal aorta
  • a. Ultrasound can delineate contour, course & size

General Information, continued …

b. Can evaluate entire course

c. Used to diagnose, follow progress of aneurysms

d. Can distinguish between normal and aneurysm aortic pulsations


Abdominal Vessels, continued …

2. Celiac axis (trunk, artery)

a. First unpaired branch off abdominal aorta (~ L-1)

b. Originates from ventral surface

c. Gives rise to splenic, common hepatic, & left gastric arteries


Abdominal Vessels, continued …

3. Superior Mesenteric Artery

a. Second, unpaired branch of abdominal aorta

b. Originates ~ lower L-1 body

c. 1 – 2 cm below celiac axis

d. Supplies small intestines, pancreas, omentum, ascending and transverse colon

abdominal vessels con t
Abdominal Vessels, con’t…

4. Inferior Mesenteric Artery

a. Arises just above the bifurcation of the aorta (~L-3/4)

b. Last unpaired branch of aorta

c. Supplies jejunum, descending and sigmoid colon, rectum


Abdominal Vessels, continued …

4. Renal arteries

a. First major paired branches from aorta

b. Arise opposite each other 1-2 cm below SMA (~L-2)

c. Multiple renal arteries occur in 20% of patients

renal arteries
Renal Arteries

Figure 19.11


Abdominal Vessels, continued …

5. Common Hepatic Artery

a. Right branch of celiac a.

b. Continues to GDA, then…

6. Proper Hepatic Artery

a. Branches within liver

b. Begin at ~porta hepatis


Abdominal Vessels, continued …

7. Inferior Vena Cava

a. Formed at ~ L-5

b. by union of Common Iliac Veins

c. Largest vein in body

d. Dilation may be due to:

1. right-sided CHF

2. Portal hypertension


Abdominal Vessels, continued …

8. Veins of Portal Circulation

a. SMV: joins with splenic vein

1. runs parallel to SMA

2. On right side of abdomen

b. IMV: terminates in splenic vein

c. Portal Vein: enters liver


Abdominal Vessels, continued …

d. Renal Veins – run parallel to renal arteries

veins of the right lower limb and pelvis
Veins of the Right Lower Limb and Pelvis

e. Femoral Veins - run parallel to femoral arteries

f. Popliteal Veins – run parallel to popliteal arteries

Figure 19.24a


II. Detailed Anatomy

    • Arteries
  • 1. Size:
  • a. ~ 2.5 cm – 0.5 mm
  • b. inside diameter
  • c. Arbitrary designation
  • 2. Structure: 3 coats or tunics

Detailed Anatomy, con’t…

    • a. Tunica intima
    • 1. aka: tunica interna
    • 2. innermost layer
    • 3. = endothelium
    • 4. thin: 1 cell layer + basement membrane
vascular tunics tunica intima
Vascular Tunics: Tunica Intima

Tunica Intima





Structure, Arteries, continued …

b. Tunica media

1. thickest layer

2. smooth muscle & connective tissue (mostly elastic)

3. in lamina

4. fibers circularly arranged around lumen


Structure arteries, continued …

c. Tunica externa

1. thinner than media

2. thicker than intima

3. white fibrous C. T.

4. A few smooth muscle fibers, arranged longitudinally


Arteries, continued …

3. Variability of arteries

a. larger elastic arteries:

1. aorta, pulmonary, carotids

2. have thicker tunica intima

3. increased elastic tissue


Arteries, variability, continued …

4. very thick tunica media

a. smooth muscle

b. obscured by elastic tissue

5. tunica externa is

a. thin but strong

b. limits stretch


Structure, arteries, continued

6. Serve as “shock absorbers”

a. expand & contract

b. accommodate the pressure from pumping of the heart

c. Maintain blood flow


Structure, arteries, continued

7. arteriosclerosis leads to:

a. decreased elasticity

b. increased blood pressure

c. High B.P., aneurysm, rupture of vessels


Variability, Arteries, continued …

b. Muscular arteries

1. farther from the heart

2. tunica media

a. more smooth muscle

b. Less elastic tissue

c. controlled by ANS

elastic vs muscular arteries
Elastic vs. Muscular Arteries

Elastic Artery

Muscular Artery


Variability, Muscular Arteries, continued …

3. actively influence blood flow, pressure

4. ANS:

a. triggers smooth muscle contraction

b. Sympathetic and parasympathetic responses


Variability, arteries, continued …

5. have capacity to establish collateral circulation

6. Especially coronary arteries

7. contract when injured

a. ANS reaction

b. Prevents blood loss


Detailed anatomy, continued …

    • B. Arterioles: small arteries < 0.5 mm
    • 1. Lie close to capillary beds
    • 2. Muscular
    • 3. Primary function: regulate capillary blood flow
    • 4. Allows for exchange of materials between blood and tissues

Detailed anatomy, continued …

    • C. Capillaries (sinusoids)
  • 1. Size: 1 mm long x 10 micrometers diameter
  • 2. Structure
  • a. Wall: 1 cell layer thick (endothelium)
  • b. inner surface contacts blood

Capillaries, continued …

c. outer surface rests on basement membrane

d. Beyond basement membrane:

1. loose connective tissue

2. contains tissue fluid ( = plasma outside of blood stream)


Capillaries, continued …

      • 3. Organization of capillaries:
    • a. Form vast, complex networks
    • b. Penetrate to reach most tissues
    • c. Pre-capillary sphincter:
    • 1. smooth muscle rings
    • 2. regulate blood flow between arterioles & capillary beds

Capillaries, continued …

    • d. Capillary beds: (~ 60,000 miles)
    • 1. Specialized for exchange of materials
    • 2. each pound of adipose tissue contains 200 miles of capillaries
capillary networks
Capillary Networks
  • Capillaries connect arterioles to venules
  • Blood flow is from the arterial to the venous vessels
  • Every millimeter of tissue has capillary blood supply

Blood Vessel Anatomy, con’t…

    • D. Venules
  • 1. Vessels closest to capillary beds
  • 2. carry deoxygenated blood
  • 3. Small venules: structurally similar to large capillaries
  • 4. Medium venules: contain a few circular muscle fibers
  • 5. Large venules: have a tunica externa

Blood Vessel Anatomy, con’t…

    • E. Veins
  • 1. Structure: same tunics, but not as distinct
  • a. Tunica media may be absent
  • b. Tunica externa: usually thickest
  • 1. Provides strength to outer wall
  • 2. Lots of smooth muscle fibers
  • 3. Less elastic tissue
vascular tunics veins
Vascular Tunics: Veins

Tunica Externa

Tunica Media

Tunica Interna


Veins, continued …

        • Valves: in veins carrying blood against gravity
  • a. Folds of tunica intima
    • b. Prevent backflow
    • c. Absent in venae cavae, pulmonary & portal veins
valves in veins
Valves in Veins

Venous Valve


Valves, continued …

    • 2. Internal jugular veins have valves
    • a. are “upside down”
    • b. blood is flowing back to heart c. when heart contracts, pushes blood up into SVC
    • d. valves keep -O2 blood from going back up into brain
valves assisted by skeletal muscles
Valves Assisted by Skeletal Muscles
  • Skeletal muscle contraction, especially in the extremities, assists the flow of blood back to the heart
  • Varicose Veins…..

Blood Vessel Anatomy, continued …

    • 3. Vasa Vasorum:
    • a. vessels that supply vessels
    • b. associated with larger arteries & veins
    • c. walls too thick for diffusion

Pathways of Major Vessels

F. Path of major vessels

1. Abdominal aorta

a. Continuous with thoracic aorta @ diaphragm.

b. Passes through @ T-12/L-1

c. Most inferior hiatus in diaphragm


Pathway of Major Vessels, continued …

d. Anterior & to the left of vertebral bodies

e. Decreases in external diameter caudally

1. 3.0 cm @ left ventricle

2. 1.5 cm @ bifurcation

f. Moves toward midline distally

path of aorta
Path of Aorta
  • Parasagittal section through the thorax and abdomen showing the path of the aorta

Pathway of Major Vessels, continued …

g. Bifurcates into R/L common iliac arteries @ L-3/L-4

h. Courses posterior to IVC near diaphragm

i. Curves anteriorly along lumbar curvature


Pathway of Major Vessels, continued …

      • 2. Celiac Artery
    • a. First unpaired branch of abdominal aorta (~T-12)
    • b. Gives rise to:
    • 1. Splenic Artery:
    • a. largest on left
    • b. supplies spleen, pancreas fundus of stomach
the celiac trunk and its branches
The Celiac Trunk and its Branches
  • The celiac trunk is the first unpaired artery of the abdominal aorta
  • It arises ~T-12/L-1 disc

Celiac Trunk


Major Paths of Vessels, Celiac Artery, continued

c. L. Gastroepiploic Artery

1. Largest branch of splenic artery

2. supplies greater curvature of stomach


Celiac artery, continued …

2. Left Gastric Artery:

a. smallest of 3 branches

b. Supplies: 1. Cardiac region

2. lesser curvature of stomach

3. Lower esophagus


Celiac artery, continued …

3. Common Hepatic Artery:

a. courses toward right

b. supplies pyloric region of stomach & duodenum

c. gives rise to gastroduodenal artery

d. Continues as proper hepatic artery

hepatic artery
Hepatic Artery

Proper Hepatic Artery

Common Hepatic Artery


Path of major vessels, continued …

      • 4. SMA
    • a. Second unpaired branch
    • b. Arises 1 – 2 cm below celiac artery
    • c. May have common origin
    • d. After ~6”,
    • 1. courses parallel to aorta
    • 2. then turns oblique toward right iliac fossa

SMA, continued …

    • d. Numerous branches that sometimes anastomose
    • e. Supplies:
    • 1. small intestines
    • 2. cecum
    • 3. appendix
    • 4. ascending & transverse colon 5. pancreas
superior mesenteric artery
Superior Mesenteric Artery

Superior mesenteric artery

SMA gives rise to the inferior pancreaticoduodenal artery

path of major vessels continued
Path of major vessels, continued …

5. Renal Arteries/Veins: a. First major paired branch of abdominal aorta

b. Arise ~L-2

c. more later


Path of major vessels, con’t…

6. IVC: arises ~L-5

a. lies to right of lumbar vertebrae

b. Largest vein

c. Occupies a fossa on posterior surface of liver

d. Receives hepatic veins



IVC, continued …

e. Penetrates diaphragm at T-10

f. passes through pericardium

g. empties into right atrium

h. IVC receives blood from lower extremities, lumbar v., renal v., adrenal v.


IVC and its Tributaries

Pathway of IVC and its major contributing veins


Path of major vessels, continued …

      • 7. Portal system:
  • a. Receives blood from digestive organs
  • b. Is high in nutrients  enters portal vein  then to liver sinusoids
  • c. then to hepatic veins  into IVC

Portal system, continued …

d. Portal Vein:

1. formed ~L-2 by union of SMV & splenic vein

2. travels superiorly surrounded by lesser omentum

3. Enters liver at porta hepatis


III. Gray Scale Anatomy

  • A. Abdominal aorta
  • 1. Circular in T.S.
  • 2. Tubular in L.S.
  • 3. Differences from IVC:
  • a. IVC lies to the right

Abdominal aorta, continued …

  • b. Near diaphragm, IVC is anterior in L.S.
      • c. IVC changes diameter with respiration
  • d. Aorta pulsates
  • 4. Slopes anteriorly to L-3/4

Gray scale anatomy, continued …


1. Extends from ~3 cm below diaphragm to umbilicus

2. Horizontal course on L.S.

3. Origin is 1 – 2 cm below celiac

4. Lies anterior to aorta


SMA, continued …

4. In T.S.:

a. sonolucent circular structure

**b. posterior to body of pancreas

5. Surrounding fat  collar

a. Different from SMV

b. SMV larger & to the right


Gray scale anatomy, continued …

    • C. Celiac trunk/axis/artery
    • 1. ID-ed on T.S. as tubular branching structure
    • 2. Originates from anterior aorta
    • 3. Short, “vertical” (really anterior) course superior to lesser curvature
    • 4. Hepatic and splenic artery branches produce “seagull” sign

The “Seagull” Sign

Splenic Artery

Hepatic Artery

Celiac Trunk


IV. Vascular Pathology

A. Tortuosity of abdominal aorta

1. Aorta becomes elongated, dilated & less elastic with age

2. Due to plaque & calcification

3. May become tortuous

4. May lie to right of midline

5. May mimic an aneurysm


Vascular Pathology, con’t….

    • B. Aneurysms
  • 1. Definitions:
  • a. circumscribed dilation of an artery
  • b. blood-containing tumor connecting with lumen of artery
  • 2. Fusiform or saccular dilations
  • 3. Usually appear distal to renal arteries

Aneurysms, continued …

4. Measurements abnormal if:

a. External A-P diameter >3.5 cm in upper abdomen

b. > 2.5 cm in distal aorta

5. Patent vessel lumen contains blood, is echolucent


Aneurysms, continued …

6. Thrombus-filled lumen is echogenic

7. Ectatic (dilated) aorta difficult to depict on single scan

8. Associated with arteriosclerotic plaque


Aneurysms, continued …

9. Excess plaque causes:

a. loss of elasticity

b. weakening in tunica media

c. Tears in tunica interna


Aneurysms, continued …

10. Fusiform aneurysms

a. usually project anterior & to the left

b. path of least resistance

c. Laminar blood flow absent in dilation

d. Eddy currents increase likelihood of thrombus


Aneurysms, continued …

11. Ultrasound is > 95% accurate in identifying AAA

a. Presence/location & serial growth

b. Diameter determination

c. Thrombus presence

d. Incidence of rupture of aneurysm increases after 7.0 cm


Aneurysms, continued …

      • 12. If dilation extends toward SMA, renal arteries may be involved
  • 13. Less common to find aneurysm above renal arteries
  • 13. If dilation is above renal arteries, suspect dissecting thoracic aneurysm
  • 14. If dilation extends distally, survey common iliac arteries

Aneurysms, continued …

    • B. Aortic Dissection
  • 1. Usually secondary to dissecting thoracic aortic aneurysm
  • 2. Dilation of abdominal aorta with double lumen
  • 3. Characteristics:
  • a. Intimal flap
  • b. Diffuse dilation

Aortic dissection, continued …

4. Pulsations of flap are visible

5. Aneurysms of ascending aorta enlarge anterior and to the right

a. May extend to mediastinum

b. May erode sternum


Vascular Pathology, con’t…

    • D. Atherosclerosis vs. Arteriosclerosis
  • 1. Atherosclerosis (reversible)
  • a. deposits of fatty materials b. in tunica intima of arteries
  • c. Genetic predisposition-- leads to 

Atherosclerosis vs. Arteriosclerosis, con’t…

  • 2. Arteriosclerosis (irreversible)
  • a. infiltration of intima by plaque
  • b. reduces lumen size
  • c. Reduces blood supply
  • d. “hardening of the arteries”

Vascular Pathology, con’t…

  • E. Types of aneurysms
    • Axial – involves entire circumference of artery
    • Compound –some tunics ruptured, some intact
    • Dilation – axial or fusiform; general enlargement
    • a. Active – growing in diameter
    • b. Passive – wall is stretching

Types of aneurysms, continued …

4. Dissecting – splitting, tearing of intima

a. Rarely encircles entire lumen

b. Usually one side only

c. May involve entire length to bifurcation

d. Usually originates from thoracic aorta (high B.P.)



Berry Aneurysm


Dissecting Aneurysm


Types of aneurysms, continued …

5. Ectatic – axial or dilating, but unruptured

6. Endogenous – stretched tunica

7. Exogenous – due to trauma

8. Fusiform – long skinny expansion


Types of aneurysms, continued …

9. False

a. bleeding from another source

b. pulsating encapsulated hematoma

c. fused with aneurysm

d. communicates with lumen of artery


Types of aneurysms, continued …

10. Saccular – sac like bulge

a. tunica externa expanded

b. tunica intima intact

11. Tubular –

a. AKA axial; passive dilation

b. Uniform dilation of entire vessel


Types of aneurysms, continued …

12. Varicose –

a. result of varicose veins

b. blood containing sac connecting artery & vein

c. seen in antecubital fossa

d. due to repeated IV sticks