Chapter 9: Abdominal Aorta

Abdominal Aorta

Considered one of the 2 great vessels (IVC is the other) - VITAL vessel; blood flowing to abdominal organs/lower extremities must pass through some part of it to reach destination; retroperitoneal; on the left of spine; originates at left ventricle but is termed AO once it passes diaphragm; bifurcates into L/R common iliacs; average measurements (cm): proximal- 2.0, mid- 1.5, distal- 1.5 (common iliacs- 0.8-1); will taper in size as it courses inferior and anterior in the body

Inferior Phrenic Artery

Most superior branch of AO

Celiac Artery/Axis/Trunk (CA)

Branches from the anterior aspect of AO; 1cm or less in diameter; branches into left gastric artery (LGA) (variable and not easily seen), splenic artery (SPA), and common hepatic artery (CHA); looks like seagull in transverse

Left Gastric Artery (LGA)

Courses superiorly; supplies left side of lesser curvature of stomach; anastomoses (connected) with RGA

Splenic Artery (SPA)

Courses horizontally to left; supplies spleen, pancreas, and left side of greater curvature of stomach

Common Hepatic Artery (CHA)

2 branches: gastroduodenal artery (GDA) and proper hepatic artery (PHA)

GDA: courses inferiorly and supplies right side of greater curvature of stomach

PHA: courses right laterally and superiorly to supply liver via RHA, MHA, and LHA

Suprarenal Artery

Origin varies; branches bilaterally from lateral of the AO between level of CA and SMA; supplies adrenal glands

Superior Mesenteric Artery (SMA)

Branches from anterior aspect of AO; supplies largest portion of small intestine, ascending colon, and part of the transverse colon

Renal Arteries

Branches from the lateral aspect of AO; courses horizontally to each kidney; RRA has longer course than LRA and courses posterior to IVC (only vessel posterior to IVC)

Gonadal Arteries

Branch from anterior aspect of the AO and course inferiorly to respective organs (testicular or ovarian artery); left often originates slightly superior to the right

Inferior Mesenteric Artery (IMA)

Branch from anterior aspect of aorta, inferior to SMA and renal arteries; courses anteroinferiorly; supplies blood to transverse colon, descending colon, and rectum

Median Sacral Artery

Most inferior branch of the abdominal aorta

Layers of Aorta/arteries

Tunica intima - inner layer

Tunica media - middle layer

Tunica adventitia - outer layer

Thickness of layers will vary; arteries have thicker tunica media to allow greater elasticity

Physiology of Aorta

Channels blood to organs and tissues to ensure oxygenation and metabolism; maintains blood flow during diastole, stored energy in vessel wall is released (stored energy is derived from expansion of vessel during systole); play critical role in homeostasis (renin is released from the kidney in the event of bleeding and acts on angiotensin II, which initiates vasoconstriction); blood pressure is maintained through vasoconstriction

Sonographic Appearance

AO: appears as anechoic tubular structure located slightly left of midline, with bright echogenic smooth wall margins, and is pulsatile

CA: seagull appearance in transverse plane with the “wings” being SPA (left) and CHA (right)

SMA: linear branch from anterior AO and inferior to CA; runs parallel to AO

Renal Arteries: most easily seen in transverse; curvilinear; small diameter

Common Iliac Arteries: AO bifurcation at umbilicus; most easily seen in transverse

Applications

Primarily used to detect aortic aneurysms, stenosis, or grafts

Hematocrit

Percentage of red blood cells to whole blood is used to measure possible bleeding from the arterial system; abnormal decrease in red blood cells may also point to bleeding

Associated Tests/Exams

Duplex Doppler sonography (both color and waveform)

Color Doppler imaging (only color)

Plethysmography and segmental blood pressure (BP cuff exam; can be painful)