Aorta Anatomy and Branches Quiz

Trunk artery
Ascending aorta arises from left ventricle; first branches are the coronary arteries.
Aortic arch starts at the level of the innominate artery and extends to distal to the left subclavian artery.
Three branches of the arch in order of origin: innominate artery, left common artery, left subclavian artery.
Descending aorta extends through the chest and abdomen until it bifurcates at the level of the umbilicus.
Descending thoracic aorta - above the diaphragm.
Descending abdominal aorta - below the diaphragm.
Courses anterior to the spine and to the left of the IVC posterior to the IVC until the level of the umbilicus.
Distributes blood to organs and limbs.
Lower resistance in the upper abdominal aorta due to low resistance branches; higher resistance in the distal aorta due to high resistance branches.
In most cases the branch is named after the organ it is feeding.

Paired Branches:
- Suprarenal arteries.
- Renal arteries.
- Gonadal arteries.
- Lumbar arteries.
- Common iliac arteries.
Unpaired Branches:
- Celiac axis.
- SMA.
- IMA.

Originate at the aortic bifurcation at L3 or L4, umbilicus level.
Supply legs and pelvis.
Bifurcate into the internal and external iliac arteries.
High resistance flow.
Above the umbilicus, arteries course posterior to veins.
Below the umbilicus, the arteries course anterior to the veins; common iliac arteries are anterior to the common iliac veins.

Travels laterally to pass under the inguinal ligament to become the common femoral artery.
Courses along the medial side of the psoas muscle.
Supplies the extremities with blood.
Triphasic, higher resistance than the common iliac.

2.5MHz to 6.5MHz curvilinear array - adult.
4MHz to 8MHz curvilinear array - pediatric.
Phased array may be used for larger patients.
Patient must be NPO to best visualize the abdominal vasculature.
Supine, oblique and decub positions may be necessary.
2D, Color and Doppler evaluation of proximal, mid and distal segments with iliac arteries at bifurcation.

Proximal-2.0-2.6 cm; portion between diaphragm and celiac axis/SMA.
Mid-1.6-2.4 cm; portion from celiac axis/SMA to just below renal artery origins.
Distal-1.1-2.0 cm; portion from below renal arteries to iliac bifurcation.
Iliacs-0.6-1.4 cm.

High resistance.
Average velocity 70 to 100 cm/sec.
Clean spectral window.
Biphasic above renal arteries due to numerous low resistance branches (organ arteries).
Triphasic below renal arteries due to high resistance branches (iliacs).
When evaluated as part of a mesenteric, iliac or renal artery exam the aorta is usually assessed with Doppler just proximal to the branch of interest to compare flow patterns.

Congenital narrowing of the aorta.
Most commonly occurs distal to the origin of the left subclavian.
Decreased flow distal to the obstruction.
Monophasic flow with continuous flow in diastole identified in the abdominal aorta.
Causes lower extremity ischemia.
Decreased bilateral pedal pulses.
Decreased bilateral ankle pressures; brachial pressures may be elevated if renal flow affected.
Because the arch is proximal to the obstruction, flow to the head and neck is usually normal.
Systemic HTN is usually present because the coarct causes renal ischemia and the renin-angiotensin system is activated causing increased systemic pressure.

Lack of tapering of the aorta as it travels distally, size remains constant from proximal to distal portions.
Can be a precursor to aneurysm formation.

True aneurysm - dilation of all 3 layers of the aorta.
False aneurysm - pulsatile hematoma, extravasation of blood from aorta into surrounding tissues.
Most commonly occur in the infrarenal portion of the aorta.
Can occur at any level of the aorta.
Risk factors: smoking, hypertension, male gender, familial predisposition, connective tissue disorders.
Size dictates management.
Less than 4 cm - observation with regular ultrasounds.
Greater than 4 cm - consider surgical repair.
Measured in transverse diameter.
Symptoms: back pain, abdominal pain, pulsatile abdominal mass.

### Aortic Dissections

Tear or separation of the intimal layer of the aortic wall that allows blood to flow between the layers creating a false lumen.
Can occur in the aortic arch, ascending aorta, or descending aorta.
Most commonly occur in the ascending aorta.
Risk factors: hypertension, connective tissue disorders, trauma.
Symptoms: sudden onset of severe chest or back pain, radiating to the neck, jaw, or abdomen.
Diagnosis: aortic CT or MRI.
Ultrasound can help to identify the presence of a dissection.
Look for a false lumen, intimal flap or thrombus within the false lumen.
May also see a decrease in aortic flow velocity in the true lumen and an increase in flow velocity in the false lumen.

Medical management: control of hypertension, pain management.
Surgical repair: to repair the tear in the aortic wall.
Endovascular repair: a less invasive procedure, with a stent placed to seal the tear.
Prognosis: depends on the location and severity of the dissection and the patient's underlying health conditions.