Ch 6: Abdominal Vascular Structures

The layers of vessel walls

Tunica Intima: inner endothelial lining

Tunica Media: middle smooth muscle layer

Tunica Adventitia: outer layer consisting of collagen fibers

Segments of the Aorta

Ascending: comes out of the heart

Arch: where a lot of cerebral vascular vessels come from

Descending: heads down after arch

Thoracic: extension of descending through thoracic cavity

Abdominal: after it enters hiatal opening in diaphragm and feeds extremities/trunk of body

What are the major abdominal aortic branches that should be recognized from superior to inferior?

Celiac trunk, superior mesenteric artery, renal arteries, inferior mesenteric artery, and common iliac arteries

Artery wall Characteristics

Thicker/more elastic, tend to maintain constant shape, do not readily collapse, pulsatile in nature, and stiff (will not collapse if you apply pressure)

Vein wall characteristics

Less smooth muscle and less elastic tissue, unable to contract to force blood flow, requires pressure gradient (which comes from breathing, skeletal muscle contractions, and valves in extremities)

Which veins form the main portal vein

Splenic vein and superior mesenteric vein (SMV)

Where do hepatic veins drain

Into the IVC

What is atherosclerosis

It is a form of arteriosclerosis where intimal lining of arteries is altered by the presence of focal accumulation of lipids, blood and blood products, or calcium deposits.

media of arterial wall is also changed/hardened (harder to contract)

Atherosclerosis risk factors/signs and symptoms

Risk factors are increased lipids, high cholesterol, hypertension, smoking, or diabetes.

Symptoms are rare until significant stenosis (narrowing of a vessel) develops, but may have pain with walking or back pain.

Atherosclerosis Sonographic appearance

Luminal irregularities (low level echoes (soft gray indicating soft plaque/not calcified yet)along internal walls of aorta), tortuosity (vessel gets wavy in appearance) which is easier to see in transverse, and wall calcification (soft plaque begins to harden/becomes more echogenic and often produces shadows). If there’s calcification on anterior wall, it can produce shadows inside the vessel, making it tricky to see inside

What is an aneurysm

Abnormal dilation of a blood vessel

True aneurysm

Involve all 3 layers of the arterial wall and has dilation greater than 3cm and lacks normal tapering

False aneurysm (pseudoaneurysm)

Extra-vascular hematoma communicating with the intravascular space, often post-procedure or from trauma. These have the yin-yang blood flow sign

What does the yin-yang sign represent in pseudoaneurysm?

Blood flowing in and out of the pseudoaneurysm sac/the swirling bidirectional flow

Aneurysm Etiology (cause/origin)

risk factors are smoking which cases hardening of the arteries, and atherosclerosis which is fatty plaque build up

Aneurysm Symptoms

Usually asymptomatic, and often suspected by a doctor during a physical exam when patient has a palpable pulsating mass in umbilicus area. patient may have vague unexplained low back/abdominal pain and doctor may hear “wooshing” sound when listening to abdominal vessels (blood flow velocity is different)

Why should you identify the origin of renal/iliac vessels

To determine AAA location or vessel involvement. If they are located near bifurcation, examination of iliacs is also necessary. Knowing the location of the AAA will help know if the patient could have a procedure done to fix it or if its too risky.

Where do most AAA occur

Below the level of the renal arteries

Most true aneurysms are what type?

fusiform and circumferential

What is a Fusiform Aneurysm

a gradual progressive dilation of the vessels circumference. they vary in diameter and length

What is a Saccular Aneurysm

A “neck” or connecting stalk in an aneurysm off the aorta. bulging in one area of the vessel

What is a Dissecting Aneurysm

Longitudinal tear of the intimal lining of the vessel, which allows bleeding into the wall. the lest common type and occur more often in the thoracic AO

Where do saccular and fusiform aneurysms often occur

In abdominal AO

Aneurysm Sonographic Appearance

Ectasia of AO, true aneurysm has dilation greater than 3cm and lacks normal tapering, thrombus is common finding within AAA (along anterior and posterior wall where vessel is dilated)

What is Ectasia

Diffuse, mild enlargement of AO without distal tapering

Normal AO measurement at diaphragm

2.5cm and tapers distally

Why most total aneurysm size be assessed rather than only patent lumen

Assessment of the total outer diameter of the blood vessel is needed because that determines the risk of rupture

What is Mural Thrombus

Thrombus that attaches/bulges out of the wall of the blood vessel

What is the crescent sign described in an AAA with mural thrombus

An anechoic crescent caused by liquification within the thrombus

How does color Doppler help when an AAA contains mural thrombus?

It demonstrates the residual flowing lumen and helps distinguish flowing blood from thrombus.

What is an aortic dissection

Separation of the layers of the arterial wall by blood or hemorrhage after a tear in the inner wall

Aortic dissection causes

Are not clear but could be hypertension (increase pressure in vascular structure), pregnancy (changes in the body/hormones), Marfan syndrome (genetic condition that affects the connective tissue and because of the tissue blood vessels are made from, it could cause problems), or general valve disease within vascular system

Aortic dissection signs/symptoms

intense chest pain (because they mostly occur in thoracic aorta), could be associated abdominal pain, headaches, syncope (fainting/passing out from temporary drop in blood flow to the brain), or transient blindness

What is the key B-mode sonographic sign of an aortic dissection?

A thin echogenic linear intimal flap within the lumen.

What happens to blood flow in an aortic dissection?

Blood may flow through the normal lumen and through a false channel created within the vessel wall.

What is DeBakey type I aortic dissection?

A dissection involving the ascending aorta and extending into the arch and potentially beyond.

What is DeBakey type II aortic dissection?

A dissection involving the ascending aorta and aortic arch, and associated with Marfan syndrome. least common type

What is DeBakey type III aortic dissection?

A dissection beginning in the descending aorta below the left subclavian artery.

Which DeBakey types have high mortality risk and why

types I and II because of their location, it will often spread to pericardium

What is an aortic rupture

Disruption of aortic wall with bleeding outside the vessel, primarily from ruptured AAA

When can an AAA rupture

at any size, but the risk increases with aneurysm is larger than 7cm

Why is an aortic rupture a medical emergency

its mortality rate is 100% if left untreated because it can cause rapid internal bleeding, hemorrhage, hypotension, or syncope

Aortic rupture signs/symptoms

central back pain (mid/lower back) or very quick drop in blood pressure (may feel faint/pass out)

Aortic rupture sonographic appearance

disruption of aorta wall and bleeding in abdomen (intra-abdominal fluid collections). Could be hard to see the aneurysm because of the wall disruption/bleeding

Most common type of splanchnic artery aneurysm

Splenic artery aneurysm

Where do splenic artery aneurysms commonly occur?

In the main splenic arterial trunk. The image is near the splenic hilum.

Which sex has a higher prevalence of splenic artery aneurysm

Females

Are splenic artery aneurysms common?

No they are rare but can be life-threatening.

Splenic artery aneurysm etiology

Pancreatic inflammation, peptic ulcer disease, mycotic lesions (fungal rashes/growths), portal hypertension, and multiple pregnancies (changes in blood flow, connective tissue, and hormones may weaken vessel walls). Overall, anything that causes increased pressure along portal system/splenic vessels

Splenic artery aneurysm symptoms

LUQ pain, N/V (nausea/vomiting), or palpable mass

How can color Doppler help evaluate a suspected splenic artery aneurysm?

It demonstrates blood flow within the dilated vascular structure and helps distinguish it from a nonvascular cystic mass

2nd most common splanchnic vessel aneurysm

Hepatic artery aneurysm

What percentage of hepatic artery aneurysms are extrahepatic

75%

Which hepatic artery is more often affected

right hepatic artery

Which sex has a higher prevalence of hepatic artery aneurysm

males

Hepatic artery aneurysm etiology

Systemic infection (liver filters toxins within the body), arteriosclerosis (hardening of arteries), blunt abdominal trauma, and chronic cholecystitis (GB inflammation, close proximity to these vessels)

Hepatic artery aneurysm symptoms

Epigastric pain, GI bleeding, hemobilia (blood in bile), and jaundice (yellowing of skin/eyes)

What important complication of hepatic artery aneurysm is emphasized?

A propensity (strong tendency) to rupture

How may a hepatic artery aneurysm appear on color Doppler?

As a dilated vessel or mass with turbulent mixed red-and-blue swirling flow

Splanchnic artery aneurysm sonographic appearance

distinguishing feature is location in abdomen, may appear as anechoic or complex abdominal mass, demonstrate continuity of mass with vessel, and doppler should always be used to assess for characteristic swirling blood flow pattern

What vessel abnormality is an iliac artery aneurysm most often associated with?

Abdominal aortic aneurysm (AAA)

What is the most common major complication of an untreated iliac artery aneurysm

rupture

Iliac artery aneurysm symptoms

Urologic, gastrointestinal, or neurologic symptoms because of proximity (such as hydronephrosis, uti, or kidney infection), pain, or a palpable mass

Iliac artery aneurysm etiology

most are arteriosclerosis in origin, external or surgical trauma, or pregnancy

Iliac artery aneurysm sonographic appearance

Primarily anechoic mass in pelvis, smaller aneurysms may be difficult to see due to bowel gas, thrombus along periphery, calcific wall changes, and may see doppler turbulent arterial signal (swirling blood flow pattern and PW doppler will show very turbulent waveform)

Why should both iliac arteries be evaluated when an iliac aneurysm is found?

Iliac aneurysms tend to be bilateral

What is an aortic graft, endograft, or prosthesis and how is it named

A man-made structure used to repair or bypass diseased vascular segments, including aortic aneurysms (taking part of one vessel and connecting it to another to to bypass damaged area). they are named in reference to the vessel they are attached to

Aortic graft sonographic appearance

A ribbed or railroad-track-like echogenic structure

What is aortofemoral bypass surgery

A graft connecting the aorta to the femoral artery to bypass diseased iliac arterial segments, placed anterior and adjacent to native vessel. The diseased segment is left intact and an end-to-end anastomotic technique is used

What is endovascular repair of an abdominal aortic aneurysm (EVAR)

a minimally invasive surgical procedure that involves deploying a stent graft into the AO with exclusion of the AAA (to direct blood through the graft and reduce pressure and flow within the aneurysm sac)

Why is surveillance important after graft or EVAR placement?

To confirm continued patency and detect complications such as leaks, thrombosis, or infection

Vascular graft complications

Pseudoaneurysm, hematoma, abscess or infection, endoleaks (persistent blood flow into aneurysm sac outside an aortic stent graft after EVAR), and graft occlusion (blood can become stagnant and clot, or the graft can become blocked because of procedural or other complications)

What happens to blood velocity at the site of a stenosis?

Velocity increases

What happens to flow immediately downstream/after from a significant stenosis?

turbulence develops and velocity drastically drops

What is renal artery stenosis

Narrowing of a renal artery that reduces renal blood flow which can produce elevated blood pressure and is associated with uncontrolled hypertension

Renal artery stenosis complications

Decreased glomerular filtration rate (GFR) and ischemic renal damage

Renal artery stenosis sonographic appearance/findings

elevated velocity in the main renal artery and parvus/tardus pattern in intrarenal arteries. must evaluate prox, mid, and dist segments of all types of arteries in the kidney (segmental, interlobar, and arcuate arteries)

What does a parvus-tardus waveform look like conceptually?

A delayed, dampened systolic upstroke with a lower, rounded systolic peak, and increase in acceleration index

What happens to the IVC caliber below an obstruction?

It increases or becomes dilated below the point of obstruction

IVC obstruction causes

Most common cause is right-sided heart failure, but could also be hepatomegaly, enlarged lymph nodes around aorta, retroperitoneal mass/tumor, or anything that can apply pressure to the IVC

IVC obstruction signs/symptoms

depends on where it is/how severe it is, but you can experience abdominal pain, ascites, or lower extremity edema (if obstruction is really severe)

IVC obstruction appearance

A distended IVC containing intraluminal echoes with absent color Doppler signal.

dilation below the obstruction, respiratory changes decrease or absent below the obstruction, or in right sided heart failure, the proximal IVC and hepatic veins become congested

What are primary IVC tumors

tumors that form in the IVC, this includes leiomyosarcoma, and they are rare

Which sex do primary IVC tumors tend to occur

women

Malignant Invasion IVC tumors

Metastasis or extension of tumors that may occur from renal cell carcinoma (most common, especially the right side because RRV is shorter than left), adrenal tumors, or hepatocellular carcinomas

IVC tumor sonographic appearance

An enlarged vessel containing an intraluminal mass of varying echogenicity. larger tumors may be heterogeneous with areas of necrosis. doppler will show distinct blood flow changed around the tumor

What is portal vein thrombosis

Thrombus within the portal venous system

Portal vein thrombosis etiology

Portal hypertension, abdominal inflammatory processes (cirrhosis), trauma, postsurgical complications, or hypercoagulable states (BCPs, pregnancy, polycythemia vera)

Portal vein thrombosis symptoms

Abdominal pain, abdominal rigidity (hardened feeling), and elevated liver function tests

Portal vein thrombosis appearance

Varies depending on stage (starts with echogenic thrombus and small collaterals).

normal caliber PV is 13mm or less but a thrombus could make it dilate because of improper flow

What is portal hypertension

Increased pressure within portal venous system

Advanced cases of Portal hypertension can cause what

ascites or GI bleeding

What is important to look for when diagnosing portal vein hypertension

secondary effects of increased pressure

What are some secondary findings of portal hypertension

Increased portal vein diameter, ascites, splenomegaly, recanalized umbilical vein (ligamentum teres/remnants of umbilical cord), and bidirectional flow (both red and blue flow on color doppler)

What is an AV (arteriovenous) Fistula

an abnormal connection between an artery and vein

What indications are there to have an AV fistula exam

Presence of bruit (buzzing/vibrations) or thrill (swishing or humming sound) associated with dilated pulsatile mass, low back and abdominal pain, or swelling of lower trunk and extremities

AV Fistula doppler findings

Pulsatile, arterialized venous waveform, increased systolic and diastolic arterial velocities proximal to fistula but reverts to normal diastolic flow distal to fistula