Aorta/IVC Abdominal Vascular

Aorta Size Portions: Proximal : superior to or at the level of the celiac axis, measures 2-3 cm Middle: below the celiac axis, above the renal arteries, measures 1.6-2.5 cm Distal: just above the bifurcation, measures 1.1 to 2.0 cm Iliac arteries: measure 0.6-1.4 cm Tapers from superior to inferior

Pathology Ectasia: when the abdominal aorta does not taper as it normally does but “kinks” is not dilated to the point of aneurysm usually occurs anteriorly and to the left

Coarctation of the Aorta Coarctation: narrowing of the aorta congenital condition narrows in the area where the ductus arteriosus inserts

Coarctation of the aorta Clinical Findings: Hypertension resulting from decreased kidney perfusion causes abnormally high blood pressure in the arms Decreased lower extremity pulses Lower extremity ischemia

Aorta Aneurysm Definition: a localized dilatation of the abdominal aorta exceeding the normal diameter by more than 50 percent Artery is aneurismal if dilated segment is 1.5 times greater is size than the adjacent normal segment Extent Focal – localized segment Diffuse – longer segment .

Pathophysiology of the Vascular System Vascular Abnormalities Arteries Arteriosclerosis: disease of the arteries; the walls lose their elasticity and become hardened Aneurysm 1. Atherosclerosis – Most common cause which are fat deposits beneath the intimal layer causing atrophy of underlying tissue 2. Trauma – Can cause an aneurysm or damage to both the the artery or the vein by forming an arteriovenous fistula 3. Congenital – Abnormalities present at and existing from the time of birth

Pathophysiology of the Vascular System Aneurysm (continued) 4. Infections – such as syphilis and mycobacterium (microorganisms that can cause TB and leprosy) Aneurysms can be classified into 2 categories: True – localized dilatation of an artery due to weakness of the wall False – wall of the blood vessel ruptures and blood escapes and is retained by surrounding tissues (pseudoaneurysm)

Pathophysiology of the Vascular System True Aneurysm Types Fusiform Dissecting Saccular Mycotic

Pathophysiology of the Vascular System Fusiform Most Common Dilatation of the entire circumference of the vessel giving it a baloonlike appearance All three layers remain intact Saccular Rare and localized weakness that causes a saclike bulge in a portion of the wall May also be associated with Berry Aneurysms

Fusiform Aneurysm

Longitudinal Image AAA

Thrombus in aneurysm Image shows the large amount of intraluminal thrombus (T) commonly found in aneurysms of the aorta and iliac arteries.  The patent lumen is indicated by the red arrow.  

AAA containing Thrombus Echogenic area seen within the AAA is thrombus

Types of Aneurysms Saccular Rare localized weakness that causes a saclike bulge in a portion of the wall Usually affects the left lateral portion of distal abdominal aorta May also be associated with Berry Aneurysms

Saccular Aneurysm

of aneurysm in the brain once it has formed it is likely to rupture, Berry Aneurysm Intracranial Berry aneurysm, also known as a saccular aneurysm, is a sac-like outpouching in a cerebral blood vessel most common kind of aneurysm in the brain once it has formed it is likely to rupture, causing a stroke

Mycotic Aneurysm Definition: is a localized, irreversible arterial dilatation due to destruction of the vessel wall by infection develop either when a new aneurysm is produced by infection of the arterial wall or when a preexisting aneurysm becomes secondarily infected majority of mycotic aneurysms are caused by bacteria may be a true or false aneurysm, involving all layers or only a portion of the arterial wall may be solitary or multiple

Mycotic aneurysms can occur anywhere in the body 31 % abdominal aortic 38 % femoral 8 % superior mesenteric 5 % carotid 6 % iliac 7 % brachial

Mycotic Aortic Aneurysm Aortogram of the supra celiac aorta with distal runoff. Double open arrow indicates saccular aneurysm, curved arrows point to right and left renal arteries, and arrowheads outline superior mesenteric artery.

Arterial Dissection Definition: tear in the intimal lining of the vessel wall Most commonly, such deterioration is associated with high blood pressure False lumen created between intima and media As the dissection advances, it can close off the points at which one or more arteries branch off from the aorta, blocking blood flow

In an aortic dissection, the inner layer (lining) of the aortic wall tears, and blood surges through the tear, separating (dissecting) the middle layer from the outer layer of the wall. As a result, a new, false channel forms in the wall.

Dissecting Aneurysms May extend from aortic valve to abdominal aorta Most common in thoracic aorta (Ascending 65 %) Dissection Classification: DeBakey system Type I - Originates in ascending aorta, propagates at least to the aortic arch and often beyond it distally. Type II – Originates in and is confined to the ascending aorta. Type III – Originates in descending aorta, rarely extends proximally but will extend distally

Sonographic Appearance Distinguishing characteristic: membrane that divides the vessel lumen into two compartments Membrane moves freely with arterial pulsations if both lumens are patent and membrane is thin Diameter in area of dissection usually larger than normal surrounding vessel

Causes of Dissection associated with hypertension up to 80 %. result of chest trauma Connective tissue disorders Marfan syndrome: genetic disorder of the connective tissue

Dissecting Aneurysm showing intimal flap

Pathophysiology of the Vascular System Pseudoaneurysm (false) Tear in the vessel wall Blood escapes into surrounding tissue They do not have a wall; surrounded by clot

Pseudoaneurysm Neck of the Pseudoaneurysm

To and Fro Doppler Waveform Biphasic

Pathophysiology of the Vascular System Abdominal Aortic Aneurysm (AAA) Usually found as a incidental finding from another imaging modality ie. CT Scan, U/S, Radiograph May present as a abdominal bruit Most common in males over the age of 50 Focal dilatation of the aorta; measures equal to or greater than 3cm in the AP diameter (outer wall to outer wall) 97% occur below the level of the renal arteries

Pathophysiology of the Vascular System AAA measurements 3-4 cm yearly follow up exam 5cm surgical consult >6cm risk of impending rupture Symptoms Usually asymptomatic Pulsatile mass and or pain in the back Dissecting AAA- excruciating chest pain that radiates to the back. 15% c/o no pain Ruptured AAA- excruciating abdominal pain, shock, and expanding abdominal mass

Risk of Rupture Risk of Rupture (5 year) 7 cm or larger : >75% < 5cm:3 % risk over 10 years Most expand at a rate of 2-4 mm/year

Rupture of AAA Acute: need immediate surgery > 50 % mortality rate Chronic: if leak is contained in surrounding tissue Demonstration of retroperitoneal hematoma = direct evidence of aortic rupture Sonographically hematoma is: Hypoechoic Unilateral or asymmetric May displace ipsilateral kidney

Acute Aortic Rupture Aortic rupture. Longitudinal color Doppler image of the abdominal aortic aneurysm demonstrates an active leak of blood (arrow) on the posterior aspect of the aorta (red color signal extending outside the lumen of the aorta). Hypoechoic areas (arrowhead), also secondary to the aortic rupture, are seen within the mural thrombus.

Chronic Ruptured Aneurysm Transverse image demonstrates rupture of an aortic aneurysm (red arrows) while the red arrowheads indicate the intact aortic wall.

Pathophysiology of the Vascular System Treatment Endograft Aortoiliac graft bypass Aortobifemoral graft bypass

Grafts can be anastomosed either end to end or end to side manner

Sonographically: Grafts are echogenic and have a textured appearance Aorto-bifemoral graft

Endograft Definition: a fabric covered metallic stent or “endograft” is inserted into an abdominal aortic aneurysm without making an incision on the abdomen an incision in the femoral artery at the level of the groin using x-ray while passing the device into the aneurysm stringent anatomical criteria must be met to allow for success iliac arteries too small or too atherosclerotic aorta above the aneurysm is too large

Transverse view of AAA (cursors) Color show two inferior ends of an endovacular stent in posterior aspect of aneurysm. Note: no color flow outside of stent

Aortoiliac/Aortobifemoral Bypass Definition: grafts are placed near a section of the blood vessel that is blocked or narrowed. The graft creates a path so that blood can move around the blockage. In this case the grafts are placed on the aorta and the iliac or femoral arteries Most bypass surgery involves a traditional, open incision

Sonographic Evaluation Document proximal and distal anastomosis for stenoses, aneurysm or pseudoaneurysm Document flow and velocity through the graft Document waveforms and velocities in vessels just beyond distal anastomosis Document any echogenic material within graft lumen(thrombus) Document any fluid collections in peri graft region

Graft Leak

Aorta Scan Procedure

Pathophysiology of the Vascular System Ultrasound Examination of the Aorta Patient must be in a basal state at least 6 hours prior to the study to reduce overlying bowel gas 3.5 5 MHz sector or linear transducer Longitudinal and transverse images of the aorta from the diaphragm to the iliac arteries must be obtained. The AP diameter must be measured in the longitudinal view

Scan Procedure AAA measurements: AP measurement in longitudinal and transverse views. Measure transverse diameter. Measurements are outer wall to outer wall. If AAA is found: obtain coronal views of right and left kidneys for renal length  check for renal artery involvement measure from SMA to aneurysm if origin of renal arteries cannot be visualized

Measurement of AAA Make sure vessel tortuosity does not cause Exaggerated measurement of AAA NOTE: deviation of tortuous aorta to left of spine—most common presentation

Measurement Aorta measurement in the coronal plane-outer to outer Aorta measurement in the transverse plane-outer to outer

Doppler Analysis Normal flow pattern: plug flow High resistive

Iliac Artery Aneurysm

Iliac Aneurysms 80-90% are in men over the age of 70 Most asymptomatic but rarely may thrombose, embolize or even rupture Usually found incidentally or in association with AAA (CT/ US/ MRI) Common iliac 10 x more common than internal Rarely occur in external Right twice as common than left Usually involve proximal or distal portion of vessel Rupture rare if less than 3cm

Iliac Artery Aneurysms Most associated with AAA Not associated called: Isolated Uncommon ½ rupture with vague abdominal or pelvic symptoms making mortality high—up to 60%

Pathophysiology of the Vascular System Arteriovenous Malformation Abnormal connection between the artery and vein High arterial pressure causes the blood to go directly from the arteries to the veins Can be congenital (rare), acquired (biopsy, trauma, surgical procedure, and ruptured aneurysm) or idiopathic Patients are usually asymptomatic but may present with hematuria, abdominal pain or bruit, HTN, and CHF

Pathophysiology of the Vascular System Ultrasound Findings of AVM A pseudoaneurysm may be seen Duplex Doppler evaluation will show a high turbulent velocity arterial-venous signal A peripheral thrombus may be seen

Great Vessels Inferior Vena Cava

Waveform Continuous waveform with respiratory variations; become more pulsatile as it empties into the right atrium. Best imaged with a slight cranial-caudal sweep in the longitudinal plane with the patient in deep inspiration Thrombosis can cause the IVC waveform to appear monophasic with high velocities ("choppy" appearance). Evaluate for thrombus in the renal veins as well. If a surgical shunt is present, be sure to check the patient's history to find out the specific type of shunt (portal/cava or mesenteric/cava) is in place

IVC Waveform demonstrating both respiratory and cardiac pulsations—Described as “saw-tooth”

IVC Location & Size The IVC is posterior to the main portal vein, caudate lobe and head of the pancreas The Right Renal Artery is posterior to the IVC IVC changes with respiration and valvsalva maneuver Upper limits of its normal diameter is 3.7cm during full inspiration Inspiration – increases in size Expiration – decreases in size Valsalva – increases in size

IVC Pathology

Pathology IVC Dilatation Occurs with Faulty tricuspid valve: allows blood to reflux through right atrium into IVC- Right Ventricular failure (CHF, hypertension) IVC fails to collapse with expiration Duplex Doppler evaluation can be helpful

IVC Dilatation 2-year history of congestive heart failure the inferior vena cava was enlarged (Fig. 2B) and failed to show any respiratory variations in diameter.

IVC Congenital Anomalies of the IVC Most occur at or below level of renal veins Often associated with other cardiac malformations Absence of the IVC is rare Major anomalies relate to the embryologic development at 6-10 weeks gestation Deviation from normal embryogenesis can result in: Duplication and Transposition

Duplication Duplication of the IVC A left IVC is present A right sided IVC is also present the left IVC usually is smaller than the right, although they can be equal in size the left IVC typically empties into the left renal vein and, subsequently, into the right IVC

Duplication of IVC Transverse lower abdominal scan demonstrates a left-sided IVC adjacent to the aorta in addition to a normal right sided IVc

Congenital Abnormalities Transposition of the IVC 0.2-0.5% IVC originates on the left side of the pelvis instead of the right; below the Renal Veins Drains into the Left Renal Vein and then crosses anteriorly over the aorta to a normal left sided upper IVC above the Renal Veins

Transposition Transverse abdominal CT image with enhancement of the left-sided inferior vena cava (in red).

IVC Tumors Tumors may involve the IVC in different ways: Extrinsic Compression- compression from an outside source Direct invasion from adjacent neoplasm Venous extension of tumor from a vein draining in to the IVC (renal cell CA) Primary tumor of the IVC wall Most common tumor is by extrinsic compression Hepatomas; adrenal; pancreatic head tumors lymphadenopathy

IVC Tumors Primary tumors are rare but is most likely to be leiomyosarcomas Appears as a large intraluminal mass with mid-level echoes on ultrasound Intravenous extensions (secondary tumors) are commonly seen with hepatomas and renal cell carcinoma Hepatomas invade the IVC and Right Atrium through the hepatic veins Renal Cell Carcinoma invades the IVC through the renal veins Primary tumor may be identified by following thrombus formation 76

IVC Tumor Thrombus

Thrombosis IVC Thrombosis May be partial or complete obstruction Compete is life threatening Patients present with leg edema, lower back pain, pelvic pain, renal and liver abnormalities Non-tumoral clots can extend from the iliacs or renal veins. Thrombus appears as a homogenous echogenic mass in the lumen of the IVC