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Aorta Pathology

Vascular Pathology

Aorta

  • The aorta is the largest artery in the body.

  • Originates at the left ventricle of the heart.

  • As it passes through the aortic hiatus of the diaphragm, it is referred to as the abdominal aorta.

  • Positioned retroperitoneally, anterior to the spine, just left of midline.

Atherosclerosis

Definition and Process

  • Atherosclerosis is a disease where arterial walls become thick and stiff due to plaque accumulation.

  • Plaque consists of fat, cholesterol, calcium, and other blood substances.

  • Over time, plaque hardens and narrows the arteries, limiting oxygen-rich blood flow to organs.

  • Accounts for 90% of abdominal aortic aneurysms.

Causes and Risk Factors

  • Contributing factors include:

    • Elevated blood pressure

    • High cholesterol and triglyceride levels

    • Smoking

    • Diabetes

    • Systemic inflammation due to diseases like arthritis or lupus

    • Family history of heart disease

    • Lack of exercise

Epidemiology

  • Most common cause of aneurysms (97%).

  • Typically occurs in persons over 50 years of age.

  • More prevalent in men (ratio 5:1).

  • Can affect the aorta and/or common iliac arteries, sometimes involving ascending and descending aorta.

Plaque Characteristics

  • Echogenicity Types:

    • Low: lipid

    • Moderate: collagen

    • High with shadow: calcification

  • Plaque appearance can be:

    • Smooth

    • Irregular

Ultrasound Appearance of Plaque

  • Types of Plaque:

    • Homogeneous echolucent

    • Homogeneous echogenic

    • Heterogeneous plaque (cauliflower-like calcification)

Abdominal Aortic Aneurysm (AAA)

Definition and Characteristics

  • An AAA is an abnormal widening of an artery due to weakness in the arterial wall.

  • Can form in any part but most commonly on the aorta wall.

Predisposing Factors

  • Common causes include:

    • Arteriosclerosis (most common)

    • Trauma

    • Congenital conditions

    • Marfan’s syndrome

    • Inflammatory conditions of the artery layers

    • Increased pressure (systemic hypertension)

    • Smoking

Clinical Symptoms

  • AAs can be asymptomatic and are often found during exams.

  • Symptoms include abdominal pain, which can radiate to back or flank, especially if expanding or ruptured.

Classification

  • True Aneurysm: involves all three tunica layers.

  • False Aneurysm: blood escapes between layers and they separate.

Shape of Aneurysms

  • Saccular Aneurysms:

    • Spherical, larger (5 to 10 cm)

    • More common in thoracic aorta.

    • Connected to vascular lumen by a neck.

  • Fusiform Aneurysms:

    • Most common type.

    • Gradual dilation affects the entire circumference of the artery.

Predisposing Factors for AAA

  • Cigarette smoking

  • Family history of AAAs

  • Older age

  • Peripheral vascular disease

  • Coronary artery disease

  • High cholesterol levels

  • Greater height

Sonographic Findings

  • Increased aortic diameter >3 cm (measured outer wall).

  • Focal dilation and lack of normal tapering distally (ectasia).

  • Thrombus along anterior or anterolateral wall, calcification appears as thick echogenic echoes with potential shadowing.

Pseudoaneurysm/Pulsatile Hematoma

Definition

  • Also known as a false aneurysm; occurs when arterial blood leaks into surrounding tissue, creating a communication with the originating artery.

Causes

  • Results from injuries to an artery, often noted in procedures, surgery, or trauma.

  • Common sites include the groin near the femoral artery post heart catheterization.

Characteristics

  • Forms a perivascular hematoma with swirling blood and a neck connecting to the artery.

  • Color Doppler flow shows turbulence within the mass, and spectral waveforms display high velocity, bidirectional "to-and-fro" signals.

Aortic Dissection

Definition and Emergency

  • A tear in the aortic wall allows blood to flow between layers, creating a false channel.

  • This condition is a medical emergency that can lead to rapid death even with proper treatment.

Symptoms

  • Intense chest pain, back pain, shock; some patients may be asymptomatic.

Causes

  • Frequently idiopathic, but linked to:

    • Hypertension

    • Marfan's syndrome

    • Trauma.

Diagnosis

  • Identification of two channels of flow using Doppler; a linear intimal flap may be noted swaying in the blood current.

Ruptured Aortic Aneurysms

  • Ruptures often intrude into the perirenal space, displacing renal vessels.

  • Commonly rupture at the lateral wall below renal arteries; hemorrhage can displace the kidney.

Symptoms

  • Classic symptoms include excruciating abdominal pain, shock, and an expanding abdominal mass.

  • Rupture operative mortality rate is between 40% and 60%.

Ultrasound Findings

  • Visualized as a heterogeneous mixed echogenicity mass.

Treatments for AAA

Options

  • Watchful Waiting:

    • For small AAAs (<5 cm) that are stable.

    • Requires regular follow-up ultrasounds to monitor growth.

  • Surgical Repair:

    • Involves longitudinal incision and graft insertion for blood flow continuation.

  • Interventional Repair:

    • Conducted via groin incision; catheter-guided stent graft placement into the aneurysm.

Renal Artery Stenosis

Definition

  • Decrease in renal artery diameter leading to restricted blood flow, resulting in renal failure or renovascular hypertension.

Demographics and Causes

  • More common in those aged 50 and older due to prevalent atherosclerosis in this age group.

Fibromuscular Dysplasia (FMD)

Definition

  • A condition leading to narrowing of the renal artery due to thickening of the tunica media, more common in women than men.

Treatment for Renal Artery Stenosis

  • Angioplasty and Stenting:

    • Involves catheter insertion to inflate a balloon, flattening plaque against arterial walls.

    • A metal mesh stent may be inserted to hold the artery open.