Pathology of the Abdominal Arterial System Flashcards
Abdominal Aortic Aneurysm
A permanent localised dilation of an artery with an increase in diameter of greater than 1.5 times its normal diameter.
S & S - Mostly asymptomatic - Pulsating mass in the region of the umbilicus - Lower back & Abdo pain Sono Appearance - Wall irregularities - Dilation of the aorta > 3 cm (norm = 1.5cm) Causes - Atherosclerosis - Trauma - Congenital Defects
What are the causes of an Abdominal Aortic Aneurysm?
- Atherosclerosis main cause
- Trauma (after transection/injury)
- Congenital defects (aortic sinus, post-coarctation of the aorta, ductus diverticulum)
- Syphilis (involving the ascending aorta and arch)
- Mycosis (fungal dissection)
- Cystic necrosis (Marfan syndrome)
- Inflammation of tunica media and tunica adventitia (rheumatic fever, polychondritis, ankylosing spondylitis)
- Increased pressure (systemic hypertension, aortic valve stenosis, pregnancy)
- Abnormal volume load (severe aortic regurgitation or valve insufficiency)
Mural Thrombus
- Blood clot within lumen of the vessel (can be in veins or arteries)
- May be caused by change to lumen size (aneurysm or atherosclerosis) or changes to blood flow dynamics
- Sonographic appearance varies depending on age of thrombus, but is within the lumen, not including the intimal layer (may see it under thrombus)
S & S - Pain, swelling & tenderness. Sono Appearance - Blood clot in the lumen of the vessels - Varies depending on the age of the thrombus. - Common with larger aneurysms Causes - Change in lumen size. - Due to aneurysm or atherosclerosis
Atherosclerosis
- Thickening under intimal layer not in lumen of vessel
- Sonographic appearance vary - hypoechoic, hyperechoic, calcification, irregular, regular
S & S - Asymptomatic Sono Appearance - Low-level echoes in the lumen wall - Tortuosity & vessel wall calcifications Causes - Thickening under intimal layer - Unknown causes but linked to hypertension hyperlipidemia, smoking & diabetes mellitus.
Types of Aneurysms
True Aneurysms
- Saccular
- Fusiform
Dissection Aneurysm
False Aneurysm
Dissection Aneurysm
Aortic dissection is a serious condition in which there is a tear in the wall of the aorta
- As the tear extends along the wall of the aorta, blood can flow in between the layers of the blood vessel wall (dissection).
- This can lead to aortic rupture or decreased blood flow (ischemia) to organs.
S & S - Chest pain most common - Abdo, lower back, arm & leg pain Sono appearance - Thin, linear echo flap within arterial lumen. Colour Doppler will show fill. - Take a spectral Doppler trace; the correct one would show arterial flow heading towards the feet Causes - Tear extending along wall of aorta. - Hypertension - Cystic medial necrosis
Classification of AAA
- Suprarenal AAA
- Pararenal AAA
- Juxtarenal AAA
- Infrarenal AAA
Other Types of AAA
- Splenic AA
- Hepatic AA
- SMA AA
- Renal AA
- Iliac AA
Treatment of AAA
Size and treatment options:
- Aneurysms < 4 cm in diameter are followed every 6 months
- For aneurysms 4 to 5 cm in diameter, surgical intervention may be suggested
- Aneurysms > 5 to 6 cm in diameter, surgical intervention is recommended
- Aneurysms > 6 to 7 cm in diameter pose the greatest risk – why?
Complications of AAA grafts
Complications vary and may be hard to image in the acute time frame:
Pseudoaneurysms Graft aneurysms Haematomas Abscesses Occlusions
Inflammatory AAA
- 5% of all AAAs are inflammatory in origin
- May involve ureters with obstruction & flank pain
- More often in younger people
- Less likely to rupture
- Associated with backache & leg oedema
Ultrasound Presentation:
Aneurysmal dilatation with extremely thickened adventitia and hypoechoic surrounding fibrosis or rind of tissue around aorta with sparing of the posterior wall
Coeliac Trunk Stenosis
Acute occlusion or atherosclerotic disease with associated significant stenosis can lead to reduced or complete lack of blood flow to the hepatic, splenic, and left gastric arteries
SMA Stenosis
Mesenteric insufficiency results from lack of adequate blood supply to the intestinal tract due to underlying vascular compromise, either acute occlusion or atherosclerotic disease with associated significant stenosis.
Renal Artery Stenosis
Renal Artery Stenosis (RAS) is a significant health issue due to its association with uncontrollable hypertension.
High prevalence in smokers, and in people with poorly controlled hypertension, AAAs, diabetics, and cerebrovascular and coronary artery disease (CAD).
RAS at origin of renal artery:
Atherosclerotic plaque
RAS in distal renal artery:
Fibromuscular dysplasia
