EXTRA CRANIAL ANEURYSMS

DR. MBIINE RONALD

OUTLINE

• Definition• Classification of aneurysms– Aortic aneurysms• Thoracic aorta• Abdominal aorta

– Carotid– Iliac– Popliteal

• Dissecting Aneurysms

Definition

• Permanent dilatation of a localised segment of an arterial system.

• Dilatation of arterial lumen by more than 50% of its luminal diameter.

• TRUE: – Localised dilatation of an arterial wall at a weakened area.

Involves all three layers of the arterial wall.• FALSE/TRAUMATIC:– Haematoma cavity communicating with the injured artery.

Contains a single layer of fibrous tissue as a wall of the sac.

TRUE ANEURYSMS

• Fusiform• Saccular• Dissecting

Dissecting aneurysm

• Dilatation of an artery formed by formation of a false channel between the intima and media by blood.

• Occurs when blood is forced through a ruptured flap of intima

Aetiology

• Degenerative: Atheromatous, most common aetiology• Traumatic• Infective: – Syphilitic– Mycotic(bacterial)– Tubercolosis

• Collagen diseases: Marfan’s syndrome, polyarteritis nodosa, Ehler-Danlos syndrome

• Congenital: Berry aneurysms

Pathogenesis

Clinical features

• Swelling exhibiting: – Pulsatile expansion – Smooth surface– Warm– Compressible– Swelling reduces in size when compressed

proximally– May have a thrill and systolic bruit

• Distal pulses have reduced volume compared to the contra-lateral pulses.

• Symptoms as a result of pressure on the surrounding structures.

Differential diagnoses

• Pyogenic abscess• Vascular tumours• Pulsating tumours: Sarcomas– Pulsating secondaries

• Pseudocysts of the pancrea• AV fistula

COMPLICATIONS

• Rupture • Pressure compression• Thrombosis• Ischaemia in the distal areas.

Investigations

• XRAY: – May show calcifications of the swelling and erosion of

subjacent bone.• USS:

– May confirm diagnosis• Duplex USS, Doppler USS• CT SCAN:

– Shows the size of the aneurysm.– CT Angiograms

• Investigations related to aetiology: RBS, lipid profile

Abdominal aortic aneurysm

• Commonest type of extra abdominal aneurysm.

• 2% population have aneurysms at autopsy• 95% rule: are atheromatous and lie below

renal arteries.• Symptoms dependent on size.– Discomfort and abdominal pain usual symptoms.

epidemiology

• Most patients between 45-85 years• Affects males more with ratios between 1:4 to

1:15 in M:F

Pathophysiology

• The aortic wall contains smooth muscle cell matrix, elastin, collagen. The elastin in the tunica media is the load bearing part, with collagen in the adventitia as a safe net to provide tensile strength.

• In the infra renal area, elastin is markedly reduced, the absence of vasa vasorum further compound this problem. The presence of atherosclerotic instability of this region cause the infra renal AA to be most prone to aneurysm formation.

• Aortic smooth muscles cells and macrophages produce the matrix metallo proteinases (MMP) and these cause proteolysis of the aortic medial wall with resultant elastin and collagen degradation and increase in diameter.

• Collagen degradation in the adventitia causes rupture.

Classified

• Asymptomatic• Symptomatic• Symptomatic ruptured

Asymptomatic AAA

• In case of an incidental finding of AAA, surgery is only done if diameter is >55mm

• Aneurysms less than 55mm,require regular follow up.

• Found during routine examination or USS

Symptomatic AAA (without rupture)

• Commonly present as back or abdominal pain• Groin or thigh pain due to nerve compression• Pressure symptoms• Rule of 80’s:– 80% of patients with AAA will be dead within a year

if they don’t have surgery.– 80% of patients with AAA will be alive if they have

surgery• Inflammatory aneurysm in 5%

• May present as an – Aortocaval fistula:• Presenting as high output cardiac failure• With continuous bruit in the abdomen• Severe lower limb ischaemia (Steal phenomenon)

– Aorto-enteric fistula:• Aneurysm erodes into the fourth part of the

duodenum.• Presents as GI bleeds.

• The risk of operation:• Hypertension• Chronic airway disease• Recent myocardial infarction• Impaired renal function

Complications

• Rupture• Infection• Thrombosis, with embolism• Distal ischaemia/gangrene• Aortocaval fistula• Aortoenteric fistula• Erosion of vertebra• Spinal cord ischaemia and thrombosis

DDX of an unruptured AAA

• Retroperitoneal mass• Pancreatic pseudocyst• Mesenteric ischaemia, acute pancreatitis and

perforated duodenal ulcer may mimic an AAA

Treatment plan

• Investigation– Blood investigations– Imaging• USS• CT• Angiography• Duplex USS

Non Surgical management

• For low risk AAA– Age below 70 years– No cardiac disease– Non inflammatory aneurysm– Diameter less than 5.5cm– If growth rate is less than 0.5cm/year

• Risk factor modification:– Quit smoking, alcohol– Control of BP, Elastase inhibitors e.g NSAIDS.

• Periodic size measurement using USS every 6months

Surgical management

• Indications for surgery:– Asymptomatic aneurysm greater than 5.5cm– Growth rate greater than 0.5cm/year– Painful and tender aneurysm– Thrombosed aneurysm, aneurysm with distal

emboli

Ruptured abdominal Aortic aneurysm

• 1% risk of rupture if diameter is >5.5cm• 20% risk if diameter is >7cm• 20% rupture anteriorly into peritioneal cavity.• 80% rupture posteriorly into retroperitioneal

space.• 50% mortality

Clinical features

• Absence of femoral pulses with a palpable mass in the abdomen.

• DX and treatment need to be rapid in order to achieve the best results.

• Typically pt has a tender palpable mass in setting of hypotension.

• Clinical diagnosis.• CT scan may have additional benefit if dx is in

doubt. USS not requirement to dx Ruptured AAA.

• Once dx is made;– IV large bore access is obtained.– Blood for grouping, xmatching– Fluid resuscitation. Target SBP should not exceed

100mmHg.– Urinary catheter is passed.– If patient is stable, surgery maybe defered until

crossmatched blood is availed. In the unstable, surgery is done even without blood.

• Treatment of ruptured aneurysm is Emergency surgery and not resuscitation and monitoring.

PRINCIPLES

• Early identification• Immediate resuscitation• Maintenance of systolic blood pressure• Urinary catheter• Cross match six units of blood• Rapid transfer to the operating room

Work up

• Full blood count • Electrolytes• Liver function tests• Coagulation tests and • Blood lipid estimation• Cross-match– if surgery is contemplated within a few days.

IMAGING

• CXR• ECG, ECHO• Isotope ventriculography• Pulmonary function• CT SCAN: Best for assessing aneurysm morphology.• MRI• Digital subtraction angiogram• Spiral CT scan

Surgical Approach

• Open Surgical method– Endo-aneurysmorrhaphy with intraluminal graft

placement.• Endoluminal procedure– Endovascular aneurysm repair(EVAR)– Aorta accessed via common femoral arteries which

are exposed surgically.– Under radiological control, delivery system guided into

aorta and an endovascular prosthesis is placed. Usually Dacron or PTFE.

Complications following surgery• Open Surgery:

– Respiratory:• Lobar consolidation• Atelectasis• Shock lung

– Cardiac:• Ischaemia• Infarction

– GIT:• Colonic ischaemia due to lack of collateral blood supply. • Occurs in 10% of cases.

– Renal failure– Infection of the graft– Haemorrhage– Graft leak

• Neurological:– Sexual dysfunction– Spinal cord ischaemia

• Aortoduodenal fistula– Rare but treatable– Suspect if haematemesis and melaena occur years

following surgery.• These complications are less in the minimally

invasive procedures.

• In the Endovascular technique– Endo leaks may occur.– Prosthetic migration– Thrombosis– Rupture

• 20% of patients need a secondary procedure to correct the endoleaks or prosthetic migration, thrombosis or rupture.

THORACIC ANEURYSMS

• Classified into:– Ascending aortic aneurysms– Aortic arch aneurysms– Descending aortic aneurysms– Thoraco-abdominal aneurysms

• Hypertension most implicated risk factor.• Atherosclerosis is an aetiological factor• 20% have concurrent AAA

PERIPHERAL ANEURYSMS

• Popliteal aneurysms:– 70% of all peripheral aneurysms– 2/3 bilateral– 1/3 accompanied by abdominal AA

Presentation

• Popliteal aneurysms present as a swelling behind the knee or

• May also present with symptoms caused by complications, such as – severe ischaemia following thrombosis or – distal ischaemic ulceration as a result of emboli.– Such symptomatic aneurysms require urgent

surgery with/out intra-arterial thrombolysis

• Asymptomatic popliteal aneurysms require elective surgical intervention to prevent future development of symptoms.

• Surgery necessary if aneurysm exceeds 25mm• Imaging involves:– USS– CT Scan

• Management:– Inlay graft– Bypass with ligation of the aneurysm

• Femoral aneurysms– Uncommon– Usually treated conservatively after ruling out

other synchronous aneurysms• Iliac aneurysms– Usually associated with aortic aneurysms– Operation is indicated, with bypass and exclusion

of the aneurysm by ligation above and below the dilatation.

Carotid artery aneurysms

• Less than 4% of peripheral aneurysms• Common site is the Common carotid artery bulb.• 10% bilateral• Swelling in neck at level below mandible• May have horners syndrome• DDX:– Carotid body tumour– Neck abscess– Neurofibroma from the vagus nerve

Arterial venous fistula

• May be traumatic, surgically created or congenital

• The veins undergo arterialisation (thickening of the wall) with dilatation of the lumen and development of a tortuous pattern.

• These may have an effect on the cardiac output if they are large.

• May present as a pulsatile swelling with detectable bruit as well as machinery murmur.

• Proximal compression causes collapse of the swelling.

• Duplex scan and angiography confirms the lesion with fast venous filling

Management of arteriovenous fistula.

• Embolisation is the best treatment mordality• Surgery done for severe deformity or serious

haemorrhage.• Ligation of feeding artery on its own not

adequate

DISSECTING ANEURYSMS

• Not an aneurysm but an aortic dissection. Occurs through the media of the aorta after splitting through the intima.

• Aetiology:– Hypertension– Cystic medial necrosis– Marfan’s syndrome– Trauma

• Always seen in the thoracic aorta, common in the ascending aorta(70%)

• May open distally to form a double barrel aorta.

Presentation

• Severe chest pain• Features of ischaemia due to blockage of

different vessels• TREATMENT:– Antihypertensives– Surgery:• Dacron graft reconstruction of the aorta under

cardiopulmonary bypass.

END