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    Abdominal Aortic Aneurysm

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    Dec.30.2024

    Abdominal Aortic Aneurysm

    Synopsis

    Key Points

    • Abdominal aortic aneurysm is focal dilation (diameter greater than 3 cm) of the abdominal aortic artery involving all layers of the wall
    • Modifiable risk factors include smoking, hypertension, elevated cholesterol level, obesity, and preexisting atherosclerotic occlusive disease r1r2r3
    • Screening and early detection are paramount in reducing rates of mortality associated with rupture
      • Many abdominal aortic aneurysms are asymptomatic until they become unstable and rupture
    • Serial surveillance by ultrasonography is necessary to evaluate for aneurysm enlargement
    • Symptoms of instability and rupture can progress rapidly or gradually, depending on whether weakness in wall extends anteriorly into the abdominal cavity (rapidly fatal) or dissects posteriorly into the retroperitoneum (slower)
    • Upon rupture, estimated mortality is greater than 80% r4
    • Surgical or endovascular aneurysm repair is indicated in patients with aneurysm diameters greater than 5.5 cm for males and 5 cm for females who are expected to have long-term benefit from intervention r5

    Urgent Action

    • There must be no delay in admitting patients for emergent operative repair when symptoms associated with impending rupture occur

    Pitfalls

    • Do not rely on clinical examination to exclude abdominal aortic aneurysm r6
    • Avoid delay in referral of symptomatic patients for emergent vascular surgery evaluation r7

    Terminology

    Clinical Clarification

    • Abdominal aortic aneurysm is focal dilation (diameter greater than 3 cm) of the abdominal aorta involving all layers of the wall

    Classification

    • By location
      • Infrarenal
        • Aneurysm originates below the renal arteries
      • Juxtarenal
        • Aneurysm originates at the level of the renal arteries (renal arteries arise from normal aorta)
      • Pararenal
        • Aneurysm involves the aorta at the level of the renal arteries (renal artery originates from an aneurysmal aorta)
      • Suprarenal
        • Aneurysm originates above the renal arteries
    • By size and rupture risk
      • Precise risk modeling is multivariate,r8r9 but size provides a useful clinical guide
      • Data from various studies support estimates as follows: r10
        • Small (3-3.9 cm)
          • No risk of rupture
        • Medium (4-4.9 cm)
          • Rupture risk is 1% per year
        • Large (5-5.9 cm)
          • Rupture risk is 5% to 10% per year
        • Very large (6-6.9 cm)
          • Rupture risk is 10% to 20% per year
        • Giant (7-7.9 cm)
          • Rupture risk is 20% to 40% per year
        • Greater than 8 cm
          • Rupture risk is 30% to 50% per year
    • By shape
      • Factors in decisions regarding timing and approach to operative repair r11
        • Fusiform
          • Involves all 3 layers of the arterial blood vessel wall; dilation involves the entire circumference of the aorta
        • Saccular
          • Involves all 3 layers of the arterial blood vessel wall, but the dilation is only on 1 side; relatively rare compared with fusiform type
          • Considered to present a higher risk of rupture than fusiform type, often prompting elective repair at smaller sizes than for fusiform
        • Pseudoaneurysm
          • Enlargement of only the outer layer of the blood vessel wall
    • By clinical presentation
      • Asymptomatic abdominal aortic aneurysm
        • Identified as a result of screening, routine physical examination, or on imaging studies for an unrelated condition
      • Symptomatic abdominal aortic aneurysm r12
        • Presents with abdominal and/or back pain, tenderness of the aneurysm on palpation, or embolic events, but without breach of the aortic wall
      • Ruptured abdominal aortic aneurysm r12
        • Acute hemorrhage from the aneurysm outside the true aortic wall with retroperitoneal and/or intraperitoneal blood
        • If hematoma is temporarily sealed by the retroperitoneum, this is known as a contained ruptured abdominal aortic aneurysm

    Diagnosis

    Clinical Presentation

    History

    • Presence and severity of symptoms depend on size and stability of aneurysm
    • Intact aneurysms are usually asymptomatic and may be discovered at screening or as an incidental finding r6r12c1
      • Approximately 90% of aneurysms identified by routine screening are 5.5 cm or smaller r13
    • Symptoms, if present, generally start when aneurysm is 4 cm or larger; symptoms include:
      • Early satiety c2
      • Nausea/vomiting c3c4
      • Urinary symptoms of bladder compression and irritation c5
      • Pain or tenderness localized to the region of aneurysm or radiating to the back or genitals r12
      • Lower limb swelling r12
    • As aneurysm becomes large and unstable, symptoms may become more prominent
      • Abdominal, flank, back, groin, or scrotal pain c6c7c8c9
      • Ripping sensation in the back c10
      • Lower extremity pain, coolness, paralysis, and paresthesia c11c12c13c14
      • Syncope may be first symptom of unstable or rupturing aneurysm c15
      • Symptoms depend on whether aneurysm is weakening anteriorly or dissecting posteriorly into retroperitoneum
    • Aneurysm rupture may result in cardiovascular collapse, abdominal and/or back pain, and abdominal distension r12
      • As many as 65% of patients with rupture die of sudden cardiovascular collapse before reaching the hospital r14c16

    Physical examination

    • Most aneurysms are small, asymptomatic, and detected as incidental findings via ultrasonography or CT scan r6c17
      • Approximately 30% of asymptomatic aneurysms are detected by a health care provider during routine physical examination r6
    • Abdominal midline pulsatile mass may be palpable c18
      • Careful abdominal examination by an experienced diagnostician can identify a pulsatile abdominal mass in the 3- to 3.9-cm range 29% of the time r6c19
      • Aneurysms larger than 5 cm are palpable 76% of the time r15c20
      • Sensitivity of this sign decreases with increasing BMI
    • Prominent popliteal pulses may be present c21
      • 15% of patients have coexisting popliteal aneurysm c22
    • Abdominal bruit may be present c23
    • As aneurysms become unstable, signs associated with complications of aneurysmal leakage and instability, including intraperitoneal hemorrhage and decreased perfusion to lower extremities, may be present
      • Turner sign (flank ecchymosis) indicates retroperitoneal hemorrhage c24
      • Femoral and popliteal pulses may be asymmetric or absent c25c26c27c28
      • Pallor, cyanosis, and skin mottling coincide with decreased perfusion c29c30
      • Embolic phenomena resulting in livedo reticularis and painful blue toes c31c32
      • Hypotension
        • Blood pressure may remain consistently elevated until late in progression of dissection c33c34
    • Shock with unstable vital signs

    Causes and Risk Factors

    Causes

    • Aneurysm formation is multifactorial involving arterial wall inflammation, smooth muscle apoptosis, and collagen matrix protein degradation c35
      • Atherosclerosis may also play a role or may result from arterial wall degradation c36
    • Abdominal aortic aneurysms progressively dilate over time

    Risk factors and/or associations

    Age
    • Incidence rises rapidly after age 60 years in males and 70 years in females c37c38c39c40
    • Affects 8% of males older than 65 years r16
    Sex
    • Males are 6 to 10 times more likely than females to have an abdominal aortic aneurysm r4c41c42
    • Abdominal aortic aneurysms tend to be more aggressive with more rapid expansion and have a higher tendency to rupture at smaller diameters in females r17
    Genetics
    • Genetic syndromes associated with abdominal aortic aneurysmr4 are as follows:
      • Ehlers-Danlos syndrome r18c43
        • Spectrum of arterial and venous anomalies, including progressive aneurysm formation with spontaneous vascular dissection and rupture
      • Marfan syndrome r19c44
        • Patients with Marfan syndrome are more likely to have thoracic aortic aneurysms but can also develop abdominal aortic aneurysms
        • Those with true abdominal aortic aneurysms tend to be younger and have short life expectancy
    • Multiple common single nucleotide polymorphisms have been implicated in development of abdominal aortic aneurysm r20
    Ethnicity/race
    • More frequent in White populations compared with Hispanic or African American populations r7c45c46c47c48

    Other risk factors/associations

    • Smoking r21
      • Strongly associated with development of abdominal aortic aneurysm r2
      • Smokers are 7.6 times more likely to have an abdominal aortic aneurysm than nonsmokers c49
      • Current smoking is associated with more rapid aneurysm growth and increased risk of rupture r20
    • Family history r20
      • Approximately 20% of first-degree relatives of a patient with an abdominal aortic aneurysm develop one as well r7c50
      • Aneurysms tend to rupture at smaller diameters in patients with family history of disease c51
    • Obesity r1c52
    • Atherosclerotic occlusive disease (coronary heart disease, peripheral artery disease) r3c53
    • Hypertension r20
    • Sedentary lifestyle is a risk factor for progression c54
    • History of both smoking (20 or more pack years) and premature menopause increases risk of abdominal aortic aneurysm in females r20
    • Chlamydophila pneumoniae has postulated but unconfirmed role in development r20r22
    • Fluoroquinolone use has been linked to development of aortic aneurysm or dissection; however, this association is now believed to be due to confounding r12
    • Patients with diabetes have slower abdominal aortic aneurysm growth rate than patients without diabetes, which may be related to protective effect of metformin treatment r12
    • Moderate alcohol consumption may have protective effect against development of abdominal aortic aneurysm r23
    • Risk factors associated with abdominal aortic aneurysm rupture generally overlap with those associated with development of abdominal aortic aneurysm and include: r7
      • Large baseline aneurysm diameter
      • Rapid expansion
      • Tobacco use
      • Hypertension
      • Elevated arterial wall stress
      • History of cardiac or kidney transplant
      • Decreased forced expiratory volume
      • Female sex

    Diagnostic Procedures

    Primary diagnostic tools

    • Suspect diagnosis based on history and physical examination findings c55
    • Diagnosis is confirmed with abdominal imaging
      • Ultrasonography is the imaging modality of first choice for asymptomatic patients with suspected abdominal aortic aneurysm based on risk factors, abdominal palpation, or a prior imaging study r6r7r12
        • Most widely studied and used imaging tool for evaluating abdominal aortic aneurysm r24c56
        • Very accurate and sensitive; avoids ionizing radiation
      • Contrast-enhanced abdominal CT scan is recommended for symptomatic patients with suspected abdominal aortic aneurysm who are hemodynamically stable r24c57
        • Accurate and sensitive for diagnosis of abdominal aortic aneurysm
        • Differentiates ruptured from nonruptured aneurysm and excludes other abdominal conditions as a cause for symptoms
      • Patients with suspected ruptured abdominal aortic aneurysm should undergo prompt imaging of the thoracoabdominal aorta and its access vessels with abdominal CT angiography, if sufficiently stable r12c58
        • Recommended modality for confirmation of rupture and to determine if patient is a candidate for emergency endovascular repair r7r12c59
      • Hemodynamically unstable patients may go directly to the operating room for emergency open aneurysm repair or intra-operative imaging for confirmation of the diagnosis and determination of the suitability for endovascular repair
    • Additional evaluation for patients diagnosed with abdominal aortic aneurysm
      • Laboratory testing
        • Initial laboratory tests in symptomatic patients may include CBC electrolytes, BUN, and creatinine
        • Laboratory tests in patients presenting with hemodynamic collapse may also include liver function tests, coagulation studies, fibrinogen, arterial blood gases, lactate level, and cardiac enzymes
      • Genetic testing
        • Recommended for patients with abdominal aortic aneurysm diagnosed at age younger than 60 years, family history of aneurysms, or physical features associated with genetic syndromes r12
      • Abdominal CT angiography is recommended for treatment planning once the diameter threshold for elective abdominal aortic aneurysm repair has been met on ultrasound r12
        • Relative to ultrasonography, considered slightly more accurate at determining aneurysm diameter r24

    Imaging

    • Abdominal aortic aneurysms are often discovered incidentally by imaging done for other reasons
    • Diagnostic accuracy depends on the size, stage, and stability of the aneurysm
      • Ultrasonography c60
        • 95% sensitivity and 100% specificity for detecting abdominal aortic aneurysm in asymptomatic patientsr25
        • Does not require contrast medium or radiation
        • Imaging may be suboptimal in patients with obesity
        • Focused abdominal sonographic findings in trauma examination will show blood from aneurysmal rupture in dependent areas of the abdomen
          • Indicated for unstable patients to direct to either immediate surgical repair (positive focused abdominal sonographic findings in trauma) or CT angiography (negative or equivocal focused abdominal sonographic findings in trauma)
          • Cannot exclude retroperitoneal aneurysmal dissection
        • In stable patients, not sufficiently precise for procedural planning
      • Abdominal CT angiography c61
        • Provides better detail and definition of abdominal structures than ultrasonography
          • Useful for poor-quality or indeterminate ultrasonography results
          • Useful pretreatment planning
        • Requires iodinated contrast medium and radiation
        • Features of an impending rupture that can be seen on CT scan include the following: r26
          • Periaortic blood
          • Hemorrhage into a mural thrombus
          • Peripheral crescent-shaped attenuation within the aneurysm
          • Increased size (assuming a comparison study is available)
      • Magnetic resonance angiography c62
        • Higher cost compared with CT angiography and ultrasonography
        • Does not require radiation
        • Contraindicated for patients with metal clips or pacemakers
        • For preintervention studies, may be substituted if CT cannot be performed r27
        • Can be obtained without the use of IV contrast, making it an option for patients with advanced chronic renal disease r24

    Differential Diagnosis

    Most common r16

    • Mesenteric ischemia c63d1
      • Thromboembolic interruption of arterial flow causing intestinal hypoperfusion
        • Patient complains of abdominal pain out of proportion to signs and symptoms
          • Arterial thrombosis c64
            • Pain onset is gradual (progressively worsening) with postprandial exacerbation of pain
          • Arterial embolism c65
            • Pain onset is acute, severe, and unrelenting
      • Differentiated by CT angiography
    • Ureteral calculus c66d2
      • Acute, severe pain in back, flank, or abdomen
        • Cannot differentiate from dissecting retroperitoneal aneurysm on clinical grounds alone
      • Differentiated by CT imaging, preferably without contrast medium on initial phase
        • Ultrasonography shows hydronephrosis in the case of obstructing renal calculus but does not rule out unstable/dissecting abdominal aortic aneurysm
    • Diverticulitis c67d3
      • Pain commonly located in left lower quadrant of abdomen or left flank
        • Typically, slower onset of pain (over 1-3 days) accompanied by low-grade fever and inflammatory peritoneal signs
      • Differentiated by CT imaging with IV and oral contrast medium
    • Pancreatitis c68d4
      • Can produce severe midabdominal pain radiating to central back d5
        • Often accompanied by nausea and vomiting
      • Typically slower onset of epigastric pain (over hours or days)
      • Differentiated by CT imaging with IV contrast medium
    • Peptic ulcer disease/perforated ulcer c69c70d6
      • Can produce severe midabdominal pain radiating to central back
        • Typically slower onset and progression of symptoms (over hours or days)
          • Bloody emesis and bowel movements accompany pain
      • Differentiated by CT imaging with IV contrast medium

    Treatment

    Goals

    • Limit aneurysm growth and reduce risk of rupture
      • Monitor and electively repair stable aneurysms once size threshold for intervention is reached
    • Ruptured or dissecting aneurysms require immediate surgical stabilization and repair regardless of size

    Disposition

    Admission criteria

    Ruptured and dissecting abdominal aortic aneurysm can cause death within seconds or minutes

    • There must be no delay in admitting patients for emergent operative repair when symptoms associated with impending rupture occur

    Patients with very large (6.0 cm or larger in diameter) asymptomatic abdominal aortic aneurysm may warrant admission and inpatient evaluation for urgent repair owing to high risk for rupture

    Criteria for ICU admission
    • Postoperative recovery after surgical or endovascular repair
    • If repair of symptomatic abdominal aortic aneurysm is delayed to optimize coexisting medical conditions, monitor patient in an ICU setting, with blood products available r7

    Recommendations for specialist referral

    • Refer patients to vascular surgeon for consultation at time of initial diagnosis with abdominal aortic aneurysm r7

    Treatment Options

    Emergency management for ruptured and symptomatic (nonruptured) abdominal aortic aneurysm

    • Immediately transfer hemodynamically unstable patients with ruptured abdominal aortic aneurysm to operating room for emergency repair of the aneurysm r12
      • Delayed volume resuscitation (permissive hypotension) until surgical control of bleeding is achieved is associated with improved outcomes
      • Unstable patients may be considered for aortic balloon occlusion under fluoroscopy guidance to obtain proximal control of bleeding while undergoing open or endovascular repair
      • Endovascular aneurysm repair is recommended as the first line option for treatment of ruptured abdominal aortic aneurysm in patients with suitable anatomy r7r12
        • Meta-analysis reported no difference in 30-day mortality between emergency endovascular aneurysm repair and open repair r28
        • Emergency endovascular aneurysm repair is associated with a long-term survival benefit and lower rate of complications compared with open surgical repair r12
    • Urgent or emergency repair of the aneurysm is generally indicated for patients with symptomatic (nonruptured) abdominal aortic aneurysm
      • Symptoms are a harbinger of rupture, and patients should be closely monitored until repair is completed
      • Some patients may benefit from delayed repair in order to first optimize of their medical status r29

    Management of asymptomatic abdominal aortic aneurysm

    • All patients with abdominal aortic aneurysms should receive cardiovascular risk factor management
      • Strongly recommend smoking cessation; this is the most important intervention r7d7
      • Encourage weight loss if patient has obesity
      • Promote physical activity and healthy diet
      • Use statins, antihypertensive drugs, and antiplatelet therapy as appropriate r7r30
        • Guidance for use of such therapies and therapeutic targets is provided in recent multidisciplinary clinical practice guidelinesr31r30r32r33r34
        • 5-Year survival rate is better in patients receiving these agents compared with rates in patients not receiving each therapy, respectively: r35
          • Statins: 68% versus 42%
          • Antihypertensives: 62% versus 39%
          • Antiplatelet drugs: 62% versus 39%
        • A 2021 systematic review indicated a beneficial effect of statins on long-term survival in patients after abdominal aortic aneurysm repair r36
      • There are currently no medications indicated for the sole purpose of reducing risk of abdominal aortic aneurysm expansion and rupture r7
        • Many classes of medication, including metformin, statins, β-blockers, ACE inhibitors, angiotensin receptor blockers, and antibiotics, have been evaluated for their potential to limit aneurysm progression and risk of rupture, but none have been shown to provide benefit in large randomized trials r20r21
          • Metformin is associated with reduced risk of abdominal aortic aneurysm growth and rupture in observational studies and is being evaluated in RCTS r20
    • Observe small asymptomatic aneurysms with diameters up to 5.5 cm in males and 5 cm in females r5r12r37
      • Small aneurysms (less than 5.5 cm in males and 5 cm in females) can rupture, and risk of death from treatment-related mortality is less than that from rupture; however, rupture risk is low for small aneurysms without other risk factors
        • A 2020 Cochrane Review reported no evidence existed of an advantage to early repair for small abdominal aortic aneurysm (4-5.5 cm) r38
        • Optimal treatment thresholds for females are not well defined, and treating females at a lower size threshold has not been shown to have a mortality benefit r17
      • Patients can be advised that it is not necessary to restrict exercise or sexual activity; use of fluoroquinolone antibiotics is not contraindicated if required r12
      • Patient fitness to drive is based on aneurysm size and varies between countries
      • Additional guidelines have been published by National Institute for Health Care and Excellence r39
    • Elective surgical or endovascular repair
      • For most patients in good health, elective surgical or endovascular repair can be considered for aneurysms with diameters larger than 5.5 cm in males and larger than 5 cm in females r5r12
        • There is a lack of high-quality evidence supporting these thresholds r12
        • It is essential to select patients who are expected to have a long-term benefit from elective intervention
      • The following circumstances may reinforce need for repair of smaller-diameter lesions:
        • Onset of symptoms (most commonly pain in abdomen, back, or flank) r7
          • Symptoms are a harbinger of rupture and require immediate referral and treatment
        • Accelerated expansion, regardless of absolute size
          • Anecdotally, expansion of diameter by more than 0.5 cm in 6-month period (or larger than 1 cm/year) is associated with increased risk of rupturer12
          • However, apparent rapid aneurysm growth may be secondary to measurement errors: first step is to repeat the measurement r12
          • There is evidence that continued imaging surveillance is safe regardless of growth pattern r12
        • Presence of a saccular aneurysm (most are fusiform)
          • Associated with a greater risk of rupture
      • Choice of open versus endovascular surgical repair
        • Decision regarding type of procedure should be individualized—based on age, overall health, anatomic features, and patient preference
          • Society for Vascular Surgery recommends calculation of perioperative risk score to aid in decision-making;r7Vascular Quality Initiative scoring toolr40 is available online
          • European Vascular Society guidelines recommend endovascular abdominal aortic aneurysm repair for most patients with suitable anatomy and reasonable life expectancy r12
            • Endovascular aneurysm repair has lower 30-day procedural morbidity and mortality, but no long-term mortality difference exists between endovascular aneurysm repair and open aneurysm repair r41r42c71
              • Elective endovascular repair has increased re-intervention rates and late aneurysm-related mortality r43
            • For patients with comorbid advanced chronic renal insufficiency and oxygen-dependent chronic obstructive pulmonary disease, endovascular aneurysm repair outcomes are superior to those achieved with contemporary open repair, particularly when it is performed under local or regional anesthesia r7
          • Open surgical repair may be preferred for younger patients with longer life expectancy as endovascular aneurysm repair has an increased rate of complications occurring after 8 to 10 years r12

    Drug therapy

    • Statins r44
      • For secondary prevention of atherosclerotic disease, use high-intensity statins for adults aged 75 years or younger (achieves greater than 50% reduction in baseline LDL cholesterol level) r32
      • Atorvastatin c72
        • Atorvastatin Calcium Oral tablet; Adults: 80 mg PO once daily. May decrease dose to 40 mg PO once daily if unable to tolerate the higher dose.
      • Rosuvastatin c73
        • Rosuvastatin Calcium Oral tablet; Adults: 20 or 40 mg PO once daily.

    Nondrug and supportive care

    Smoking cessation r2

    • Can reduce risk of abdominal aortic aneurysm formation and progression c74
    • Evidence-based strategies include nicotine replacement products, pharmacotherapy (eg, bupropion, varenicline), and counseling c75c76c77c78c79

    Aerobic exercise c80

    • Prolonged sedentary lifestyle may promote abdominal aortic aneurysm progressionr45c81c82
    Procedures
    Open or laparoscopic surgical repair c83c84
    General explanation
    • Removes dilated section of abdominal aorta and replaces it with synthetic graft material
      • Discharge is typically 4 to 9 days after procedure
      • Normal activity can be resumed in about 4 weeks
    Indication
    • Aneurysm 5.5 cm or larger in males
    • Aneurysm 5 cm or larger in females
    • Symptomatic aneurysm of any size
    Contraindications
    • Uncorrected coagulopathy
    Complications
    • Perioperative mortality is 5% for elective repair r16
    • Ischemic colitis and spinal cord ischemia are common postoperative complications
    Endovascular aneurysm repair c85
    General explanation
    • Aneurysmal section of aorta is not replaced. A stent is placed inside aneurysm via femoral artery cannulation
    • Procedure involves incision into the groin to expose femoral artery
    • A catheter is threaded into aorta under radiographic fluoroscopic guidance
      • A stent graft is placed into the aneurysm, and a balloon is inflated to stabilize the aorta
    • Blood flows through graft instead of dilated aorta
    • Typically reserved for infrarenal abdominal aortic aneurysms with sufficient normal aorta above graft to allow for anchoring without occluding renal arteries
    • Evidence suggests that for repair of ruptured abdominal aortic aneurysms, endovascular repair and open surgical repair produce similar outcomes, complication rates, and 30-day mortality rates r28
    • Evidence suggests no long-term mortality benefit exists compared with open surgical repair r46
    Indication
    • Aneurysm 5.5 cm or larger in males
    • Aneurysm 5 cm or larger in females
    • Symptomatic aneurysm of any size
    Contraindications
    • Uncorrected coagulopathy
    • Anatomically unfavorable aneurysms

    Complications

    • Grafts occasionally leak into excluded aneurysm sacs, requiring urgent reintervention in some cases
    • Perioperative mortality (1%-2%) is lower than for open repair; however, midterm and long-term data proving an all-cause mortality benefit are lacking
      • Approximately 20% to 30% of patients who undergo endovascular repair require secondary intervention within 6 years
    • Ischemic colitis and spinal cord ischemia are common postoperative complications

    Comorbidities

    • Other cardiovascular diseases c86
      • In patients with abdominal aortic aneurysm between 4 and 5.5 cm in diameter, only 16% of deathsr47 were due to rupture or repair, whereas over 50% were caused by other cardiovascular diseases (mostly myocardial infarction and stroke) c87c88
        • Hypertension frequently coexists in patients with abdominal aortic aneurysm c89
          • Cause-and-effect relationship has not been convincingly established
            • Manage and control hypertension to minimize shearing effect on abdominal aortic aneurysm wall and risk of aneurysm rupture, as well as occurrence of other cardiovascular events (eg, myocardial infarction)
        • Atherosclerosis frequently coexists with abdominal aortic aneurysm c90
          • Cause-and-effect relationship is firmly established
          • Management is indicated to minimize risk of rupture and occurrence of other cardiovascular events (eg, myocardial infarction, cerebrovascular accident)
    • Lower extremity aneurysm c91
      • 15% of patients have popliteal aneurysm r48c92
      • Test for popliteal aneurysm using ultrasonography if physical examination finds prominent popliteal pulse

    Monitoring

    • Ultrasonographic surveillance
      • Follow abdominal aortic aneurysms with repeated sonography at specified intervals, according to size
        • Greater than 2.5 cm but less than 3 cm r7r12
          • Repeat sonography after 5 to 10 years c93
        • 3 to 3.9 cm r7r12r49
          • Repeat sonography every 3 years c94
        • 4 to 4.4 cm (females) or 4.9 cm (males) r7r12r49
          • Repeat sonography annually c95
        • 4.5 cm or greater (females) or 5 cm (males) r7r12r49
          • Repeat sonography every 6 months c96
        • Refer patients with abdominal aortic aneurysms to a vascular subspecialist for treatment when larger than 5 cm in females and larger than 5.5 cm in males r5c97
      • Discontinue surveillance in patients with small abdominal aortic aneurysms who are either not expected to reach the threshold for repair within their life expectancy or are not candidates for repair r12
    • Follow up after aneurysm repair r49
      • Non–contrast-enhanced CT of entire aorta is recommended at 5-year intervals after aneurysm repair (either endovascular or open) r7c98
    • Monitor and control blood pressure and fasting serum lipid values r30c99c100

    Complications and Prognosis

    Complications

    • Aneurysm rupture c101
      • Size and expansion rate are greatest predictors of rupture
      • Aneurysm size greater than 8 cm has a 30% to 50% risk of rupture r10
      • Upon rupture, estimated mortality is greater than 80% r4
      • Expansion is more rapid in smokers
    • Arterial embolism c102
      • Cholesterol plaques and thrombotic material embolize off the aneurysmal wall and cause interruption of arterial blood flow distally
    • Hydronephrosis c103
      • From aneurysm compression on ureter (typically left side)
        • Pain is more common in lumbar area
      • Ureter becomes compressed in approximately 20% of aneurysms
    • Infected (mycotic) aneurysm c104
      • Bacterial infection of aneurysm
      • Suggested by fever and other systemic manifestations of infection
      • Exceedingly poor prognosis with or without surgical repair r50
    • Aortoenteric fistula c105
      • Communication develops between inflamed aortic aneurysm and portion of intestine
        • Sentinel bleed occurs when blood from aorta enters gastrointestinal tract for a brief period, then stops
          • Period of time between sentinel bleed and exsanguinating gastrointestinal bleed is variable (anywhere from 5 hours to 5 months) r51
      • May be secondary to abdominal aortic aneurysm repair
      • Any patient with history of abdominal aortic aneurysm repair presenting with gastrointestinal bleeding requires immediate CT angiography to investigate for aortoenteric fistula r52

    Prognosis

    • For patients with large aneurysms, the annual rupture rate was 3.5% in aneurysm diameter of 5.5 to 6.0 cm, 4.1% in those with diameter of 6.1 to 7.0 cm, and 6.3% in those larger than 7 cm diameter r12
    • Without immediate repair, ruptured abdominal aortic aneurysm is almost always fatal; even with repair, the estimated mortality is greater than 80% r4
    • Emergency open repair for ruptured or symptomatic aneurysms has 30-day mortality of 29.9%: mortality rates are lower after endovascular repair r43
    • Following elective abdominal aortic aneurysm repair, average survival is about 9 years r12
    • Elective open repair has a 30-day mortality of 2.5%; elective endovascular repair has lower early mortality but increased re-intervention rates and late aneurysm-related mortality r43
    • Survival at 1 year after elective open repair was 72% compared with 46.7% after emergency repair; however, there was no significant difference in survival at 10 years r43
    • Mortality is higher among females compared with males, and risk of rupture is higher at smaller diameters; outcomes for elective aneurysm repair are also worse in females r17
      • 13% to 20% of females with abdominal aortic aneurysm experience rupture at diameters of 5.5 cm or less compared with 5% to 12% of males
    • Cardiovascular and pulmonary disease are leading causes of early and late death after both open surgical and endovascular aneurysm repair r7
    • Nonmodifiable prognostic risk factors associated with poor patient survival after elective repair include end-stage renal disease and chronic obstructive pulmonary disease requiring supplementary oxygen r53

    Screening and Prevention

    Screening

    At-risk populations

    • Screening recommendations vary between organizations
    • US Preventive Services Task Force recommends performing sonography 1 time to screen males aged 65 to 75 years with history of tobacco use r13c106
      • Clear linear dose-response relationship exists between development of abdominal aortic aneurysm and duration of smoking r2
        • Each year of smoking increases relative risk of abdominal aortic aneurysm by 4% r2
    • US Preventive Services Task Force recommends selectively offering screening sonography in males aged 65 to 75 years who have never smoked rather than routinely screening all males in this group r13c107
      • Consider the balance of benefits and harms based on evidence relevant to the patient's medical history, family history, other risk factors, and personal values
    • US Preventive Services Task Force recommends against routine screening in females who have never smoked and have no family history of abdominal aortic aneurysm, but concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for abdominal aortic aneurysm with ultrasonography in females aged 65 to 75 years who have ever smoked or have a family history of abdominal aortic aneurysm r13c108
    • Canadian Task Force on Preventive Health Care recommends performing 1-time sonography to screen all males aged 65 to 80 years regardless of tobacco use history, owing to data showing reduced abdominal aortic aneurysm–related mortality and rupture r54c109
    • Canadian Task Force on Preventive Health Care recommends against screening females, regardless of smoking history r54
    • Society for Vascular Surgery recommends the following: r7
      • 1-time ultrasonographic screening for abdominal aortic aneurysms in males or females aged 65 to 75 years with history of tobacco use r7c110
      • 1-time ultrasonographic screening for abdominal aortic aneurysms in males or females older than 75 years with history of tobacco use and in otherwise good health who have not previously received a screening ultrasonographic examination r7c111
      • Ultrasonographic screening for abdominal aortic aneurysms in first-degree relatives of patients who present with an abdominal aortic aneurysm; perform screening in first-degree relatives aged between 65 and 75 years or in those older than 75 years and in good health r7c112
    • American Institute of Ultrasound in Medicine recommends ultrasound screening evaluation for the following: r49
      • Males aged 65 years or older who have ever smoked r49
      • Females aged 65 years or older with cardiovascular risk factors r49
      • Individuals aged 50 years or older with a family history of aortic and/or peripheral vascular aneurysmal disease r49
      • Individuals with a personal history of peripheral vascular aneurysmal disease r49
      • Individuals with other risk factors for an abdominal aortic aneurysm r49
    • Canadian Society for Vascular Surgery r55
      • Recommends 1-time screening ultrasonography for all males aged 65 to 80 years r55
      • Suggests 1-time screening ultrasonography for all females aged 65 to 80 years with a history of smoking or cardiovascular disease r55
      • Suggests consideration of screening on an individual basis in males and females older than 80 years, based on life expectancy and patient choice r55
      • Suggests 1-time screening ultrasonography in those aged 55 years or older for all first-degree relatives of patients with abdominal aortic aneurysm r55
      • Suggests consideration of repeat ultrasonography 10 years after initial screening for patients with initial aortic diameter larger than 2.5 cm and less than 3 cm, based on life expectancy and patient choice r55

    Screening tests

    • Ultrasonography is sensitive and specific for detection of stable abdominal aortic aneurysm c113

    Prevention

    • Risk-factor modification
      • Avoid smoking c114
      • Avoid high-fat diet c115
      • Participate in aerobic exercise for at least 150 minutes every week c116
      • Avoid or treat obesity c117
      • Actively manage blood pressure and cholesterol level c118c119
    • Treat patients with vascular Ehlers-Danlos syndrome with prophylactic celiprolol r12
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