Abdominal Aortic Aneurysms

An aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms is the abnormal dilation of a segment of the aorta. Abdominal aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms is the most common aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms, occurring frequently in the infrarenal area. Degenerative aortic disorders are the prevalent etiology, affecting patients > 60 years of age. Most aneurysms are asymptomatic, but can cause compression of surrounding structures or rupture, which is a life-threatening emergency. Diagnosis is often made by ultrasound. As aneurysmal rupture carries a high mortality rate, surveillance is recommended for asymptomatic cases to monitor aortic diameter. Elective surgery (the majority via endovascular aortic repair) is an effective way to reduce complications and aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms-related death. This surgery is performed based on aortic size, underlying condition, and associated symptoms.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definitions

  • Abdominal aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms (AAA): infradiaphragmatic dilation of the aorta (to an aortic diameter of ≥ 3 cm)
  • Types:
    • True aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms: dilation of the aorta involving all 3 layers (intima, media, adventitia)
      • Fusiform-shaped: bulges on all sides of the aorta (more common)
      • Saccular-shaped: bulges on one side 
    • Pseudoaneurysm: 
      • Dilation caused by a disruption of the aortic wall
      • Extravasated blood contained by periarterial connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue, not by all wall layers
      • Extravascular hematoma communicates with the intravascular space.
  • Location:
    • Suprarenal: involves visceral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries; below the chest
    • Pararenal: involves origin of the renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries
    • Juxtarenal: 
      • No aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms in origin of renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries but aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms starts just beyond renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries 
      • No normal aortic segment between renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms
    • Infrarenal (most common):
      • Below renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries 
      • There is a normal aortic segment between renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms.

Epidemiology

  • AAAs: more common than thoracic aortic aneurysms Thoracic Aortic Aneurysms Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Thoracic Aortic Aneurysms (TAAs)
  • In the United States:  
    • More than 50% of patients with ruptured AAA die before reaching the hospital.
    • Over the past 30 years, AAA-related mortality has decreased, possibly due to: 
      • Disease screening
      • Decline in smoking 
      • Use of endovascular aortic repair

Etiology

  • Degenerative disorders:
    • Most common cause of AAA
    • Risk factors:
      • Age (> 60) and male sex
      • Smoking
      • Atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis (more common in AAA)
      • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
      • Caucasian race
    • Decreased risk noted in: females, non-Caucasians, and patients with diabetes
  • Genetic or developmental disorders:
    • Marfan’s syndrome
    • Turner’s syndrome
    • Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome
    • Loeys-Dietz syndrome
    • Polycystic kidney disease
  • Family history of AAA and presence of other arterial aneurysms (popliteal, femoral, intracranial)
  • Vasculitis:
    • Giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis
    • Behcet’s disease
    • Takayasu’s arteritis
    • HLA-B27–associated spondyloarthropathies
  • Infection:
    • Syphilis Syphilis Syphilis is a bacterial infection caused by the spirochete Treponema pallidum pallidum (T. p. pallidum), which is usually spread through sexual contact. Syphilis has 4 clinical stages: primary, secondary, latent, and tertiary. Syphilis (tertiary)
    • Tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis
    • Mycotic ( Salmonella Salmonella Salmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium). Salmonella, staphylococcal, streptococcal, fungal infection) 
  • Trauma: includes prior aortic procedure

Pathophysiology

Contributing factors

  • Embryology:
    • Embryologic origin can affect the response of aorta to cytokines and growth factors.
    • Abdominal aorta: derived from mesoderm
  • Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics:
    • 20% from familial predisposition
  • Biomechanics, structure, and growth of artery:
    • Wall thickness of aorta decreases from the thoracic area to the distal aorta
    • Abdominal aorta:
      • Lower elastin, collagen content
      • Has avascular media (poor nutrition delivery)
      • Grows by ↑ thickness of lamellar units
      • Fewer lamellar units = more tension per lamellar unit
      • ↑ Pulse pressures and more wall shear stress: 
        • Noted in distal aorta, especially infrarenal aorta (most common location of aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms)
  • Atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis:
    • AAA is associated with severe atherosclerosis.
    • High likelihood of progression of fatty streak to atheroma (compared with TAA TAA Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Thoracic Aortic Aneurysms)
  • Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation affects both TAA TAA Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Thoracic Aortic Aneurysms and AAA:
    • Predominantly T cells T cells T cells, also called T lymphocytes, are important components of the adaptive immune system. Production starts from the hematopoietic stem cells in the bone marrow, from which T-cell progenitor cells arise. These cells migrate to the thymus for further maturation. T Cells and macrophages
    • In AAA, both pro- and anti-inflammatory cytokines noted
  • Proteolysis by matrix metalloproteinases (MMPs):
    • ↑ Breakdown of extracellular matrix
    • MMP-9 proportional to aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms diameter
    • MMP-2: ↑ growth of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms

Pathogenesis

  • Regular vascular remodeling (synthesis, degradation, and repair) of extracellular matrix (ECM) components maintain the functional and structural integrity of the artery.
  • Above factors, in combination with age and environment (i.e. smoking, trauma) → result in breakdown of ECM → arterial medial degeneration → weakened vascular wall → dilation
  • The dilation + rapid expansion of aorta: ↑ risk of rupture or aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a "false lumen." Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection 
  • Widening of the vessel disrupts laminar blood flow → turbulence + inflammation → possible thrombus formation within the vessel (with risk of embolism)

Clinical Presentation

Symptoms

  • Commonly asymptomatic 
  • Depending on size and location:
    • Compression or erosion of surrounding structures: pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain in the abdomen, lower back/flank (most common manifestations)
    • Rupture typically into retroperitoneum: sudden severe flank or back pain Back pain Back pain is a common complaint among the general population and is mostly self-limiting. Back pain can be classified as acute, subacute, or chronic depending on the duration of symptoms. The wide variety of potential etiologies include degenerative, mechanical, malignant, infectious, rheumatologic, and extraspinal causes. Back Pain
    • Distal abdominal aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms compression and/or rupture: pelvic, groin or thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh, lower extremity pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain 
    • Thromboembolic events: claudication (limb ischemia), painful pulseless extremity (embolism)
    • Aortoduodenal fistula: upper gastrointestinal bleeding Gastrointestinal bleeding Gastrointestinal bleeding (GIB) is a symptom of multiple diseases within the gastrointestinal (GI) tract. Gastrointestinal bleeding is designated as upper or lower based on the etiology's location to the ligament of Treitz. Depending on the location of the bleeding, the patient may present with hematemesis (vomiting blood), melena (black, tarry stool), or hematochezia (fresh blood in stools). Gastrointestinal Bleeding
    • Aortic infection: fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, weight loss, vague abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Inflammatory aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms: patients are younger; abdominal and/or back pain Back pain Back pain is a common complaint among the general population and is mostly self-limiting. Back pain can be classified as acute, subacute, or chronic depending on the duration of symptoms. The wide variety of potential etiologies include degenerative, mechanical, malignant, infectious, rheumatologic, and extraspinal causes. Back Pain

Signs

  • AAA often found incidentally in imaging studies
  • AAA rupture: 
    • Life-threatening emergency!
    • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension, tachycardia 
  • Pulsatile abdominal mass (in 62% of ruptured AAAs)
  • Abdominal tenderness, abdominal bruit on examination
  • Ecchymosis (sign of retroperitoneal hematoma and blood extravasation into subcutaneous tissues)
    • Flank (Grey-Turner sign)
    • Proximal thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh (Fox’s sign)
    • Periumbilical (Cullen’s sign)
    • Scrotum (Bryant’s sign) 
  • Reduced femoral and pedal pulses in thromboembolism

Diagnosis

History

  • Risk factors (hypertension, smoking, hypercholesterolemia)
  • Family history of aortic pathology
  • Known history of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms in other areas (intracranial, iliac, femoral, popliteal aneurysms)
  • Prior aortic dissection Aortic dissection Aortic dissection occurs due to shearing stress from pulsatile pressure causing a tear in the tunica intima of the aortic wall. This tear allows blood to flow into the media, creating a "false lumen." Aortic dissection is most commonly caused by uncontrolled hypertension. Aortic Dissection
  • Other conditions: Marfan’s syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome, and other connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue diseases
  • Prior aortic procedure

Diagnostic tests Diagnostic tests Diagnostic tests are important aspects in making a diagnosis. Some of the most important epidemiological values of diagnostic tests include sensitivity and specificity, false positives and false negatives, positive and negative predictive values, likelihood ratios, and pre-test and post-test probabilities. Epidemiological Values of Diagnostic Tests

  • Abdominal ultrasound: 
    • Used for screening, diagnosis, and serial measurements
    • Determines the location and size of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms 
    • Screening:
      • Best initial step for asymptomatic patients
      • One-time ultrasound is: 
        • Recommended in men aged 65–75 years who have smoked 
        • Suggested in women and men aged 65–75 years with family history of AAA or AAA rupture
    • Symptomatic patients: can be used bedside in unstable patients
    • Diagnosis of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms: > 3 cm outer aortic diameter
    • Limited in detecting rupture, leakage, and other vessel involvement
    • Affected by body habitus and bowel gas
  • Abdominal computed tomography (CT) with contrast: 
    • For stable symptomatic patients and planning operative repair
    • Defines extent of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms, leakage, rupture, vessel involvement
    • Signs of impending rupture: 
      • Hyperattenuating crescent sign (93% specificity)
      • Thrombus fissuration
      • Aortic blebs from surface of aorta
      • Irregular aortic wall
      • Draped aorta sign (rupture sealed by vertebral body)
    • Signs of rupture: 
      • Intra- and/or retroperitoneal hematoma
      • Periaortic stranding
      • Indistinct aortic wall
  • Magnetic resonance imaging (MRI): 
    • No radiation or dye (may be used for patients with contrast allergy)
    • Limited availability and higher cost
  • Arteriography: 
    • Cannot accurately measure aortic diameter
    • Used intraoperatively (endovascular repair)
Ultrasonography of abdominal aortic aneurysm

Ultrasound showing an abdominal aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms with a mural thrombus

Image: “Ultrasonography of abdominal aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms with mural thrombus” by Mikael Häggström, M.D.. License: Public Domain

Management

Non-surgical management

  • Reduce cardiovascular risk:
    • Smoking cessation (most effective nonsurgical intervention to reduce aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms-related complications and death)
    • Exercise: 
      • Avoid heavy lifting.
      • Avoid activities that lead to Valsalva (↑ blood pressure).
    • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension control:
      • Antihypertensives given to reach recommended blood pressure goals
      • Unlike TAA TAA Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Thoracic Aortic Aneurysms, no specific medication recommended to limit AAA expansion
    • Lipid control with statins Statins Statins are competitive inhibitors of HMG-CoA reductase in the liver. HMG-CoA reductase is the rate-limiting step in cholesterol synthesis. Inhibition results in lowered intrahepatocytic cholesterol formation, resulting in up-regulation of LDL receptors and, ultimately, lowering levels of serum LDL and triglycerides. Statins (target LDL < 70 mg/dL)
  • Avoid fluoroquinolones Fluoroquinolones Fluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms. Fluoroquinolones (may ↑ risk of dissection or rupture)
  • Surveillance: Asymptomatic AAA < 5.5 cm, periodic evaluation and aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms diameter surveillance
Table: Management of asymptomatic patients by AAA size
AAA management of asymptomatic patients (ultrasound) AAA size
Rescreen after 10 years ≥ 2.5 cm but < 3 cm
Imaging every 3 years 3–3.9 cm
Imaging every 12 months 4–4.9 cm
Imaging every 6 months 5–5.4 cm
Consider elective repair ≥ 5.5 cm

Consider repair if 5 cm in women; expansion of < 0.5 cm/6 months or > 1 cm/1 year; associated femoral, iliac, popliteal aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms, or PAD requiring revascularization

Surgical management

Indications for operative repair

  • AAA rupture: emergency repair
  • Elective repair: most effective way of preventing rupture and aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms-related death
    • Symptomatic AAA
    • Rapidly expanding (> 0.5 cm/6 months or > 1 cm/1 year)
    • Asymptomatic AAA:  when diameter ≥ 5.5 cm  (5 cm in women: higher rate of rupture)
    • AAA with coexisting iliac, femoral, or popliteal artery aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms
    • AAA associated with symptomatic peripheral arterial disease (PAD) undergoing revascularization

Operative options

  • Open surgical repair: 
    • Midline transperitoneal or retroperitoneal incision
    • Diseased aorta replaced with tube or prosthetic graft
    • Indicated for younger patients, low perioperative risk, or those who have contraindications for endovascular aortic repair (EVAR)
    • Higher perioperative mortality but long-term durability
    • Surveillance: CT angiography 5 years later, look for aortic dilation or pseudoaneurysm
  • EVAR:
    • In the United States: 80% of AAA surgical repair 
    • Access through iliac or femoral arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries and endograft placed within AAA lumen 
    • Requires anatomic suitability (site and structure of aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms and access vessels)
    • Decreased operative mortality but higher rate of re-intervention
    • Surveillance: 
      • CT angiography 1 month and 1 year post-operatively, then duplex ultrasonography/CT annually if with uncomplicated surgery 
      • Look for endoleak, sac enlargement, migration of stents, and device integrity

Differential Diagnosis

  • Ruptured viscus: a condition in which gastrointestinal wall integrity is lost with subsequent leakage of enteric contents into the peritoneal cavity, resulting in peritonitis. A ruptured viscus is life-threatening and requires surgical management.
  • Mesenteric ischemia Mesenteric Ischemia Mesenteric ischemia is a rare, life-threatening condition caused by inadequate blood flow through the mesenteric vessels, which results in ischemia and necrosis of the intestinal wall. Mesenteric ischemia can be either acute or chronic. Mesenteric Ischemia: a rare, life-threatening syndrome caused by inadequate blood flow through the mesenteric vessels resulting in ischemia and gangrene of the bowel wall. Mesenteric ischemia Mesenteric Ischemia Mesenteric ischemia is a rare, life-threatening condition caused by inadequate blood flow through the mesenteric vessels, which results in ischemia and necrosis of the intestinal wall. Mesenteric ischemia can be either acute or chronic. Mesenteric Ischemia can be acute or chronic. Acute mesenteric ischemia is a surgical emergency, while the chronic condition requires risk factor modification, as it is related to vascular disease.
  • Strangulated hernia: Hernias are protrusions of abdominal content ( peritoneum Peritoneum The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). Peritoneum and Retroperitoneum, visceral fat, and/or viscera) through a congenital or acquired defect in the abdominal wall. Strangulation involves the constriction of hernial contents leading to bowel ischemia and requires emergency surgery to avoid bowel loss, perforation, and sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock.
  • Acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis: a condition characterized by inflammation of the gallbladder Gallbladder The gallbladder is a pear-shaped sac, located directly beneath the liver, that sits on top of the superior part of the duodenum. The primary functions of the gallbladder include concentrating and storing up to 50 mL of bile. Gallbladder and Biliary Tract, most often due to obstruction of the cystic duct by a gallstone. Management includes IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control, and IV antibiotics for secondary infection. Complicated cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis and progressive symptoms are indications for emergency cholecystectomy Cholecystectomy Cholecystectomy is a surgical procedure performed with the goal of resecting and extracting the gallbladder. It is one of the most common abdominal surgeries performed in the Western world. Cholecystectomy is performed for symptomatic cholelithiasis, cholecystitis, gallbladder polyps > 0.5 cm, porcelain gallbladder, choledocholithiasis and gallstone pancreatitis, and rarely, for gallbladder cancer. Cholecystectomy: Approaches and Technique.
  • Acute pancreatitis Acute pancreatitis Acute pancreatitis is an inflammatory disease of the pancreas due to autodigestion. Common etiologies include gallstones and excessive alcohol use. Patients typically present with epigastric pain radiating to the back. Acute Pancreatitis: an inflammation of the pancreas Pancreas The pancreas lies mostly posterior to the stomach and extends across the posterior abdominal wall from the duodenum on the right to the spleen on the left. This organ has both exocrine and endocrine tissue. Pancreas that typically causes epigastric pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain that radiates to the back. This condition is often treated with aggressive fluid resuscitation, bowel rest, and pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control. Surgery is indicated if the condition is associated with gallstones.
  • Diverticular abscess: a group of various intestinal conditions characterized by abnormal outpouchings of the colonic mucosa (diverticula). Over time, these diverticula may accumulate intestinal content, become infected, swell, and develop into an abscess. Intravenous antibiotics are the recommended treatment, with percutaneous drainage needed for large abscess or failed medical treatment.

References

  1. Aortic aneurysm (n.d.). Cdc.gov. Retrieved 3 Sept 2020, from https://www.cdc.gov/heartdisease/aortic_aneurysm.htm
  2. Creager, M., Elmore, J. & Givens, J. (2020, Jul). Screening for abdominal aortic aneurysm. UpToDate. Retrieved 3 Sept 2020, from https://www.uptodate.com/contents/screening-for-abdominal-aortic-aneurysm
  3. Chung, J., Eidt, J., Mills, J., Creager, M., Collins, K. (2020, Mar). Epidemiology, risk factors, pathogenesis and natural history of abdominal aortic aneurysm. UpToDate. Retrieved 3 Sept 2020, from https://www.uptodate.com/contents/epidemiology-risk-factors-pathogenesis-and-natural-history-of-abdominal-aortic-aneurysm
  4. Dalman, R., Mell, M., Mills, J.; Eidt, J.,Clement, D., Creager, M., Collins, K. (Eds.).(2020, Jun).Management of asymptomatic aortic aneurysm. UpToDate. Retrieved 30 Aug 2020, from https://www.uptodate.com/contents/management-of-asymptomatic-abdominal-aortic-aneurysm
  5. Erbel R, Aboyans V, Boileau C, et al. (2014) ESC Guidelines on the diagnosis and treatment of aortic diseases: Document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC). Eur Heart J .35:2873. Retrieved 30 Aug 2020, from https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Aortic-Diseases
  6. Guoledge, J, Guo-Ping, S.; Norman, P., Fitridge, R., Thompson, M. (2011). Pathogenesis of aortic aneurysm in Mechanisms of Vascular disease: A Reference Book for Vascular Specialists. Adelaide (AU): University of Adelaide Press. Retrieved 29 Aug 2020, from https://www.ncbi.nlm.nih.gov/books/NBK534278/
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