Overview

Definition

An aneurysm is a bulging, weakened area of a blood vessel, usually an artery, that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel.

Classification

• Types:
  • True aneurysm: involves all 3 layers of the vessel wall with ≥ 1 layer intact
  • Pseudoaneurysm: blood escapes into surrounding tissues and forms a hematoma around the artery as a result of a tear in the vessel wall.
• Shape:
  • Saccular aneurysm: sac-like bulging on 1 side of a blood vessel
  • Fusiform aneurysm: elongated spindle-shaped dilation of a blood vessel

Etiology

• 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 (both extremity and visceral aneurysms)
• Trauma
• Iatrogenic (e.g., dialysis Dialysis Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD). Overview and Types of Dialysis fistula)
• Behçet syndrome (most commonly pulmonary artery aneurysm)
• Hereditary conditions:
  • Marfan syndrome Marfan syndrome Marfan syndrome is a genetic condition with autosomal dominant inheritance. Marfan syndrome affects the elasticity of connective tissues throughout the body, most notably in the cardiovascular, ocular, and musculoskeletal systems. Marfan 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

Visceral Artery Aneurysms

Visceral artery aneurysms (VAAs) can affect the celiac artery, the superior and inferior mesenteric 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, or their branches.

Epidemiology: 

• Rare; incidence is 0.1%–0.2%.
• Splenic artery aneurysm (60% of VAAs): 
  • 80% > age 50
  • Incidence: 4x more common in women than in men
  • Seen after liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver transplantation
• Hepatic artery aneurysm (20% of VAAs)
  • 80% are extrahepatic
  • Twice as common in men as in women
  • Higher risk of rupture than other VAAs
  • Many individuals have other VAAs or nonvisceral aneurysms.
• Superior mesenteric artery aneurysm (5%–7%):
  • Usually due to atherosclerosis
  • Associated with polyarteritis nodosa, Behçet syndrome, and systemic 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 disorders
• Celiac artery aneurysm (3%–4% of VAAs)

Risk factors: 

• 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 (32% of VAAs)
• Medial degeneration in fibromuscular dysplasia Fibromuscular dysplasia Fibromuscular dysplasia (FMD) is a nonatherosclerotic, noninflammatory, medium-sized angiopathy due to fibroplasia of the vessel wall. The condition leads to complications related to arterial stenosis, aneurysm, or dissection. Fibromuscular Dysplasia (24%)
• Abdominal trauma (22%)
• Conditions of increased blood flow:
  • Pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care
  • Portal hypertension Portal hypertension Portal hypertension is increased pressure in the portal venous system. This increased pressure can lead to splanchnic vasodilation, collateral blood flow through portosystemic anastomoses, and increased hydrostatic pressure. There are a number of etiologies, including cirrhosis, right-sided congestive heart failure, schistosomiasis, portal vein thrombosis, hepatitis, and Budd-Chiari syndrome. Portal Hypertension (splenic artery aneurysm)
  • Liver transplantation
• Heart valve infection
• Connective tissue disorders
  • Marfan syndrome Marfan syndrome Marfan syndrome is a genetic condition with autosomal dominant inheritance. Marfan syndrome affects the elasticity of connective tissues throughout the body, most notably in the cardiovascular, ocular, and musculoskeletal systems. Marfan 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
  • Kawasaki disease Kawasaki disease Kawasaki disease (KD), also known as mucocutaneous lymph node syndrome or infantile polyarteritis, is a medium-sized necrotizing febrile vasculitis that affects children < 5 years of age. Multiple systems are involved but the most serious is the predilection of the coronary arteries. Kawasaki Disease
  • Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease)

Clinical presentation:

• Most VAAs are found incidentally on abdominal imaging done for other reasons.
• Nonspecific symptoms:
  • Malaise
  • 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
  • Nausea or vomiting
  • Celiac artery aneurysms can mimic pancreatitis.
• Embolic event → acute 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
• Rupture: 
  • Hemorrhagic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
  • Acute abdomen 

Diagnosis:

• Abdominal x-ray may show crescent-shaped calcification.
• Duplex ultrasonography
  • Round, hypoechoic mass seen
  • Ideal for intrahepatic aneurysm
  • Indicated in pregnant individuals
• CTA or MRA for surgical planning

Management:

• Early elective treatment is the general approach to minimize the risk of rupture, but there is no consensus guideline for observation versus surgery in VAAs < 2.5 cm.
• Definite surgical indications:
  • Symptomatic VAAs
  • Asymptomatic aneurysms with rapid expansion > 0.5 cm/year
  • Pregnant individuals
  • Pseudoaneurysms (regardless of symptoms) due to higher risk of rupture
• Ruptured VAA:
  • Stabilize individual; transfuse blood and platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets
  • Specific embolization techniques depend on the location, affected organ, and availability of a skilled interventional radiologist.
  • Endovascular repair with coils
  • Percutaneous thrombin injection (rarely used)
  • Surgical exploration with clipping and evacuation of any hematoma present

Prognosis:

• Ruptured VAAs: 25%–70% mortality rate
• Repaired aneurysm: immediate success in 90%

Differential Diagnosis

Extremity aneurysms

• Popliteal cyst (Baker cyst): most common cause of a palpable mass in the popliteal fossa Popliteal fossa The popliteal fossa or the "knee pit" is a diamond-shaped, fat-filled, shallow depression on the posterior aspect of the knee joint. The popliteal fossa is located at the dorsal aspect of the knee and contains an increased number of lymph nodes as well as structures of the neurovascular system that travel from the thigh to the lower leg. Popliteal Fossa. Popliteal cysts are formed by the extrusion of synovial fluid from the knee joint Knee joint The knee joint is made up of the articulations between the femur, tibia, and patella bones, and is one of the largest and most complex joints of the human body. The knee is classified as a synovial hinge joint, which primarily allows for flexion and extension with a more limited degree of translation and rotation. Knee Joint and may present similarly to a ruptured aneurysm, with an acute onset of severe knee 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 if it ruptures. Diagnosis can be made by physical exam, but ultrasonography is confirmatory. These cysts are commonly associated with osteoarthritis Osteoarthritis Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis or inflammatory arthritis. Treatment is with direct injection or aspiration of the cyst.
• Peripheral arterial disease (PAD): result of atherosclerosis gradually obstructing the arterial lumen and causing decreased blood flow to the distal limbs. Symptoms range from claudication to skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin discoloration and ischemic ulcers to gangrene. Diagnosis is made by physical exam with decreased palpable pulses. Additional studies include ankle brachial index testing and angiography if needed for surgical evaluation. Management is with lifestyle change (e.g., smoking cessation), antiplatelet therapy, and revascularization.

Visceral aneurysms

• Biliary colic: aneurysm in the hepatic 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 may cause RUQ 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 mimicking biliary colic, especially if there is rupture and the individual has associated jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice. Imaging with ultrasonography or CT is essential for differentiating from other etiologies, such as gallstones. Treatment is based on the underlying etiology.
• Pancreatitis: aneurysm of the celiac artery may mimic pancreatitis owing to its retroperitoneal location. Presentation is with dull 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 epigastric region that radiates to the back. Ultrasonography is an important diagnostic tool in identifying an aneurysm, and laboratory findings may include elevated amylase and lipase.